Cosmic inflation, proposed back in 1980, is a theory that precedes and sets up the hot Big Bang. After thorough testing, is it still valid?
So, you want to know how the Universe began? You’re not alone. Every other curious member of humanity, for as long as recorded history exists (and probably much longer), has wondered about exactly this question, “where does all this come from?” In the 20th century, science advanced to the point where a large suite of evidence pointed to a singular answer: the hot Big Bang. As first proposed by Georges Lemaître and later expanded upon by George Gamow, the Big Bang was the idea that the Universe began from a state of arbitrarily small size, high temperature and high density. It only became the vast, cold, and relatively empty place it is today because of the great amount of time that’s elapsed since its birth.
If we imagine the Universe as it was farther back in time, the Big Bang tells us:
- it must have been smaller, since it’s expanding today,
- that all the matter within it was closer together, and so it was denser,
- that it was more uniform early on, since it takes time for gravitation to cause matter to clump…
