Jul 20th 2017, 05:16 PM
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| Physics Team
Join Date: Apr 2009 Location: Boston's North Shore
Posts: 1,574
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Originally Posted by NikPerk  How could we know anything that happened before the big bang? The question cannot be answered. |
I disagree. At this point in time nobody has figured out a way to adduce what happened even at the moment of the big bang, if such a moment exists. That cannot be taken to imply that we never will.
I've been strongly influenced by Peebles text on cosmology in which he wrote on page 6 |
If there were an instant, at a "big bang," when our universe started expanding, it is not in the cosmology as now accepted, because no one has thought of a way to adduce objective physical evidence that such an event really happened.
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My point being that just because nobody has to date "thought of a way to adduce objective physical evidence that such an event really happened" it doesn't mean that nobody ever will. In fact I'm sure that proponents of the Pre-Big Bang Scenario would agree with this point.
A friend of mine pointed out to me the following recently
We don't know whether the first moment of the Big Bang (the moment of maximum contraction) was a singularity; and even if it was, the singularity would have had distinctive properties that somehow had to be imposed on the universe.
There are good reasons to suppose that the Einstein equations at extreme curvature might have higher-order modifications, that is, terms quadratic or higher in the Riemann curvature. Such terms can prevent the universe from becoming singular, so the Big Bang merely represents a moment of maximum, but finite, curvature. Geodesics could then be extrapolated backward through the Big Band, and the state of the pre-Big Bang universe would determine the state after.
And even if we assume that the Big Bang was a true singularity, there are different kinds of singularities, for instance, in the Friedmann models, the closed, open, and flat cases all have singularities at t = 0, but these singularities are distinct, even at t = 0.
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We were discussing the BS comments made by Hawking at The Beginning of TIme - Stephen Hawking |
Since events before the Big Bang have no observational consequences, one may as well cut them out of the theory, and say that time began at the Big Bang. Events before the Big Bang, are simply not defined, because there's no way one could measure what happened at them. This kind of beginning to the universe, and of time itself, is very different to the beginnings that had been considered earlier. These had to be imposed on the universe by some external agency. There is no dynamical reason why the motion of bodies in the solar system can not be extrapolated back in time, far beyond four thousand and four BC, the date for the creation of the universe, according to the book of Genesis. Thus it would require the direct intervention of God, if the universe began at that date. By contrast, the Big Bang is a beginning that is required by the dynamical laws that govern the universe. It is therefore intrinsic to the universe, and is not imposed on it from outside.
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Hawking is an example of a brilliant man who makes dumb statements. That's why I don't follow his work. I was told that he claims all black holes will eventually evaporate from Hawking radiation. What Hawking fails to mention is that all black holes are absorbing the 3k CMBR and interstellar material while at the same time emitting Hawking radiation. Its far from clear whether all the 3k radiation will disappear at some point in time or that interstellar space well ever become a perfect vacuum. If it will then Hawking neglected to mention that fact in the book in which he made that claim.
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