Question

Discuss two distinct and independent observations that support the Big Bang theory, made between the 1960s and today. For each of the two observations you must:

-describe exactly what is observed along with how the observations are made, and

-describe how that observation addresses or relates to a distinct prediction of Big Bang theory.

Answer 1

In 1990, measurements from the COBE satellite showed that the spectrum of the CMB matches a 2.725 K black-body to very high precision; deviations do not exceed 2 parts in 100000. This showed that earlier claims of spectral deviations were incorrect, and essentially proved that the universe was hot and dense in the past, since no other known mechanism can produce a black-body to such high accuracy. Further observations from COBE in 1992 discovered the very small anisotropies of the CMB on large scales, approximately as predicted from Big Bang models with dark matter. From then on, models of non-standard cosmology without some form of Big Bang became very rare in the mainstream astronomy journals.

In 1998, measurements of distant supernovae indicated that the expansion of the universe is accelerating, and this was supported by other observations including ground-based CMB observations and large galaxy redshift surveys. In 1999-2000, the BOOMERanG and Maxima balloon-borne CMB observations showed that the geometry of the universe is close to flat, then in 2001 the 2dFGRS galaxy redshift survey estimated the mean matter density around 25-30 percent of critical density.