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New Proofs for the Existence of God
Contributions of Contemporary Physics and Philosophy
By Robert J. Spitzer
William B. Eerdmans Publishing Company
Copyright © 2010 Robert J. Spitzer
All right reserved.
Chapter One Indications of Creation in Big Bang Cosmology
The General Theory of Relativity, Hubble's redshifts, Penzias's and Wilson's universal background radiation, black holes, quantum cosmology, inflationary theory, and a host of other ideas and discoveries have led to a grand scheme of universal origins called the "Big Bang theory." In the view of many physicists, this remarkable cosmological theory points to a creation event as well as an ordered unfolding of the universe.
I. The Big Bang Theory
What the Big Bang theory says is that everything in the "observable universe" is the remnant of a huge explosion called the big bang that took place about 13.7 billion years ago. (The term "observable universe" is used to refer to that portion of the universe that can be observed at the present time from earth. There is a "horizon" beyond which we cannot see, no matter how powerful the telescopes we use, because light has simply not had time since the big bang to reach us from more distant places. As time goes on, more and more of the universe will be observable to us. In a billion years from now, if we are still here, we shall be able to see a billion light-years further). While people still talk of the Big Bang "theory," it is no longer doubted by cosmologists that the big bang actually happened, i.e., that it is a historical fact. In science the word "theory" does not necessarily imply that an idea is merely a hypothesis. Often it means a very solidly established and well-tested explanation of a body of phenomena, in which case it is regarded as "the theory," the correct theoretical explanation of the experimental and observational data. (One talks about the "BCS theory" of superconductivity, for example, despite its having been completely confirmed as correct). Moreover, cosmologists think they have a fairly good overall picture of the history of the observable universe since the big bang. What, if anything, may have happened before the big bang and what may exist beyond the bounds of the observable universe (i.e., beyond the "horizon" of what can be seen from our place in the universe) is the subject of much speculation, some of it reasonable and some of it pretty wild. The generally agreed-upon "overall picture" of what has happened within the observable universe since the Big Bang is sometimes called the "standard" model of cosmology.
In the standard model of cosmology, space-time is described by Einstein's theory of gravity, which is called General Relativity. According to Einstein's theory, space-time is a four-dimensional manifold, which acts somewhat like an elastic medium. It can stretch, warp, and vibrate. When cosmologists say that the universe is expanding, they do not simply mean that objects within the universe are flying away from each other through space, they mean that space itself is stretching. Galaxies that are very distant from each other are getting farther apart, not because they are moving through space (which is a relatively small effect), but because the space in between them is getting stretched out. In an analogy that is often used to explain this expansion, the universe is likened to the surface of an expanding balloon with all of the galactic clusters like little spots painted on the surface of the balloon. As the universe (balloon) expands, the galactic clusters (paint spots) all move away from one another. So, it is not that the paint spots are sliding over the balloon's surface (though they are a bit), but instead the balloon has more area (or in the case of the universe, volume).
All of this stretching of space is described by Einstein's theory. How space-time stretches and warps is determined by the matter and energy filling the space and how it is distributed. In the vicinity of a massive object like the earth, for instance, space-time is warped in such a way that objects moving near the earth have their trajectories affected, and they seem to be attracted to it by the "force" of gravity. In the Big Bang theory, the fact that the galaxies are flying apart from each other is explained by the space of the universe expanding. As one looks back in time, the galaxies were closer together, because there was actually less space! The farther back one looks, the smaller the distance between galaxies was. Extrapolating back, one can deduce that all the matter in our observable universe would have been in the same place about 13.7 billion years ago. In fact, they had to be in the same place, because the volume of space of our presently observable universe was —13.7 billion years ago—either zero or very close to zero. At that point, all the matter we see in the universe today (i.e., that is now within our horizon) was compressed into a fantastically dense, hot mass, which flew apart with inconceivable speed—an explosion.
Fr. Georges Lemaitre, the Belgian physicist (and priest) who proposed the Big Bang theory, called this dense hot mass the "primeval atom." We now call it, and the explosion which emanated from it, the big bang. Lemaitre was one of the first people to realize that Einstein's theory of gravity implied an expansion of space, and he combined this idea with the fact that galaxies were observed to be receding from each other to come up with the Big Bang theory. The recession of the galaxies from each other was discovered in 1929 by the American astronomers Hubble and Humason, following up on earlier work of Slipher. This is now called the "Hubble expansion."
