Big Freeze

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The Big Freeze is a scenario in which the universe simply becomes too cold to sustain life due to continued expansion. The Big Freeze is a theory of a possible fate of the universe. For other theories, see Ultimate fate of the universe. The Big Freeze could occur if the universe's geometry is either flat or hyperbolic, because either of those would mean that the universe would expand infinitely, causing a permanent fate.

Contents

1 Geometry

1.1 Possible Universe Shapes
1.2 Density

2 Expansion
3 See also
4 External links

Geometry

For the universe to expand indefinitely, the shape of the universe as a whole needs to be flat or hyperbolic; this requirement stems from the density of the universe in those particular geometric shapes. There are three likely possibilities for the universe's shape.

Possible Universe Shapes

Spherical, a curved, ball shape.

Hyperbolic, a "saddle shape".

Flat, two-dimensional shape, like a piece of paper.

Density

For the Big Freeze theory to happen, the shape of the Universe must be either hyperbolic or flat. If it is hyperbolic, which is usually pictured as a saddle shape, then the density must be lower than the critical density, which means that the universe isn't heavy enough to collapse under gravity. If our Universe is flat, then the density will be exactly at the critical point, preventing the universe from collapsing as well. If the universe is heavier than the critical point, it will result in a shrinking universe, which leads to another theory, called the Big Crunch. For the Big Crunch to occur, the shape of the Universe would have to be spherical. The problem with measuring the current density of our Universe is that we cannot see most of the matter in it, and it is theorized that most of the universe may be made up of dark matter, a hypothetical, invisible form of matter in space.

Expansion

Expansion of the Universe is the entire basis of the Big Freeze theory. If the shape of the Universe is hyperbolic, then the Universe will reach a fixed expansion rate and expand forever, which means that the universe will never really "die". If the universe is flat, then the Universe will continue to expand until it reaches an expansion rate of zero; a Universe in this scenario wouldn't ever "die" either.

External links

http://home.cwru.edu/~sjr16/advanced/cosmos_death.html