Beyond Big Bang Cosmology

The Big Bang model is not complete. For example, it does not explain why the universe is so uniform on the very largest scales or, indeed, why it is so non-uniform on smaller scales, i.e., how stars and galaxies came to be.

The Big Bang model is based on the Cosmological Principle which assumes that matter in the universe is uniformly distributed on all scales - large and small. This is a very useful approximation that allows one to develop the basic Big Bang scenario, but a more complete understanding of our universe requires going beyond the Cosmological Principle. Many cosmologists suspect that inflation theory, an extension of the Big Bang theory, may provide the framework for explaining the large-scale uniformity of our universe and the origin of structure within it.

The first two pages below provide an overview of the origin and growth of structure in our universe. The last page presents an overview of the inflationary universe model and explains how inflation answers the some of the puzzles of the standard Big Bang model.

Structure in the universe

The Big Bang theory makes no attempt to explain how structures like stars and galaxies came to exist in the universe.

Fluctuations in the cosmic microwave background (CMB) radiation

The temperature of the CMB is observed to vary slightly across the sky. What produced these fluctuations and how do they relate to stars and galaxies?

The inflationary universe

A very short, but especially rapid burst of growth in the very early universe (“inflation”) provides an elegant, yet untested, explanation of the above puzzles.