What propelled the Big Bang into motion?

1 Answer
Jul 29, 2018

A period of rapid growth preceded the Big Bang.


The Big Bang was preceded by a short (10^(-32) sec) period of exponential expansion, called inflation.. This expansion is needed to explain the fact that the entire universe has a size of 91 billion light years, but only an age of 13.8 billion years, which means two galaxies 20 billion years away (one in front of us, the other one, behind) cannot have communicated. Without being in contact, they cannot equalize their temperature. The conclusion was that a faster expansion was needed. That exponential growth period was called inflation, and was due to Alan Guth in 1979.

The universe, viewed by particle physicists, cooled off from a high temperature symmetric state where all interactions are unified, down to our less symmetric universe, a process familiar from condensed matter physics. Guth proposed that the universe was in an initial state which was not the state of lowest energy, but which was attainable by quantum tunneling, Quantum tunneling is the ability a quantum system has to go through an energy barrier and emerge on the other side, if the new state has lower energy.

After this initial rapid expansion, the universe continued to expand at a slower rate. The Big Bang began.