The Cosmological Argument (part 4)

September 02, 2007     Time: 00:36:18

We have arrived at our point in the class which is the scientific confirmation of the beginning of the universe. So this is what we will deal with today – the scientific evidence that the universe began to exist.

In 1917 Albert Einstein applied his newly discovered General Theory of Relativity (which is a theory of gravitation that he developed) to cosmology, that is, the study of the large scale nature and history of the universe. In applying the General Theory of Relativity to the universe, Einstein assumed that the universe is basically the same at all times and all places. It exists in a steady state and has a constant curvature. Einstein however discovered to his chagrin that in fact his equations from the General Theory of Relativity would not permit such a static, changeless universe unless he introduced into these equations a certain fudge factor to ensure a static universe. But Einstein’s universe was in fact balanced on a razor’s edge and the least perturbation – even the transport of matter from one part of the universe to another – would upset the balance and cause the universe to either begin to expand or to collapse in upon itself.

By taking this feature of Einstein’s model seriously the Russian mathematician Alexander Friedman and the Belgian astronomer George Lemaitre were able to formulate independently during the 1920s solutions to Einstein’s gravitational equations which predicted an expanding universe. That is to say, they predicted that the universe is actually growing apart. The monumental significance of this Friedman-Lemaitre model of the universe lay in the fact that it gave the universe a significant history. Up until this time people assumed that the universe was just eternal and unchanging and that it had always existed in a static form. As one commentator has remarked, up until this time the idea of the expansion of the universe was absolutely beyond comprehension. Throughout all of human history, he says, the universe was regarded as fixed and immutable and the idea that it might be actually changing was inconceivable. But if this Friedman-Lemaitre model were correct, the universe could no longer be treated adequately as a sort of timeless object. Rather, the universe has a history and time will be an important factor in our understanding the nature of the cosmos.

In 1929 the American astronomer Edwin Hubble showed that the light emanating from distant galaxies appears to be redder than it should. The reason for this, Hubble said, is because the galaxies are moving away from us and therefore the light from these distant galaxies is effected. If the galaxy is moving away from us then the light from the distant galaxies will be stretched – the wavelength will be stretched – and therefore it will appear to us redder than it would if the galaxy were not moving in relationship to us. This redshift that Hubble observed was universal. Everywhere in the night sky that he looked, he observed this same redshift.

Incredibly, what Hubble discovered was the expansion of the universe predicted by Friedman and Lemaitre on the basis of Einstein’s General Theory of Relativity. This marked a veritable turning point in the history of science. The physicist John Wheeler has said, “Of all the great predictions that science has ever made over the centuries, was there ever one greater than this, to predict, and predict correctly, and predict against all expectation a phenomenon so fantastic as the expansion of the universe?”[1]

So according to the Friedman-Lemaitre model, as time goes on the distances separating galaxies becomes greater.[2] It is important to understand that as a theory based upon the General Theory of Relativity, what this model describes is not the expansion of the material content of the universe into a preexisting empty space. Rather, what is described by the model is the expansion of space itself. The galaxies are actually thought to be at rest with respect to space, but they grow further and farther apart from each other because the space in between them is literally growing and therefore the galaxies recede from one another even though they are conceived to be at rest with respect to space. We can get an illustration of this by imagining a balloon with buttons glued to its surface. If we imagine this balloon with the buttons glued to its surface in the form of a triangle then as we inflate the balloon the buttons, though glued to the surface of the balloon, will get further and further apart. So even though the buttons are at rest with respect to the surface of the balloon the buttons recede from one another as the balloon inflates because the surface of the balloon is stretching – it is expanding. Those buttons on the surface of the balloon are just like the galaxies in outer space. As time goes on everything grows further and further apart as space expands.

