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The '''ultimate fate of the universe''' is a valid question because according to most models on the universe, the universe is finite, and will end.<ref name="religious">''When he opened the sixth seal, I looked, and behold, there was a great earthquake, and the sun became black as sackcloth, the full moon became like blood, and the stars of the sky fell to the earth as the fig tree sheds its winter fruit when shaken by a gale. The sky vanished like a scroll that is being rolled up, and every mountain and island was removed from its place. (Revelation 6:12–14)''</ref><ref name="bigbang">^ a b Lemaître, Georges (1927). "Un univers homogène de masse constante et de rayon croissant rendant compte de la vitesse radiale des nébuleuses extra-galactiques". Annales de la Société Scientifique de Bruxelles A47: 49–56. Bibcode 1927ASSB...47...49L translated by A. S. Eddington: Lemaître, Georges (1931). "Expansion of the universe, A homogeneous universe of constant mass and increasing radius accounting for the radial velocity of extra-galactic nebulæ". Monthly Notices of the Royal Astronomical Society 91: 483–490. Bibcode 1931MNRAS..91..483L</ref><ref name="static">Thomson, William. (1851). "On the Dynamical Theory of Heat, with numerical results deduced from Mr Joule’s equivalent of a Thermal Unit, and M. Regnault’s Observations on Steam." Excerpts. [§§1–14 & §§99–100], Transactions of the Royal Society of Edinburgh, March, 1851; and Philosophical Magazine IV. 1852, [from Mathematical and Physical Papers, vol. i, art. XLVIII, pp. 174]</ref> The only question logically, is what will happen at the end of the universe.  There are many different scientific scenarios, and religious scenarios as well. When the Big Bang theory became the foremost explanation for the current state of the universe, the fate of the universe became a valid question.

The '''ultimate fate of the universe''' is a valid question because according to most models on the universe, the universe is finite, and will end.<ref name="religious">''When he opened the sixth seal, I looked, and behold, there was a great earthquake, and the sun became black as sackcloth, the full moon became like blood, and the stars of the sky fell to the earth as the fig tree sheds its winter fruit when shaken by a gale. The sky vanished like a scroll that is being rolled up, and every mountain and island was removed from its place. (Revelation 6:12–14)''</ref><ref name="bigbang">^ a b Lemaître, Georges (1927). "Un univers homogène de masse constante et de rayon croissant rendant compte de la vitesse radiale des nébuleuses extra-galactiques". Annales de la Société Scientifique de Bruxelles A47: 49–56. Bibcode 1927ASSB...47...49L translated by A. S. Eddington: Lemaître, Georges (1931). "Expansion of the universe, A homogeneous universe of constant mass and increasing radius accounting for the radial velocity of extra-galactic nebulæ". Monthly Notices of the Royal Astronomical Society 91: 483–490. Bibcode 1931MNRAS..91..483L</ref><ref name="static">Thomson, William. (1851). "On the Dynamical Theory of Heat, with numerical results deduced from Mr Joule’s equivalent of a Thermal Unit, and M. Regnault’s Observations on Steam." Excerpts. [§§1–14 & §§99–100], Transactions of the Royal Society of Edinburgh, March, 1851; and Philosophical Magazine IV. 1852, [from Mathematical and Physical Papers, vol. i, art. XLVIII, pp. 174]</ref> The only question logically, is what will happen at the end of the universe.  There are many different scientific scenarios, and religious scenarios as well. When the [[Big Bang theory]] became the foremost explanation for the current state of the universe, the fate of the universe became a valid question.

==Background==

==Background==

The universe is currently expanding at a rate of 73.8 ± 2.4 kilometers per second per Megaparsecs. (''A megaparsec is 3.08x10¹⁹ kilometers'') Under the big bang model, expansion is currently accelerating.<ref>M. Stone (1976). "Lifetime and decay of excited vacuum states". Phys. Rev. D 14 (12): 3568–3573. Bibcode 1976PhRvD..14.3568S. doi:10.1103/PhysRevD.14.3568.</ref> When [[catholic]] priest George Lemaitre proposed that the universe was born from a singularity, which was expounded on by Edwin Hubble, using the theory of relativity, it became clear that all theories implied an ultimate fate to the universe.

The [[universe]] is currently expanding at a rate of 73.8 ± 2.4 kilometers per second per Megaparsecs. (''A megaparsec is 3.08x10¹⁹ kilometers'') Under the big bang model, expansion is currently accelerating.<ref>M. Stone (1976). "Lifetime and decay of excited vacuum states". Phys. Rev. D 14 (12): 3568–3573. Bibcode 1976PhRvD..14.3568S. doi:10.1103/PhysRevD.14.3568.</ref> When [[catholic]] priest George Lemaitre proposed that the universe was born from a [[singularity]], which was expounded on by [[Edwin Hubble]], using the [[theory of relativity]], it became clear that all theories implied an ultimate fate to the universe.

==Scientific theories==

==Scientific theories==

There are three commonly accepted theories on how the universe will end. They are the Big crunch, where the universe collapses on itself, the Big Rip scenario, where acceleration destroys the bonding of atoms, and all matter decays, and the Heat death, where the universe reaches a maximum state of entropy.

There are three commonly accepted theories on how the universe will end. They are the Big crunch, where the universe collapses on itself, the Big Rip scenario, where acceleration destroys the bonding of atoms, and all matter decays, and the Heat death, where the universe reaches a maximum state of [[entropy]].

