Question

explain eternal inflation theory.

100 points

Answer 1

Hey Mate

Inflation is the idea that the universe expanded massively around the time of the big bang.  There are a lot of reasons for thinking that inflation happened and you can find them all over quora.

However, from a physics point of view, getting inflation is really easy.  The hard part is to get inflation to *stop*.  The universe is expanding massively, then it's really hard to find a mechanism to get the universe to slow down to "ordinary" expansion.

Eternal inflation is the idea that most of the universe *doesn't* stop inflating.  The idea is that you can create a mechanism that causes our part of the universe to stop expanding (via quantum mechanical tunneling), but that this is just our small part of the universe, and most of the universe has *always* been inflating and always will be inflating.

That fixes the "so how do you get the universe to stop inflating", and it also deals with what happened before the big bang (i.e. we are in a much bigger universe that is always expanding rapidly forever, and our part of that bigger universe is unique only that it stopped expanding rapidly and started expanding at "normal" speeds.)

Answer 2

Answer:

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In modern cosmological models, the very, very early Universe was dominated by a period of exponential growth, known as inflation. As inflation stretched and smoothed the expanding space, particles that were once right next to each other would soon find themselves at the edges of each other’s cosmological horizons, and after that they wouldn’t be able to see each other at all. It was a time of little matter and radiation — an almost complete void except for the immense vacuum energy that drove the expansion.