The CMB is so remarkably smooth, that for 25 years after its discovery, no variations could be detected. Increasingly precise instruments were designed and launched into space to look for variations in the CMB’s intensity, because the big bang theory said large variations had to be there if stars and galaxies were to form. Without billions of large concentrations of matter, other matter could not gravitationally contract around those concentrations to form today’s untold billions of galaxies. If stars and galaxies did not form, we would not be here!
Finally, after 25 years of searching, variations amounting to only one part in 100,000 were found. Obviously, with such uniformly dispersed matter, galaxies could not gravitationally form, even over billions of years. Experts recognized this problem.
But this uniformity [in the CMB] is difficult to reconcile with the obvious clumping of matter into galaxies, clusters of galaxies and even larger features extending across vast regions of the universe, such as “walls” and “bubbles.” 2
The theorists know of no way such a monster [a massive accumulation of galaxies, called the Great Wall] could have condensed in the time available since the Big Bang, especially considering that the 2.7 K background radiation reveals a universe that was very homogeneous in the beginning.3 Gravity can’t, over the age of the universe, amplify these [tiny] irregularities enough [to form huge clusters of galaxies].4
Also, the Hubble Space Telescope has photographed the extreme edges of the visible universe. Most experts expected to see diffuse matter slowly gravitating together to form galaxies. That is what one would expect if the extremely smooth CMB was left over from the big bang. Instead, galaxies were already “bunched together”—having formed very early in the history of the universe.
... tremendously distant galaxies are just as clustered as today and are arranged in the same filamentary, bubbly structures that nearby galaxies are.5
In each of the five patches of sky surveyed by the team, the distant galaxies bunch together instead of being distributed randomly in space. “The work is ongoing, but what we’re able to say now is that galaxies we are seeing at great distances are as strongly clustered in the early universe as they are today,” says [Charles C.] Steidel, who is at the California Institute of Technology in Pasadena.6