hypothesis on origin of the universe

Origins of the universe, explained

The most popular theory of our universe's origin centers on a cosmic cataclysm unmatched in all of history—the big bang.

The best-supported theory of our universe's origin centers on an event known as the big bang. This theory was born of the observation that other galaxies are moving away from our own at great speed in all directions, as if they had all been propelled by an ancient explosive force.

A Belgian priest named Georges Lemaître first suggested the big bang theory in the 1920s, when he theorized that the universe began from a single primordial atom. The idea received major boosts from Edwin Hubble's observations that galaxies are speeding away from us in all directions, as well as from the 1960s discovery of cosmic microwave radiation—interpreted as echoes of the big bang—by Arno Penzias and Robert Wilson.

Further work has helped clarify the big bang's tempo. Here’s the theory: In the first 10^-43 seconds of its existence, the universe was very compact, less than a million billion billionth the size of a single atom. It's thought that at such an incomprehensibly dense, energetic state, the four fundamental forces—gravity, electromagnetism, and the strong and weak nuclear forces—were forged into a single force, but our current theories haven't yet figured out how a single, unified force would work. To pull this off, we'd need to know how gravity works on the subatomic scale, but we currently don't.

It's also thought that the extremely close quarters allowed the universe's very first particles to mix, mingle, and settle into roughly the same temperature. Then, in an unimaginably small fraction of a second, all that matter and energy expanded outward more or less evenly, with tiny variations provided by fluctuations on the quantum scale. That model of breakneck expansion, called inflation, may explain why the universe has such an even temperature and distribution of matter.

After inflation, the universe continued to expand but at a much slower rate. It's still unclear what exactly powered inflation.

Aftermath of cosmic inflation

As time passed and matter cooled, more diverse kinds of particles began to form, and they eventually condensed into the stars and galaxies of our present universe.

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By the time the universe was a billionth of a second old, the universe had cooled down enough for the four fundamental forces to separate from one another. The universe's fundamental particles also formed. It was still so hot, though, that these particles hadn't yet assembled into many of the subatomic particles we have today, such as the proton. As the universe kept expanding, this piping-hot primordial soup—called the quark-gluon plasma—continued to cool. Some particle colliders, such as CERN's Large Hadron Collider , are powerful enough to re-create the quark-gluon plasma.

Radiation in the early universe was so intense that colliding photons could form pairs of particles made of matter and antimatter, which is like regular matter in every way except with the opposite electrical charge. It's thought that the early universe contained equal amounts of matter and antimatter. But as the universe cooled, photons no longer packed enough punch to make matter-antimatter pairs. So like an extreme game of musical chairs, many particles of matter and antimatter paired off and annihilated one another.

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Somehow, some excess matter survived—and it's now the stuff that people, planets, and galaxies are made of. Our existence is a clear sign that the laws of nature treat matter and antimatter slightly differently. Researchers have experimentally observed this rule imbalance, called CP violation , in action. Physicists are still trying to figure out exactly how matter won out in the early universe.

Building atoms

Within the universe's first second, it was cool enough for the remaining matter to coalesce into protons and neutrons, the familiar particles that make up atoms' nuclei. And after the first three minutes, the protons and neutrons had assembled into hydrogen and helium nuclei. By mass, hydrogen was 75 percent of the early universe's matter, and helium was 25 percent. The abundance of helium is a key prediction of big bang theory, and it's been confirmed by scientific observations.

Despite having atomic nuclei, the young universe was still too hot for electrons to settle in around them to form stable atoms. The universe's matter remained an electrically charged fog that was so dense, light had a hard time bouncing its way through. It would take another 380,000 years or so for the universe to cool down enough for neutral atoms to form—a pivotal moment called recombination. The cooler universe made it transparent for the first time, which let the photons rattling around within it finally zip through unimpeded.

We still see this primordial afterglow today as cosmic microwave background radiation , which is found throughout the universe. The radiation is similar to that used to transmit TV signals via antennae. But it is the oldest radiation known and may hold many secrets about the universe's earliest moments.

From the first stars to today

There wasn't a single star in the universe until about 180 million years after the big bang. It took that long for gravity to gather clouds of hydrogen and forge them into stars. Many physicists think that vast clouds of dark matter , a still-unknown material that outweighs visible matter by more than five to one, provided a gravitational scaffold for the first galaxies and stars.

Once the universe's first stars ignited , the light they unleashed packed enough punch to once again strip electrons from neutral atoms, a key chapter of the universe called reionization. In February 2018, an Australian team announced that they may have detected signs of this “cosmic dawn.” By 400 million years after the big bang , the first galaxies were born. In the billions of years since, stars, galaxies, and clusters of galaxies have formed and re-formed—eventually yielding our home galaxy, the Milky Way, and our cosmic home, the solar system.

Even now the universe is expanding , and to astronomers' surprise, the pace of expansion is accelerating. It's thought that this acceleration is driven by a force that repels gravity called dark energy . We still don't know what dark energy is, but it’s thought that it makes up 68 percent of the universe's total matter and energy. Dark matter makes up another 27 percent. In essence, all the matter you've ever seen—from your first love to the stars overhead—makes up less than five percent of the universe.

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Origins of the Universe 101

How old is the universe, and how did it begin? Throughout history, countless myths and scientific theories have tried to explain the universe's origins. The most widely accepted explanation is the big bang theory. Learn about the explosion that started it all and how the universe grew from the size of an atom to encompass everything in existence today.

Earth Science, Astronomy

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October 1, 1994

17 min read

The Evolution of the Universe

Some 15 billion years ago the universe emerged from a hot, dense sea of matter and energy. As the cosmos expanded and cooled, it spawned galaxies, stars, planets and life

By P. James E. Peebles , David N. Schramm , Edwin L. Turner & Richard G. Kron

GALAXY CLUSTER is representative of what the universe looked like when it was 60 percent of its present age. The Hubble Space Telescope captured the image by focusing on the cluster as it completed 10 orbits. This image is one of the longest and clearest exposures ever produced. Several pairs of galaxies appear to be caught in one another’s gravitational field. Such interactions are rarely found in nearby clusters and are evidence that the universe is evolving.

Editor’s Note (10/8/19): Cosmologist James Peebles won a 2019 Nobel Prize in Physics for his contributions to theories of how our universe began and evolved. He describes these ideas in this article, which he co-wrote for  Scientific American  in 1994.

At a particular instant roughly 15 billion years ago, all the matter and energy we can observe, concentrated in a region smaller than a dime, began to expand and cool at an incredibly rapid rate. By the time the temperature had dropped to 100 million times that of the sun’s core, the forces of nature assumed their present properties, and the elementary particles known as quarks roamed freely in a sea of energy. When the universe had expanded an additional 1,000 times, all the matter we can measure filled a region the size of the solar system.

At that time, the free quarks became confined in neutrons and protons. After the universe had grown by another factor of 1,000, protons and neutrons combined to form atomic nuclei, including most of the helium and deuterium present today. All of this occurred within the first minute of the expansion. Conditions were still too hot, however, for atomic nuclei to capture electrons. Neutral atoms appeared in abundance only after the expansion had continued for 300,000 years and the universe was 1,000 times smaller than it is now. The neutral atoms then began to coalesce into gas clouds, which later evolved into stars. By the time the universe had expanded to one fifth its present size, the stars had formed groups recognizable as young galaxies.

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When the universe was half its present size, nuclear reactions in stars had produced most of the heavy elements from which terrestrial planets were made. Our solar system is relatively young: it formed five billion years ago, when the universe was two thirds its present size. Over time the formation of stars has consumed the supply of gas in galaxies, and hence the population of stars is waning. Fifteen billion years from now stars like our sun will be relatively rare, making the universe a far less hospitable place for observers like us.

Our understanding of the genesis and evolution of the universe is one of the great achievements of 20th-century science. This knowledge comes from decades of innovative experiments and theories. Modern telescopes on the ground and in space detect the light from galaxies billions of light-years away, showing us what the universe looked like when it was young. Particle accelerators probe the basic physics of the high-energy environment of the early universe. Satellites detect the cosmic background radiation left over from the early stages of expansion, providing an image of the universe on the largest scales we can observe.

Our best efforts to explain this wealth of data are embodied in a theory known as the standard cosmological model or the big bang cosmology. The major claim of the theory is that in the largescale average the universe is expanding in a nearly homogeneous way from a dense early state. At present, there are no fundamental challenges to the big bang theory, although there are certainly unresolved issues within the theory itself. Astronomers are not sure, for example, how the galaxies were formed, but there is no reason to think the process did not occur within the framework of the big bang. Indeed, the predictions of the theory have survived all tests to date.

Yet the big bang model goes only so far, and many fundamental mysteries remain. What was the universe like before it was expanding? (No observation we have made allows us to look back beyond the moment at which the expansion began.) What will happen in the distant future, when the last of the stars exhaust the supply of nuclear fuel? No one knows the answers yet.

Our universe may be viewed in many lights—by mystics, theologians, philosophers or scientists. In science we adopt the plodding route: we accept only what is tested by experiment or observation. Albert Einstein gave us the now well-tested and accepted Theory of General Relativity, which establishes the relations between mass, energy, space and time. Einstein showed that a homogeneous distribution of matter in space fits nicely with his theory. He assumed without discussion that the universe is static, unchanging in the large-scale average [see “How Cosmology Became a Science,” by Stephen G. Brush; SCIENTIFIC AMERICAN, August 1992].

In 1922 the Russian theorist Alexander A. Friedmann realized that Einstein’s universe is unstable; the slightest perturbation would cause it to expand or contract. At that time, Vesto M. Slipher of Lowell Observatory was collecting the first evidence that galaxies are actually moving apart. Then, in 1929, the eminent astronomer Edwin P. Hubble showed that the rate a galaxy is moving away from us is roughly proportional to its distance from us.

MULTIPLE IMAGES of a distant quasar ( left ) are the result of an effect known as gravitational lensing. The effect occurs when light from a distant object is bent by the gravitational field of an intervening galaxy. In this case, the galaxy, which is visible in the center, produces four images of the quasar. The photograph was produced using the Hubble telescope.

The existence of an expanding universe implies that the cosmos has evolved from a dense concentration of matter into the present broadly spread distribution of galaxies. Fred Hoyle, an English cosmologist, was the first to call this process the big bang. Hoyle intended to disparage the theory, but the name was so catchy it gained popularity. It is somewhat misleading, however, to describe the expansion as some type of explosion of matter away from some particular point in space.

That is not the picture at all: in Einstein’s universe the concept of space and the distribution of matter are intimately linked; the observed expansion of the system of galaxies reveals the unfolding of space itself. An essential feature of the theory is that the average density in space declines as the universe expands; the distribution of matter forms no observable edge. In an explosion the fastest particles move out into empty space, but in the big bang cosmology, particles uniformly fill all space. The expansion of the universe has had little influence on the size of galaxies or even clusters of galaxies that are bound by gravity; space is simply opening up between them. In this sense, the expansion is similar to a rising loaf of raisin bread. The dough is analogous to space, and the raisins, to clusters of galaxies. As the dough expands, the raisins move apart. Moreover, the speed with which any two raisins move apart is directly and positively related to the amount of dough separating them.

The evidence for the expansion of the universe has been accumulating for some 60 years. The first important clue is the redshift. A galaxy emits or absorbs some wavelengths of light more strongly than others. If the galaxy is moving away from us, these emission and absorption features are shifted to longer wavelengths—that is, they become redder as the recession velocity increases. This phenomenon is known as the redshift.

Hubble’s measurements indicated that the redshift of a distant galaxy is greater than that of one closer to the earth. This relation, now known as Hubble’s law, is just what one would expect in a uniformly expanding universe. Hubble’s law says the recession velocity of a galaxy is equal to its distance multiplied by a quantity called Hubble’s constant. The redshift effect in nearby galaxies is relatively subtle, requiring good instrumentation to detect it. In contrast, the redshift of very distant objects—radio galaxies and quasars—is an awesome phenomenon; some appear to be moving away at greater than 90 percent of the speed of light.

Hubble contributed to another crucial part of the picture. He counted the number of visible galaxies in different directions in the sky and found that they appear to be rather uniformly distributed. The value of Hubble’s constant seemed to be the same in all directions, a necessary consequence of uniform expansion. Modern surveys confirm the fundamental tenet that the universe is homogeneous on large scales. Although maps of the distribution of the nearby galaxies display clumpiness, deeper surveys reveal considerable uniformity.

The Milky Way, for instance, resides in a knot of two dozen galaxies; these in turn are part of a complex of galaxies that protrudes from the so-called local supercluster. The hierarchy of clustering has been traced up to dimensions of about 500 million light-years. The fluctuations in the average density of matter diminish as the scale of the structure being investigated increases. In maps that cover distances that reach close to the observable limit, the average density of matter changes by less than a tenth of a percent.

To test Hubble’s law, astronomers need to measure distances to galaxies. One method for gauging distance is to observe the apparent brightness of a galaxy. If one galaxy is four times fainter in the night sky than an otherwise comparable galaxy, then it can be estimated to be twice as far away. This expectation has now been tested over the whole of the visible range of distances.

HOMOGENEOUS DISTRIBUTION of galaxies is apparent in a map that includes objects from 300 to 1,000 million light-years away. The only inhomogeneity, a gap near the center line, occurs because part of the sky is obscured by the Milky Way. Michael Strauss of the Institute for Advanced Study in Princeton, N.J., created the map using data from NASA’s Infrared Astronomical Satellite .

Some critics of the theory have pointed out that a galaxy that appears to be smaller and fainter might not actually be more distant. Fortunately, there is a direct indication that objects whose redshifts are larger really are more distant. The evidence comes from observations of an effect known as gravitational lensing. An object as massive and compact as a galaxy can act as a crude lens, producing a distorted, magnified image (or even many images) of any background radiation source that lies behind it. Such an object does so by bending the paths of light rays and other electromagnetic radiation. So if a galaxy sits in the line of sight between the earth and some distant object, it will bend the light rays from the object so that they are observable [see “Gravitational Lenses,” by Edwin L. Turner; SCIENTIFIC AMERICAN, July 1988]. During the past decade, astronomers have discovered more than a dozen gravitational lenses. The object behind the lens is always found to have a higher redshift than the lens itself, confirming the qualitative prediction of Hubble’s law.

Hubble’s law has great significance not only because it describes the expansion of the universe but also because it can be used to calculate the age of the cosmos. To be precise, the time elapsed since the big bang is a function of the present value of Hubble’s constant and its rate of change. Astronomers have determined the approximate rate of the expansion, but no one has yet been able to measure the second value precisely.

Still, one can estimate this quantity from knowledge of the universe’s average density. One expects that because gravity exerts a force that opposes expansion, galaxies would tend to move apart more slowly now than they did in the past. The rate of change in expansion is therefore related to the gravitational pull of the universe set by its average density. If the density is that of just the visible material in and around galaxies, the age of the universe probably lies between 12 and 20 billion years. (The range allows for the uncertainty in the rate of expansion.)

Yet many researchers believe the density is greater than this minimum value. So-called dark matter would make up the difference. A strongly defended argument holds that the universe is just dense enough that in the remote future the expansion will slow almost to zero. Under this assumption, the age of the universe decreases to the range of seven to 13 billion years.

DENSITY of neutrons and protons in the universe determined the abundances of certain elements. For a higher density universe, the computed helium abundance is little different, and the computed abundance of deuterium is considerably lower. The shaded region is consistent with the observations, ranging from an abundance of 24 percent for helium to one part in 1010 for the lithium isotope. This quantitative agreement is a prime success of the big bang cosmology.

To improve these estimates, many astronomers are involved in intensive research to measure both the distances to galaxies and the density of the universe. Estimates of the expansion time provide an important test for the big bang model of the universe. If the theory is correct, everything in the visible universe should be younger than the expansion time computed from Hubble’s law.

These two timescales do appear to be in at least rough concordance. For example, the oldest stars in the disk of the Milky Way galaxy are about nine billion years old—an estimate derived from the rate of cooling of white dwarf stars. The stars in the halo of the Milky Way are somewhat older, about 15 billion years—a value derived from the rate of nuclear fuel consumption in the cores of these stars. The ages of the oldest known chemical elements are also approximately 15 billion years—a number that comes from radioactive dating techniques. Workers in laboratories have derived these age estimates from atomic and nuclear physics. It is noteworthy that their results agree, at least approximately, with the age that astronomers have derived by measuring cosmic expansion.

Another theory, the steady state theory, also succeeds in accounting for the expansion and homogeneity of the universe. In 1946 three physicists in England—Hoyle, Hermann Bondi and Thomas Gold—proposed such a cosmology. In their theory the universe is forever expanding, and matter is created spontaneously to fill the voids. As this material accumulates, they suggested, it forms new stars to replace the old. This steady state hypothesis predicts that ensembles of galaxies close to us should look statistically the same as those far away. The big bang cosmology makes a different prediction: if galaxies were all formed long ago, distant galaxies should look younger than those nearby because light from them requires a longer time to reach us. Such galaxies should contain more shortlived stars and more gas out of which future generations of stars will form.

The test is simple conceptually, but it took decades for astronomers to develop detectors sensitive enough to study distant galaxies in detail. When astronomers examine nearby galaxies that are powerful emitters of radio wavelengths, they see, at optical wavelengths, relatively round systems of stars. Distant radio galaxies, on the other hand, appear to have elongated and sometimes irregular structures. Moreover, in most distant radio galaxies, unlike the ones nearby, the distribution of light tends to be aligned with the pattern of the radio emission.

Likewise, when astronomers study the population of massive, dense clusters of galaxies, they find differences between those that are close and those far away. Distant clusters contain bluish galaxies that show evidence of ongoing star formation. Similar clusters that are nearby contain reddish galaxies in which active star formation ceased long ago. Observations made with the Hubble Space Telescope confirm that at least some of the enhanced star formation in these younger clusters may be the result of collisions between their member galaxies, a process that is much rarer in the present epoch.

DISTANT GALAXIES differ greatly from those nearby—an observation that shows that galaxies evolved from earlier, more irregular forms. Among galaxies that are bright at both optical ( blue ) and radio ( red ) wavelengths, the nearby galaxies tend to have smooth elliptical shapes at optical wavelengths and very elongated radio images. As redshift, and therefore distance, increases, galaxies have more irregular elongated forms that appear aligned at optical and radio wavelengths. The galaxy at the far right is seen as it was at 10 percent of the present age of the universe. The images were assembled by Pat McCarthy of the Carnegie Institute.

So if galaxies are all moving away from one another and are evolving from earlier forms, it seems logical that they were once crowded together in some dense sea of matter and energy. Indeed, in 1927, before much was known about distant galaxies, a Belgian cosmologist and priest, Georges Lemaître, proposed that the expansion of the universe might be traced to an exceedingly dense state he called the primeval “super-atom.” It might even be possible, he thought, to detect remnant radiation from the primeval atom. But what would this radiation signature look like?

When the universe was very young and hot, radiation could not travel very far without being absorbed and emitted by some particle. This continuous exchange of energy maintained a state of thermal equilibrium; any particular region was unlikely to be much hotter or cooler than the average. When matter and energy settle to such a state, the result is a so-called thermal spectrum, where the intensity of radiation at each wavelength is a definite function of the temperature. Hence, radiation originating in the hot big bang is recognizable by its spectrum.

In fact, this thermal cosmic background radiation has been detected. While working on the development of radar in the 1940s, Robert H. Dicke, then at the Massachusetts Institute of Technology, invented the microwave radiometer—a device capable of detecting low levels of radiation. In the 1960s Bell Laboratories used a radiometer in a telescope that would track the early communications satellites Echo-1 and Telstar. The engineer who built this instrument found that it was detecting unexpected radiation. Arno A. Penzias and Robert W. Wilson identified the signal as the cosmic background radiation. It is interesting that Penzias and Wilson were led to this idea by the news that Dicke had suggested that one ought to use a radiometer to search for the cosmic background.

