The Inflation Theory proposes a period of extremely rapid (exponential) expansion of the universe during its first few moments in which energydensity of the universe was dominated by a cosmological constant-type of vacuum energy that later decayed to produce the matter and radiation that fill the universe today.
It wasdeveloped around 1980 by Alan Guth, Andrei Linde, Paul Steinhardt, and Andy Albrecht to explain several puzzles with the standard Big Bang theory and to offer solutions to several openquestions in cosmology, in which the universe expands relatively gradually throughout its history.
According to inflation theory, our universe doubled in size 100,000 times in just afraction of a second right after the Big Bang. This could mean that an infinite number of universes exist, each with their own laws of physics.____________________________________________________________
The reason why something like inflation was needed in cosmology was highlighted by discussions of two key problems in the 1970s. Thefirst of these is the horizon problem: the puzzle that the Universe looks the same on opposite sides of the sky (opposite horizons) even though there has not been time since the BigBang for light (or anything else) to travel across the Universe and back. So how do the opposite horizons "know" how to keep in step with each other? The second puzzle is called theflatness problem.This is the puzzle that the spacetime of the Universe is very nearly flat, which means that the Universe sits just on the dividing line between eternal expansion andeventual recollapse.
Inflation theory says that are universes on the skin of a giant bubble created by the big bang and this giant bubble is not the only one