The Density Contrast is a parameter used in galaxy formation to indicate where there are local enhancements in matter density.
It is believed that after inflation, although the universe was mostly uniform, some regions were slightly denser than others with contrast densities on the order of 1 trillionth. As the horizon distance expanded, the enclosed causally connected (i.e. gravitationally connected) masses increased until they reached the Jeans mass and began to collapse, which allowed galaxies, galaxy clusters, superclusters, and filaments to form.
Famous quotes containing the word contrast:
“In contrast to the flux and muddle of life, art is clarity and enduring presence. In the stream of life, few things are perceived clearly because few things stay put. Every mood or emotion is mixed or diluted by contrary and extraneous elements. The clarity of art—the precise evocation of mood in the novel, or of summer twilight in a painting—is like waking to a bright landscape after a long fitful slumber, or the fragrance of chicken soup after a week of head cold.”
—Yi-Fu Tuan (b. 1930)