Astronomers have studied this radiation in great detail using the Cosmic Background Explorer (COBE) satellite and a number of rocket-launched, balloon-borne and ground-based experiments. The cosmic background radiation has two distinctive properties. First, it is nearly the same in all directions. (As George F. Smoot of Lawrence Berkeley Laboratory and his team discovered in 1992, the variation is just one part per 100,000.) The interpretation is that the radiation uniformly fills space, as predicted in the big bang cosmology. Second, the spectrum is very close to that of an object in thermal equilibrium at 2.726 kelvins above absolute zero. To be sure, the cosmic background radiation was produced when the universe was far hotter than 2.726 degrees, yet researchers anticipated correctly that the apparent temperature of the radiation would be low. In the 1930s Richard C. Tolman of the California Institute of Technology showed that the temperature of the cosmic background would diminish because of the universe’s expansion.

The cosmic background radiation provides direct evidence that the universe did expand from a dense, hot state, for this is the condition needed to produce the radiation. In the dense, hot early universe thermonuclear reactions produced elements heavier than hydrogen, including deuterium, helium and lithium. It is striking that the computed mix of the light elements agrees with the observed abundances. That is, all evidence indicates that the light elements were produced in the hot, young universe, whereas the heavier elements appeared later, as products of the thermonuclear reactions that power stars.

The theory for the origin of the light elements emerged from the burst of research that followed the end of World War II. George Gamow and graduate student Ralph A. Alpher of George Washington University and Robert Herman of the Johns Hopkins University Applied Physics Laboratory and others used nuclear physics data from the war e›ort to predict what kind of nuclear processes might have occurred in the early universe and what elements might have been produced. Alpher and Herman also realized that a remnant of the original expansion would still be detectable in the existing universe.

Despite the fact that significant details of this pioneering work were in error, it forged a link between nuclear physics and cosmology. The workers demonstrated that the early universe could be viewed as a type of thermonuclear reactor. As a result, physicists have now precisely calculated the abundances of light elements produced in the big bang and how those quantities have changed because of subsequent events in the interstellar medium and nuclear processes in stars.

Our grasp of the conditions that prevailed in the early universe does not translate into a full understanding of how galaxies formed. Nevertheless, we do have quite a few pieces of the puzzle. Gravity causes the growth of density fluctuations in the distribution of matter, because it more strongly slows the expansion of denser regions, making them grow still denser. This process is observed in the growth of nearby clusters of galaxies, and the galaxies themselves were probably assembled by the same process on a smaller scale.

The growth of structure in the early universe was prevented by radiation pressure, but that changed when the universe had expanded to about 0.1 percent of its present size. At that point, the temperature was about 3,000 kelvins, cool enough to allow the ions and electrons to combine to form neutral hydrogen and helium. The neutral matter was able to slip through the radiation and to form gas clouds that could collapse to star clusters. Observations show that by the time the universe was one fifth its present size, matter had gathered into gas clouds large enough to be called young galaxies.

A pressing challenge now is to reconcile the apparent uniformity of the early universe with the lumpy distribution of galaxies in the present universe. Astronomers know that the density of the early universe did not vary by much, because they observe only slight irregularities in the cosmic background radiation. So far it has been easy to develop theories that are consistent with the available measurements, but more critical tests are in progress. In particular, different theories for galaxy formation predict quite different fluctuations in the cosmic background radiation on angular scales less than about one degree. Measurements of such tiny fluctuations have not yet been done, but they might be accomplished in the generation of experiments now under way. It will be exciting to learn whether any of the theories of galaxy formation now under consideration survive these tests.

The present-day universe has provided ample opportunity for the development of life as we know it—there are some 100 billion billion stars similar to the sun in the part of the universe we can observe. The big bang cosmology implies, however, that life is possible only for a bounded span of time: the universe was too hot in the distant past, and it has limited resources for the future. Most galaxies are still producing new stars, but many others have already exhausted their supply of gas. Thirty billion years from now, galaxies will be much darker and filled with dead or dying stars, so there will be far fewer planets capable of supporting life as it now exists.

The universe may expand forever, in which case all the galaxies and stars will eventually grow dark and cold. The alternative to this big chill is a big crunch. If the mass of the universe is large enough, gravity will eventually reverse the expansion, and all matter and energy will be reunited. During the next decade, as researchers improve techniques for measuring the mass of the universe, we may learn whether the present expansion is headed toward a big chill or a big crunch.

In the near future, we expect new experiments to provide a better understanding of the big bang. As we improve measurements of the expansion rate and the ages of stars, we may be able to confirm that the stars are indeed younger than the expanding universe. The larger telescopes recently completed or under construction may allow us to see how the mass of the universe affects the curvature of spacetime, which in turn influences our observations of distant galaxies.

We will also continue to study issues that the big bang cosmology does not address. We do not know why there was a big bang or what may have existed before. We do not know whether our universe has siblings—other expanding regions well removed from what we can observe. We do not understand why the fundamental constants of nature have the values they do. Advances in particle physics suggest some interesting ways these questions might be answered; the challenge is to find experimental tests of the ideas.

In following the debate on such matters of cosmology, one should bear in mind that all physical theories are approximations of reality that can fail if pushed too far. Physical science advances by incorporating earlier theories that are experimentally supported into larger, more encompassing frameworks. The big bang theory is supported by a wealth of evidence: it explains the cosmic background radiation, the abundances of light elements and the Hubble expansion. Thus, any new cosmology surely will include the big bang picture. Whatever developments the coming decades may bring, cosmology has moved from a branch of philosophy to a physical science where hypotheses meet the test of observation and experiment.

Cosmic History

The Universe’s History

The origin, evolution, and nature of the universe have fascinated and confounded humankind for centuries. New ideas and major discoveries made during the 20th century transformed cosmology – the term for the way we conceptualize and study the universe – although much remains unknown. Here is the history of the universe according to cosmologists’ current theories.

Cosmic Inflation

Around 13.8 billion years ago, the universe expanded faster than the speed of light for a fraction of a second, a period called cosmic inflation. Scientists aren’t sure what came before inflation or what powered it. It’s possible that energy during this period was just part of the fabric of space-time. Cosmologists think inflation explains many aspects of the universe we observe today, like its flatness, or lack of curvature, on the largest scales. Inflation may have also magnified density differences that naturally occur on space’s smallest, quantum-level scales, which eventually helped form the universe’s large-scale structures.

Big Bang and Nucleosynthesis

When cosmic inflation stopped, the energy driving it transferred to matter and light – the big bang. One second after the big bang, the universe consisted of an extremely hot (18 billion degrees Fahrenheit or 10 billion degrees Celsius) primordial soup of light and particles. In the following minutes, an era called nucleosynthesis, protons and neutrons collided and produced the earliest elements – hydrogen, helium, and traces of lithium and beryllium. After five minutes, most of today’s helium had formed, and the universe had expanded and cooled enough that further element formation stopped. At this point, though, the universe was still too hot for the atomic nuclei of these elements to catch electrons and form complete atoms. The cosmos was opaque because a vast number of electrons created a sort of fog that scattered light.

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Recombination

Around 380,000 years after the big bang, the universe had cooled enough that atomic nuclei could capture electrons, a period astronomers call the epoch of recombination. This had two major effects on the cosmos. First, with most electrons now bound into atoms, there were no longer enough free ones to completely scatter light, and the cosmic fog cleared. The universe became transparent, and for the first time, light could freely travel over great distances. Second, the formation of these first atoms produced its own light. This glow, still detectable today, is called the cosmic microwave background. It is the oldest light we can observe in the universe.

After the cosmic microwave background, the universe again became opaque at shorter wavelengths due to the absorbing effects of all those hydrogen atoms. For the next 200 million years the universe remained dark. There were no stars to shine. The cosmos at this point consisted of a sea of hydrogen atoms, helium, and trace amounts of heavier elements.

First Stars

Gas was not uniformly distributed throughout the universe. Cooler areas of space were lumpier, with denser clouds of gas. As these clumps grew more massive, their gravity attracted additional matter. As they became denser, and more compact, the centers of these clumps became hotter – hot enough eventually that nuclear fusion occurred in their centers. These were the first stars. They were 30 to 300 times more massive than our Sun and millions of times brighter. Over several hundred million years, the first stars collected into the first galaxies.

Reionization

At first, starlight couldn’t travel far because it was scattered by the relatively dense gas surrounding the first stars. Gradually, the ultraviolet light emitted by these stars broke down, or ionized, hydrogen atoms in the gas into their constituent electrons and protons. As this reionization progressed, starlight traveled farther, breaking up more and more hydrogen atoms. By the time the universe was 1 billion years old, stars and galaxies had transformed nearly all this gas, making the universe transparent to light as we see it today.

For many years, scientists thought the universe’s current expansion was slowing down. But in fact, cosmic expansion is speeding up. In 1998, astronomers found that certain supernovae, bright stellar explosions, were fainter than expected. They concluded this could only happen if the supernovae had moved farther away, at a faster rate than predicted.

Scientists suspect a mysterious substance they call dark energy is accelerating expansion. Future research may yield new surprises, but cosmologists suggest it’s likely the universe will continue to expand forever.

Discover More Topics From NASA

Dark Matter & Dark Energy

The Big Bang

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National Academy of Sciences (US). Science and Creationism: A View from the National Academy of Sciences: Second Edition. Washington (DC): National Academies Press (US); 1999.

Science and Creationism: A View from the National Academy of Sciences: Second Edition.

• Hardcopy Version at National Academies Press

The Origin of the Universe, Earth, and Life

The term "evolution" usually refers to the biological evolution of living things. But the processes by which planets, stars, galaxies, and the universe form and change over time are also types of "evolution." In all of these cases there is change over time, although the processes involved are quite different.

In the late 1920s the American astronomer Edwin Hubble made a very interesting and important discovery. Hubble made observations that he interpreted as showing that distant stars and galaxies are receding from Earth in every direction. Moreover, the velocities of recession increase in proportion with distance, a discovery that has been confirmed by numerous and repeated measurements since Hubble's time. The implication of these findings is that the universe is expanding.

Hubble's hypothesis of an expanding universe leads to certain deductions. One is that the universe was more condensed at a previous time. From this deduction came the suggestion that all the currently observed matter and energy in the universe were initially condensed in a very small and infinitely hot mass. A huge explosion, known as the Big Bang, then sent matter and energy expanding in all directions.

This Big Bang hypothesis led to more testable deductions. One such deduction was that the temperature in deep space today should be several degrees above absolute zero. Observations showed this deduction to be correct. In fact, the Cosmic Microwave Background Explorer (COBE) satellite launched in 1991 confirmed that the background radiation field has exactly the spectrum predicted by a Big Bang origin for the universe.

As the universe expanded, according to current scientific understanding, matter collected into clouds that began to condense and rotate, forming the forerunners of galaxies. Within galaxies, including our own Milky Way galaxy, changes in pressure caused gas and dust to form distinct clouds. In some of these clouds, where there was sufficient mass and the right forces, gravitational attraction caused the cloud to collapse. If the mass of material in the cloud was sufficiently compressed, nuclear reactions began and a star was born.

Some proportion of stars, including our sun, formed in the middle of a flattened spinning disk of material. In the case of our sun, the gas and dust within this disk collided and aggregated into small grains, and the grains formed into larger bodies called planetesimals ("very small planets"), some of which reached diameters of several hundred kilometers. In successive stages these planetesimals coalesced into the nine planets and their numerous satellites. The rocky planets, including Earth, were near the sun, and the gaseous planets were in more distant orbits.

The ages of the universe, our galaxy, the solar system, and Earth can be estimated using modem scientific methods. The age of the universe can be derived from the observed relationship between the velocities of and the distances separating the galaxies. The velocities of distant galaxies can be measured very accurately, but the measurement of distances is more uncertain. Over the past few decades, measurements of the Hubble expansion have led to estimated ages for the universe of between 7 billion and 20 billion years, with the most recent and best measurements within the range of 10 billion to 15 billion years.

A disk of dust and gas, appearing as a dark band in this Hubble Space Telescope photograph, bisects a glowing nebula around a very young star in the constellation Taurus. Similar disks can be seen around other nearby stars and are thought to provide the (more...)

The age of the Milky Way galaxy has been calculated in two ways. One involves studying the observed stages of evolution of different-sized stars in globular clusters. Globular clusters occur in a faint halo surrounding the center of the Galaxy, with each cluster containing from a hundred thousand to a million stars. The very low amounts of elements heavier than hydrogen and helium in these stars indicate that they must have formed early in the history of the Galaxy, before large amounts of heavy elements were created inside the initial generations of stars and later distributed into the interstellar medium through supernova explosions (the Big Bang itself created primarily hydrogen and helium atoms). Estimates of the ages of the stars in globular clusters fall within the range of 11 billion to 16 billion years.

A second method for estimating the age of our galaxy is based on the present abundances of several long-lived radioactive elements in the solar system. Their abundances are set by their rates of production and distribution through exploding supernovas. According to these calculations, the age of our galaxy is between 9 billion and 16 billion years. Thus, both ways of estimating the age of the Milky Way galaxy agree with each other, and they also are consistent with the independently derived estimate for the age of the universe.

Radioactive elements occurring naturally in rocks and minerals also provide a means of estimating the age of the solar system and Earth. Several of these elements decay with half lives between 700 million and more than 100 billion years (the half life of an element is the time it takes for half of the element to decay radioactively into another element). Using these time-keepers, it is calculated that meteorites, which are fragments of asteroids, formed between 4.53 billion and 4.58 billion years ago (asteroids are small "planetoids" that revolve around the sun and are remnants of the solar nebula that gave rise to the sun and planets). The same radioactive time-keepers applied to the three oldest lunar samples returned to Earth by the Apollo astronauts yield ages between 4.4 billion and 4.5 billion years, providing minimum estimates for the time since the formation of the moon.

The oldest known rocks on Earth occur in northwestern Canada (3.96 billion years), but well-studied rocks nearly as old are also found in other parts of the world. In Western Australia, zircon crystals encased within younger rocks have ages as old as 4.3 billion years, making these tiny crystals the oldest materials so far found on Earth.

The best estimates of Earth's age are obtained by calculating the time required for development of the observed lead isotopes in Earth's oldest lead ores. These estimates yield 4.54 billion years as the age of Earth and of meteorites, and hence of the solar system.

The origins of life cannot be dated as precisely, but there is evidence that bacteria-like organisms lived on Earth 3.5 billion years ago, and they may have existed even earlier, when the first solid crust formed, almost 4 billion years ago. These early organisms must have been simpler than the organisms living today. Furthermore, before the earliest organisms there must have been structures that one would not call "alive" but that are now components of living things. Today, all living organisms store and transmit hereditary information using two kinds of molecules: DNA and RNA. Each of these molecules is in turn composed of four kinds of subunits known as nucleotides. The sequences of nucleotides in particular lengths of DNA or RNA, known as genes, direct the construction of molecules known as proteins, which in turn catalyze biochemical reactions, provide structural components for organisms, and perform many of the other functions on which life depends. Proteins consist of chains of subunits known as amino acids. The sequence of nucleotides in DNA and RNA therefore determines the sequence of amino acids in proteins; this is a central mechanism in all of biology.

Experiments conducted under conditions intended to resemble those present on primitive Earth have resulted in the production of some of the chemical components of proteins, DNA, and RNA. Some of these molecules also have been detected in meteorites from outer space and in interstellar space by astronomers using radio-telescopes. Scientists have concluded that the "building blocks of life" could have been available early in Earth's history.

An important new research avenue has opened with the discovery that certain molecules made of RNA, called ribozymes, can act as catalysts in modem cells. It previously had been thought that only proteins could serve as the catalysts required to carry out specific biochemical functions. Thus, in the early prebiotic world, RNA molecules could have been "autocatalytic"—that is, they could have replicated themselves well before there were any protein catalysts (called enzymes).

Laboratory experiments demonstrate that replicating autocatalytic RNA molecules undergo spontaneous changes and that the variants of RNA molecules with the greatest autocatalytic activity come to prevail in their environments. Some scientists favor the hypothesis that there was an early "RNA world," and they are testing models that lead from RNA to the synthesis of simple DNA and protein molecules. These assemblages of molecules eventually could have become packaged within membranes, thus making up "protocells"—early versions of very simple cells.

For those who are studying the origin of life, the question is no longer whether life could have originated by chemical processes involving nonbiological components. The question instead has become which of many pathways might have been followed to produce the first cells.

Will we ever be able to identify the path of chemical evolution that succeeded in initiating life on Earth? Scientists are designing experiments and speculating about how early Earth could have provided a hospitable site for the segregation of molecules in units that might have been the first living systems. The recent speculation includes the possibility that the first living cells might have arisen on Mars, seeding Earth via the many meteorites that are known to travel from Mars to our planet.

Of course, even if a living cell were to be made in the laboratory, it would not prove that nature followed the same pathway billions of years ago. But it is the job of science to provide plausible natural explanations for natural phenomena. The study of the origin of life is a very active research area in which important progress is being made, although the consensus among scientists is that none of the current hypotheses has thus far been confirmed. The history of science shows that seemingly intractable problems like this one may become amenable to solution later, as a result of advances in theory, instrumentation, or the discovery of new facts.

Creationist Views of the Origin of the Universe, Earth, and Life

Many religious persons, including many scientists, hold that God created the universe and the various processes driving physical and biological evolution and that these processes then resulted in the creation of galaxies, our solar system, and life on Earth. This belief, which sometimes is termed "theistic evolution," is not in disagreement with scientific explanations of evolution. Indeed, it reflects the remarkable and inspiring character of the physical universe revealed by cosmology, paleontology, molecular biology, and many other scientific disciplines.

The advocates of "creation science" hold a variety of viewpoints. Some claim that Earth and the universe are relatively young, perhaps only 6,000 to 10,000 years old. These individuals often believe that the present physical form of Earth can be explained by "catastrophism," including a worldwide flood, and that all living things (including humans) were created miraculously, essentially in the forms we now find them.

Other advocates of creation science are willing to accept that Earth, the planets, and the stars may have existed for millions of years. But they argue that the various types of organisms, and especially humans, could only have come about with supernatural intervention, because they show "intelligent design."

In this booklet, both these "Young Earth" and "Old Earth" views are referred to as "creationism" or "special creation."

There are no valid scientific data or calculations to substantiate the belief that Earth was created just a few thousand years ago. This document has summarized the vast amount of evidence for the great age of the universe, our galaxy, the solar system, and Earth from astronomy, astrophysics, nuclear physics, geology, geochemistry, and geophysics. Independent scientific methods consistently give an age for Earth and the solar system of about 5 billion years, and an age for our galaxy and the universe that is two to three times greater. These conclusions make the origin of the universe as a whole intelligible, lend coherence to many different branches of science, and form the core conclusions of a remarkable body of knowledge about the origins and behavior of the physical world.

Nor is there any evidence that the entire geological record, with its orderly succession of fossils, is the product of a single universal flood that occurred a few thousand years ago, lasted a little longer than a year, and covered the highest mountains to a depth of several meters. On the contrary, intertidal and terrestrial deposits demonstrate that at no recorded time in the past has the entire planet been under water. Moreover, a universal flood of sufficient magnitude to form the sedimentary rocks seen today, which together are many kilometers thick, would require a volume of water far greater than has ever existed on and in Earth, at least since the formation of the first known solid crust about 4 billion years ago. The belief that Earth's sediments, with their fossils, were deposited in an orderly sequence in a year's time defies all geological observations and physical principles concerning sedimentation rates and possible quantities of suspended solid matter.