This has the astonishing implication that as you reverse the expansion and go back in time everything gets closer and closer together until finally the entire universe is contracted down to a mathematical point before which the universe did not exist. That initial point is called a singularity. It represents the beginning – the edge – of space and time. P. C. W. Davies, who is a British physicist, describes that event in these words:

If we extrapolate this prediction to its extreme, we reach a point when all distances in the universe have shrunk to zero. An initial cosmological singularity therefore forms a past temporal extremity to the universe. We cannot continue physical reasoning, or even the concept of space-time, through such an extremity. For this reason most cosmologists think of the initial singularity as the beginning of the universe. On this view the big bang represents the creation event; the creation not only of all the matter and energy in the universe, but also of space-time itself.[3]

So not only all matter and energy, but physical space and time themselves came into being at the initial singularity.

Fred Hoyle, a Cambridge astronomer who was rather unhappy with this model of the universe, coined the derisive expression “Big Bang” to describe the Friedman-Lemaitre model of the expanding universe. Ironically, the expression caught on and stuck. So the model has now come to be known as the Big Bang model. This standard Big Bang model of the origin of the universe is the controlling model or paradigm for contemporary cosmology. On this model the universe is not eternal in the past. It has not always existed. Rather, the universe came into being at some point in the finite past. Moreover, and I want to emphasize this point, the origin that is described by the standard Big Bang model is an absolute origin out of nothing. Not only all matter and all energy, but even physical space and time themselves come into existence at the initial cosmological singularity. So as the physicists Barrow and Tipler emphasize, at this singularity space and time came into existence. Literally nothing existed before the singularity. So if the universe originated at such a singularity we would truly have a creation ex nihilo – that is, out of nothing.[4]

We can graphically represent space-time on this model as an inverted cone. On this model of the universe, space is represented by the horizontal slices of the cone and time is the vertical dimension. As you go back in time the spatial size of the universe just shrinks down and shrinks down until finally you come to the initial cosmological singularity before which the universe does not exist. So on this model of the universe, the universe comes into being out of nothing in the sense that at that initial singularity it is true that there is no earlier space-time point. That is what it means to say that the universe came into existence out of nothing. At the singularity it is true that there is no earlier space-time point. To put it another way, it is false that something existed prior to the singularity.

This conclusion is deeply puzzling for anybody who reflects on it deeply. The question cannot be suppressed – why does the universe exist? Sir Arthur Eddington, a scientist, contemplating the beginning of the universe said that the expansion of the universe was “so preposterous and incredible that I feel almost an indignation that anyone should believe in it, except myself.” He finally felt forced to conclude “the beginning seems to present insuperable difficulties unless we agree to look on it as frankly supernatural.” So the standard Big Bang model of the origin of the universe presents tremendous challenge to naturalism or atheism which thinks of the universe as eternal and uncaused, because on this model the universe is not eternal. It came into being a finite number of years ago, and that is, of course, the second premise of the cosmological argument.

Therefore many people have felt uncomfortable with this model of the origin of the universe, and they’ve tried to avoid it by crafting other models. Very often people will say to you when you share this information with them, “Oh, well, there are all these other theories of the origin of the universe and nobody knows which one is right and some of them don’t involve a beginning. There is no good evidence to think that the universe began to exist.” The fact of the matter is is the history of 20th century cosmology is, in a sense, a history of failed attempts to try to avoid the absolute beginning of the universe predicted by the standard Big Bang model. The devil is in the details, and once you look at the details what you discover is that there is no other theory of the origin of the universe which is as mathematically consistent or as confirmed by the evidence as the standard Big Bang theory. Let’s just do a review of some of the principal theories that have been proposed in order to try to avoid the beginning of the universe predicated by the standard Big Bang model.

The first of these theories was the steady state theory. This was proposed in 1948 by Fred Hoyle along with Hermann Bondi and Thomas Gold. According to this theory, the universe is in a state of cosmic expansion all right, but Hoyle believed as the universe expands new matter comes into being in the voids left by the retreating galaxies. So over time nothing really changes. We can illustrate this theory by means of the following diagram. On the steady state theory, as the galaxies expand and retreat from each other, new matter comes into being out of nothing in the voids left by the retreating galaxies. So even though the universe is expanding it never gets any less dense because new matter in contradiction to the first law of thermodynamics (which says that energy can never be destroyed or created) comes into being spontaneously out of nothing to replace the matter that is retreating away. On this model we can think of the universe as kind of like a rubber sheet with buttons glued on it.[5] As the sheet is stretched and the buttons recede from each other, new buttons come into existence out of nothing in the voids left by the retreating buttons. So the condition of the sheet will remain the same over time and therefore you don’t have to have any beginning of the process. As you trace the expansion back in time the galaxies never get any denser because as they approach each other the matter just vanishes. It just goes out of existence as you go back in time and the galaxies approach one another.