There was a lot of skepticism about Lemaitre's Big Bang theory at first. The idea of a beginning of the universe was unpalatable to not a few scientists, because it seemed too much like a religious idea. But also, there was for a time some evidence that didn't seem to square with it. In particular, the age of the universe (deduced from the recession of the galaxies in the Big Bang theory) came out less than the age of stars and planets (deduced in other ways). It was then discovered that the calculation of the recession speeds had been in error by a significant factor, and this objection went away. The breakthrough happened with the discovery by Penzias and Wilson in the 1960s of the so-called Cosmic Microwave Background Radiation (CMB or CBR for short), whose characteristics were consistent with its being the light from the Big Bang explosion, once very intense, but now made very faint (and red-shifted into microwaves) by billions of years of cosmic expansion. Very precise measurements and refined mathematical analyses of this radiation (and, in particular, of the tiny fluctuations in its intensity in different parts of the sky) show a complex structure that is in remarkable agreement with the predictions of the Big Bang theory. Also, calculations based on the Big Bang theory correctly account for the relative amounts of the smaller elements (especially hydrogen and helium) in the universe. There are other pieces of confirmatory evidence, so that by now there is no serious doubt that the big bang happened.
The details of the Big Bang theory have undergone refinement from the time Lemaitre proposed it to the present. One refinement was the idea of a brief period in the first moments after the big bang when the universe suddenly underwent a huge increase in size. We shall mention this "inflationary era" again shortly. There are several powerful theoretical reasons to believe that such an inflationary period occurred (that we needn't get into), and there are now several predictions of this idea that have been confirmed. Another refinement is the discovery of dark matter. Several pieces of evidence point to the fact that about a quarter of the mass in the universe is in the form of particles that do not emit or absorb light. This is called "dark matter." It is not yet known what these particles are—they cannot be any of the kinds we already have seen in the laboratory.
A third refinement has been the discovery of dark energy, not to be confused with dark matter. For most of the history of the universe (at least the history of the part we can now observe), the expansion of the universe slowed with time. Basically that is because all the matter of the universe is mutually attracting by gravity, and that tends to oppose matter flying apart. In 1998, it was discovered that several billion years ago the expanding universe actually started to speed up! This implied the existence of some matter in the universe which gravitates differently from ordinary matter. This dark energy is not made up of particles, but is more like a "field."
Further refinements will undoubtedly be required to describe the very first moments of the big bang for the following reason. Almost all the history of the observable universe after the big bang can be described using Einstein's theory of gravity—General Relativity—in its "classical" (meaning "non-quantum") form. For an exceedingly brief era right at the big bang, however, within a so-called "Planck time" of the big bang, it is known that a classical description of gravity does not suffice. (A Planck time is 10-43 seconds.) The mass densities during this "Planck era" would have been so large that quantum gravity effects would have been important and the mathematics of classical General Relativity would therefore not be adequate to describe them. What is needed to describe physics in the Planck era is a theory of gravity that fully incorporates the principles of quantum mechanics. At the moment, only one such theory is known, and it is called "superstring theory." But people do not yet understand how to calculate in superstring theory well enough to handle the Planck era. In any event, all these refinements — post-Big Bang inflation, dark energy, dark matter, and quantum effects in the Planck era—are now part of the standard Big Bang model of cosmology.
A common misconception is that the big bang says that the universe has a finite size. People think this because they reason that if the universe started at zero size and has been in existence for only a finite time, then it can only have gotten to a finite size. But the standard Big Bang model allows for both the possibility that the universe is finite in size (the so-called "closed universe" case) and the possibility that it is infinite in size (the so-called "open universe" case). In the closed universe case, space-time curves around on itself, analogous to the way the surface of a balloon curves around on itself, and just as the balloon's surface is finite in area but has no edges, the closed universe has a finite volume but no edges. In the open universe, space curves but goes on forever in every direction. How then can an infinite "open" universe be said to expand? Think of a closed universe as being not a balloon but an infinite sheet of rubber. Again, the clusters of galaxies are painted on the rubber. Imagine now the whole sheet of rubber being uniformly stretched in every direction—the sheet is still infinite, but now all the little spots of paint are stretched farther apart from each other. No one knows if the universe is open or closed. What determines this is a parameter called ω (omega) that is related to the average energy density in the universe and also to how curved three-dimensional space is at some time after the Big Bang. If ω > 1, the universe is closed. If ω < 1 it is open. In fact, W is observed to be very close to 1. Moreover, there are theoretical arguments that suggest that it is so close to 1 that we shall never be able to measure it accurately enough to tell if it is just a bit less or a bit more than 1. Whether the universe is open or closed will be a hard thing to find out—maybe impossible. But whether it is open or closed, the same arguments that tell us that ω is very close to 1 also imply that the universe is probably vastly bigger than the part we can see, i.e., the part within our horizon.