Geologists have constructed a detailed history of sediment deposition that links particular bodies of rock in the crust of Earth to particular environments and processes. If petroleum geologists could find more oil and gas by interpreting the record of sedimentary rocks as having resulted from a single flood, they would certainly favor the idea of such a flood, but they do not. Instead, these practical workers agree with academic geologists about the nature of depositional environments and geological time. Petroleum geologists have been pioneers in the recognition of fossil deposits that were formed over millions of years in such environments as meandering rivers, deltas, sandy barrier beaches, and coral reefs.

The example of petroleum geology demonstrates one of the great strengths of science. By using knowledge of the natural world to predict the consequences of our actions, science makes it possible to solve problems and create opportunities using technology. The detailed knowledge required to sustain our civilization could only have been derived through scientific investigation.

The arguments of creationists are not driven by evidence that can be observed in the natural world. Special creation or supernatural intervention is not subjectable to meaningful tests, which require predicting plausible results and then checking these results through observation and experimentation. Indeed, claims of "special creation" reverse the scientific process. The explanation is seen as unalterable, and evidence is sought only to support a particular conclusion by whatever means possible.

• Cite this Page National Academy of Sciences (US). Science and Creationism: A View from the National Academy of Sciences: Second Edition. Washington (DC): National Academies Press (US); 1999. The Origin of the Universe, Earth, and Life.
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What happened in the early universe?

About 13.8 billion years ago, the Big Bang gave rise to everything, everywhere, and everywhen—the entire known Universe. What caused the Big Bang? What happened that first moment at the beginning of the Big Bang? When did the first stars form?

Our knowledge of the events and forces that shaped the early Universe is dependent on our ability to understand the most extreme conditions.   On one hand, the Universe’s origin was incomprehensibly small, on dimensions much tinier than the smallest known subatomic particles, and it was completely transformed over an immeasurably brief period, much shorter than any observable time scale. On the other, the densities and temperatures were extraordinarily large, far exceeding anything existing in the present-day Universe.

To study the birth of the Universe, Scientists at the Center for Astrophysics | Harvard & Smithsonian travel to the most remote observing site on the planet: the South Pole. Due to the lack of water vapor in the air, this is one of the best sites to observe the CMB. The Amundsen-Scott South Pole Station includes BICEP3, the Keck Array, and the South Pole Telescope, all specifically designed to look for signatures of Inflation in the CMB. 

Large clouds of hydrogen give off radio waves at a particular frequency.  Astronomers study the signal to weigh “nearby” galaxies and measure their motion through space.  To study the distant cosmic dark age, LEDA works with a custom radio telescope to identify corresponding signals from hydrogen generated at the end of the dark age, less than 100 million years after the Big Bang or less than  1% of the age of the universe. The signal will be very, very faint, but study will lay out how the first large-scale structures in the universe and the first small-scale structures–stars and black holes, formed.

To complement LEDA’s cosmic dark age research, scientists at the CFA Institute for Theory and Computation run simulations of the early Universe and how the first stars formed. After dark matter first clumped together, it attracted large clouds of hydrogen. When the clouds grew large enough, the heat and pressure from gravity started fusing the hydrogen, igniting the first star.

Simulations predict that these first stars were enormous, perhaps hundreds of times larger than our sun. Stars this size burn their fuel extremely quickly and die spectacularly in a supernova, sometimes leaving behind a black hole. These black holes may be the seeds of the supermassive black holes we now find in the center of large galaxies, including the Milky Way.   Studies into the Early Universe can provide meaningful insight into our origins, and scientists at the Center for Astrophysics are leading the way.

Looking Into The Distant Past

In a moment so fleetingly, immeasurably small, scientists theorize that the Big Bang was preceded by an “Inflationary Period.” In a billionth of a trillionth of a trillionth of a second, the Universe grew by a factor of 10 26 , comparable to a single bacterium expanding to the size of the Milky Way.

Inflation projected infinitesimal quantum fluctuations in the young Universe into cosmic scales, leaving some patches with a little more or a little less matter. These variations became the scaffolding for the structure of the Universe.

As the Universe expanded, the seething plasma of subatomic particles cooled to form hydrogen, the first atoms. Light was able to travel unimpeded through the Universe for the first time, a faint glow of radiation that permeates the entire Universe. This Cosmic Microwave Background (CMB) is the oldest observable source of light, a relic left over from when the Universe was only 380,000 years old.

Scientists believe the CMB still holds traces of Inflation, and with it, a window into the earliest moments of our Universe. Center for Astrophysics | Harvard & Smithsonian scientists are hard at work building and operating telescopes, like BICEP3, to observe the intricate features of this radiation, providing clues into the structure and history of the Universe. 

While the theory of inflation is the most popular proposal, the Big Bang might in fact have a different origin. For example, in some other theories the Big Bang was a result of a bounce from a Big Crunch of the entire universe. Scientists at the Institute for Theory and Computation work to propose new methods of deciding which theory is correct through astrophysical observations and discovering the exact origin of the Big Bang from experiments.

A depiction of the universe's 13.8 billion-year history, with the Big Bang at the left and the present day at the right. Researchers seek indirect ways to study the first instants of cosmic history, which are hidden from us.

Cosmic Dark Ages

After the Universe cooled sufficiently to allow atoms to form, what was once an incredibly hot and bright place turned cold and dark. Gravity slowly amplified tiny inhomogeneities in the distribution of gas, forming empty voids and massive clouds of hydrogen.  As gravity drove clouds to collapse further, they became peppered with something new – stars.  How long was it between the Big Bang and "cosmic dawn"?

Scientists hypothesize that unlike stars today, the earliest ones were massive and short-lived.  As generation after generation died, were black holes left behind in droves? Were these seeds for the supermassive singularities known to exist in the centers of galaxies today?  Scientists have no direct observations of this era with which to test hypotheses.  It is a literal and figurative “dark age.”

Center for Astrophysics | Harvard & Smithsonian scientists formulated the Large Aperture Experiment to Detect the Dark Ages (LEDA) in an effort to zero in on when the first stars and black holes formed, and to test cosmologists' hypotheses about conditions in the universe before stars.

• Atomic & Molecular Data
• Cosmic Microwave Background
• Dark Energy and Dark Matter
• Early Universe
• Large Scale Structure
• Theoretical Astrophysics
• Computational Astrophysics
• Laboratory Astrophysics
• Extragalactic Astronomy
• Atomic and Molecular Physics
• Optical and Infrared Astronomy
• Radio and Geoastronomy

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13 Origins and the Universe

Formative Assessment: Timeline of the Universe

The Big Bang: Origins of our Universe

The Big Bang is the best-supported scientific theory for how the universe was created. 13.7 billion years ago there was nothing and nowhere. Everything that ever existed was contained in a subatomic particle that was billions of times smaller than an atom. Within a fraction of a second, this amazingly tiny particle stretched and inflated to an unimaginably huge size. Space, time, and the fundamental particles of the universe were created in this instant.

Key Takeaway

Although the word “bang” is part of the name, the Big Bang was an expansion or an inflation rather than an explosion.

Although there are alternate theories, the Big Bang theory is supported by multiple sources of scientific evidence.

• Edwin Hubble discovered that the universe is still expanding today. If it is constantly expanding and growing now, that means it was smaller before–and likely the size of an unimaginably small particle at the beginning.
• Scientists detected Cosmic Microwave Background, a type of radiation that is present everywhere in the universe. Evidence suggests that this is leftover radiation from the energy of the Big Bang.

For more explanation of the Big Bang theory, watch the following video.

Video credit: “ Big Bang Introduction ” by Khan Academy is licensed under CC BY-NC-SA 3.0 . Note: All Khan Academy content is available for free at khanacademy.org .

The Life Cycle of Stars

All stars begin their lives as clouds of gas and dust which are called nebulae . The particles in a nebula start to attract, so their combined mass increases. Therefore, they have more gravity which pulls in even more particles. Eventually, there will be enough particles under intense heat and pressure in the center core and nuclear fusion can occur. The star ignites and becomes a fully functioning star.

The image, below, shows the life cycles of different types of stars.

Depending on the amount of material in the nebula, an average star (like the Sun) or a supermassive star is formed. As the star burns through its fuel, it loses mass; therefore, it has less gravity and its size increases.  An average star turns into a red giant . As it continues burning fuel, the red giant becomes very large. Then, the outer layers are blown off creating a planetary nebula and the inner core of the star remains, called a white dwarf star. 

A supermassive star turns into a super red giant. These stars have more mass so they burn through their fuel more quickly, therefore losing gravity and becoming extremely large. Eventually, the super red giant will run out of fuel, collapse in on itself, and create a giant explosion called a supernova . From there, the star can either form a black hole or an extremely compact neutron star.

Interesting Fact: We Are Made of Stardust

• Nuclear fusion in stars begins with hydrogen atoms which fuse together to make helium. Eventually, the reactions increase and atoms continue fusing into different elements; stars can fuse all of the elements up to iron on the periodic table.
• When the dust and debris from a star is blown away in a planetary nebula or supernova, all of these elements scatter into space where they will become the basis for all new stars and matter in the universe. Therefore, we are made of stardust.

Origins of the Sun, Earth, and Moon

Our solar system was most likely formed from a giant rotating  nebula after a former star underwent a supernova . 4.65 billion years ago, this rotation and intense gravity caused the nebula to collapse on itself. This caused it to spin faster and flatten into a disk shape, the Plane of the Ecliptic . Much of this material was pulled toward the center of the disk and a star was formed: the Sun. The Sun contains 99.8% of the mass in our solar system.

Although it is enormous compared to the size of Earth, the Sun is an average-sized star. It is mostly made of hydrogen and helium. Currently, it is halfway through its fuel supply. In around 5-6 billion years, the Sun will burn all of its fuel and become a white dwarf star.

After the Plane of the Ecliptic was formed, the planets formed from the leftover gas and dust orbiting around the Sun. One theory says that when the Sun turned on and became a star, the force of its energy blew off the gas clouds around the four inner planets which is why they are rocky and the outer planets are gaseous. Earth, a rocky planet, is about 4.65 billion years old. Scientists believe that life on Earth appeared approximately 3.5 billion years ago, based on evidence found in fossils.

For more detail of how space dust turns into planets, watch the video below:

Video credit: “ The Dust Bunnies That Build Our Planet ” by Lorin Swint Matthews/ TED-Ed   is licensed under CC BY-NC-ND 4.0

Earth was NOT formed during the Big Bang. 

• The Big Bang occurred 13.7 billion years ago.
• Earth was formed 4.65 billion years ago.
• This means there is a lapse of 9 billion years between the Big Bang and the formation of Earth.

The Moon was formed when a Mars-sized object named Theia collided with the Earth. Early in its creation, Earth was molten. When it collided with Theia, chunks of Earth’s crust were ejected into space. Gravity bounded these pieces together and the Moon was formed, eventually cooling and hardening into its current rocky state. Evidence which supports this theory include that the Moon and Earth have very similar composition including an iron core, mantle, and crust, although the Moon is less dense since it was formed from lighter elements in Earth’s crust. The Moon is held to Earth by gravity and it is Earth’s only natural satellite object, although the distance between them is increasing by about 1.6 inches per year.

Characteristics of the Moon

• Distance from Earth : 239,000 miles
• Size : As seen in the image, below, the Moon is about 1/4 the size of Earth.

• Very similar to Earth
• Has an iron core , mantle , and crust
• It does not have an atmosphere to protect it from the impact of objects such as asteroids in space.
• There is no wind on the Moon to erode existing craters.
• Climate : The Moon has no atmosphere, wind, or weather. Thus, the temperature can range from extremely hot to extremely cold since there is no atmosphere to protect it from the Sun’s heat or insulate the surface.
• The Moon’s gravity, although weaker than Earth’s gravity, has enough pull to move water. This is what causes tides on Earth. As Earth rotates on its axis, the area on the near side of the Moon feels its gravity. As seen in the image below, this causes the water on that side–as well as the opposite side of Earth–to bulge out and create a high tide. As Earth continues to rotate, the gravitational pull weakens and the water recedes, creating a low tide. Since Earth completes one full rotation on its axis each day, most areas have two high tides and two low tides per day.

Sides of the Moon

There are two sides of the moon: the near side (the side we can see from Earth) and the far side (also known as the dark side). The Moon does not create its own light; it gets light from the Sun. As such, the dark side is not actually dark–it is just called the dark side because we cannot see it from Earth.

Since Earth has a larger mass, it exerts a stronger gravitational pull on the Moon. Earth’s pull controls the Moon’s orbit so that the Moon rotates once on its axis in the same amount of time it takes to orbit Earth. Therefore, the same side of the Moon is always facing Earth and we have a near side and a dark side. This effect is called tidal locking.

Click this link to see an animation of how tidal locking works as the Moon orbits Earth.

A galaxy is a collection of billions of stars, gas, and dust held together by gravity in space. Using the Hubble Space Telescope, scientists can take images of space. In one small area, called the eXtreme Deep Field or XDF (image below) each of the bright spots is an entire galaxy–there are 5,550 galaxies within the image. There are probably 100 hundred billion galaxies in the entire universe.

The Milky Way

A galaxy is a collection of billions of stars, gas, and dust held together by gravity in space. Our solar system is located in the Milky Way Galaxy. As seen in the image, below, it got its name because it appears as a milky band of light in the sky.

As seen in the image, below, the Milky Way is a large spiral-shaped galaxy which contains hundreds of billions of stars. At the center of the Milky Way is a supermassive black hole named Sagittarius A which has a mass of 4 million suns. Our Sun, Earth, and all the planets are located halfway between the center and the outer edge on a small partial arm called the Orion Spur.

As seen in the image, below, there are 3 shapes of galaxies: spiral, elliptical, and irregular. Our galaxy, the Milky Way, is a spiral galaxy. Most galaxies have a supermassive black hole at the center which has an extremely strong gravitational pull that holds the entire galaxy together.

Past, Present, and Future of Space Travel: Sputnik and the Space Race

On October 4th, 1957 the Soviet Union successfully launched Sputnik, the world’s first artificial satellite, into Earth’s orbit.  This successful launch of Sputnik sparked the Space Race between the Soviet Union and the United States. These two countries competed to get the first human to land on the Moon.

On January 31, 1958, the United States launched Explorer 1, a satellite that discovered the magnetic radiation belts around Earth. That same year, the United States created the National Aeronautics and Space Administration (NASA). In 1959, the Soviet Union launched Luna 2, the first spacecraft to land on the Moon. In April 1961, the Soviet astronaut Yuri Gagarin became the first person in space when he orbited Earth. Shortly after, astronaut Alan Shepard became the first American in space in May 1961.

The Space Race heated up and President John F. Kennedy claimed that the United States would put a man on the Moon before the end of the decade. In 1962, American astronaut John Glenn successfully orbited the Earth. In 1968, American mission Apollo 8 orbited the Moon. Finally, in 1969, the American mission Apollo 11 successfully landed the first two people on the Moon: astronauts Neil Armstrong and Buzz Aldrin.

Interesting Fact

Dr. James Van Allen from the University of Iowa created the radiation detector that launched on the Explorer 1 satellite. This led to the discovery of magnetic radiation belts around Earth which are known as Van Allen radiation belts in his honor. Van Allen Hall on Iowa’s campus is also named after him.

Women and Space

Traditionally, the story of the Space Race features male scientists and astronauts. However, women have played a key role in the history of American space exploration. NASA mathematicians Katherine Johnson and Dorothy Vaughan along with engineer Mary Jackson were key members of the team that launched John Glenn into space in 1962. In addition to this mission, these women had long careers at NASA. Their stories have recently been popularized in the movie  Hidden Figures .

Initially, women were seen to have a physical advantage as astronauts; they tend to be lighter, shorter, and consume less food. In 1960, astronaut Jerrie Cobb had logged twice as many flying hours as John Glenn. But NASA made a requirement that astronauts had to be military pilots, a job only men could have. A group of 13 female astronauts, including Cobb, was gathered and subjected to the same tests as the male astronauts. The women passed all of the tests, and in many cases, performed better than the men. Still, NASA refused to support the female astronauts. In 1983, Sally Ride became the first female astronaut in space.

Black Holes

A black hole is an area in space with extremely strong gravity from which no light can escape. Thus, the area appears black. At the end of its lifecycle, a supermassive star collapses in on itself which causes a huge explosion called a supernova ; this results in the formation of a black hole.

Seen below, scientists captured the first image of a black hole in 2019 using powerful telescopes.

Since black holes trap all light inside, the dark spot in the center of the image is the black hole’s shadow surrounded by a ring of glowing gas in space. Based on this image, scientists were able to determine that the this black hole’s mass is 6.5 billion times larger than the mass of our Sun.

Katie Bouman, a female graduate student at MIT, led the creation of the computer algorithm that made it possible to get this first image of a black hole.

For more explanation of black holes, watch the following video.

Video credit: “ What is a Black Hole? ” by NASA Space Place  is public domain

Performance Expectations

fifth grade

ESS1.A: The Universe and its Stars

• The sun is a star that appears larger and brighter than other stars because it is closer. Stars range greatly in their distance from Earth. (5-ESS1-1)

middle school

ESS1.A: The Universe and Its Stars

• Patterns of the apparent motion of the sun, the moon, and stars in the sky can be observed, described, predicted, and explained with models. (MS-ESS1-1)
• Earth and its solar system are part of the Milky Way galaxy, which is one of many galaxies in the universe. (MS-ESS1-2)

ESS1.B: Earth and the Solar System

• The solar system consists of the sun and a collection of objects, including planets, their moons, and asteroids that are held in orbit around the sun by its gravitational pull on them. (MS-ESS1-2),(MS-ESS1-3)
• The solar system appears to have formed from a disk of dust and gas, drawn together by gravity. (MS-ESS1-2)

Crosscutting Concepts

Scale, Proportion, and Quantity

• Natural objects exist from the very small to the immensely large. (5-ESS1-1)
• Patterns can be used to identify cause-and-effect relationships. (MS-ESS1-1)
• Time, space, and energy phenomena can be observed at various scales using models to study systems that are too large or too small. (MS-ESS1-3)

Systems and System Models

• Models can be used to represent systems and their interactions. (MS-ESS1-2)

– – – – – – – – – – – – – – – – – – – – – – – – – – –

Scientific theory for how the universe was created.

A cloud of gas and dust in space.

The process by which stars get their energy. Atoms fuse together creating a nuclear reaction which releases energy in the form of heat and light in the star.

Phase in a star's life cycle where it greatly increases in size as it burns fuel through nuclear fusion.

The giant explosion of a supermassive star at the end of its life cycle.

An area in space with extremely strong gravity from which no light can escape.

The disk-shaped plane in which everything in our solar system orbits around the Sun.

The innermost layers of Earth; made of a liquid outer core and a solid inner core.

The middle layer of Earth between the crust and the core.

The outermost layer of Earth.

Depression formed by an impact.

A meteoroid that survives its trip through the atmosphere and lands somewhere on Earth. The impact of a meteorite can cause a crater on the surface of a planet.

Rocky celestial bodies left over from the formation of the solar system that are smaller than planets and orbit the Sun.

Process by which broken down rocks are carried to a new location.

A collection of billions of stars, gas, and dust held together by gravity in space.

Our Sun and all of the planets and other bodies in space (comets, asteroids, meteoroids) that orbit around the Sun in the plane of the ecliptic.

