An Open Universe
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STScI
An Eternal Universe
If the universe does not contain enough matter to stop its expansion it will continue to expand forever.
Using the currently understood laws of physics we can project into the future what the Universe may look like in very distant eras. Two astrophysicists at the University of Michigan have outlined the future history of the Universe.
They have divided the future into Eras. The current Era is known as the Stelliferous or Star-Filled era. In this era the Universe is filled with stars and galaxies and planets as it is today. At the end of this era all stars have exhausted their fuel and have died leaving behind only remnants of their once glorious era.
The next era is known as the Degenerate era. In this era the universe is made of dead planets, brown dwarfs, white dwarfs, nuetron stars, black holes, and some theoretical forms of dark matter. At the end of this era all protons, which compose the nuclei of all atoms, disintigrate.
The next Era is the Black Hole era because black holes will be the only gravitaionally important objects left in the universe. However, Black holes do not last forever. They evaporate by a strange radiation process.
After that the Universe shall be composed of only radiation and particles which have an infinite lifetime such as electrons, positrons, and neutrinos. From this point on interesting things might continue to happen but we have reached the limits of our knowledge.
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