The simplest version of the standardmodel of cosmology assumes that it describes the whole universe. In other words, it assumes (a) that there was no universe "before" the big bang, and (b) that the part of the universe beyond the "horizon" looks essentially the same as the part within the horizon. It is important to emphasize that there is at the moment not a shred of empirical evidence that these two assumptions are wrong. The simple version of standard cosmology, which makes these assumptions, we shall call the Standard Big Bang Model (SBBM). In the Standard Big Bang Model, the big bang was actually the beginning of the universe in a very strong sense: it was the beginning of time itself (and of space too). Thus, in the Standard Big Bang Model it is quite meaningless to ask what went on "before" the "big bang"—there was no "before." This is a very difficult concept to grasp. How can there not be a "before" the big bang? The physicist answers this as follows: Time is a feature of the physical universe. It is something physical, just like atoms or light. Time and space form a manifold that, as we noted, can stretch, warp, and vibrate. Since time is just a physical part of our physical universe, it follows that if the physical universe had a beginning, then time and space themselves began then too.
Interestingly, the first person to understand this was not a physicist, but a bishop: St. Augustine of Hippo (A.D. 354-430). Ancient pagans had taunted Christians and Jews for believing that the universe had a "Beginning." What, they asked, was God doing for the infinite time preceding this Beginning? Why did he wait so long—infinitely long—to get things started? St. Augustine gave an answer that deeply impresses modern cosmologists. He said that there was no time "before" the Beginning. His argument was theological, but parallels the argument of the modern cosmologists. Time, noted Augustine, is something created—it is not God, so it must be something created by God. Therefore, if the created world had a beginning, then time had a beginning too. There could not have been time passing before the Beginning, since if time was passing, that meant something (namely time) had already been created. He said that it was meaningless to ask what God was doing "before" the beginning because there was no "before": "Do not ask what [God] was doing 'then', there was no 'then' where there was no time." As the physicist Steven Weinberg noted, it is common in research papers on quantum cosmology to quote the very prescient comments made by St. Augustine in his famous discussions of time. In any event, in the Standard Big Bang Model, time itself has a beginning at the big bang.
However, a variety of modifications and extensions of the SBBM have been proposed over the years that postulate things happening before the big bang. In one extension, it is supposed that the universe has undergone many cycles of expansion and contraction and will undergo many more—perhaps ad infinitum—with the big bang having been just the beginning of the latest cycle. This is usually called the "bouncing universe" scenario.
Another speculative scenario supposes that the observable universe is a part of an island, as it were, that is one of many islands within a much vaster universe. In each of these islands, space is expanding in a relatively slow and sedate way. For example, in our island, it takes billions of years for the universe to appreciably increase its size. But between these islands, the universe is supposed to be doing something very different: it is undergoing an extremely rapid "exponential expansion"—in fact, doubling in size every 10-40 seconds, in a typical version of this scenario. When the universe, or some part of it, is undergoing exponential expansion, it is said to be "inflating." Such exponential expansion is described by a solution to Einstein's equations of gravity that was found in the 1920's by a physicist named Willem de Sitter. Thus, a universe, or part of one, that is inflating exponentially is said to be in a de Sitter phase. The speculative scenario we are talking about is called the "eternal inflation" scenario. In this scenario, the big bang was not the beginning of the whole universe, but only the formation of our "island."
Excerpted from New Proofs for the Existence of God by Robert J. Spitzer Copyright © 2010 by Robert J. Spitzer. Excerpted by permission of William B. Eerdmans Publishing Company. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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