Heat-death of the Universe
The
heat death is a possible final state of the
universe, in which it has reached maximum
entropy. If the universe lasts for an infinite time, then it will
asymptotically approach a state where all energy is evenly distributed.
Despite its name, in the heat death scenario, the entire universe would be very close to absolute zero.
See also: Big Bang, Dyson's eternal intelligence, Ultimate fate of the Universe