Science for Developing Scientifically Literate Citizens Copyright © 2019 by Dr. Ted Neal is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

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The Latest James Webb Image Reveals New Clues About the Origins of the Universe

T he universe was a busy place 11 to 12 billion years ago—or just 2 to 3 billion years after the Big Bang . That is the period astronomers refer to as the “cosmic noon,” when young galaxies were forming stars at a fast and furious rate. High noon for the cosmos has long since passed—or it would seem to have. But there is one pocket in which it persists. And, in another in a growing series of triumphs, the James Webb Space Telescope has returned an eye-popping image of that small region—revealing new secrets about the origins of the universe.

The object featured in the just-released picture is known as NGC 346, a portion of the Small Magellanic Cloud (SMC)—a dwarf galaxy located just 200,000 light years from Earth. NGC 346 was already known as a nursery for infant stars , as are many parts of the modern universe. Those areas form stars more slowly than during the cosmic noon, because they are known to be low in metals and other elements heavier than hydrogen and helium. Those heavier elements make up space dust—which contributes to the formation of stars; due to their low metal content, however, modern star-forming regions are thought to be relatively dust-free. That doesn’t stop them from creating stars—just not at the pace they were formed during the cosmic noon. The Webb’s observations of NGC 346, however, revealed just the opposite of what was expected: great clouds of dust that accelerate the formation of stars.

“A galaxy during cosmic noon wouldn’t have one NGC 346 like the Small Magellanic Cloud does; it would have thousands,” said Margaret Meixner, a principal investigator in the study that produced the new image, in a NASA statement . “But even if NGC 346 is now the one and only massive cluster furiously forming stars in its galaxy, it offers us a great opportunity to probe conditions that were in place at cosmic noon.”

The presence of so much dust in NGC 346 confirms the pre-existing theory that galaxies during the cosmic noon were also heavy in dust—offering, effectively, a close-up artifact of the ancient universe. It also suggests that NGC 346 might not only be forming stars, but planets too, which accrete from swirls of metallic dust. If that’s so, it means Earth-like planets may have formed during the cosmic noon as well—much earlier in the history of the universe than planetologists had originally believed.

“Since the Small Magellanic Cloud has a similar environment to galaxies during cosmic noon,” said astronomer Guido de Marchi, a co-investigator for the study, in the NASA statement, “it’s possible that rocky planets could have formed earlier in the universe than we have thought.”

The image itself tells part of that star- and planet-formation story. The various ridges of pink and orange material represent clouds of dust being broken down by young stars beginning to accrete and exert their gravitational muscle. The pink clouds represent energized, or superheated hydrogen, which sizzles at temperatures of 10,000º C (18,000º F). The orange regions represent colder, molecular hydrogen, made up of two hydrogen atoms, which has much lower temperatures of -200º C (-300º F). It is the colder hydrogen that joins with the primordial dust to form the young stars.

Whatever the chemistry and stellar physics at play, it is undeniable that the new Webb image is yet another dazzler from a machine that has been in space for just over a year now and has done every little thing its designers and mission planners have asked of it. The new picture is just the latest in the album of cosmic landscapes the telescope has beamed home. In the 20 years of life the Webb has ahead of it, that science-rich image will not remotely be the last.

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13.7 Cosmos & Culture

The origin of the universe: from nothing everything.

Marcelo Gleiser

A computer simulation of the formation of large-scale structures in the Universe, showing a patch of 100 million light-years and the resulting coherent motions of galaxies flowing towards the highest mass concentration in the centre. The snapshot refers to an epoch about 10 billion years back in time. Klaus Dolag/VIMOS-VLT Deep Survey/ESO hide caption

A computer simulation of the formation of large-scale structures in the Universe, showing a patch of 100 million light-years and the resulting coherent motions of galaxies flowing towards the highest mass concentration in the centre. The snapshot refers to an epoch about 10 billion years back in time.

Last week, I started a discussion of what I call "The Three Origins," focusing first on the origin of life. Although we are far from knowing how non-living matter became living organisms on primitive Earth some 3.5 billion years ago (or more), or how to repeat the feat in the laboratory, I consider this the "easiest" of the three questions.

Contrary to the origin of the Universe and the origin of mind, the origin of life is something we can study from the outside in, where we can have an external and objective view of what is going on. Even if, as I have argued, it seems impossible to know exactly how life originated on Earth (unless it could be proven that there is only one pathway from nonlife to life), we can still investigate the biochemical pathways leading to what we may call a living organism. In the case of the cosmos or the mind, things are subtler.

From what we know, all cultures have a creation narrative describing the origin of the world, of how everything came from nothing. As I explored in The Dancing Universe: From Creation Myths to the Big Bang , there are only a small number of possible answers to the origin of the cosmos. All creation myths presuppose the existence of some kind of divine or absolute power capable of creating the world. In the vast majority of cases, the Bible being one example, this absolute power is embodied in God, or a group of gods. In others, the Universe is eternal, without a starting moment in the distant past: it has existed forever and will exist forever. In others still, the cosmos emerges without any divine interference from a primal Nothingness, from an innate tendency to exist. This Nothing can be complete emptiness, a primal egg, or even a struggle between chaos and order. Not every creation myth uses divine intervention or supposes that time started in some moment in the past.

According to modern science, the origin of the universe is part of cosmology. In trying to describe a creation process through scientific language we encounter a serious challenge: if every effect results from a cause, we can follow the chain of causation backwards in time until we arrive at the First Cause. But what caused this cause? Aristotle, for one, used some kind of divine entity to solve this conundrum, the Unmoved Mover, the one that can cause without having been caused. Very convenient, but not scientifically satisfying.

As current astronomical observations resolutely point to a Universe with a beginning in the distant past (according to the latest measurements from the Planck satellite related here last week , at about 13.8 billion years ago), scientific models of the origin of the Universe must face the challenge of explaining or doing away with the problem of the First Cause.

The fundamental question is this: even if a scientific explanation exists, is it an acceptable answer to the question of the origin of the Universe? Defenders of scientism might argue that this is the best that we can do, that it is the only reasonable thing that we can do. Fair enough, if you believe that science should provide an answer to this question and if you are happy with the answers given.

The best answer we have at this point is that the Universe emerged spontaneously from a random quantum fluctuation in some sort of primordial quantum vacuum, the scientific equivalent of "nothing." However, this quantum vacuum is a very loaded nothing: it assumes the whole machinery of quantum field theory, the modern description of how elementary particles of matter interact with one another, was already in operation.

In the quantum realm, even the lowest energy state, the "vacuum," is not empty. Even if the energy of a quantum system is zero, it is never really zero due to the inherent quantum fluctuations about this state. A zero energy quantum state is as impossible as a perfectly still lake, with absolutely no disturbances on its surface. This quantum jitteriness amounts to fluctuations on the value of the energy; if one of these fluctuations is unstable it may grow big, like a soap bubble that blows itself up. The energy remains zero on average because of a clever interplay between the positive energy of matter and the negative energy of attractive gravity. This is the result that physicists like Stephen Hawking, Lawrence Krauss, Mikio Kaku and others speak of when they state that the "universe came out of quantum nothingness," or something to that extent.

The essential question, though, is whether this is indeed a satisfactory explanation to the question of cosmic origins, or simply part of one. The philosopher David Albert raised similar points in a recent review of Lawrence Krauss's book. Here is Krauss's response.

It is obvious that this quantum nothingness is very different from an absolute nothingness. Physicists may shrug this away stating that concepts like absolute nothingness are not scientific and hence have no explanatory value. It is indeed true that there is no such thing as absolute nothingness in science, since the vacuum is pregnant with all sorts of stuff. Any scientific explanation presupposes a whole conceptual structure that is absolutely essential for science to function: energy, space, time, the equations we use, the laws of Nature. Science can't exist without this scaffolding. So, a scientific explanation of the origin of the universe needs to use such concepts to make sense. It necessarily starts from something, which is the best that science can ever hope to do.

Even if we move on to the multiverse, things still need to be formulated in terms of fields, energy, spacetime, derivatives, etc. Furthermore, scientific hypotheses need to be testable and falsifiable, and we don't yet know how to do this with a quantum fluctuation that generates a universe. We can't set this experiment in the laboratory and examine the right conditions for universes to emerge from the quantum vacuum. Contrary to the origin of life question, we can't step out of the Universe to examine it from the outside in. At best, and this should be quite enough for a scientific explanation of cosmic origins, a model for the quantum origin of the Universe should lead to a cosmos compatible with current observations. Stepping out into the abstract multiverse may provide us with different plausible cosmoids and help us understand why our own Universe is so special. But unless there is a very clear selection principle that doesn't predicate our existence, the question as to why this Universe and not another will remain open.

And this is not at all bad. The fact that science answers so many questions doesn't mean it should answer all; or that some questions should only be answered through science. Before I am accused of advocating obscurantism, let me be clear. What I mean is that a scientific explanation to the origin of the Universe, at least one based in the current way we do science, cannot be self-contained. Sometimes we must have the humility to accept that our modes of explanation have limits and make peace with what we can do; and marvel at how much we can do without the pretense of knowing how to do everything.

You can keep up with more of what Marcelo is thinking on Facebook and Twitter: @mgleiser

• the big bang

Science and Creationism: A View from the National Academy of Sciences, Second Edition (1999)

Chapter: the origin of the universe, earth, and life, the origin of the universe, earth, and life.

The term "evolution" usually refers to the biological evolution of living things. But the processes by which planets, stars, galaxies, and the universe form and change over time are also types of "evolution." In all of these cases there is change over time, although the processes involved are quite different.

In the late 1920s the American astronomer Edwin Hubble made a very interesting and important discovery. Hubble made observations that he interpreted as showing that distant stars and galaxies are receding from Earth in every direction. Moreover, the velocities of recession increase in proportion with distance, a discovery that has been confirmed by numerous and repeated measurements since Hubble's time. The implication of these findings is that the universe is expanding.

Hubble's hypothesis of an expanding universe leads to certain deductions. One is that the universe was more condensed at a previous time. From this deduction came the suggestion that all the currently observed matter and energy in the universe were initially condensed in a very small and infinitely hot mass. A huge explosion, known as the Big Bang, then sent matter and energy expanding in all directions.

This Big Bang hypothesis led to more testable deductions. One such deduction was that the temperature in deep space today should be several degrees above absolute zero. Observations showed this deduction to be correct. In fact, the Cosmic Microwave Background Explorer (COBE) satellite launched in 1991 confirmed that the background radiation field has exactly the spectrum predicted by a Big Bang origin for the universe.

As the universe expanded, according to current scientific understanding, matter collected into clouds that began to condense and rotate, forming the forerunners of galaxies. Within galaxies, including our own Milky Way galaxy, changes in pressure caused gas and dust to form distinct clouds. In some of these clouds, where there was sufficient mass and the right forces, gravitational attraction caused the cloud to collapse. If the mass of material in the cloud was sufficiently compressed, nuclear reactions began and a star was born.

Some proportion of stars, including our sun, formed in the middle of a flattened spinning disk of material. In the case of our sun, the gas and dust within this disk collided and aggregated into small grains, and the grains formed into larger bodies called planetesimals ("very small planets"), some of which reached diameters of several hundred kilometers. In successive stages these planetesimals coalesced into the nine planets and their numerous satellites. The rocky planets, including Earth, were near the sun, and the gaseous planets were in more distant orbits.

The ages of the universe, our galaxy, the solar system, and Earth can be estimated using modem scientific methods. The age of the universe can be derived from the observed relationship between the velocities of and the distances separating the galaxies. The velocities of distant galaxies can be measured very accurately, but the measurement of distances is more uncertain. Over the past few decades, measurements of the Hubble expansion have led to estimated ages for the universe of between 7 billion and 20 billion years, with the most recent and best measurements within the range of 10 billion to 15 billion years.

A disk of dust and gas, appearing as a dark band in this Hubble Space Telescope photograph, bisects a glowing nebula around a very young star in the constellation Taurus. Similar disks can be seen around other nearby stars and are thought to provide the raw material for planets.

The age of the Milky Way galaxy has been calculated in two ways. One involves studying the observed stages of evolution of different-sized stars in globular clusters. Globular clusters occur in a faint halo surrounding the center of the Galaxy, with each cluster containing from a hundred thousand to a million stars. The very low amounts of elements heavier than hydrogen and helium in these stars indicate that they must have formed early in the history of the Galaxy, before large amounts of heavy elements were created inside the initial generations of stars and later distributed into the interstellar medium through supernova explosions (the Big Bang itself created primarily hydrogen and helium atoms). Estimates of the ages of the stars in globular clusters fall within the range of 11 billion to 16 billion years.

A second method for estimating the age of our galaxy is based on the present abundances of several long-lived radioactive elements in the solar system. Their abundances are set by their rates of production and distribution through exploding

supernovas. According to these calculations, the age of our galaxy is between 9 billion and 16 billion years. Thus, both ways of estimating the age of the Milky Way galaxy agree with each other, and they also are consistent with the independently derived estimate for the age of the universe.

Radioactive elements occurring naturally in rocks and minerals also provide a means of estimating the age of the solar system and Earth. Several of these elements decay with half lives between 700 million and more than 100 billion years (the half life of an element is the time it takes for half of the element to decay radioactively into another element). Using these time-keepers, it is calculated that meteorites, which are fragments of asteroids, formed between 4.53 billion and 4.58 billion years ago (asteroids are small "planetoids" that revolve around the sun and are remnants of the solar nebula that gave rise to the sun and planets). The same radioactive time-keepers applied to the three oldest lunar samples returned to Earth by the Apollo astronauts yield ages between 4.4 billion and 4.5 billion years, providing minimum estimates for the time since the formation of the moon.

The oldest known rocks on Earth occur in northwestern Canada (3.96 billion years), but well-studied rocks nearly as old are also found in other parts of the world. In Western Australia, zircon crystals encased within younger rocks have ages as old as 4.3 billion years, making these tiny crystals the oldest materials so far found on Earth.

The best estimates of Earth's age are obtained by calculating the time required for development of the observed lead isotopes in Earth's oldest lead ores. These estimates yield 4.54 billion years as the age of Earth and of meteorites, and hence of the solar system.

The origins of life cannot be dated as precisely, but there is evidence that bacteria-like organisms lived on Earth 3.5 billion years ago, and they may have existed even earlier, when the first solid crust formed, almost 4 billion years ago. These early organisms must have been simpler than the organisms living today. Furthermore, before the earliest organisms there must have been structures that one would not call "alive" but that are now components of living things. Today, all living organisms store and transmit hereditary information using two kinds of molecules: DNA and RNA. Each of these molecules is in turn composed of four kinds of subunits known as nucleotides. The sequences of nucleotides in particular lengths of DNA or RNA, known as genes, direct the construction of molecules known as proteins, which in turn catalyze biochemical reactions, provide structural components for organisms, and perform many of the other functions on which life depends. Proteins consist of chains of subunits known as amino acids. The sequence of nucleotides in DNA and RNA therefore determines the sequence of amino acids in proteins; this is a central mechanism in all of biology.

Experiments conducted under conditions intended to resemble those present on primitive Earth have resulted in the production of some of the chemical components of proteins, DNA, and RNA. Some of these molecules also have been detected in meteorites from outer space and in interstellar space by astronomers using radio-telescopes. Scientists have concluded that the "building blocks of life" could have been available early in Earth's history.

An important new research avenue has opened with the discovery that certain molecules made of RNA, called ribozymes, can act as catalysts in modem cells. It previously had been thought that only proteins could serve as the catalysts required to carry out specific biochemical functions. Thus, in the early prebiotic world, RNA molecules could have been "autocatalytic"—that is, they could have replicated themselves well before there were any protein catalysts (called enzymes).

Laboratory experiments demonstrate that replicating autocatalytic RNA molecules undergo spontaneous changes and that the variants of RNA molecules with the greatest autocatalytic activity come to prevail in their environments. Some scientists favor the hypothesis that there was an early "RNA world," and they are testing models that lead from RNA to the synthesis of simple DNA and protein molecules. These assemblages of molecules eventually could have become packaged within membranes, thus making up "protocells"—early versions of very simple cells.

For those who are studying the origin of life, the question is no longer whether life could have originated by chemical processes involving nonbiological components. The question instead has become which of many pathways might have been followed to produce the first cells.

Will we ever be able to identify the path of chemical evolution that succeeded in initiating life on Earth? Scientists are designing experiments and speculating about how early Earth could have provided a hospitable site for the segregation of

molecules in units that might have been the first living systems. The recent speculation includes the possibility that the first living cells might have arisen on Mars, seeding Earth via the many meteorites that are known to travel from Mars to our planet.

Of course, even if a living cell were to be made in the laboratory, it would not prove that nature followed the same pathway billions of years ago. But it is the job of science to provide plausible natural explanations for natural phenomena. The study of the origin of life is a very active research area in which important progress is being made, although the consensus among scientists is that none of the current hypotheses has thus far been confirmed. The history of science shows that seemingly intractable problems like this one may become amenable to solution later, as a result of advances in theory, instrumentation, or the discovery of new facts.

Creationist Views of the Origin of the Universe, Earth, and Life

Many religious persons, including many scientists, hold that God created the universe and the various processes driving physical and biological evolution and that these processes then resulted in the creation of galaxies, our solar system, and life on Earth. This belief, which sometimes is termed "theistic evolution," is not in disagreement with scientific explanations of evolution. Indeed, it reflects the remarkable and inspiring character of the physical universe revealed by cosmology, paleontology, molecular biology, and many other scientific disciplines.

The advocates of "creation science" hold a variety of viewpoints. Some claim that Earth and the universe are relatively young, perhaps only 6,000 to 10,000 years old. These individuals often believe that the present physical form of Earth can be explained by "catastrophism," including a worldwide flood, and that all living things (including humans) were created miraculously, essentially in the forms we now find them.

Other advocates of creation science are willing to accept that Earth, the planets, and the stars may have existed for millions of years. But they argue that the various types of organisms, and especially humans, could only have come about with supernatural intervention, because they show "intelligent design."

In this booklet, both these "Young Earth" and "Old Earth" views are referred to as "creationism" or "special creation."

There are no valid scientific data or calculations to substantiate the belief that Earth was created just a few thousand years ago. This document has summarized the vast amount of evidence for the great age of the universe, our galaxy, the solar system, and Earth from astronomy, astrophysics, nuclear physics, geology, geochemistry, and geophysics. Independent scientific methods consistently give an age for Earth and the solar system of about 5 billion years, and an age for our galaxy and the universe that is two to three times greater. These conclusions make the origin of the universe as a whole intelligible, lend coherence to many different branches of science, and form the core conclusions of a remarkable body of knowledge about the origins and behavior of the physical world.

Nor is there any evidence that the entire geological record, with its orderly succession of fossils, is the product of a single universal flood that occurred a few thousand years ago, lasted a little longer than a year, and covered the highest mountains to a depth of several meters. On the contrary, intertidal and terrestrial deposits demonstrate that at no recorded time in the past has the entire planet been under water. Moreover, a universal flood of sufficient magnitude to form the sedimentary rocks seen today, which together are many kilometers thick, would require a volume of water far greater than has ever existed on and in Earth, at least since the formation of the first known solid crust about 4 billion years ago. The belief that Earth's sediments, with their fossils, were deposited in an orderly sequence in a year's time defies all geological observations and physical principles concerning sedimentation rates and possible quantities of suspended solid matter.

Geologists have constructed a detailed history of sediment deposition that links particular bodies of rock in the crust of Earth to particular environments and processes. If petroleum geologists could find more oil and gas by interpreting the record of sedimentary rocks as having resulted from a single flood, they would certainly favor the idea of such a flood, but they do not. Instead, these practical workers agree with academic geologists about the nature of depositional environments and geological time. Petroleum geologists have been pioneers in the recognition of fossil deposits that were formed over millions of years in such environments as meandering rivers, deltas, sandy barrier beaches, and coral reefs.

