Heat Death of the Universe...Your Thoughts

Good day fellow members. I wanted to take this opportunity to discuss something that I have recently taken a great interest in. Like all interesting topics, I happened upon this one by pure coincidence. Since then, however, I have devoted much time to researching this topic, and would like to spark some discussion with you here on this. The topic I ran across was that of entropy; or as it’s also referred to here, heat death of the universe.

The “heat death” is one of many possible final states of the universe. In this scenario, the universe has run down to a state of no free energy. This makes it impossible to sustain motion or life.

The idea of heat death stems from the second law of thermodynamics, which states that entropy tends to increase in an isolated system. Therefore, if the universe lasts for a sufficient time, it will asymptotically approach a state where all energy is evenly distributed. (1)

In a heat death, the temperature of the entire universe would be extremely close to absolute zero. Heath death is, however, not the same as “cold death” or the “Big Freeze”, in which the universe simply becomes too cold to sustain life due to continued expansion, though the result is almost identical.

Inflationary cosmology suggests that in the early universe, before cosmic expansion, energy was uniformly distributed (2), and thus the universe was in a state similar to heat death. However, the two states are in fact very different: in the early universe, gravity was a very important force, and in a gravitational system, if energy is uniformly distributed, entropy is quite low, compared to a state in which most matter has collapsed into black holes. Thus, such a state is not in thermal equilibrium, and in fact there is no thermal equilibrium for such a system, as it is thermodynamically unstable. However, in the heat death scenario, the energy density is so low that the system can be thought of as non-gravitational, such that a state in which energy is uniformly distributed is a thermal equilibrium state, i.e., the state of maximal entropy.

The final state of the universe depends on the assumptions made about its ultimate fate, and these assumptions have varied considerably over the late 20th century and early 21st century. In a "closed" universe that undergoes recollapse, a heat death is expected to occur, with the universe approaching arbitrarily high temperature and maximal entropy as the end of the collapse approaches. In an "open" or "flat" universe that continues expanding indefinitely, a heat death is also 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. There is dispute over 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 farther away from heat death. Finally, some models of dark energy cause the universe to expand in ways that result in some amount of usable energy always being available, preventing the universe from ever reaching a state of maximum entropy. The expectation of the scientific community as of 2007 is that the universe will continue expanding indefinitely.

I’d like to get your thoughts on this and whether or not you think this is a realistic fate for our universe or not. Any comments welcome.

nYk

(1) en.wikipedia.org...
(2) An introduction to cosmological inflation (arxiv.org...) .

Anyone interested in this? Personally I find the subject fascinating. I discovered the topic while reading about the character Doomsday from the Superman comics. This was one of the ways Doomsday was killed. He was taken to the edge of space where he was killed by entropy.

Sure, this stuff is interesting for theoretical physicists, but for us mere mortals - why waste the brain energy on it as it will not matter to us and will not happen for billions of millions of years if things plod along as they are now. Sure humanity will end and God fearing souls will have to deal with the big letdown, that he/she/it made a crappy Universe, but there is nothing we humans will be able to do about it....

I saw a PBS special of what would happen to earth if one of those enigmatic GRB's happened to be aligned with our planet within 10 light years or so. Extra bacon and one fried behind planet would result. Nasa putting a new 360 degree grb detector in orbit next year, not a swift that has to detect then swivel to origin. Most recent reports from physicists seem to indicate dark matter splatter encounters. Truly one of the biggest enigmas of all.