Big Bang may have been a Big Bounce, ABC / Discovery News, Larry O'Hanlon, 24 May 2006 ...
[Graphic & legend see PhysOrg.com]
I have split this post into two parts because I want to add some more comments from a Christian perspective about the Big Bang and what if there was a "before" it.]
... If their new mathematical simulations are correct, what came before the Big Bang was a previous universe a lot like our own. [And Oh, what a big "if"! How could any cosmologist know that his/her "mathematical simulations are correct" of what happened "before the Big Bang" (assuming there even can be such a `time' - see below) in "a previous universe"? There is no way to re-run the origin of the Universe to experimentally test such simulations. All that such simulations could do is be tweaked until they are consistent with the known evidence.
But then there are many cosmologists who each have their own, mutually exclusive, "mathematical simulations" that have been tweaked until they are consistent with the known evidence. The problem they all have is something that affects all historical sciences (i.e. sciences of past unique and unrepeatable events), and that is, "the problem of equifinality," namely "the fact that different processes can lead to similar end-forms":
"The problems of explanation in physical geography caused by the number of factors involved and their interaction, by the difficulties of scale, by the frequency of change and by the problem of deciphering the role of man as against that of nature are heightened by the fact that different processes can lead to similar end-forms - the problem of equifinality. When seeking an explanation for a particular phenomenon it is important to remember that, although certain phenomena appear to be broadly similar in type, their form may be an inadequate guide to their origin. One should not be dogmatic as to the origins of many natural phenomena. ... When conducting one's own fields investigations, therefore, it is necessary to adopt the principal of multiple working hypotheses, seeking to formulate and test as many explanations as possible." (Goudie A., "The Nature of the Environment," , Basil Blackwell: Oxford UK, 1989, Second edition, 1990, reprint, p.340. Emphasis in original)
So there is simply no way that cosmologists could ever know that their particular theory of "what came before the Big Bang" was what actually happened.
That is assuming that there even can be a "before the Big Bang," which would be a time before time, a self-contradictory absurdity. Paul Davies points out that "it is not possible to extend space and time through ... a singularity" and therefore "the big bang must be the origin of time itself," therefore "there was no `before' for anything to happen in":
"Clearly, if the universe is growing bigger, it must have been smaller in the past. We can imagine running the great cosmic movie backwards until all the galaxies are squashed together. This compressed state corresponds to the time of the big bang, and in a certain sense the expansion of the universe can be considered as a vestige of that initial explosion. Today it is normal for cosmologists to claim that the universe began with the big bang. This weighty conclusion follows if you trace the expansion back in time to some idealized point of origin at which all the matter of the universe is concentrated in one place. Such a state of infinite density represents an infinite gravitational field and infinite spacetime curvature -i.e., a singularity. The big-bang singularity is similar to the situation at the center of a black hole that I described in the previous chapter, but lying in the past rather than the future. As it is not possible to extend space and time through such a singularity, it follows that the big bang must be the origin of time itself. People, especially journalists who get angry about scientists explaining everything, often ask: What happened before the big bang? If this theory is correct, the answer is simple: nothing. If time itself began with the big bang, there was no `before' for anything to happen in. Although the concept of time being abruptly `switched on' at some singular first event is a hard one to grasp, it is by no means new. Already in the fifth century, Augustine proclaimed that: `The world was made, not in time, but simultaneously with time.' [Augustine, "Confessions," Penguin, 1961, p.294] Keen to counter jibes about what God was doing before he made the universe, Augustine placed God outside of time altogether, making him the creator of time itself. ... the idea of time coming into being with the universe therefore fits very naturally into Christian theology. ... we shall see that recent ideas in quantum physics have changed our picture of the origin of time somewhat, but the essential conclusion remains the same: time did not exist before the big bang." (Davies, P.C.W., "About Time: Einstein's Unfinished Revolution", Penguin Books: London, 1995, pp.131-132. Emphasis original)
And Stephen Hawking noted that, "even if there were events before the big bang, one could not use them to determine what would happen afterward, because predictability would break down at the big bang" and so "we could not determine what happened beforehand" and "events before the big bang ... should not form part of a scientific model of the universe":
