by Coel Hellier

[The first part of this essay can be found here.]

Inflation

The comparison of cosmological models with high-quality and detailed observations of the early universe has led to the “inflationary” version of the Big Bang. This hypothesizes that, very early in the first second after the initial quantum fluctuation, only about 10^-35 seconds later, our universe started an episode of exceptionally rapid exponential expansion, growing by a huge factor of about 10³⁰ in only a tiny fraction of a second. This “inflation” was proposed in order to explain several otherwise puzzling features of the universe, including: (1) the similarity of the universe in opposite directions in the sky; (2) the exceptional smoothness of the cosmic microwave background (CMB); (3) the fact that the universe appears to have a very close balance between the total amount of matter and energy and the expansion rate, thus…