Within popular science, cosmic inflation is a highly discussed and rather popular topic. Why not? It basically explains why the universe looks the way it does, right? Well, that really depends on who you ask. Instead of going into a long discussion on inflation today, I decided to sum up almost every lecture on inflationary pocket universes I’ve been to with series of sarcastic Pokémon-themed panels (Why, Pokémon, you ask? You clearly haven’t been to enough lectures on “Pocket Universes”).
(If for some reason you want it all as a single image).
The universe started out very, very small. There is very little reason to doubt that this is a true statement – both theory (just wait for the post/paper that is coming on this) and experiment strongly suggest that there was some type of Big Bang at the beginning of the universe. The universe is rather large now. There is also very little reason to doubt this, although “how large” is still a valid and exciting question (also be excited for the “small universe” posts that will be coming).
So, we know we started small and now we are much larger. Obviously, there has to be some function to map “tiny, early universe” into “large, current universe”. In the broadest sense, we call this function “inflation”. Beyond that, ie. the existence of some process that took the very small early universe into the one that we see today (via some unusual expansion mechanism when it was young), we don’t know as many things for sure about inflation as many people seem to think we do. Unfortunately, that topic is for another day.