Posted: Jan 15, 2012 8:11 pm
Teuton wrote:"All the evidence we have says that the universe had a beginning." – Alexander Vilenkin
"[The Borde-Guth-Vilenkin theorem] has been used by William Lane Craig to argue that the universe itself had to have a beginning. We saw that cosmologists I contacted, including Vilenkin, Carroll, and Aguirre, all of whom have published works on the subject, agreed that no such conclusion is warranted."
(Stenger, Victor J. The Fallacy of Fine-Tuning: Why the Universe is not Designed for Us. Amherst, NY: Prometheus, 2011. p. 145)
Are there two Vilenkins or is there one schizophrenic Vilenkin?
"I contacted Aguirre and Vilenkin, the latter whom I have known professionally for many years. I greatly admire the work of each, which will be referred to often on these pages. I first asked Vilenkin if Craig's statement is accurate. Vilenkin replied:
'I would say this is basically correct, except the words “absolute beginning” do raise some red flags. The theorem says that if the universe is everywhere expanding (on average), then the histories of most particles cannot be extended to the infinite past. In other words, if we follow the trajectory of some particle to the past, we inevitably cometo a point where the assumption of the theorem breaks down—that is, where the universe is no longer expanding. This is true for all particles, except perhaps a set of measure zero. In other words, there may be some (infinitely rare) particles whose histories are infinitely long.'
…
I then asked Vilenkin, “Does your theorem prove that the universe must have had a beginning?” He immediately replied,
'No. But it proves that the expansion of the universe must have had a beginning. You can evade the theorem by postulating that the universe was contracting prior to some time.'
Vilenkin further explained,
'For example, Anthony in his work with Gratton, and Carroll and Chen, proposed that the universe could be contracting before it started expanding. The boundary then corresponds to the moment (that Anthony referred to as t = 0) between the contraction and expansion phases, when the universe was momentarily static. They postulated in addition that the arrow of time in the contracting part of space-time runs in the opposite way, so that entropy grows in both time directions from t = 0.'
…
I also checked with Caltech cosmologist Sean Carroll, whose recent book From Eternity to Here provides an excellent discussion of many of the problems associated with early universe cosmology. Here was his response:
'I think my answer would be fairly concise: no result derived on the basis of classical spacetime can be used to derive anything truly fundamental, since classical general relativity isn't right. You need to quantize gravity. The BGV [Borde, Guth, Vilenkin] singularity theorem is certainly interesting and important, because it helps us understand where classical GR breaks down, but it doesn't help us decide what to do when it breaks down. Surely there's no need to throw up our hands and declare that this puzzle can't be resolved within a materialist framework. Invoking God to fill this particular gap is just as premature and unwarranted as all the other gaps.'
(Stenger, Victor J. The Fallacy of Fine-Tuning: Why the Universe is not Designed for Us. Amherst, NY: Prometheus, 2011. pp. 127-30)