The example of petroleum geology demonstrates one of the great strengths of science. By using knowledge of the natural world to predict the consequences of our actions, science makes it possible to solve problems and create opportunities using technology. The detailed knowledge required to sustain our civilization could only have been derived through scientific investigation.

The arguments of creationists are not driven by evidence that can be observed in the natural world. Special creation or supernatural intervention is not subjectable to meaningful tests, which require predicting plausible results and then checking these results through observation and experimentation. Indeed, claims of "special creation" reverse the scientific process. The explanation is seen as unalterable, and evidence is sought only to support a particular conclusion by whatever means possible.

While the mechanisms of evolution are still under investigation, scientists universally accept that the cosmos, our planet, and life evolved and continue to evolve. Yet the teaching of evolution to schoolchildren is still contentious.

In Science and Creationism , The National Academy of Sciences states unequivocally that creationism has no place in any science curriculum at any level.

Briefly and clearly, this booklet explores the nature of science, reviews the evidence for the origin of the universe and earth, and explains the current scientific understanding of biological evolution. This edition includes new insights from astronomy and molecular biology.

Attractive in presentation and authoritative in content, Science and Creationism will be useful to anyone concerned about America's scientific literacy: education policymakers, school boards and administrators, curriculum designers, librarians, teachers, parents, and students.

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Origin Of The Universe: 8 Different Theories

How did the Universe we know come into existence? And how do we explain its origin? These are some of the questions cosmologists and physicists have been trying to unravel for decades.

Undoubtedly, every piece of evidence and data collected over the years by cosmologists points toward the possibility that it all might have started with a ‘big bang.’ But what if there is more?

Table of Contents

What Is The Big Bang Theory? A Brief Introduction

In 1927, Belgian astronomer Georges Lemaitre proposed the theory of an expanding universe (later confirmed by Edwin Hubble). He theorized that an expanding universe could be traced back to a singular point, which he termed the “primeval atom,” back in time. It laid the foundation for the modern Big Bang theory.

The Big Bang Theory is an explanation, based mostly on mathematical models, of how and when the Universe came into existence.

The cosmological model of the Universe described in the Big Bang theory explains how it initially expanded from a state of infinite density and temperature, known as the primordial (or gravitational) singularity.

This expansion was followed by cosmic inflation and a massive temperature drop. During this phase, the Universe ballooned at a much faster rate than the speed of light (by a factor of 10 26 ).

Subsequently, the Universe was reheated to a point where elementary particles (quarks, leptons, and so on) before a gradual decrease in temperature (and density) led to the formation of the first protons and neutrons .

A few minutes into the expansion, protons and neutrons combine to form primordial hydrogen and helium-4 nuclei. The estimated radius of the observable Universe during this phase was 300 light-years. The earliest stars and galaxies appeared about 400 million years after the event.

A crucial piece of the Big Bang model is the cosmic microwave background (CMB), which is the electromagnetic radiation left from the time when the Universe was in its infancy. CMB remains the most definitive proof of the Big Bang.

While the theory remains widely accepted across the scientific spectrum, a few alternative explanations — such as steady-state Universe and eternal inflation, have gained attraction over the years.

Below, we have discussed seven of the most popular alternatives of the Big Bang, explaining the origin of the Universe.

8. Quantum Fluctuation Theory 

According to quantum mechanics, particles and antiparticles can spontaneously appear and annihilate in empty space. While doing so, they create temporary fluctuations in energy called vacuum fluctuations. 

The quantum fluctuation theory proposes that our universe might have formed from one of those vacuum fluctuations. Image a very small space where an energy fluctuation occurs. Instead of quickly annihilating, this fluctuation could potentially increase and develop something more substantial. 

This theory suggests that the initial fluctuation expanded rapidly, which eventually led to the birth of our universe. This rapid expansion can be associated with comic inflation. 

As our universe expanded and cooled, the energy from the initial fluctuation might have transformed into particles and antiparticles. These particles would ultimately become the building blocks of matter throughout the cosmos.

Although the concept seems intriguing, it is just a theoretical framework. The precise details of how our universe formed from a quantum fluctuation remain a subject of active research. Scientists continue to study and refine this theory to get deeper insights into the origin of the universe. 

Reference Sources –

Spontaneous creation of the universe from nothing, arXiv :1404.1207

Massive galaxy clusters hint at primordial quantum diffusion, Physics Review Letters  

7. Theory of Eternal Inflation

The concept of the inflationary universe was first introduced by cosmologist Alan Guth in 1979 to explain why the Universe is flat, something that was missing from the original Big Bang theory.

Though Guth’s idea of inflation explains the flat Universe, it creates a scenario that prevents the Universe from escaping that inflation . If this were the case, reheating of the Universe wouldn’t have taken place, and neither would the formation of stars and galaxies.

This particular problem was solved by Andreas Albrecht and Paul Steinhardt in their “new inflation” model. They argued that rapid inflation of the Universe happened just for a few seconds before ceasing. It demonstrated how the Universe can go through rapid inflation and still end up getting heated.

Based on the previous works of Steinhardt and Alexander Vilenkin, Andrei Linde, a professor at Stanford University, proposed an alternative to Guth’s inflation theory called chaotic inflation or ‘eternal inflation theory.

The theory argues that the inflationary phase of the Universe goes on forever; it didn’t end for the Universe as a whole. In other words, cosmic inflation continues in some parts of the Universe and ceases in others. This leads to a multiverse scenario, wherein space is broken into bubbles. It’s like a universe inside a universe.

In a multiverse, different universes may have different laws of nature and physics at work. So, instead of a single expanding cosmos, our Universe might be an inflationary multiverse with many small universes with varying properties.

However, Paul Steinhardt believes that his ‘new inflation’ theory doesn’t lead to or predict anything and argues that the multiverse notion is a “fatal flaw” and unnatural.

Eternal inflation and its implications, arXiv :hep-th/0702178

Inflationary paradigm in trouble after Planck2013, arXiv :1304.2785

6. Conformal Cyclic Model

The conformal cyclic cosmological (CCC) model speculates that the Universe goes through repeated cycles of the Big Bang and subsequent expansions. The general idea is that the ‘Big Bang’ was not the beginning of the Universe but rather a transition phase. It was developed by renowned theoretical physicist and mathematician Roger Penrose.

The theory suggests that the universe goes through a series of cycles, each involving a Big Bang followed by expansion, contraction, and another Big Bang. These cycles are infinite, which means the universe goes through this process repeatedly with no end. 

This concept is often compared with a spring oscillation, where the universe expands and contracts periodically. 

Unlike the standard Big Bang theory that postulates a singular beginning of the universe, the Cyclic Universe theory avoids the singularity problem by suggesting that our universe had no initial singularity but has always existed in this cyclical pattern. 

As a basis for his model, Penrose used multiple FLRW (Friedmann–Lemaître–Robertson–Walker) metric sequences. He argued that the conformal boundary of one FLRW sequence could be attached to the boundary of another.

The FLRW metric is the closest approximation of the nature of the Universe and a part of the Lambda-CDM model . Each sequence begins with a big bang, followed by inflation and subsequent expansion.

The cyclic or oscillating model, wherein the Universe reiterates over and over in an indefinite cycle, first came into the spotlight in the 1930s, when Albert Einstein investigated the idea of an ‘everlasting’ universe. He considered that after reaching a certain point, the Universe starts collapsing and ends with a Big Crunch before going through the Big Bounce.

Right now, there are four different variations of the cyclic model of the Universe, one of which is the Conformal Cyclic Cosmology.

Read: Does Universe Iterate Through Infinite Numbers of Big Bangs?

This theory has been studied extensively, but it faces some serious challenges in terms of observational evidence. One of the major challenges has been detecting remnants of past cycles in our current universe. 

5. Black Hole Mirage

A study conducted by a group of researchers in 2013 speculated that our Universe might have originated from the debris spewed out of a collapsed four-dimensional star or a black hole.

According to the cosmologists associated with the research, one of the limitations of the Big Bang theory is to explain the temperature equilibrium found in the Universe.

While most scientists concur that the inflationary theory gives an adequate explanation of how a small patch with uniform temperature would rapidly expand to become the Universe we observe today, the group found it implausible due to the chaotic nature of the Big Bang.

To solve this problem, the team proposed a model of the cosmos, in which our three-dimensional Universe is a membrane and is floating inside a four-dimensional ‘bulk universe.’

They argued that if the 4-D ‘bulk universe’ has 4-D stars, it’s likely they will collapse into 4-D black holes. These 4-D black would have a 3-D event horizon (just like the 3-D ones have a 2-D event horizon ), which they named ‘hypersphere.’

Read:  11 Biggest Unsolved Mysteries in Physics

When the team simulated the collapse of a 4-D star, they discovered that the ejected debris from the dying star was likely to cast a 3-D membrane around that 3-D event horizon. Our Universe might be one such membrane.

The ‘4-D black hole’ model of the cosmos does explain why the temperature is almost uniform throughout the Universe. It may also give valuable insights into exactly what triggered the cosmic inflation a few seconds after its genesis.

However, a recent observation by ESA’s Planck satellite has uncovered small variations in the cosmic microwave background (CMB) temperature. These satellite readings differ from the proposed model by about four percent.

4. Plasma Universe Theory

Our current understanding of the Universe is mostly influenced by gravity, specifically Einstein’s General Theory of Relativity, through which cosmologists explain the nature of the Universe. Coincidentally, just like most other things, an alternative to gravity has also been entertained by scientists over the years.

The plasma cosmology (or plasma universe theory) speculates that electromagnetic forces and plasma play a much more important role in the Universe than gravity.

Although the approach has many different flavors, the basic idea remains the same: every astronomical body, including the sun, stars, and galaxies, results from some electrical process.

The first prominent plasma universe theory was proposed by Nobel laureate Hannes Alfvén in the 1960s. He was later joined by Swedish theoretical physicist Oskar Klein to develop the Alfvén–Klein model .

The model is built around the assumption that the Universe sustains equal amounts of matter and antimatter (that’s not the case according to modern particle physics). The boundaries of these two regions are marked with cosmic electromagnetic fields. And thus, interactions between the two would produce plasma, which Alfvén named ‘ambiplasma.’

According to the theory, such plasma would form large sections of matter and antimatter throughout the Universe. Furthermore, it theorized that our current location in the cosmos must be in a section where the matter is much more abundant than the antimatter – hence solving the matter-antimatter asymmetry problem.

Read:  Could Life Form In a Two-Dimensional Universe?

3. Slow Freeze Theory

Decades of mathematical modeling and research have led cosmologists to a valid conclusion that our Universe started from a single point of infinite density and temperature called the singularity. The subsequent expansion of the cosmos allowed it to cool, which led to the formation of galaxies, stars, and other astronomical objects.

However, as we know, the standard Big Bang model has not gone unchallenged, and one such challenging theory was proposed by Christof Wetterich, a professor at Germany’s Heidelberg University.

Wetterich argued that the Universe we know today might have actually started as cold and sparse, awakened from a long freeze. Over time, the fundamental particles in the early Universe became heavier while the gravitational constant decreased.

Furthermore, he explained that if masses of the particles have been increasing, radiation from the early Universe could make space appear hotter and move away from each other even if it wasn’t the case.

The basic idea of Wetterich’s Slow Freeze cosmic model is that the Universe has no beginning and no future. Instead of a hot Big Bang, the theory advocates for a cold and slowly evolving Universe.

According to Wetterich, the theory explains density fluctuations in the early Universe (primordial fluctuations) and why our current cosmos is dominated by dark energy.

Read: All Interesting Facts About Black Holes and White Holes

2. Hindu Cosmology

Religion and science have been the best of enemies since at least the time of Copernicus and Galileo. There is perhaps no room for science when we talk about religion and vice-versa. However, there is one religion whose cosmological beliefs sit well with the current model of the Universe.

Creation theories in Hindu mythology are widely considered one of the most ancient and significant of all other religious counterparts.

Over the years, prominent physicists and cosmologists, including Carl Sagan and Niels Bohr, have admired Hindu cosmological beliefs for its close similarity with the timelines in the standard cosmological model of the Universe.

According to Hindu mythology, the Universe follows an infinite cyclic model. It means that our current Universe will be replaced by an endless number of universes. Each iteration of the Universe is divided into two phases, ‘Kalpa’ (or the day of Brahma) and ‘pralaya’ (the night of Brahma), and each is 4.32 billion years long.

According to Hindu mythology, the age of the Universe (8.64 billion years) is more than the currently estimated age of the solar system.

1. Steady State Universe

The Steady-State model asserts that the observable Universe remains the same at any place and time. In the Universe, which is forever expanding, matter is continuously created to fill the space.

The idea of the steady-state theory was first proposed in 1948 by cosmologists Hermann Bondi, Fred Hoyle, and Thomas Gold. It was derived from the perfect cosmological principle, which itself states that the Universe is the same no matter where you look, and it will always be the same.

According to the model, galaxies and other large astronomical bodies near us should appear similar to those that are far away. However, the Big Bang tells us that distant galaxies should look younger than those at close proximity (when observed from the Earth) since light takes much longer to reach us.

The Steady-State theory gained widespread popularity in the early and mid-20th century. However, by the 1960s, it was mostly discarded by the scientific community in favor of the Big Bang after the discovery of the cosmic microwave background.

Interestingly, according to a 1931 manuscript that was discovered by researchers in 2014, Albert Einstein was working on an alternative to the Big Bang theory. It was identical to Fred Hoyle’s Steady State model, proposing that the universe has expanded steadily. However, the idea was shortly abandoned by Einstein.

More to Know

How old is the universe.

The universe is nearly 14 billion years old (13.78 billion, to be exact). Scientists have reached this conclusion after extensive studies of the cosmic microwave background and analyzing data from the Plack Space Observatory, WMAP, and other space probes.

However, a team of researchers in 2019 calculated the age of the universe to be a couple of billion years younger than the age predicted by the Plank study. The team used the movement of galaxies and stars to estimate how fast the universe is expanding. A higher expansion rate means that the universe reached its current size faster, and thus, it must be younger.

To put an end to the discrepancy, an international team of astronomers analyzed the data from the Atacama Cosmology Telescope (ACT) in Chile in 2020 to find out the approximate age of the universe.

The team determined the age of the universe to be 13.77 billion years , give or take 40 million years, which is in line with the estimate from the Plank research team.

What is the Age of the Sun?

The estimated age of the Sun is about 4.56 billion years. How did they reach this number? Well, it is a combination of nuclear cosmochronology and simulations of the stellar evolution model.

8 Biggest Black Holes In The Universe | As Per Their Solar Masses

15 Brightest Stars In The Sky | Based On Apparent Magnitude

Different Types of Galaxies In The Universe

Varun Kumar

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In reference to the big bang, you never explain where all the material in the universe derived from. No matter what thoughtful possibility, Where did all the material derive from? It cannot come out of nothingness. Where is your explanation. What are you saying that I already said that? Is that any excuse for not being able to explain?

Its easier and more plausible that : (a) The universe has ALWAYS existed and WILL always exist. And that : (b) Is always subject to change dispite long periods of static in some regions. (c) contains an amount of energy which is infinite and dispite chemical interactions, remains the same. And (d) is composed of elements and particles, atoms and sub-atomic particles which can be known and are limited thou thier by-products may be unlimited. AND : (e) Life and living beings almost d i dont happen at all and so is unlikely to exist elsewhere at least anywhere near where we are. (f) 99.9 % of space is freezing cold and 0.001% is way hotter than any life form could ever tolerate. And percentages of infinite amounts are abstract. (g) the human mind and brain is the most complex thing in the known universe. (h) the universe is mainly harmless. (i) always take a towel !

Just came across your comment. I have searched for the words to extract your very questions, not really knowing just how to express such inquiries. I now have reference material to go forward. Yours. LOL.

Thanks for putting the words in my mouth. Brilliantly said.

do you have evidence about the theory of Steady State??

I’ve read it all, and I can see a preference for the big bank theory, in some version or other. What I cannot seem to find, in any writings, is a definition of the place at which the bang started, be it a point, line, or plane. If the universe is expanding, there are a lot of theories about it. But no one seems to be able to tell me from where?

If the Big Bang theory is correct and if the red-shift/ blue-shift theory is correct, they would lend credence to the idea of all expanding or outward flow of stars and galaxies all being red ( going away) vs blue ( coming in towards us). Under this scenario – trajectories at various galaxies and stars could be calculated to determine a point of origin of where the Big Bang started from. Is that spot then to be found void of all matter …? To date … blank spaces seem to hold much intrigue following Hubble’s highly successful 12 day synchronized stare into one of those many blank spaces, and most astronomers do not come away disappointed upon seeing developed plates of those blank spots. Every cubic light-year is chocked full of matter. So with this theory one could say …”bye – bye Big Bang theory”…

A Kansan's Guide to Science, page 3 of 4 Prev Page--History

The Origin of the Universe

What does science say about the origin of the universe.

Scientific evidence points to an origin sometime between 10 and 20 billion years ago. The Big Bang theory is universally accepted by those who do research on the development of the universe, galaxies, and stars as the cause of the origin of the universe. The Big Bang theory says that the universe has developed by expanding from a hot dense state with everything exploding away from everything else. What caused this explosion is not part of the Big Bang theory. It must be regarded as unknown at this time, although there are many ideas about the cause.

How do we know the universe is expanding?

The evidence indicates that as the Big Bang occurred, everything in the universe was an expanding mass of hot gas. As this mass of gas expanded, it cooled. Knots of matter formed that became the objects we see--including galaxies, stars, and planets such as our Earth. These objects continue to move away from one another even today, and, thus, our knowledge that the universe is expanding is based on observation. Evidence for the expanding universe comes from a phenomenon referred to as the redshift . When objects move apart rapidly, the light emitted by one and received by the other changes in a specific way. The light of an object moving rapidly shifts to the red end of the visible spectrum, and a redshift occurs. In the 1920's, scientists discovered that distant galaxies are moving away from us. Moreover, the farther away galaxies are, the faster the motion is relative to us and the greater the observed redshift. It happens that this kind of expansion is predicted by Einstein's general theory of relativity. This aspect of Einstein's theory has been tested by a number of experiments, and no test has been able to falsify the hypothesis. Over the years, many other scientific hypotheses have been introduced to explain the redshift without invoking an expanding universe. None of these hypotheses has a simple and direct connection with effects we can measure in the laboratory. It also is true that nearly all of them make other kinds of predictions about light that are not observed, so these hypotheses are no longer taken seriously.

Is there any other evidence for the Big Bang?

Three other major pieces of evidence indicate that the Big Bang occurred. The first is called the cosmic microwave background radiation (CMBR) , which is a weak form of radiation that comes from the sky and is energy that is left over from the very early universe (fig. 14). The CMBR was predicted during World War II, and in the 1960's it was detected for the first time. Since then, it has been measured and remeasured and now ranks as the most precise scientific measurement ever made. The second major piece of evidence concerns the fraction of various kinds of atoms in the universe. Scientists have calculated the amount of helium and other light atoms that should have been formed in the first few minutes after the Big Bang. The predictions agree remarkably well with what is observed. The third piece of evidence comes from our own eyes. Telescopes currently in use in Kansas and elsewhere allow us to see faraway galaxies as they appeared close to the time of the Big Bang because light takes so long to reach us from such distant objects. The observations continue to fit our interpretation of a universe that was very different early in its history. At the present time, we do not understand everything about the development of the universe. The work of science is not finished. We do not yet know how it started or what the dark matter is. We are, however, very confident that, in general, the Big Bang model is correct, and many physicists and astronomers are now working to fill in the details.

