mercredi 30 mars 2022

How does General Relativity conclude that there is a Big Bang?

The mods can merge this with the other currently active thread but I thought that this specific question should be considered only from the GR point of view without all of the other baggage that generally gets thrown into "origin of the universe" debates.

We are constantly told that thanks to GR, we know that the universe has an origin. We refer to that origin as the "Big Bang". Descriptively, it says that all space-time existed as a singularity and started expanding and hasn't stopped expanding since.

To me, that suggest that there must be a series of calculations in GR that suggest that the point (0, 0, 0, 0) actually exists in this universe (and presumably it is the same point in all reference frames). This point represents the origin of the universe at t=0.

However, in my research, I find no such calculations. Instead, I find that data shows that the universe is expanding and if we extrapolate backwards, we would at some point get the singularity. Maybe GR loops time into all of this but I don't see how we could say that if it wasn't for GR we would not be able to extrapolate the data backwards.

Maybe some people more knowledgeable than me could weigh in.


via International Skeptics Forum https://ift.tt/SuTfWlY

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