#cosmology
The galaxies are all moving rapidly away from us
The spectrum lines of the galaxies are shifted to redder wavelengths
It is a a faint, uniform, radio signal.
The burst of radiation from the big bang as it cooled toward 10,000 K
The expansion of the Universe has cooled the radiation and stretched its wavelengths
The shift in spectrum lines of the galaxies
The Universe is expanding.
The cosmological constant is forcing space to expand faster now than in the past