Fig. 14 --The cosmic microwave background is the afterglow radiation left over from the Big Bang. Shown here are cosmological fluctuations in the microwave background temperature made by the Cosmic Background Explorer (COBE) satellite (Spergel et al., 1999). Although extremely uniform all over the sky, tiny temperature variations can offer great insight into the origin, development, and initial structure of the universe.

Where did the Earth come from?

Most of the matter in the universe consists of such light elements as hydrogen and helium, plus an additional kind of unknown cold dark matter that is not yet well understood. Such heavier elements as carbon, oxygen, and silicon that are needed to form rocks and living organisms formed in earlier generations of stars that exploded, scattering the elements across the galaxy. These elements, sometimes referred to as ashes, were part of the matter that clumped together to form our solar system. Planets like our Earth are made primarily of the heavier elements. The Earth is known to be about 4.5 billion years old; the universe is at least three times older. A lot had to happen before the Earth could form!

What will happen to the universe in the future?

Scientists believe there are two possible scenarios. One is that the universe may collapse again into sort of a reverse of the Big Bang. The other is that it may continue to expand forever, eventually growing cold and dark. At present, the weight of evidence seems to indicate that it will expand forever. Our understanding of the nature of the cold dark matter, a subject being actively investigated by many scientists, may help us answer the question of the ultimate fate of the universe. If cold dark matter is sufficiently abundant, it could halt and possibly even reverse the universe's expansion.

Acknowledgments

We would like to thank Keith Miller, Charles Higginson, and Helen Alexander for comments on earlier versions of this booklet. Thanks go also to The Kansas Citizens for Science.

Bardack, D. , 1965, Anatomy and evolution of chirocentrid fishes: University of Kansas, Paleontological Contributions, v. 10, p. 1-87. [ Available Online ]

Brower, J.C., and Veinus, J. , 1981, Allometry in pterosaurs: University of Kansas, Paleontological Contributions, v. 105, p. 1-32. [ Available Online ]

Darwin, C., and Wallace, A.R. , 1858, On the tendency of species to form varieties; and on the perpetuation of varieties and species by natural means of selection: Journal of the Proceedings of the Linnean Society of London, Zoology, v. 3, p. 53-62.

Donovan, D.T., and Forsey, G.F. , 1973, Systematics of Lower Liassic Ammonitina: University of Kansas, Paleontological Contributions, v. 64, p. 1-24. [ Available Online ]

Eaton, T.H., Jr. , 1960, A new armored dinosaur from the Cretaceous of Kansas: University of Kansas, Paleontological Contributions, v. 8, p. 1-24. [ Available Online ]

Evans, C.S. , 1988, From sea to prairie--A primer of Kansas geology: Kansas Geological Survey, Educational Series 6, 60 p. [ Available Online ]

Martin, L. , 1984, A new hesperornithid and the relationships of the Mesozoic birds: Kansas Academy of Science, Transactions, v. 87, p. 141-150.

National Academy of Sciences , 1999, Science and creationism--A view from the National Academy of Sciences, 2nd ed.: Washington, D.C., National Academy Press, p. 24.

Peabody, F.E. , 1952, Petrolacosaurus kansensis Lane, a Pennsylvanian reptile from Kansas: University of Kansas, Paleontological Contributions, v. 1, p. 1-41. [ Available Online ]

Purves, W.K., Orians, G.H., Heller, H.C., and Sadava, D. , 1998, LIFE: The Science of Biology, 5th Edition: Sunderland, Massachusetts, Sinauer Associates, p. 438.

Reisz, R. , 1981, A diapsid reptile from the Pennsylvanian of Kansas: Museum of Natural History, University of Kansas, Special Publication, v. 7, p. 1-74.

Spergel, D.N., Hinshaw, G., and Bennett, C.L. , 1999, Introduction to Cosmology: NASA, [ Available Online ]

Zallinger, R.F. , 1989, The age of reptiles: Peabody Museum of Natural History, mural.

Adaptation --A trait that is particularly suited to an environment. It is the result of natural selection.

Big Bang Theory --The most supported explanation for the formation of the universe. All matter and energy in the universe came from a condensed hot mass that exploded and expanded in all directions.

Cambrian Explosion --An important event in the history of life that began around 540 million years ago and concluded around 510 million years ago. During this interval nearly all the major types of organisms now known on Earth, as well as several novel extinct types, appeared in the fossil record.

Cosmic Microwave Background Radiation (CMBR) --Radiation left over from the Big Bang. Fluctuation in the distribution of this energy is evidence of the structure of the universe right after the Big Bang.

Dark Matter --Invisible material in the universe that may mean that the universe is sufficiently heavy that it will not expand forever.

Ediacaran --A term used to describe the earliest known multicellular organisms, which appeared about 600 million years ago and largely went extinct just before the Cambrian explosion.

Evolution --Evolution is change through time. Biological evolution means change that has accompanied descent from a common ancestor.

Fossils --Any evidence of past life preserved in rocks.

Geologic Era --A long interval of geologic time recognized by the origination and extinction of a large number of plant and animal species. The boundaries usually correspond to times of major environmental change that lead to extinction and also spur evolutionary change. An example is the Mesozoic Era, when the large terrestrial dinosaurs lived. The average duration of an era is on the order of tens to hundreds of millions of years. We currently are in the Cenozoic Era, which began 65 million years ago.

Geologic Period --A long interval of geologic time, but shorter than an era, and again, defined by the origination or extinction of a large number of species. The number of species that evolve and go extinct at period boundaries, however, is less than at era boundaries. The boundaries also usually correspond to times of major environmental change, although not as major as those changes occurring at era boundaries. An example is the Cambrian Period, when animal life first appears in abundance in the fossil record. The average duration of a period is on the order of tens of millions of years. We currently are in the Quaternary Period which began 10,000 years ago.

Hominids --A group of primates that includes humans and several extinct species such as Homo erectus and the Neanderthals that all shared an upright posture.

Hypothesis --An explanation for observed phenomena. A hypothesis is used as a basis for further observations or experiments.

Law --A scientific statement that always applies, such as the law of gravity.

Macroevolution --Evolutionary changes that involve the production of new species. These occur over time scales of thousands of years. They are produced by a series of microevolutionary changes, but not all microevolutionary changes lead to macroevolution.

Microevolution --Evolutionary changes that occur within species. These occur over a range of time scales, from months to millions of years.

Natural Selection --Greater survival or reproductive success among some members of a population due to inherited traits that confer an advantage in the environment in which the population lived.

Radioactive Isotopes --Chemical elements that differ in their number of neutrons. For any radioactive isotope, the rate of decay into other elements is constant and therefore can be used to measure geologic time.

Red Shift --Light from an object that is moving away from an observer is shifted toward the red or longer wavelength end of the spectum relative to the light emitted at the source of the object. The fact that stars inside and outside of our galaxy predominantly show a red shift is evidence that the universe is expanding.

Species --A group of organisms that can interbreed with each other and produce fertile offspring. It is the fundamental unit of biological evolution.

Theory --An explanation for natural events that is based on a large number of observations and has been tested repeatedly.

Suggested Readings and Educational Resources

Publications on evolution.

Eldredge, Niles , 1999, The Pattern of Evolution: New York, W. H. Freeman.

Fortey, Richard , 1998, Life--A Natural History of the First Four Billion Years of Life on Earth: New York, Alfred P. Knopf.

Tattersall, Ian , 1998, Becoming Human: New York, Harcourt Brace.

Longair, Malcolm S. , 1996, Our Evolving Universe: New York, Cambridge University Press.

Gould, Stephen Jay , 1989, Wonderful Life--The Burgess Shale and the Nature of History: New York, W. W. Norton.

Dawkins, Richard , 1986, The Blind Watchmaker: New York, W. W. Norton.

Eldredge, Niles , 1985, Time Frames: Princeton, N. J., Princeton University Press.

Gould, Stephen Jay , 1977, Ever Since Darwin--Reflections in Natural History: New York, W. W. Norton.

Publications on the Nature of Science, the Relationship Between Science and Religion, and Creationism

Gould, Stephen Jay , 1999, Rock of Ages: New York, Harmony Books.

National Academy of Sciences , 1999, Science and Creationism, A View from the National Academy of Sciences, 2nd Ed.: Washington, D.C., National Academy Press.

Godfrey, Laurie , (editor), 1983, Scientists Confront Creationism: New York, W. W. Norton.

Eldredge, Niles , 2000, The Triumph of Evolution and the Failure of Creationism: New York, W. H. Freeman.

Scott, Eugenie C. , 2004, Evolution vs. Creationism: An Introduction: Westport, CT, Greenwood Press

Kansas Citizens for Science-- http://www.kcfs.org/

Kansas Geological Survey-- http://www.kgs.ku.edu/

NASA-- http://www.nasa.gov/index.html

National Academy of Sciences-- http://www.nasonline.org/

National Center for Science Education-- http://ncse.com/

Public Education Facilities

University of Kansas, Museum of Natural History and Biodiversity Research Center, Lawrence, Kansas [ http://naturalhistory.ku.edu/ ]

Sternberg Museum of Natural History, Hays, Kansas [ http://sternberg.fhsu.edu/ ]

Prev Page--History

The beginnings of modern science shaped how philosophers saw alien life – and how we understand it today

Emeritus Professor in the History of Religious Thought, The University of Queensland

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Speculation about extraterrestrials is not all that new. There was a vibrant debate in 17th-century Europe about the existence of life on other planets.

This was the consequence of the transition from a Ptolemaic view , in which Earth was at the centre of the universe and everything revolved around it, to a Copernican view in which the Sun was at the centre and our planet, along with all the others, revolved around it.

It followed that if we were now more like other planets and moons close to us that revolved around the Sun, then they were more like Earth. And if other planets were like Earth, then they most likely also had inhabitants.

Robert Burton’s remarks in his The Anatomy of Melancholy (1621) were common:

If the Earth move, it is a Planet, and shines to them in the Moone, and to the other Planitary inhabitants, as the Moone and they doe to us upon the Earth.

Similarly, the Dutch astronomer Christiaan Huygens (1629–95) believed life on other planets was a consequence of the Sun-centred view of Copernicus. But his speculation on such matters proceeded from the doctrine of the “ divine plenitude ”. This was the belief that, in his all-powerfulness and goodness, having created matter in all parts of the universe, God would not have missed the opportunity to populate the whole universe with living beings.

In his The Celestial Worlds Discover’d (1698), Huygens suggested that, like us, the inhabitants of other planets would have hands, feet and an upward stance. However, in keeping with the greater size of other planets, particularly Jupiter and Saturn, they might be much larger than us. They would enjoy social lives, live in houses, make music, contemplate the works of God, and so on.

Others were much less confident in speculating on the nature of alien lives. Nevertheless, as Joseph Glanvill, a member of the Royal Society alongside Isaac Newton, suggested in 1676, even though details of life on other planets were unknown, this did not prejudice “the Hypothesis of the Moon’s being habitable; or the supposal of its being actually inhabited”.

That other worlds were inhabited also seemed an appropriate conclusion to draw from early modern science focused, as it was, on God’s work in nature.

This was a theme developed at length by the most influential work on the plurality of worlds in the latter part of the 17th century, the Copernican Bernard Fontenelle’s Entretiens sur la pluralité des mondes (Conversations on the Plurality of Worlds, 1686).

To Fontenelle, there was an infinite number of planets and an infinite number of inhabited worlds. For him, this was the result of the analogy, as a consequence of Copernicanism, between the nature of our Earth and that of other worlds.

But it was also the result of the fecundity of the divine being from whom all things proceed. It is this idea “of the infinite Diversity that Nature ought to use in her Works” which governs his book, he declared.

Read more: Chariots of the gods, ships in the sky: how unidentified aerial phenomena left their mark in ancient cultures

The seed of Adam

But there was a significant problem. If there were intelligent beings on the Moon or the planets, were they “men”? And, if they were, had they been redeemed by the work of Jesus Christ as people on Earth had been?

John Wilkins (1614–72), one of the founders of the new science, wrestled with the theological implications of the Copernican universe. He was convinced the Moon was inhabited. But he was quite uncertain whether the lunar residents were of “the seed of Adam”.

Wilkins’s simple solution was to deny their human status. The inhabitants of the Moon, he suggested in his The Discovery of a World in the Moone (1638), “are not men as wee are, but some other kinde of creatures which beare some proportion and likenesse to our natures”.

In the end, Fontenelle was also to adopt this solution. It would be “a great perplexing point in Theology,” he declared, should the Moon be inhabited by men not descended from Adam. He only wished to argue, he wrote, for inhabitants “which, perhaps, are not Men”.

The existence of aliens – human, just like us – threatened the credibility of the Christian story of the redemption of all humans through the life, death and resurrection of Jesus Christ. This was intellectual space in which only the theologically brave – or foolish – dared to travel.

It was much easier to reject the humanity of the alien. Thus, our modern belief that aliens are not like us originated as the solution to a theological problem. They became “alien”, literally and metaphorically. And, therefore, threatening and to be feared.

A product of the divine?

We no longer live in a universe that is seen as the product of the divine plenitude. Nor one in which our planet can be viewed as the centre of the universe. As a result, ironically, we have become aliens to ourselves: modern “alienation” is that sense of being lost and forsaken in the vast spaces of a godless universe.

In the early modern period, aliens were not looked upon as threatening to us. They were, after all (even if they were not “men”), the product of divine goodness. But, in the modern world, they both personify and externalise the threat to our personal meaning, one that results from our being in a world without ultimate meaning or purpose.

As projections of our own alienation, they terrify us, even as they continue to fascinate us.

Read more: For 600 years the Voynich manuscript has remained a mystery. Now we think it's partly about sex

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8.1: Origin of the Universe

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The universe appears to have an infinite number of galaxies and solar systems and our solar system occupies a small section of this vast entirety. The origins of the universe and solar system set the context for conceptualizing the Earth’s origin and early history.

Big-Bang Theory

The mysterious details of events prior to and during the origin of the universe are subject to great scientific debate. The prevailing idea about how the universe was created is called the big-bang theory . Although the ideas behind the big-bang theory feel almost mystical, they are supported by Einstein’s theory of general relativity [ 1 ]. Other scientific evidence, grounded in empirical observations, supports the big-bang theory.

The big-bang theory proposes the universe was formed from an infinitely dense and hot core of the material. The bang in the title suggests there was an explosive, outward expansion of all matter and space that created atoms. Spectroscopy confirms that hydrogen makes up about 74% of all matter in the universe. Since its creation, the universe has been expanding for 13.8 billion years and recent observations suggest the rate of this expansion is increasing [ 2 ].

Spectroscopy

Spectroscopy is the investigation and measurement of spectra produced when materials interact with or emit electromagnetic radiation. Spectra is the plural for spectrum which is a particular wavelength from the electromagnetic spectrum . Common spectra include the different colors of visible light, X-rays, ultraviolet waves, microwaves, and radio waves. Each beam of light is a unique mixture of wavelengths that combine across the spectrum to make the color we see. The light wavelengths are created or absorbed inside atoms, and each wavelength signature matches a specific element. Even white light from the Sun, which seems like an uninterrupted continuum of wavelengths, has gaps in some wavelengths. The gaps correspond to elements present in the Earth’s atmosphere that act as filters for specific wavelengths. These missing wavelengths were famously observed by Joseph von Fraunhofer (1787–1826) in the early 1800s [ 3 ], but it took decades before scientists were able to relate the missing wavelengths to atmospheric filtering. Spectroscopy shows that the Sun is mostly made of hydrogen and helium. Applying this process to light from distant stars, scientists can calculate the abundance of elements in a specific star and visible universe as a whole. Also, this spectroscopic information can be used as an interstellar speedometer.

The Doppler effect is the same process that changes the pitch of the sound of an approaching car or ambulance from high to low as it passes. When an object emits waves, such as light or sound, while moving toward an observer, the wavelengths get compressed. In sound, this results in a shift to a higher pitch. When an object moves away from an observer, the wavelengths are extended, producing a lower-pitched sound. The Doppler effect is used on light emitted from stars and galaxies to determine their speed and direction of travel. Scientists, including Vesto Slipher (1875–1696) [ 6 ] and Edwin Hubble (1889–1953) [ 7 ], examined galaxies both near and far and found that almost all galaxies outside of our galaxy are moving away from each other, and us. Because the light wavelengths of receding objects are extended, visible light is shifted toward the red end of the spectrum, called a redshift . In addition, Hubble noticed that galaxies that were farther away from Earth also had a greater amount of redshift, and thus, the faster they are traveling away from us. The only way to reconcile this information is to deduce the universe is still expanding. Hubble’s observation forms the basis of the big-bang theory.

Cosmic Microwave Background Radiation

Another strong indication of the big-bang is cosmic microwave background radiation . Cosmic radiation was accidentally discovered by Arno Penzias (1933–) and Robert Woodrow Wilson (1936–) [ 8 ] when they were trying to eliminate background noise from a communication satellite. They discovered very faint traces of energy or heat that are omnipresent across the universe. This energy was left behind from the big bang, like an echo.

Stellar Evolution

Astronomers think the big bang created lighter elements, mostly hydrogen and smaller amounts of elements helium, lithium, and beryllium. Another process must be responsible for creating the other 90 heavier elements. The current model of stellar evolution explains the origins of these heavier elements.

Birth of a Star

Stars start their lives as elements floating in cold, spinning clouds of gas and dust known as nebulas . Gravitational attraction or perhaps a nearby stellar explosion causes the elements to condense and spin into a disk shape. In the center of this disk shape, a new star is born under the force of gravity. The spinning whirlpool concentrates material in the center, and the increasing gravitational forces collect even more mass. Eventually, the immensely concentrated mass of material reaches a critical point of such intense heat and pressure it initiates fusion.

Fusion is not a chemical reaction. Fusion is a nuclear reaction in which two or more nuclei, the centers of atoms, are forced together and combine creating a new larger atom. This reaction gives off a tremendous amount of energy, usually as light and solar radiation. An element such as hydrogen combines or fuses with other hydrogen atoms in the core of a star to become a new element, in this case, helium. Another product of this process is energy, such as solar radiation that leaves the Sun and comes to the Earth as light and heat. Fusion is a steady and predictable process, which is why we call this the main phase of a star’s life. During its main phase, a star turns hydrogen into helium. Since most stars contain plentiful amounts of hydrogen, the main phase may last billions of years, during which their size and energy output remains relatively steady.

The giant phase in a star’s life occurs when the star runs out of hydrogen for fusion. If a star is large enough, it has sufficient heat and pressure to start fusing helium into heavier elements. This style of fusion is more energetic and the higher energy and temperature expand the star to a larger size and brightness. This giant phase is predicted to happen to our Sun in another few billion years, growing the radius of the Sun to Earth’s orbit, which will render life impossible. The mass of a star during its main phase is the primary factor in determining how it will evolve. If the star has enough mass and reaches a point at which the primary fusion element, such as helium, is exhausted, fusion continues using new, heavier elements. This occurs over and over in very large stars, forming progressively heavier elements like carbon and oxygen. Eventually, fusion reaches its limit as it forms iron and nickel. This progression explains the abundance of iron and nickel in rocky objects, like Earth, within the solar system. At this point, any further fusion absorbs energy instead of giving it off, which is the beginning of the end of the star’s life [ 9 ].

