Question: Can black holes be used to prevent the heat death of the universe?

Sheila Kanani answered on 24 Mar 2011:

Black holes could be the key in the idea of the heat death scenario of the fate of the universe.

In the heat death scenario, the energy density is so low that the system can be thought of as non-gravitational, and in a state of thermal equilibrium, energy is uniformly distributed and we are in a state of maximal entropy.

In an “open” or “flat” universe that continues expanding indefinitely, a heat death is expected to occur, with the universe cooling to approach absolute zero temperature and approaching a state of maximal entropy over a very long time period.

No one knows whether or not an expanding universe can approach maximal entropy; it has been proposed that in an expanding universe, the value of maximum entropy increases faster than the universe gains entropy, causing the universe to move progressively further away from heat death.

*brain ache*

There is also some uncertainty remaining on the exact value of the current entropy of the universe. A recent analysis of entropy suggests that the visible universe has more entropy than previously thought. This is because we reckon that supermassive black holes are the largest contributor.

Right now the universe is not in thermodynamic equilibrium and objects can do physical work. The decay time for a supermassive black hole of roughly 10^11 solar masses is on the order of 10^100 years so entropy can be produced until at least that time, we are safe til then!

So black holes could provide the longer time for the universe to decay and a way of stopping the thermal equilibrium but it also could provide the entropy. Argh!