Now that I'm at the beginning of my final year of studies (Q77), I've been reading through the books for my courses, to get a heads up for the official start of my modules. Today I finished a cursory readthrough of Block One of Mathematical Methods and Fluid Mechanics, and hence began to read the first chapter of Observational Cosmology for The Relativistic Universe. And in doing the latter, I came to find myself reflecting on a physics theory about the Big Bang.
We ask "Where did the big bang occur?" and we are given various answers: The universe began everywhere, at every point of space and time, etc. We ask, "If the universe is expanding, what is it expanding into?" and it is suggested that, since the big bang happened at all points of space and time, it is not really expanding into anything; moreover, it is just expanding. We ask, "What happened before the big bang?" and we find that there are various answers - Penrose suggests conformal cyclic cosmology; that the universe is composed of a multitude of previous universes, that somehow information seeps through from past epochs to present epochs and from present epochs to subsequent epochs. I am no expert on the latter theory, but I like it, yet I have to work out the details, etc. But it is also said that there was nothing before the big bang, because that is where the universe began, including matter, radiation, gravity, space and time. That is, the big bang constitutes the beginning of time itself.
I found myself previously unable to imagine this idea, of time having a beginning. But when we look at that other cosmological idea, black holes, we often hear of those infinite solutions to Einstein's field equations, namely, singularities. These are the objects at the centre of a black hole, and have infinite curvature and infinite mass (I think), and from them nothing (bar Hawking radiation) can escape.
It is said that the beginning of the universe constitutes such a singularity; that the universe came from this singularity. Now it makes sense to me that this latter notion could be true.
It is a known fact of physics that time runs slow for moving clocks. That is, in the strength of a gravitational field, observers find clocks run slow. And now time runs slow for moving clocks, consider this: At the beginning of the universe, when all in existence was a singularity, this singularity must, from its infinite curvature, have contained time in its slowest form known, namely, a grinding halt!
That is, if moving clocks run slow, and singularities constitute the required infinite curvature, time at the beginning of the universe, before the big bang, must have been very, very slow.
So time did exist at the beginning of the universe, but it was at a full stop. This was the beginning of time.
Now, if that is true, then it is viable to consider that after the big bang happened, and thus time was born, there must have been a period in which time was able to "get up to speed". It so happens that such a period has been suggested, namely, inflation.
But could it be possible that all moments from the big bang up until and including now were part of this inflationary period? The big bang is in the distant past, but perhaps we are more related to it than we know?
Anyway, in short, that's the theory. In the beginning of the universe time was so slow that it was effectively stopped. Somehow, this was disrupted, and there was a period of inflation in which time increased to the pace we feel it today.
There are other theories, some claiming that lightspeed was faster in the distant past. I feel this accords with this little idea I've been explaining.
Anyway, it's time for sleep.
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