Big Freeze
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| Physical Cosmology |
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| Physical Cosmology |
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Universe · Big Bang |
| Early universe |
| Expanding universe |
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Redshift · Hubble's law |
| Structure formation |
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Shape of the universe |
| Components |
| History |
| Cosmology experiments |
| Scientists |
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Einstein · Lemaître · Friedman |
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The Big Freeze (also Big Chill) is a scenario in which the universe becomes too cold to sustain life due to continued expansion and the decay of free energy due to the action of entropy. The Big Freeze is a theory of a possible fate of the universe. The Big Freeze could occur if the universe's geometry is either flat or hyperbolic, as either of those would mean that the universe would expand indefinitely eventually reaching absolute zero (-273.15°C or -459.67°F, also defined as 0 Kelvin or 0 Rankine).
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[edit] 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.
[edit] Possible Universe Geometries
- Spherical, a curved, ball shape.
- Hyperbolic, a "saddle shape".
- Flat, two-dimensional shape, like a piece of paper.
[edit] 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 is approximately three hydrogen atoms per cubic meter), 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.
[edit] 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.
