Cosmology: SNC 1D

Cosmology: the study of the origin and evolution of the Universe

When Hubble looked at galaxies, he discovered that all galaxies appeared to be moving away from us (and each other).

He could tell this because their light was redshifted.

Lemaitre suggested that all matter and energy in the Universe expanded from a very hot and very dense beginning that was called “The Big Bang.” The Big Bang happened about 13.7 billion years ago.

Evidence for the Big Bang Theory The Big Bang Theory predicted that the first matter would have been about 3/4 hydrogen and 1/4 helium. This is what is observed in the oldest stars. All other elements have been made by stars.

Also, we can see the remnants of the energy of the Big Bang in the very redshifted Cosmic Microwave Background radiation (CMB).

Future of the Universe The Universe may continue to expand (Heat Death: the Universe gets very cold) or may contract again (Big Crunch).

The Big Crunch will happen if the gravitational attraction of all matter (including dark matter) is strong enough. Dark matter is matter that does not emit or absorb light.

The Heat Death will happen if the repulsive force of dark energy is strong enough. The effects of dark energy may be observed, but dark energy is not yet understood.