Image: the Silk scale relates the lengthscales of galaxies to anisotropies in the CMB of about 1° . At smaller scales, corresponding to the Silk mass, damping of the growth of anisotropies by photon diffusion eliminates structure in the early universe.
Silk discovered the damping mass, a key component of the Big Bang theory of modern cosmology, and predicted infinitesimal temperature fluctuations in the Cosmic Microwave Background (CMB), the fossil radiation from the beginning of the universe. His predictions have been verified by several experiments that are currently running, on the ground at the South Pole and on the Atacama plateau in Chile, and on satellites in space. Such anisotripies in the CMB are the signature of inhomogeneities in the matter distribution at the onset of the Dark Ages, the origns of all stars and galaxies.