This state steady theory never secured a single piece of experimental verification. It was always trying to explain away the evidence rather than to predict or explain it. Moreover, the discovery of progressively more radio-galaxies at ever greater distances undermine the theory by showing that the universe was different in the past than it is today. That contradicts the idea that it is in a steady state. But the decisive nails in the coffin for the steady state theory came through two additional discoveries which constituted (by the way) in addition to the redshift of the light from distant galaxies two other important confirmations of the Big Bang theory. Namely, the synthesis of the light elements in the Big Bang and then also the so-called microwave background radiation.

Scientists believe that the heavy elements like carbon and iron and so forth were synthesized in the hot interior of the stars, but light elements like deuterium and hydrogen could not have been synthesized in the stellar interiors – the energies and temperatures simply aren’t high enough. Therefore, in order to explain the origin of these light elements you need to have the extreme temperatures and densities that were present in the Big Bang itself. No other furnace is available cosmically that would be able to synthesize these light elements.

With regard to the microwave background radiation, in 1965 a couple of scientists working for the Bell Telephone Laboratories named A. A. Penzias and R. W. Wilson discovered that the entire universe is bathed with a background of microwave radiation. This is the same kind of radiation that you use in your microwave oven at home. This radiation background in the universe is a relic or a vestige of an earlier very hot and very dense state of the universe. Since, in the steady state theory, no such condition of the universe could have ever existed, the steady state model was decisively discredited.

Therefore the steady state theory has now been laid to rest as a result of these clear cut observations of how the universe has changed over time.

The second alternative model to the standard Big Bang model that came along were oscillating models of the universe. Certain scientists thought that if the universe is dense enough then eventually the internal pull of its own gravity would overcome the force of the expansion, bring the expansion to a halt, and then with ever greater speed pull everything back together again into a kind of Big Crunch, the opposite of the Big Bang. The thought was that if the universe was not absolutely even in its matter distribution, then as the universe collapsed in upon itself some of the matter might pass by rather than collide so the universe would appear to re-expand again. It would exhibit a sort of bounce back to a new expansion. The thought was that then that expansion might be reversed by the force of gravity, it might come together again, and again if it didn’t have perfect smoothness of the matter is might miss as it collapses and then you would get another expansion. So on this model of the universe, the universe is sort of like an accordion – expanding and contracting, expanding and contracting, world without end, oscillating from eternity to eternity.[6]

This theory was extraordinarily speculative but it had metaphysical motivations behind it. The proponents of this model were bent on trying to avoid the implications of an absolute beginning of the universe. In 1970, however, the prospects for this sort of model were severely dimmed because two scientists named Roger Penrose and Stephen Hawking formulated what are called singularity theorems. These are equations about how singularities form. What Hawking and Penrose showed was that under very general conditions an initial cosmological singularity is inevitable for a universe that is under gravitational self-collapse. The universe’s matter would not pass each other by, rather, it would just suck right down like a black hole to a state of a singularity that would mark the very beginning of the universe. Hawking, reflecting on the implications of the singularity theorems that bear his and Penrose’s name said that these theorems led to the abandonment of attempts (mainly by the Russians) to argue that there was a previous contracting phase and a non-singular bounce into expansion. Instead, he says, almost everyone now believes that the universe and time itself had a beginning at the Big Bang.

Despite the fact that no space-time path can go through a singularity and that therefore the singularity marks an edge to space and time, this oscillating model exhibited a stubborn persistence even after the discovery of the Penrose-Hawking singularity theorems. But then three further strikes were lodged against it.