"All of the Friedmann solutions have the feature that at some time in the past (between ten and twenty thousand million-years ago) the distance between neighboring galaxies must have been zero. At that time, which we call the big bang, the density of the universe and the curvature of spacetime would have been infinite. Because mathematics cannot really handle infinite numbers, this means that the general theory of relativity (on which Friedmann's solutions are based) predicts that there is a point in the universe where the theory itself breaks down. Such a point is an example of what mathematicians call a singularity. In fact, all our theories of science are formulated on the assumption that space-time is smooth and nearly flat, so they break down at the big bang singularity, where the curvature of space-time is infinite. This means that even if there were events before the big bang, one could not use them to determine what would happen afterward, because predictability would break down at the big bang. Correspondingly, if, as is the case, we know only what has happened since the big bang, we could not determine what happened beforehand. As far as we are concerned, events before the big bang can have no consequences, so they should not form part of a scientific model of the universe. We should therefore cut them out of the model and say that time had a beginning at the big bang. Many people do not like the idea that time has a beginning, probably because it smacks of divine intervention. ... There were therefore a number of attempts to avoid the conclusion that there had been a big bang." (Hawking, S.W., "A Brief History of Time: From the Big Bang to Black Holes," , Bantam: London, 1991, reprint, p.50) ]
It collapsed on itself, then some weird physics caused it to inflate into the universe we have today. Physicist Dr Abhay Ashtekar of Pennsylvania State University and team publish their results in a recent issue of Physical Review Letters. .... To peer into that unimaginable crush, Ashtekar and colleagues started again without assuming that the "fabric" of space-time continuum existed in the earliest moments of the universe. "The general belief is that the continuum may be just an approximation," says Ashtekar. ...[So their entire theory depends on that assumption, that there was no "space-time continuum" existing at "the earliest moments of the universe." But then how can they meaningfully speak of "space" and 'time" if there was none?]
Instead, the team applied what's called loop quantum gravity, a strategy that has been developed to join quantum physics with Einstein's General Relativity. ... Using this concept, the researchers concluded that a previous universe collapsed in on itself in a gigantic gravitational Big Crunch. Then, when the density of that crunch reached super astronomical values, gravity flipped into a repulsive force - another weird outcome of this physics - and inflated the new universe in which we live. [It sounds like this "loop quantum gravity ... strategy" just an excercise in circular reasoning? That is, it is hand-crafted' to get around the singularity? If so, it cannot non-circularly be used to prove that there was no singularity.]
"It's long been speculated that as you get to the Big Bang, quantum theory was going to be important," says physicist Dr Jorge Pullin of Louisiana State University. It's also been speculated that if you could work out the equations, you'd probably see that the Big Bang was a Big Bounce, he says. But this is the first time that anyone has actually done a thorough job working through the physics back through the Big Bang, he says. ... As for what it tells us about the previous universe, it's not much, says Pullin. [This is because of astrophysicist Robert Jastrow's point that, "in the first moments of its existence the Universe was compressed to an extraordinary degree" and "The shock of that instant must have destroyed every particle of evidence that could have yielded a clue to the cause" and even if something "may have existed before our Universe appeared" (assuming that there can be a "before") "if it did, science cannot tell what ... it was":
"Consider the enormity of the problem. Science has proven that the Universe exploded into being at a certain moment. It asks, What cause produced this effect? Who or what put the matter and energy into the Universe? Was the Universe created out of nothing, or was it gathered together out of preexisting materials? And science cannot answer these questions because, according to the astronomers, in the first moments of its existence the Universe was compressed to an extraordinary degree, and consumed by the heat of a fire beyond human imagination. The shock of that instant must have destroyed every particle of evidence that could have yielded a clue to the cause of the great explosion. An entire world, rich in structure and history, may have existed before our Universe appeared; but if it did, science cannot tell what kind of world it was. A sound explanation may exist for the explosive birth of our Universe; but if it does, science cannot find out what the explanation is. The scientist's pursuit of the past ends in the moment of creation. This is an exceedingly strange development, unexpected by all but the theologians. They have always accepted the word of the Bible: In the beginning God created heaven and earth." (Jastrow, R., "God and the Astronomers," , W.W. Norton: New York NY, Second edition, 1992, p.106) ]
"The only thing you can conclude is that the bounce occurs," he says. [No - one cannot "conclude ... that the bounce occurs" if that is a starting assumption of the theory, and of the "loop quantum gravity ... strategy." In that case it would just be circular reasoning, concluding to be true what one had already assumed to be true in the premises. To be continued in part #2.]