Death of a Star

The death of a star can range from spectacular to other-worldly (see figure). Stars like the Sun form a planetary nebula, which comes from the collapse of the star’s outer layers in an event like the implosion of a building. In the tug-of-war between gravity’s inward pull and fusion’s outward push, gravity instantly takes over when fusion ends, with the outer gasses puffing away to form a nebula. More massive stars do this as well but with a more energetic collapse, which starts another type of energy release mixed with element creation known as a supernova. In a supernova , the collapse of the core suddenly halts, creating a massive outward-propagating shock wave. A supernova is the most energetic explosion in the universe short of the big bang. The energy release is so significant the ensuing fusion can make every element up through uranium [ 10 ].

The death of the star can result in the creation of white dwarfs, neutron stars, or black holes. Following their deaths, stars like the Sun turn into white dwarfs.

White dwarfs are hot star embers, formed by packing most of a dying star’s mass into a small and dense object about the size of Earth. Larger stars may explode in a supernova that packs their mass even tighter to become neutron stars. Neutron stars are so dense that protons combine with electrons to form neutrons. The largest stars collapse their mass even further, becoming objects so dense that light cannot escape their gravitational grasp. These are the infamous black holes and the details of the physics of what occurs in them are still up for debate.

1. Einstein A (1917) Cosmological Reflections on the General Relativity Theory. Sitzungsberichte der Königlich Preußischen Akademie der Wissenschaften (Berlin), Seite 142-152 142–152

2. Perlmutter S, Aldering G, Goldhaber G (1999) Measurements of Omega and Lambda from 42 high-redshift supernovae. Astrophys J 517:565–586

3. Fraunhofer J (1817) Bestimmung des Brechungs-und des Farbenzerstreungs-Vermögens verschiedener Glasarten, in Bezug auf die Vervollkommnung achromatischer Fernröhre. Ann Phys 56:264–313. https://doi.org/10.1002/andp.18170560706

6. Slipher VM (1913) The radial velocity of the Andromeda Nebula. Lowell Observatory Bulletin 2:56–57

7. Hubble E (1929) A relation between distance and radial velocity among extra-galactic nebulae. Proc Natl Acad Sci U S A 15:168–173

8. Penzias AA, Wilson RW (1965) A Measurement of Excess Antenna Temperature at 4080 Mc/s. Astrophys J 142:419–421

9. Salaris M, Cassisi S (2005) Evolution of stars and stellar populations. John Wiley & Sons

10. Timmes FX, Woosley SE, Weaver TA (1995) Galactic chemical evolution: Hydrogen through zinc. The Astrophysical journal Supplement series 98:617–658

What Are the Theories of the Universe?

Humans have pondered the beginning of the universe since our species evolved. Generations of people have looked towards the sky as a source of amazement, religion, and wonder. Thankfully, over the last several centuries , scientists from around the world have begun to piece together empirical data to support a variety of hypotheses about how all of life as we know it began. Today, let’s take a closer look at an age-old question: what are the theories of the universe?

The Big Bang Theory

The most robust, well-supported theory as to the origins of the universe is the Big Bang Theory. A Belgian priest, Georges Lemaître , first suggested the idea of big bang theory in the 1920s. Since then, Einstein’s theory of relativity and modern science has lent credibility to this developing theory.

Big Bang Assumptions

Before we can get into specifics, let’s understand a few basic assumptions concerning the Big Bang Theory. Each of the following points is assumed to be true in the universe, and this notion is part of the foundation upon which the Big Bang rests. 

• The universe is constant . This one is first for a reason; it’s important. Our modeling and understanding of the world hinge on the idea that physical properties are the same everywhere. For example, we assume gravity , electricity, magnetism, and light all behave the same way, even in far off places in the galaxy and universe. 
• The universe is homogenous . Secondly, we assume that the universe is roughly the same in all directions. You can think of these like shovelfuls of dirt. Some scoops might have big rocks, some might have worms, and some may have more clay than others. But, in the long term, every 100 shovelfuls will be roughly the same in composition.
• The universe is not centered around us. Physicists refer to this notion as the “ privileged location .” This means that earth is somewhere in the universe, but we really have no idea where it is in relation to the “edge” (more on that later).
• The universe has a beginning. All matter and energy that has ever been and that will ever be were created during the Big Bang. No new material or energy has been created since then.

Basics of the Big Bang

The Big Bang is the leading theory as to the origins of the universe as we know it. It describes the mechanism by which everything we know started as a small singularity that ballooned into the earth, solar system, galaxy, and universe. The easiest way to understand this theory is through a timeline, so let’s dig in.

• 1 second. During the first second, the temperature around the big bang was about 5.5 billion degrees celsius (10 billion Fahrenheit). There would have been nothing to see at this point, though. According to NASA , “the free electrons would have caused light (photons) to scatter the way sunlight scatters from the water droplets in clouds.”
• 3 seconds. The initial explosion contained all the necessary subatomic particles for atoms and molecules: neutrons, protons, and electrons. The first basic elements form at this point: hydrogen, helium, and lithium. 
• 380,000 years. For the first time, light emerges into the universe. This radiation (light) is referred to as the cosmic microwave background. First predicted to exist in 1948 by Ralph Alpher , it is a signature mark of the Big Bang. This background of microwaves can still be observed today, and it used to estimate the age of the universe. 
• 300 million years. We’re jumping forward a bit here. As the initial burst of atoms and gas expands, gravity starts to become a relevant factor. Pockets of different densities of gas give birth to stars and collections of stars start to form galaxies. 
• ~9 billion years. Our sun forms. The universe is roughly 14 billion years old, and our sun is approximately 4.6 billion years old. 

Steady State Universe

The steady state universe hypothesis breaks one of the key Big Bang Theory assumptions. The steady state hypothesis states that matter and energy are being created continuously, steadily. First theorized in the 1920s by Sir James Jeans, the theory imagines a universe without a real beginning or end. 

In the steady state view, the universe has always been expanding and creating matter, and it will continue to do so. Although the theory has been revised and updated throughout the middle of the 20th century, an overwhelming amount of contradictory evidence supports the notion that the steady state hypothesis is largely false . 

Level II Multiverse

The multiverse concept is complicated . And, that may still be an understatement. One of the driving factors leading to the development of this theory is the seemingly perfect nature of physics in our universe. Light, gravity, physics… they all seem to work together perfectly to allow life to exist in our universe. This can be viewed as a major coincidence or an inevitability given a large number of trials. 

The multiverse concept postulates that multiple universes exist, simultaneously, and they each have different physical constants. For example, maybe a universe 2.0 (or 3.0 or 18.0 or 821.0) exists along with ours where light travels at a different speed. Changing this speed changes an exceptionally large number of other universal constants, and thus, everything we know about our universe.

Correct Hypothesis?

So, where does that leave us? What is the “correct” theory for the origin of the universe? By a large margin, the Big Bang is the most well-supported, evidence-based theory. That being said, new technology and new instruments allow us to gather different data every decade, so we will have to see what the future holds!

What other theories of the universe have you heard of? How do you think this all got here?

[Featured image by FelixMittermeier via Pixabay ]

Check us out on  EarthSnap , a free app brought to you by Eric Ralls and Earth.com.

Unlocking Earth's origins

New asu researcher recreates extreme planet formation conditions to better understand habitable earth-like worlds.

Damanveer Grewal, assistant professor in Arizona State University’s School of Molecular Sciences, utilizes ASU's state-of-the-art high pressure experimental facilities at FORCE to understand the formation of habitable worlds in our solar system and beyond. Photo by Meghan Finnerty/ASU

Looking up at a vast, star-studded sky, people have always wondered: Are we alone in this universe?

It’s a fundamental question that has intrigued and inspired curious minds across all corners of our world. With recent advancements in science and research, this question, once thought to be purely philosophical, is becoming a perfectly testable hypothesis.

Damanveer Grewal , a cosmochemist and assistant professor in Arizona State University’s School of Molecular Sciences , studies the conditions of planet formation and how key elements like carbon, nitrogen, and water behave and are distributed as earth-like worlds form.

“In order for us to think about other potential life, we need to first understand the formation of earth itself, you need to understand the seeds,” said Grewal who also has a dual appointment in ASU’s School of Earth and Space Exploration. “My work aims to understand what happened in the seeds of earth’s formation, and I use high-pressure experiments and meteorites to benchmark data on.”

Grewal’s work allows scientists to gain a deeper understanding of how our own planet works, how Earth has sustained life, and provides clues about the far reaches of the solar system and beyond.

Exploring the inner workings of our planet 

Earth did not form suddenly. 

Over millions of years, born from a cloud of dust and gas that collapsed to form a spinning disk hovering in space, tiny particles clumped together to form rocks; those rocks collided with one another, melted together, and, over time, the planet grew.

But Earth is unique. During the formation process, just the right distribution of essential elements — nitrogen, carbon and water — remained on the planet, allowing for life to thrive. 

Too much or too little of these critical elements during planet formation can have dramatic impacts on a planet's climate and environment. 

“Venus has too much carbon dioxide in its atmosphere, making it inhabitable with surface temperatures of around 700 degrees Celsius,” Grewal said. “These are the things we need to understand: You can't have too many of these elements on the planet, but how do you find those sweet spots?” 

Combining FORCE and meteorites 

To find that elemental sweet spot, Grewal’s research uses ASU’s Facility for Open Research in a Compressed Environment, or better known as the  FORCE  facility, to recreate and put elements under the extreme conditions of early planet formation. 

Within the state-of-the-art high-pressure experimental facilities, a variety of large presses crush, blast and heat rocks and elemental samples to trace the journey of these elements through each and every step of the planet formation sequence.

“This is a unique capability that no other university in the country has,” Grewal said.

Grewal then takes his work one step further by combining the high-pressure, high-temperature experiments with existing meteorite data. Meteorites provide valuable insights into the chemical composition of early bodies, almost as an elemental time capsule, while the experiments simulate the physical processes.

“What I'm interested in is trying to combine constraints on meteorite data and high-pressure experiments to understand processes that took place very, very, very early in the solar system history and then try to use that information to move ahead in time.”

Already, Grewal’s past work has contributed significantly to the field of astrochemistry, with several papers published in Nature Astronomy , upending a previously held notion that early planetesimals within the inner solar system didn't contain water, showing that they do, and in a separate paper uncovering that early planetesimals, or smaller protoplanets, within the inner solar system also contained nitrogen and carbon . 

The freestyle scientist 

For Grewal, he says, like anyone who’s ever looked up toward the night’s sky and gazed with wonder, his research is rooted in his own curiosity. 

Through his research and teaching at ASU, he hopes to encourage his students to approach science as a creative endeavor.

“My passion as a human being is to understand things,” said Grewal, who created and teaches a new ASU class on the chemistry of planet formation . “(Research) has to be creative, it should be something that you're challenging, that brings interdisciplinary fields together, and of course when you're doing these kinds of risky sciences, sometimes you're going to be proven wrong, but that's also what moves science forward. 

“I'm never going to constrain myself to what I know and what I don't know, and I want to instill that into my students and their research.” 

Unbound, the possibilities — like the universe — are limitless.

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The Universe Could Be Eternal, According to This Controversial Theory

The idea of a static universe would mean our cosmos will live forever, and it isn’t expanding after all.

✅ Quick Facts:

• This idea says the universe is neither expanding, nor contracting; instead it is steady, and has no beginning and no end.
• But for other scientists, the suggestion is a leap in logic and the Big Bang is the best description of the creation of the universe we currently have.

What if the Big Bang , the prevailing theory of how our universe came to be, never happened? What if the universe hasn’t been expanding from a tiny dense fireball, but has instead been in a steady state for 13.8 billion years with no beginning and no end? An intriguing analysis published in Progress in Physics in 2022 claims that the Big Bang might be a bust because it relies on the Doppler effect, or Doppler shift , a landmark theory in physics that Austrian mathematician and physicist Christian Doppler proposed in 1842 .

​​The Doppler effect explains that the perceived increase or decrease in the frequency of light, sound, or other waves (note the word waves here) depends on how a source and an object move toward each other. In space, the Doppler effect influences the light planetary bodies emit: if a body in space is moving away from us, its light spreads apart, or “redshifts” (as it moves toward longer wavelengths). However, if a body is moving toward us, its lightwaves compact, or “blueshift” (because the light moves toward shorter wavelengths). This is because in space blue means near, and red means farther away; this principle is clear as day to astronomers. Measurements of starlight have so far concluded that all galaxies redshift . In other words, this evidence supports the Big Bang theory, which says the universe is constantly expanding.

But Jack Wilenchik, author of the provocative study, highly doubts whether redshift means movement. In fact, he believes the Doppler effect may actually be an Achilles’ heel that fells the Big Bang theory.

A Reason to Assume the Universe Did Not Start With a Big Bang?

“The Doppler’s effect is a 180-year old theory nobody has backed up with experimental evidence,” Wilenchik tells Popular Mechanics . To look at different planets and moons in the solar system, Wilenchik, who is a lawyer by trade and an amateur astronomer, borrowed a simple spectroscopy test English astronomer William Huggins had first used in 1868. Spectroscopy is the study and measurement of spectra , or the charts or graphs that depict the intensity of light from an astronomical body like a star. Wilenchik also used data from the Hawaii-based Keck Observatory’s spectrometers— available online —and had a professional astrophysicist process it for him. The results of his study align with a different, incompatible idea about the universe: the tired light model.

The 1929 brainchild of Swiss astronomer Fritz Zwicky , the tired light hypothesis attributes the universe’s redshift to the fact that photons , the tiny packets of electromagnetic energy that make up light, lose energy as they pass through the great cosmos. Therefore, a decrease or increase in energy doesn’t necessarily mean movement, so no stretching universe can exist. This model indicates that light simply loses energy over time—and so the universe must be static.

.css-2l0eat{font-family:UnitedSans,UnitedSans-roboto,UnitedSans-local,Helvetica,Arial,Sans-serif;font-size:1.625rem;line-height:1.2;margin:0rem;padding:0.9rem 1rem 1rem;}@media(max-width: 48rem){.css-2l0eat{font-size:1.75rem;line-height:1;}}@media(min-width: 48rem){.css-2l0eat{font-size:1.875rem;line-height:1;}}@media(min-width: 64rem){.css-2l0eat{font-size:2.25rem;line-height:1;}}.css-2l0eat b,.css-2l0eat strong{font-family:inherit;font-weight:bold;}.css-2l0eat em,.css-2l0eat i{font-style:italic;font-family:inherit;} "We do not live in a world of alternative facts. We must go where the evidence points. There is nothing to suggest that the Big Bang is a myth at present."

“No, the universe did not start as an exploding atom or anything,” Wilenchik says. “There’s no beginning and no end to the universe,” he says, disputing the primeval atom theory that Belgian priest, physicist, and astronomer Georges Lemaître first proposed in 1927. (Later, astronomer Fred Hoyle coined the term “Big Bang” for Lamaitre’s cosmic origins idea, and it stuck.)

Whether a star reddens or turns bluer ultimately boils down to Isaac Newton’s corpuscular theory of light , says Wilenchik. The Newtonian theory posits that light is made up of tiny particles, or “corpuscles,” which are constantly traveling in a straight line. In essence, the blue or red shifts we see in space are simply the result of the different corpuscle sizes: a blue light means larger bodies, while a red light means smaller ones. “If light is not in waves, then there goes the Doppler theory, because the entire theory is based on the idea that light is in waves,” says Wilenchik.

But particularly intriguing is his view that galaxies are atoms and stars are light (he’s written a book about it that’s freely available online). “Since the universe neither expands nor contracts, what we have in the sky is giant spirals. And we’ve got something very strange and unique called stars,” he says.

Here’s what he means: it was in the late 1800s when Scottish-Irish physicist William Thomson, better known as Lord Kelvin , suggested that the atom is a “ vortex” in the “aether.” In full agreement, Wilenchik says atoms have spirals at their core, and so do galaxies, and so do large clusters of galaxies or supergalaxies, because the same vortex structure permeates the whole cosmos, from the macroscopic to the microscopic level. The universe is infinitely big, infinitely small, and never-ending; stars are strange bundles of light; and we need to reconsider the Doppler effect theory, Wilenchik concludes.

But not everyone agrees.

Why the Big Bang Theory Is Our Best Explanation So Far

“The premise that the Big Bang is a big bust due to its reliance on the Doppler effect is a big leap in logic. Doppler’s theory has been tested repeatedly and has held up,” Stephen Holler , Ph.D., an associate professor of physics at Fordham University, tells Popular Mechanics .

The Doppler effect is a wave phenomenon we are all familiar with. Take sound, for example. The way the pitch of a moving vehicle, especially a rapidly moving vehicle such as an ambulance or a fire truck, hurts your ears or fades away as the vehicle moves near or away from you is a fine illustration of the “compression or elongation of the wave” in relation to you, the observer, says Holler. Medical applications such as Doppler velocimetry (a test that measures blood flow and 3D ultrasound images) also owe their existence to the Doppler effect. And when it comes to the heart of Wilenchik’s argument, which is that red and blue shifts do not correspond to predictions of how planetary objects move, Holler says that we would have practically failed to engage in extraterrestrial exploration without Doppler.

“ Extraterrestrially , we have been able to reconcile the chemical composition of stars and planets by noting the correspondence of spectral lines with known lines observed from chemicals on the Earth through Doppler spectroscopy,” Holler says. True, we may never know if the Big Bang theory is correct, but currently it is our best description for the origin of the universe, he continues. “An obvious originalist who relied on others to analyze the data for him, Wilenchik highlights the primeval atom theory’s improbability,” Holler adds. But the theory entered the realms of science nearly an eon ago when evidence was just beginning to come in and be interpreted, or, in other words, when we didn’t know what we didn’t know: “We do not live in a world of alternative facts. We must go where the evidence points. There is nothing to suggest that the Big Bang is a myth at present,” Holler says.

In ancient Greek mythology, deities govern the skies and, together, the dynamics of birth and annihilation. For Wilenchik, this is no coincidence: that we still have planets named after Greek gods, (even if Romans “romanized” the names of most later on), bears some kind of cosmic symbolism. “If the divine is somebody that creates or destroys things, then galaxies might be the divine in their own way,” the Phoenix-based lawyer suggests. This symbolic heritage might go beyond theory, implies Wilenchik, drawing enticing if not esoteric parallels between the symbolic and the pragmatic. It could inspire a fresh examination of the principles of cosmological theory, such as the Doppler effect, which is crucial for comprehending the universe’s expansion.

“We could reinvestigate the Doppler theory through observing the behavior of a planet like Mercury, for which we know when it’s moving toward or away from us and how fast,” says Wilenchik. In this way, we could see whether it redshifts or blueshifts correspondingly.

An in-depth investigation like this could provide us with a deeper understanding of how the universe works, as Wilenchik suggests we’ve been too comfortable with the Big Bang theory for too long now. Did we begin with a bang or are new beginnings overrated?

Stav Dimitropoulos’s science writing has appeared online or in print for the BBC, Discover, Scientific American, Nature, Science, Runner’s World, The Daily Beast and others. Stav disrupted an athletic and academic career to become a journalist and get to know the world.

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This Is the Coldest Place in the Universe

The Institute for Creation Research

In April 2024, some of the world’s leading cosmologists convened at the Royal Society in London to question the cosmological principle—the assumption that the universe is the same everywhere and in every direction. 1,2 This is a highly significant development since the cosmological principle is a foundational assumption of the Big Bang model for the universe’s origin.

