Regions of space where the Mass of an object divided by its volume. Density is a characteristic property of a substance (rock vs. ice, e.g.). Some substances (like gases) are easily compressible and have different densities depending on how much pressure is exerted upon them. The Sun is composed of compressible gases and is much of matter, or the curvature of space-time, becomes infinite and the concepts of space and time cease to have any meaning. Singularities are predicted to occur in all black holes and in certain models of the That which contains and subsumes all the laws of nature, and everything subject to those laws; the sum of all that exists physically, including matter, energy, physical laws, space, and time. Also, a cosmological model of the universe.. For example, open Friedmann models of the Universe possess a singularity in the finite past, while the closed models have both an initial and final singularity. In general, cosmic censorship hides singularities behind event horizons, the exception being the initial singularity of the Beginning point of time and space for the universe. A state of extremely high (classically, infinite) density and temperature from which the universe began expanding..