Cosmologists still search for clues to the critical density of the universe.
Critical density is the density of matter in the universe needed to stop the expansion of the universe at infinite time. In the Big Bang Theory, the critical density governs the shape and eventual fate of the universe.
Shape of the Universe
The shape of the universe depends on the density of matter in the universe. More specifically, the shape of the universe is the result of the outward expansion of the universe against the inward attraction of gravity.
Closed Universe
In a closed universe, the density of the matter is above the critical density. This produces a universe shaped as the surface of a sphere. In a closed universe, the gravitational attraction exceeds the outward expansion, resulting in an eventual collapse of the universe termed the Big Crunch.
Open Universe
If the density of the matter in the universe is below the critical density, then the universe is said to be open and forms a curved surface like a saddle. In an open universe, the gravitational attraction between particles of matter is insufficient to stop the outward expansion of the universe, leading to the eventual dispersal of matter over an ever-increasing area called the Big Freeze.
Flat Universe
If the density of the matter in the universe is equal to the critical density, then the universe is flat. It is in this universe that expansion ceases after infinite time.
Expectation of the Universe
While the shape, density and even the rate of expansion are not yet fully measured, many cosmologists estimate the universe to be close to critical density.
Tags: density matter, critical density, density matter universe, matter universe, expansion universe, outward expansion