The cosmological principle assumes that the universe is both homogenous and isotropic . Homogeneity means the distribution of matter and energy in the universe is roughly uniform if one looks at the big picture and ignores differences at smaller distance scales. Isotropy (pronounced i-sä-tro-pee) means that every direction in the sky looks the same as every other direction in the sky. This implies there are no special or “preferred” directions in space. When cosmologists use Einstein’s theory of general relativity to study the universe, they make these two assumptions at the very beginning of their calculations because this greatly simplifies the mathematics involved. In fact, proposed creationist cosmologies have generally assumed isotropy as well, but not homogeneity. However, creationists are open to the possibility of special directions in space. Thus, conventional cosmologists questioning or challenging the cosmological principle is no small matter.

Previous Creation Science Updates have highlighted discoveries of structures in the universe that are so large they have caused even mainstream cosmologists to question the assumption of homogeneity, 3,4,5 and there are indications that the universe may not be isotropic. Even the cosmic microwave background (CMB) radiation, admittedly one of the strongest arguments for the Big Bang, shows signs that it is not truly isotropic as it should be if the Big Bang and its accompanying inflation theory are correct. 6

Professor Subir Sarkar, a cosmologist at Oxford University and one of the organizers of the meeting, said, “We are, in cosmology, using a model that was first formulated in 1922....We have great data, but the theoretical basis is past its sell-by date.” 2

This conference follows high-profile articles questioning whether the Big Bang theory is in crisis, 7,8 which we have commented upon. 9,10

Clearly, the Big Bang model is in crisis. Yet many Christians embrace it, because it ostensibly “proves” the universe had a beginning, as taught by Genesis. Yet, the Big Bang contradicts Genesis in practically every other way, both in regard to the age of the universe and the sequence in which God brought the heavenly bodies into being. Moreover, Big Bang scientists have long sought ways to “do away” with a beginning of the universe, as the late Stephen Hawking made clear in his book A Brief History of Time . 11 It is long overdue for Christians to “wise up” and reject the Big Bang for what it really is: an “argument” and “high thing that exalts itself against the knowledge of God.” 12 The Lord Jesus Christ, not a presumed Big Bang, deserves the credit for our universe’s existence.

• Cosmology is the study of the universe at the largest scale: its structure, origin, and ultimate fate.
• Devlin, H. World’s top cosmologists convene to question conventional view of the universe . The Guardian . Posted on theguardian.com April 14, 2024, accessed April 15, 2024.
• Thomas, B. Massive Quasar Cluster Refutes Core Cosmology Principle . Creation Science Update . Posted on ICR.org January 18, 2013, accessed April 15, 2024.
• Hebert, J. Giant Galaxy Ring Shouldn’t Exist . Creation Science Update . Posted on ICR.org August 24, 2015, accessed April 15, 2024.
• Hebert, J. A Cosmic ‘Supervoid’ vs. the Big Bang . Creation Science Update . Posted on ICR.org May 7, 2015, accessed April 15, 2024.
• Hebert, J. 2018. Does the Cosmic Microwave Background Confirm the Big Bang? Acts & Facts . 47 (6): 10–14.
• Hooper, D. Is the Big Bang in Crisis? Astronomy . Posted on astronomy.com May 14, 2020, accessed April 15, 2024.
• Frank, A. and M. Gleiser. The Story of Our Universe May Be Starting to Unravel . New York Times . Posted September 2, 2023 at nytimes.com, accessed April 15, 2024.
• Hebert, J. Astronomy Magazine: Big Bang in Crisis? Creation Science Update . Posted on ICR.org May 21, 2020, accessed April 15, 2024.
• Hebert, J. New York Times Editorial: Big Bang Unraveling? Creation Science Update . Posted on ICR.org September 24, 2023, accessed April 15, 2024.
• Hawking, S. 1988. A Brief History of Time . New York, NY: Bantam Books, Chapter 8, second paragraph.
• 2 Corinthians 10:5.

* Dr. Jake Hebert is a research associate at the Institute for Creation Research and earned his Ph.D. in physics from the University of Texas at Dallas.

Evidence for Creation

Dark energy could be getting weaker, suggesting the universe will end in a 'Big Crunch'

"The discovery of evolving dark energy would be as revolutionary as the discovery of the accelerated expansion of the universe itself, if confirmed."

The current "standard model" of the cosmos, its history, and its evolution is called the Lambda Cold Dark Matter (LCDM) model — but the supremacy of this model, in which lambda represents the cosmological constant and dark energy, may now be under serious threat. 

In short, that is because new observations of the cosmos have suggested that dark energy , the force causing our universe to expand faster and faster, seems to be weakening. That may not sound like much in and of itself, but this finding actually has the potential to cause the first major paradigm shift in cosmology since the discovery of the accelerated expansion of the universe just over 25 years ago. It could even suggest out universe won't end in a "Big Rip," or a "Big Chill," but rather a "Big Crunch." More on that shortly, first, let's dive into these fascinating results.

Related: Largest 3D map of our universe could hint that dark energy evolves with time

The new clues about dark energy evolving came as part of one of the deepest maps of the cosmos ever created, built using the first year of data collected by the Dark Energy Spectroscopic Instrument (DESI) . The instrument's 5,000 robotic eyes collect light from millions of galaxies across over a third of the entire sky as we see it from Earth. This light is then broken down into a spectrum of colors, allowing scientists to measure the expansion of the universe over billions of years by measuring a change in light wavelength called " redshift ."

Collected over no more than a fifth of DESI's mission operating time, data gleaned with the survey already promises major shake-ups and has cosmologists excited about what comes next.

"The release of these results was a great day for cosmology, pointing to a 'decreasing' effect of the dark energy over time, meaning it is evolving and, therefore, not constant after all," Luz Ángela García Peñaloza, former DESI team member and a cosmologist at the Universidad ECCI in Columbia, told Space.com. "The discovery of evolving dark energy would be as revolutionary as the discovery of the accelerated expansion of the universe itself, if confirmed with future data."

What is the standard model of cosmology?

The LCDM model suggests that, immediately following the Big Bang , the universe was majorly dense and incredibly hot — but also remarkably smooth and more or less the same, or homogenous, in all directions.

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As the universe expanded, small fluctuations in density began to appear, and these dense patches grew. Clumps of dark matter began to condense as the universe evolved, and newly formed atoms gathered and spurred gas molecules within these clumps. This resulted in a universe filled with little more than hydrogen and helium (the two lightest and simplest chemical elements) — and dark matter.

The bonding of electrons to protons to create the first atoms meant that light was suddenly free to travel, and this first light is seen today as the cosmic microwave background (CMB) , "fossil" radiation that can tell us a lot about the history of the universe.

Regions of higher density drew gas and dark matter together, forming the seeds for the first galaxies in the LCDM model that collapsed to birth proto-galaxies . In these early galaxies, the hydrogen and helium gas created the first stars. Finally, proto-galaxies and the halos around them merged to form larger and larger galaxies . 

Importantly, however, in this model, dark energy is represented by lambda. And lambda is supposed to be constant over time.

"DESI saw that the 'equation of state' of the universe isn't consistent with the usual LCDM model, but instead, it is showing a hint that dark energy is varying with time," García Peñaloza said. "These findings open a window for variable dark energy models because they show a departure for the constant equation of state.

"This was pretty surprising because most cosmological observations thus far have favored the LCDM model. The entire cosmological community was really shocked." 

If these novel findings from DESI prove accurate — and they are currently extremely robust, it would appear — then the cosmological constant may no longer be a suitable representative for the mysterious force of dark energy.

Some physicists may welcome doing away with the cosmological constant, however. Not only has it been a headache for decades, but this wouldn't be the first time that our burgeoning understanding of the cosmos had warranted its disposal. 

Back to the theoretical dustbin

The cosmological constant, represented by the Greek letter Lambda, has posed quite the problem for physicists since the early 20th century. 

In 1915, Albert Einstein released what is arguably his most revolutionary theory, general relativity , which described gravity as a concept that emerges from the curvature of space and time — a curvature caused by bodies with mass.

Two years after this, in 1917, Einstein and Dutch astronomer Willem de Sitter demonstrated that the equations of general relativity could be used to describe the universe, albeit a highly simplified universe. There was a problem, however; the universe described by the equations of general relativity didn't describe a universe that sits still. At that time, in physics, the general consensus was that the universe was static, neither expanding nor contracting, and Einstein agreed with that consensus. So, he added a sort of "fudge factor" to his equations: The cosmological constant, or lambda. 

This balanced the universe, adding the right push and pull to keep it static.

Around 12 years later, in 1929, Edwin Hubble was studying distant galaxies and found that light from them was being stretched, or "redshifted." The further away a galaxy was, he saw, the greater this effect was. This indicated that the universe was not static but was, in fact, expanding. Scientists would spend the next seven decades trying to measure the rate of this expansion, determined by a value called the " Hubble constant ."

No longer needing to describe a static universe, Einstein removed the cosmological constant from his equations of the universe, allegedly describing the introduction of lambda as his " greatest blunder ." But the cosmological constant wouldn't stay in the cosmic dustbin for long. Before the end of the 20th century, lambda would be back in a big way, and with a new role.

In 1998, two separate teams of astronomers were making observations of distant Type1a supernovas and using them as cosmic distance measurements when they discovered that the expansion of the universe isn't actually slowing as one might expect. It's speeding up. Then, dark energy was introduced as a placeholder for whatever seems to be causing this accelerating expansion.

"Despite the fact that it makes up 70% of the universe's total matter and energy budget, nobody knows what it is," García Peñaloza said.

In many models of the cosmos, including the prevalent LCDM model, dark energy is represented by the rescued cosmological constant, or lambda, that's now acting to oppose gravity and push the very fabric of space and time apart at a quickening rate. 

Still, after being introduced as a value for the accelerating expansion of space, the cosmological constant remained a problem. Values delivered by observing distant supernovas and the value predicted by theories of quantum physics continue to vary wildly, diverging by as much as 10 to the power of 121 (1 followed by 121 zeroes). 

Are any closer to understanding dark energy?

To understand why dark energy and the accelerating expansion of the universe is so shocking, consider this very Earthly analogy: Imagine giving a child on a swing one big push. That is analogous to the Big Bang, which kicked off the expansion of the universe. Over time, the swing would probably slow and reaches progressively lower points in its arc, right? That's akin to the expansion of the universe slowing down as the cosmos ages.

But then, suddenly, without you applying a further push when the swing has almost come to a halt, imagine that it suddenly resumes moving. Not only this, but imagine that it swings faster and faster, reaching higher and higher points. That is equivalent to the action of dark energy that the cosmological constant is used to describe.

It's no wonder scientists are eager to determine the cause of this extra cosmic push; the discovery that dark energy seems to be getting weaker adds a layer of complexity to the situation.

"This is a really good indication that maybe an LCDM model is not exactly 'the ultimate answer' to the nature of dark energy," García Peñaloza explained. "It's huge progress, but these results probably don't get us much closer to that answer; they are more telling us is more how to describe dark energy with a bearing to time, probably as a fluid that fills the universe and can be described with an equation of a state that is not constant."

Returning to the swing analogy, discovering what caused the extra, unseen push is critical to understanding the fate of the child on that swing: Will they land in the bushes, safely on the ground or get launched into space? Similarly, understanding dark energy is critical because its evolution, or lack thereof, will determine the fate of the universe . It could even show us what our view from Earth may look like in the future.

"There is one scenario in which, if dark energy is the unchanging cosmological constant, in eons, all the galaxies will have moved so far away from each other that the night sky over Earth will be empty," García Peñaloza said. 

This could result in the universe ending as a cold cosmos of widely separated dead galaxies, the so-called "Big Chill" scenario. Alternatively, the continued accelerated expansion could cause the very fabric of spacetime to tear, a scenario called the " Big Rip ."

The new DESI map, however, could indicate a different cosmic fate that sees the universe collapsing once again into the hot, dense state seen moments after the Big Bang. "If what the first year of DESI results suggests is true, then the accelerated expansion of the universe will cease and eventually reverse, and the universe could begin drawing together under the influence of gravity," García Peñaloza added. "This could eventually lead to the universe ending in a ' Big Crunch ' scenario."

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García Peñaloza and other cosmologist are keen to see what the next four years of DESI observations bring to our understanding of the universe, its origins and its fate. 

In particular, García Peñaloza said that the second and third years of DESI operations should see the telescope exploring redshift space distortions, with this data making the already robust DESI results even more impressive. The final year of DESI results should coincide with the release of the first year of data from the Euclid space telescope , which launched on 1 July 2023, providing a powerful  "double-punch" to our understanding of the universe.

"We're going to have a very complementary vision of the universe from two completely different missions," García Peñaloza concluded. "They are going give us a completely and brand new vision of how the universe is behaving and how dark energy is shaping the larger scale universal structure ."

Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at: [email protected].

Robert Lea is a science journalist in the U.K. whose articles have been published in Physics World, New Scientist, Astronomy Magazine, All About Space, Newsweek and ZME Science. He also writes about science communication for Elsevier and the European Journal of Physics. Rob holds a bachelor of science degree in physics and astronomy from the U.K.’s Open University. Follow him on Twitter @sciencef1rst.

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• LordElfa This could, if true, point to a constantly repeating big bang/big crunch cycle of universal renewal. Reply
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An MCU Theory Ties the Celestials to the X-Men's Origin

• Eternals ' Tiamut could be the starting point for the mutants' arrival in the Marvel Cinematic Universe.
• The Celestial energy released during Tiamut's death may have made the X-Gene more dominant in the human population.
• The MCU's mutants could be introduced in the next few years with the upcoming films Deadpool and Wolverine and Captain America: Brave New World .

Marvel Comics revealed that Earth is dense with superheroes because of a sick Celestial who came to the planet after being infected by the Horde, an insectoid race that serves the Fulcrum and balances the universe in opposition to the Celestials. When the Celestial died, its bodily fluid seeped into the ground and water, changing the course of Earth's evolution. Loki, who told this story to Captain America, explained that this gave rise to the superhuman abilities in the planet's populace. A Reddit fan theory suggests the Eternals ' Tiamut, locked in stone within the Earth, could be the Marvel Cinematics Universe's way of explaining superheroes and mutants using the same decay principle.

In the 2021 film Eternals , the Celestial Tiamut is effectively killed by Sersi and the other Eternals when she turns it to stone. But u/Black-kage explains that because comic books revealed a similar origin of superhumans, Eternals ' Tiamut could be setting up the MCU to include mutants in the same way. It goes on to say that after the Eternals defeated Tiamat, its corpse could have oozed enough energy into the Earth to activate the mutant gene, which will cause their numbers to rise.

Updated by Jordan Iacobucci on March 18, 2024: The Marvel Cinematic Universe has begun introducing mutants in small doses, with characters like Kamala Khan and Namor the Sub-Mariner boasting powerful mutant abilities. Nevertheless, the franchise has yet to explain where the mutants come from and how they are created. Some theories suggest that a certain infamous MCU movie could have hidden the answers in plain sight — and might be revealed in one of the franchise's next films.

The Stone Celestial Could Birth the X-Gene in the MCU

Mcu theory: ego isn't a celestial - he's something worse, marvel comics trivia:.

• Tiamut, also known as the Dreaming Celestial, first appeared in Marvel Comics in 1977's Eternals #18 by Jack Kirby, Mike Royer, and Glynis Wein.

In the Marvel Comics Universe, fans recently learned that, once The Avengers defeated the Final Host, the First Celestial Host lifted this dead Celestial out of its grave for them to use as a base of operations. This Celestial corpse became Avengers Mountain, a new headquarters for the superhero team. Yes, The Avengers meet up in a dead body. With this information, it could be possible that the MCU will use Tiamut's corpse the same way the comics used the Progenitor Celestial. Presumably, Tiamut is only turned to stone and not dead. Still, if there is a leeching process similar to what was seen in the comics, this could be the MCU's X-Gene origin story.

While the theory is interesting, it might be headed in the right direction using the wrong vehicle. Another comic fact states that the Celestial's experimentation on early humans created the X-Gene . In Eternals , the Celestials didn't necessarily experiment. Still, they made life on Earth and may have planted a latent mutant gene. In the comics, the Celestial due to emerge is called the Dreaming Celestial. Its presence could have given off loads of energy, activating the X-Gene.

There May Be More to Mutants' Arrival Than Tiamut's Emergence

Marvel's 30 most powerful celestials, ranked, mcu eternals trivia.

• While there have been reports that Marvel Studios is developing Eternals 2 , there has been no official statement about any such film. Given the MCU's recent course correction, the film may not ever be made.

Tiamut could still be responsible for the emergence of the mutant genome and could still be how the MCU brings in mutants, but there is more to the story. When Tiamut was awakening due to Hulk's snap, it could have provided enough power to jump-start the birth of more mutants. The Reddit theory picks up on the hints Eternals provides. However, it seems more likely that the MCU will use immense energy related to the Infinity Gauntlet to introduce mutants instead of dead Celestial juices leaking into the groundwater.

Additionally, Tiamut's "death" doesn't happen far enough back in the timeline to affect human DNA. Evolutionary changes take thousands of years to produce noticeable results, and the Eternals don't defeat the Celestial until after Thanos . The corpse wouldn't have been on Earth for long enough to start affecting people's genomes.

For mutants to arrive in the MCU, it seems more likely that Hulk's snap and the developing Celestial ignited something in human DNA to make the X-Gene more dominant. But it also looks possible that some mutants were around for all this time, hiding in the shadows. That would allow mutants like Professor X and Magneto the chance to operate undercover during the earlier films.

When Will the MCU Finally Introduce the Mutants?

10 best x-men villains who should appear in the mcu, mcu movie trivia.

• The MCU's next film, Deadpool and Wolverine , hits theaters on July 26, 2024, and will act as a bridge between the Marvel Cinematic Universe and Fox's X-Men Universe.

The X-Men are coming to the MCU, the question is merely when they will arrive. Deadpool and Wolverine seems like the most likely place for mutants to start appearing in the MCU, as the two titular characters from Fox's X-Men movies make the leap from their universe to the other during the events of the film. However, the film has given no indication that it will include any mutants who are wholly original to the MCU. Even so, if Tiamut turns out to be instrumental in the birth of the MCU's mutants, then Captain America: Brave New World might be the best place to get the ball rolling.

Brave New World is setting itself up to be one of the most important entries in Phase 5 of the MCU. It features the return of several long-forgotten characters and will include a storyline dealing with the President of the United States himself. Some theories suggest that the film will even bring back Tiamut, whose stone corpse could become the target of several major powers, including the United States of America. If the dead Celestial in the Indian Ocean is really going to play a major role in Brave New World , the film could lay the groundwork for the introduction of the MCU's mutants. Though audiences shouldn't expect to see any mutants appear in the film, Brave New World could show the government's panic as more and more superpowered individuals with a previously latent X-Gene begin to show themselves. Brave New World could become the effective starting point of the MCU's mutant storyline, building up to other movies and television series starring the newly rebooted X-Men.

The arrival of the X-Men in the MCU is imminent. While many of the Multiverse Saga's storylines have felt unrelated and jumbled, some, like the emergence of Tiamut, could play into a larger arc involving the birth of the mutants in the MCU. Audiences should be on the lookout for any Easter eggs or hints that could tie the mutants' arrival into films like Deadpool and Wolverine or Captain America: Brave New World . The stage is set, and all that remains is for Marvel Studios to finally pull the trigger and bring the mutants back for another chance at a live-action franchise.

Marvel Cinematic Universe

Created by Marvel Studios, the Marvel Cinematic Universe follows heroes across the galaxy and across realities as they defend the universe from evil.

First Film Iron Man

Latest Film The Marvels

First TV Show WandaVision

Latest TV Show Loki

Character(s) Black Panther, Ms. Marvel, Iron Man, Loki, The Hulk, Hawkeye, Thor, Captain Marvel, Captain America, Black Widow, Scarlet Witch, Monica Rambeau, Falcon