===Big Crunch===

===Big Crunch===

The Big Crunch theory is a symmetric view of the ultimate fate of the Universe. Just as the Big Bang started a cosmological expansion, this theory assumes that the average density of the universe is enough to stop its expansion and begin contracting. The end result is unknown; a simple estimation would have all the matter and space-time in the universe collapse into a dimensionless singularity, but at these scales unknown quantum effects need to be considered.

The Big Crunch theory is a symmetric view of the ultimate fate of the Universe. Just as the Big Bang started a cosmological expansion, this theory assumes that the average density of the universe is enough to stop its expansion and begin contracting. The end result is unknown; a simple estimation would have all the [[matter]] and space-time in the universe collapse into a dimensionless singularity, but at these scales unknown quantum effects need to be considered.

This scenario allows the Big Bang to be immediately after the Big Crunch of a preceding universe. If this occurs repeatedly, we have a cyclic model which is also known as an oscillatory universe. The universe could then consist of an infinite sequence of finite universes, each finite universe ending with a Big Crunch that is also the Big Bang of the next universe. Theoretically, the cyclic universe could not be reconciled with the second law of thermodynamics: entropy would build up from oscillation to oscillation and cause heat death. Other measurements suggested the universe is not closed. These arguments caused cosmologists to abandon the oscillating universe model. A somewhat similar idea is embraced by the cyclic model, but this idea evades heat death, because of an expansion of the branes that dilutes entropy accumulated in the previous cycle. In the big crunch, the universe will end approximately 30 billion years from now.

This scenario allows the Big Bang to be immediately after the Big Crunch of a preceding universe. If this occurs repeatedly, we have a cyclic model which is also known as an oscillatory universe. The universe could then consist of an infinite sequence of finite universes, each finite universe ending with a Big Crunch that is also the Big Bang of the next universe. Theoretically, the cyclic universe could not be reconciled with the second law of thermodynamics: [[entropy]] would build up from oscillation to oscillation and cause heat death. Other measurements suggested the universe is not closed. These arguments caused cosmologists to abandon the oscillating universe model. A somewhat similar idea is embraced by the cyclic model, but this idea evades heat death, because of an expansion of the branes that dilutes entropy accumulated in the previous cycle. In the big crunch, the universe will end approximately 30 billion years from now.

 

===Big Rip===

===Big Rip===

In the special case of phantom dark energy, which has even more negative pressure than a simple cosmological constant, the density of dark energy increases with time, causing the rate of acceleration to increase, leading to a steady increase in the Hubble constant. As a result, all material objects in the universe, starting with galaxies and eventually, all forms, no matter how small, will disintegrate into unbound elementary particles and radiation, ripped apart by the phantom energy force and shooting apart from each other. The end state of the universe is a singularity, as the dark energy density and expansion rate becomes infinite. A possible timeline based on current physical theories suggests a time of 10¹⁹ seconds or more. This universe will end approximately 100 billion years from now.

In the special case of phantom [[dark energy]], which has even more negative pressure than a simple cosmological constant, the density of dark energy increases with time, causing the rate of acceleration to increase, leading to a steady increase in the [[Hubble constant]]. As a result, all material objects in the universe, starting with [[galaxies]] and eventually, all forms, no matter how small, will disintegrate into unbound [[Fundamental particles|elementary particles]] and [[radiation]], ripped apart by the phantom energy force and shooting apart from each other. The end state of the universe is a singularity, as the dark energy density and expansion rate becomes infinite. A possible timeline based on current physical theories suggests a time of 10¹⁹ seconds or more. This universe will end approximately 100 billion years from now.

===Heat death===

===Heat death===

After the Stelliferous Epoch, all hydrogen in the universe will be exhausted. Then, only remnants remain. Some Grand Unified Theories predict that [[protons]] will decay into a positron, and a pion<ref>http://io9.gizmodo.com/5958012/how-one-tiny-particle-could-end-the-universe</ref>. Experiments have not detected proton decay, suggesting that the half life of a [[proton]] is at least 10³⁴ years<ref>http://www.symmetrymagazine.org/article/do-protons-decay</ref>. All that will remain will be [[fundamental particles]] such as [[lepton]]s and [[photon]]s. The rate of entropy will be at a maximum. There will be no real structure to the universe, such as stars. The universe will be devoid of life.

After the Stelliferous Epoch, all hydrogen in the universe will be exhausted. Then, only remnants remain. Some Grand Unified Theories predict that [[protons]] will decay into a [[positron]], and a pion<ref>http://io9.gizmodo.com/5958012/how-one-tiny-particle-could-end-the-universe</ref>. Experiments have not detected proton decay, suggesting that the half life of a [[proton]] is at least 10³⁴ years<ref>http://www.symmetrymagazine.org/article/do-protons-decay</ref>. All that will remain will be [[fundamental particles]] such as [[lepton]]s and [[photon]]s. [[Entropy]] will be at a maximum. There will be no real structure to the universe, such as stars. The universe will be devoid of life.

==Religious Views==

==Religious Views==

===Fringe groups===

===Fringe groups===

Certain fringe groups, such as Scientology, hold that the universe is static, and will never change.<ref name="scientology" /> Specifically, it states that all consciousness will follow the same pattern of birth and rebirth, forever.

Certain fringe groups, such as [[Scientology]], hold that the universe is static, and will never change.<ref name="scientology" /> Specifically, it states that all consciousness will follow the same pattern of birth and rebirth, forever.

==References==

==References==

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[[Category:Cosmology]]

[[Category:Cosmology]]