First of all, there are no known physics which could cause a collapsing universe to bounce back to a new expansion. If, in defiance of the Hawking-Penrose singularity theorems, the universe were somehow to bounce back, this would require a whole new physics which is completely unknown. Physics predicts that a universe collapsing upon itself will not bounce back like a basketball hitting the floor. Rather, it would be like a lump of wet clay hitting the floor – it will just collapse down into a singularity and end.

Secondly, the observational evidence has continued to indicate that the density of the universe is not sufficient to generate enough gravitational contraction in order to halt the expansion. Rather, the expansion would just go on and on forever and will not reverse. In fact, the most recent evidence discovered as of the year 2000 and since indicates that the expansion appears to be actually accelerating rather than slowing down. As the universe reaches a certain density, a kind of anti-gravity force of some nature kicks in, and the expansion of the universe actually accelerates. So it becomes even more difficult to explain how the universe could re-contract.

Finally, number three, the thermodynamic properties of an oscillating model predict the very origin of the universe that the proponents of this model sought to avoid. On the typical oscillating model, the universe expands and then re-contracts, and then it expands and re-contracts, and so on and so forth. But the thermodynamic properties of an oscillating model imply that entropy is preserved from cycle to cycle. This has the effect of generating a larger expansion radius and a longer expansion time. In other words, as you trace the cycles back in time they get smaller and smaller until you finally come to the smallest cycle and an origin of the universe. Therefore, in the words of the great Russian pair of physicists Zeldovich and Novikov, the multi-cycle model has an infinite future but only a finite past.[7] In fact, the astronomer Joseph Silk estimates on the basis of current entropy levels in the universe that the universe could not have gone through more than about 100 previous oscillations. Therefore, the thermodynamic properties of the oscillating model predicted the very origin of the universe that its proponents sought to avoid. The oscillating model, frankly, drew its life from the fact that it tried to avoid the beginning of the universe. But once other models became available that tried to offer the same benefit, then the oscillating model collapsed under the weight of its own evident deficiencies, and now is no longer taken as a serious alternative.

The next class of models that we want to think about are vacuum fluctuation models. It was soon realized that a physical description of the universe during its first fraction of a second of its existence would require the addition of quantum physics in addition to the General Theory of Relativity. Quantum physics is the physics of the subatomic realm. On this subatomic level, certain types of particles called virtual particles are thought to arise due to fluctuations in the energy that is locked up in the vacuum. These particles exist for just a fleeting moment before dissolving back into the vacuum again.

In 1973 a scientist named Edward Tryon speculated whether the universe itself might not be a long-lived virtual particle which was born out of the primordial vacuum. This seemingly bizarre speculation gave rise to a new class of models which we can call vacuum fluctuation models. On these models the universe that we observe is not really the whole universe. Rather, the universe that we observe is just a tiny part of a wider mother universe – a kind of universe as a whole. This wider mother universe is just an empty vacuum which is filled with energy at the subatomic level. Throughout this wider universe as a whole, fluctuations are forming which produce particles. By means of these fluctuations mini-universes are born within the womb of this mother universe. So we can diagram that in the following way. Again, imagine this is a corner of a box and the vertical dimension represents time and the two horizontal dimensions represent space. Throughout this wider universe, fluctuations in the energy are forming which grow into mini-universes. Ours is just one of these mini-universes that has formed within the wider mother universe as a whole. So the beginning of our universe doesn’t represent the beginning of the universe as a whole. It is merely a change in this eternal, uncaused universe as a whole.

These models are still bandied about in the popular press. You hear all the time in the popular press about the universe being a fluctuation formed out of the primordial vacuum or some such expression. But in fact these models did not outlive the decade of the 1980s among professional cosmologists. Not only were there all kinds of theoretical problems involved in them, but these models faced a deep internal incoherence, namely, according to these models it is impossible to specify just where and when a vacuum fluctuation would occur that would grow into a universe. At every point in space there is a positive probability within a finite interval of time that a universe will form there and grow into a universe like ours.[8] So what that means is that if there is a positive probability given enough time that a universe will form at any point in the vacuum then given an infinite past, given infinite time, universes will have formed at every point in the cosmic vacuum and then began to expand and so will begin to collide with one another and coalesce. So in infinite time these universes will have all run into each other so to speak and coalesce into one universe filling the entire vacuum of the mother universe. Therefore, given infinite past time, we should by now be observing an infinitely old universe, not a relatively young one as we do today.

