Heat Death

**misskitty** · Mar15-05, 04:31 PM

My physics class is currently studying thermodynamics. As I was reading my assignment I came across something very intriguing. Eventually, approximately 100 trillion years from now, the universe will reach thermal equilibrium and maximum entropy. When this happens all physical, chemical, and biological processes will cease to exsist. Work will be impossible. All energy will still exsist, but it will all be unusable energy.

I thought this was pretty amazing. Let me know what you think about the topic. This is some pretty heavy stuff. One thing I would like to know is what will happen to all matter? Things that we use everyday and us...I know we'll all die, but how would it be. What happens to all the energy? The universe is such a vast place to reach thermal equilibrium.

**Gold Barz** · Mar15-05, 04:33 PM

heat Death is the most likely fate of the universe, atoms would be so spread apart, very spread apart

**SpaceTiger** · Mar15-05, 05:05 PM

Originally Posted by misskitty

My physics class is currently studying thermodynamics. As I was reading my assignment I came across something very intriguing. Eventually, approximately 100 trillion years from now, the universe will reach thermal equilibrium and maximum entropy. When this happens all physical, chemical, and biological processes will cease to exsist. Work will be impossible. All energy will still exsist, but it will all be unusable energy.

I would be extremely hesitant to extrapolate our current knowledge of cosmology that far into the future. However, given the most popular models and their simplest extrapolation, that is correct.

**ohwilleke** · Mar15-05, 05:13 PM

Let's just say, it doesn't keep me up at night worrying. :P Call me parochial, but I'm far more concerned about asteroids striking Earth and the Sun discontinuing its business as usual operations (not that either of those are insomnia pill generators themselves) which are far nearer term, than I am about the heat death of the universe.

**Phobos** · Mar15-05, 07:29 PM

Originally Posted by misskitty

When this happens all physical, chemical, and biological processes will cease to exsist.

Biology will likely be gone long before then. Most chemistry too (atoms too far apart).

One thing I would like to know is what will happen to all matter?

Eventually, matter will fall apart (decay into its subatomic particles...maybe further to fundamental particles?).

What happens to all the energy?

All converted to heat (lower and lower frequency as this background radiation keeps cooling toward absolute zero).

**misskitty** · Mar15-05, 08:10 PM

Could absolute zero theoretically be achieved in the universe?

**misskitty** · Mar15-05, 08:14 PM

How long does anyone think it might take for the biological and chemical processes to fall apart? How would these processes cease? Would the atoms just break down one subatomic particle at a time? What would happen to the neutrons, protons and electrons? Would they break down too?

**Lord Flasheart** · Mar15-05, 08:15 PM

I've been reading some of Stephen Baxter's Manifold and Xeelee Sequence stories, and quite a few of them deal with the "upcoming" heat Death. What a depressing future.

Personally, I've always felt a bit skeptical about the Heat Death. Although the surviving particles are still rather far apart, I'd think that gravity would actually shift them together again. Anyway, it's about time (er, not for a few ten-to-the-umptillion years) that the weakling force found his destiny: The reconstruction/crunch of the Universe!

Now where did my drasted marbles go?

**Lord Flasheart** · Mar15-05, 08:18 PM

Originally Posted by misskitty

Could absolute zero theoretically be achieved in the universe?

If there is Zero-Point-Energy, no. I need to check that up myself.

**misskitty** · Mar15-05, 08:26 PM

How would the universe reconstruct itself after reaching maximum entropy? When maximum entropy is reached, particles have a high tendency to remain in maximum entropy.

How far apart are we talking when we say far apart?

Check under your bed for the missing marbles

.

**Andromeda321** · Mar15-05, 09:56 PM

You have to remember at this point that there are a few outcomes for what can happen in the universe based on its acceleration and how much mass there is in it to slow down the acceleration. Right now we can't definitively rule any of these out, although most cosmologists believe that #s 1 and 2 in the following list aren't the likely outcomes.
1. The universe collapses back in on itself. In this case you don't really need to worry about the entropy thing as it'll all end in the Big Crunch anyway.
2. The universe stops expanding and just stays the way it is. If this happens then eventually it will all just get more and more disordered: stars will stop being formed because there's nothing left for fusion and it'll all just be sitting around more or less, decaying into smaller and smaller particles.
3. The universe keeps expanding the way it is now. If this happens then all the matter in the universe will just keep going further and further away from everything else. There's nothing really to stop the distances between masses to be infinite. So you'll have absolute entropy but it's not like anything's going to have the ability to collide with everything else anyway.
4. The universe begins accelerating at a faster pace. Known as "The Big Rip" in cosmology, if the universe increases its expansion acceleration atoms themselves will literally become ripped apart due to the forces involved (as implied by the name). Sort of like number 3 but a heck of a lot more brutal.
I think that's it... if I messed up somewhere someone please point it out.

**misskitty** · Mar15-05, 10:22 PM

Could we have some expanision on the second idea?

**SpaceTiger** · Mar15-05, 10:27 PM

Originally Posted by misskitty

Could we have some expanision on the second idea?

I suppose it's possible, in theory, but I haven't seen it suggested in respected circles. It would require a delicate balance akin to that present in Einstein's original formulation of the cosmological constant.

**Andromeda321** · Mar15-05, 10:34 PM

Sure thing.
Basically right now it's been observed that the universe is expanding with a certain amount of acceleration and in order to reverse this acceleration you would need a sufficient amount of mass in order to slow down and stop the acceleration. If you don't have this mass then the universe just keeps going and going in expansion. In order to slow down the expansion of the universe to a constant you need an exact amount of matter: a little more then that and it'll collapse into the Big Crunch, a little less and it'll just keep expanding. Think Goldielocks only finding one mass value that's just right.

The problem with this is right now we really don't know how much mass there is out there because the baryonic stuff (ie what we're made out of in the form of ordinary atoms and such) make up only 3% of the stuff in the universe. We don't know much about the grand majority of the matter and as a result can't tell what's going to happen just yet.

**SpaceTiger** · Mar15-05, 11:01 PM

Originally Posted by Andromeda321

Basically right now it's been observed that the universe is expanding with a certain amount of acceleration and in order to reverse this acceleration you would need a sufficient amount of mass in order to slow down and stop the acceleration. If you don't have this mass then the universe just keeps going and going in expansion.

Ok, I thought this might be what you were talking about. In actuality, with what we currently know, the acceleration implies that it's already too late and there's not enough matter to slow the expansion. The models you're referring to would require that the universe be decelerating, something we simply assumed until the Type 1a supernova measurements.

However, we don't know anything about the dark energy, so there's no way to say how it will behave in the future. It might continue inducing acceleration or it might change its behavior and begin slowing the expansion. Until we figure out what it is, it's anybody's guess.

In order to slow down the expansion of the universe to a constant you need an exact amount of matter: a little more then that and it'll collapse into the Big Crunch, a little less and it'll just keep expanding.

Even in the old models, that wasn't quite the case. A perfectly balanced universe, as you describe, would still expand forever, it would just do so at an ever-decreasing rate. In mathematical terms, the limit of the scale factor as time goes to infinity would be infinity in both open and perfectly balanced universes.

The problem with this is right now we really don't know how much mass there is out there because the baryonic stuff (ie what we're made out of in the form of ordinary atoms and such) make up only 3% of the stuff in the universe. We don't know much about the grand majority of the matter and as a result can't tell what's going to happen just yet.

If WMAP is to be believed, we do know how much mass is out there and it adds up to about 27% (mostly dark matter). Most of the rest is dark energy.