Lecture 41 - Eternal Inflation and Multiverse

“It’s hard to build models of inflation that don't lead to a multiverse. It’s not impossible, so I think there’s still certainly research that needs to be done. But most models of inflation do lead to a multiverse, and evidence for inflation will be pushing us in the direction of taking [the idea of a] multiverse seriously.” ― Alan H. Guth

In 1983, Andrei Linde forcefully argued that inflation (exponential expansion) does not require a cosmological phase transition, or any contrived potential. Rather, it is a ‘generic cosmological regime’. If one accepts this, then one of the possibilities is that “inflation is eternal” and the universe constantly “reproduces itself”. This is the concept of the MULTIVERSE – an infinitely large number of universes. This raises many questions such as the following. Will the ‘laws of physics’ be the same in all the universes? Will the fundamental constants of nature have the same values in all the universes? Was there a beginning to the universe? If so, how did this “creation” happen, and what was there before the beginning? In this final lecture of this series, I shall discuss many of these fascinating but speculative ideas.