In the end of 1970's, Alan Guth who studied at MIT came with inflation theory. The theory explained why the universe is so uniform and so smooth.
Inflation theory begins with the idea of the forming universe. Â That everything exists now comes from a symmetry breaking, little time after the Big Bang. Symmetry breaking is something like the spinning pencil that fallen. Another example is liquid-solid phase transition. A water molecule of two hydrogen atoms attached to an oxygen atom is shaped like a shallow V. Above the freezing point (0 degree Celcius), an individual water molecule can point in any direction it wants to- all directions are equal- space to the molecule is symmetric.
Below 0 degree Celsius, the molecules hook up into crystalline structure of ice. A molecule is no longer free. Symmetry was broken.
The change from liquid to solid is called phase transition. Steven Weinberg (Alan's classmate) suggested that the universe underwent phase transitions as it went from high energy (seconds after Big Bang) to low energy now. Only in this case what froze was the Higgs Field (Overbye, 1991)
Higgs Field is the field separates "observable universe" and the "real universe" in inflation theory. Observable universe is universe that currently we can observe, which lights from the edge of it can be received. Real universe contains false vacuum that we cannot observe because lights cannot reach us due to it was being flattened/ ironed out in the seconds of inflationary phase, seconds after Big Bang.
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The idea of inflation was that the current observable universe -- a sphere roughly 10 billion light years in radius was about the size of a grapefruit in the beginning. And when Higgs Energy- false vacuum which include "real universe that out of our sphere", the universe blew up.
Different from Hubble Expansion where it was 1 foot across when it was 1 second old, 2 feet across when it was 4 seconds old, then 3 feet in 10 seconds, universe with false vacuum in it, it expanded exponentially. With every tick of the cosmic clock (a tick in this case is 10^-34 second), the size of the universe doubled. If it started 1 foot across, by the second it would be 4 feet, by the tenth tick it would be 1028 feet across. The bigger it got, the faster it would grow to keep doubling. In no time at all, the universe would double in size 100 times becoming a trillion trillion trillion times larger. The more false vacuum energy there was, the faster the universe would push itself apart (Overbye, 1991)
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It's like a dot size balloon with very very tiny picture on it that blown into a mountain sized balloon. It creates cosmological horizon that separates observable and real universe. The blow irons and smoothens, dilutes, and hides the original spec in the dots to a very very big smooth balloon. We'd never know what's the original picture on it because it was blown in a very rapid rate.
"Two widely separated regions of the observable universe cannot exchange information because they moved apart faster that the speed of light- no interaction in the early universe" *
