It used to seem to be the same in all directions. Then at the beginning of 1980 came hints of a quadruple anisotropy . . The Big Bang theory includes a microwave background . . Recent measurements of the density fluctuations in the cosmic microwave background radiation show no fluctuations greater than 2.5 parts in 100,000. But this is not true either.
Light loses energy as it passes the gravitational fields of stars.
The year after Sirius B was found to have its astonishing properties, Albert Einstein presented his general theory of relativity, which was mainly concerned with new ways of looking at gravity. This was a point in favor not only of Einstein's theory but also of the superdensity of Sirius B, for in an ordinary star such as our sun, the redshift effect would be only one thirtieth as great. Redshift observations are, of course, crucial to our modern view of the evolution of the cosmos. Usually, it is assumed that the observed redshifts are entirely due to the Doppler effects. The anomaly here is that these young galaxies do not seem much bluer than nearby old galaxies, 16-18 billion years of age.