Why is there something rather than nothing? (Humans)

by dhw, Sunday, April 03, 2011, 22:39 (4779 days ago) @ David Turell

DAVID: This is an interesting commentary that discusses the possibility of God:-http://preposterousuniverse.com/writings/dtung/-Once again, many thanks to David for an article which I can't recommend too highly. Sean Carroll sets out with wonderful clarity the current theories about the universe, their shortcomings, and their implications. He is obviously sceptical about the God theory, but his scepticism is totally rational and admirably free from polemic. I've picked out three passages which seem to me highly relevant to all our previous discussions, including the one on time:-"One sometimes hears the claim that the Big Bang was the beginning of both time and space; that to ask about spacetime "before the Big Bang" is like asking about land "north of the North Pole." This may turn out to be true, but it is not an established understanding. The singularity at the Big Bang doesn't indicate a beginning to the universe, only an end to our theoretical comprehension. It may be that this moment does indeed correspond to a beginning, and a complete theory of quantum gravity will eventually explain how the universe started at approximately this time. But it is equally plausible that what we think of as the Big Bang is merely a phase in the history of the universe, which stretches long before that time ... perhaps infinitely far in the past. The present state of the art is simply insufficient to decide between these alternatives; to do so, we will need to formulate and test a working theory of quantum gravity."-"There are a number of avenues currently being explored by physicists that hope to provide a complete and self-contained account of the universe, including the Big Bang. Roughly speaking they can be divided into two types: "beginning" cosmologies, in which there is a first moment of time, and "eternal" cosmologies, where time stretches to the past without limit."-"The issue of whether or not there actually is a beginning to time remains open. Even though classical general relativity predicts a singularity at the Big Bang, it's completely possible that a fully operational theory of quantum gravity will replace the singularity by a transitional stage in an eternal universe. A variety of approaches along these lines are being pursued by physicists: bouncing cosmologies in which a single Big Crunch evolves directly into our observed Big Bang, [7] cyclic cosmologies in which there are an infinite number of epochs separated by Big Bangs, [8] and baby-universe scenarios in which our Big Bang arises spontaneously out of quantum fluctuations in an otherwise quiet spacetime. [9] There is no way to decide between beginning and eternal cosmologies on the basis of pure thought; both possibilities are being actively pursued by working cosmologists, and a definitive judgment will have to wait until one or the other approach develops into a mature scientific theory that makes contact with observations."