Christoper Isham, who is Great Britain’s leading quantum cosmologists, has called this problem “fairly lethal” to vacuum fluctuation models. He says therefore they did not find wide acceptance. About the only way to avert this problem would be to posit an expansion of the primordial vacuum itself, but then of course you are right back to the original problem – that expansion would have an origin and require a finite past. So according to Isham these models were jettisoned about twenty years ago and nothing much has been done with them since.

The next alternative to come along to the standard model is the so-called chaotic inflationary model. One of the most fertile of the inflation theorists has been the Russian cosmologist Andrei Linde. According to the cosmologist Robert Brandenburger, Linde’s chaotic inflationary scenario is the only viable inflationary model in the sense that it is not plagued with internal inconsistencies in the way that the other models are. On Linde’s view, as the universe expands certain domains in it because to blow up and expand in a super-rapid way. They begin to inflate, as he calls it. When those domains reach a certain size or density then they also produce inflation. So you have a kind of eternal inflation into the future. So rather than the universe being like a balloon being blown up, it would be like a Mickey Mouse balloon where ears sprout out of the balloon, and then those ears sprout other ears, and so on and so forth ad infinitum.

On Linde’s chaotic inflationary model, each inflating domain of the universe inflates into another domain. It just keeps going on and on forever. Thus, on Linde’s view, the universe has an infinite future – it will just keep inflating and reproducing forever. But Linde is very troubled at the idea of the beginning of the universe. He writes as follows:

The most difficult aspect of this problem is not the existence of the singularity itself, but the question of what was before the singularity. . . . This problem lies somewhere at the boundary between physics and metaphysics.[9]

Between science and philosophy in other words. So what Linde says is that not only is inflation endless into the future, it is also beginningless into the past. Every domain in the universe is the product of inflation in some previous domain and that the product of some previous domain, and so on and so forth back to infinity. So the universe never began to exist. In this way, Linde says we can avoid the question of what came before.

In 1994, however, two scientists Arvind Borde and Alexander Vilenkin showed that a universe which is eternally inflating to the future cannot be beginningless in the past. That is to say, there must have existed at some place in the indefinite past an initial singularity. This is what Borde and Vilenkin wrote,

A model in which the inflationary phase has no end . . . naturally leads to this question: Can this model also be extended to the infinite past, avoiding in this way the problem of the initial singularity?

. . . this is in fact not possible in future-eternal inflationary spacetimes as long as they obey some reasonable physical conditions: such models must necessarily possess initial singularities.

. . . the fact that inflationary spacetimes are past incomplete forces one to address the question of what, if anything, came before.[10]

In his response to Borde and Vilenkin, Linde throws in the towel. He says, yes, I see it, there must have been a Big Bang singularity at some point in the past.

Thus far, what we’ve seen is none of these alternative models to avoid the beginning of the universe has provided a successful means of escape from the prediction of the standard model that the universe began to exist.

Next time we will look at two of the more recently proposed models to try to avoid the beginning of the universe and see whether or not they can do better than these failed predecessors.[11]

[1] John A. Wheeler, “Beyond the Hole,” in Some Strangeness in the Proportion, ed. Harry Woolf (Reading, Mass.: Addison-Wesley, 1980), p. 354.

[2] 5:11

[3] P.C.W. Davies, “Spacetime Singularities in Cosmology” in The Study of Time III, ed. J. T. Fraser (Berlin: Srpinger Verlag, 1978), pp 78-79.

[4] 10:09

[5] 15:06

[6] 20:03

[7] 25:01

[8] 29:58

[9] A. D. Linde, “The Inflationary Universe,” Reports on Progress in Physics 47 (1984): p. 9760.

[10] A. Borde and A. Vilenkin, “Eternal Inflation and the Initial Singularity,” Physical Review Letters 72 (1994): pp. 3305, 3307.

[11] Total Running Time: 36:18 (Copyright © 2007 William Lane Craig)