Second Law of Thermodynamics and Universe

I am currently studying Thermodynamics in school and have a big question about the second law, which states that entropy eventually increases in the universe.

So all energy is moving from higher level to lower level which is heat, which means that the universe should be getting warmer.

But as you might already know, it isn\'t the case, the universe is getting colder, then where is the heat going to?

Someone in my class pointed to expansion. Then second law of thermodynamics proves that the universe is expanding?

Surf

Originally posted by surfupSo all energy is moving from higher level to lower level which is heat, which means that the universe should be getting warmer.

Hu? Think about it like this: You have a blazing fire in a small room. The room is warm because of the small space holding in the heat. Now if you were to open a window the heat would equalize with the temperature of a larger space. It is still the same 'heat', but because it is spread out more in a larger space, its intensity disperses. If the temperature of the outside (universe) was warmer it would be different, but most 'space' is quite cold.

Originally posted by surfup
So all energy is moving from higher level to lower level which is heat, which means that the universe should be getting warmer.

Heat is but one form of energy. There are other (and plenty) ways to distribute energy, such as neutrinos etc.

But as you might already know, it isn\'t the case, the universe is getting colder, then where is the heat going to?

Imagine that a star slowly dies and becomes extinct. It's energy has been shed via all sorts of radiation. Now, this radiation keeps traveling in space. So what we have here is redistribution of energy from concentrated locations (such as stars that support life like ours), to space. This is how entropy increases and can be perceived as cooling.

Someone in my class pointed to expansion. Then second law of thermodynamics proves that the universe is expanding?

No, it doesn't say that.


Even if the Universe stays the same size, due to entropy, it will become effectively cold.

Originally posted by Aelita
Imagine that a star slowly dies and becomes extinct. It's energy has been shed via all sorts of radiation. Now, this radiation keeps traveling in space. So what we have here is redistribution of energy from concentrated locations (such as stars that support life like ours), to space. This is how entropy increases and can be perceived as cooling.

Ok, I get how the entropy increases in the universe, but how can that be perceived as cooling? You mean like heat spreds out, it becomes more and more cold?

So, that kind of explains universe expanding(sorry for pointing to this again, I mean that if energy is concentrated in one place and it is really hot and as the place becomes bigger, energy decreases, then by logic we can say that one place is expanding and that is universe.

I think I get it now. (Sorry for re-explaining what you explained, I find it easier to learn this way, if I put things into my own words and I also want to make sure I didn't misunderstood you.)

Thanks.

The temperature will drop to absolute zero in an unimaginably distant future, when all nitrogen in the universe has been used up, when there can be no fusion and all stars are cold and dead. Fore some hundred of billions of years there will still be some renegade electrons flying around in the vastness, but eventually they too will drop to a halt, and then there will be nothing. Absolute stillness -> absolute zero.

The end.

At least that's one theory on how the universe will end. Not with a bang, but rather with a sigh.



[edit on 2004-9-14 by EyesOfTheFuture]

That seems like a plausible explanation. I've also read that the only way to have an infinite universe is to have the whole thing at an equal temperature, meaning, no entropy. BUT, then that would make that theory unlikely, as a finite universe cannot become infinite over night (... few billion years, ok?). I would source it if I had one... I read that a long time ago. I'll try and find it and post it later.

Originally posted by WaStEdDeAtH777
That seems like a plausible explanation. I've also read that the only way to have an infinite universe is to have the whole thing at an equal temperature, meaning, no entropy.

That would be maximum entropy.

I don't think infinity has to do with temperature though.

Originally posted by surfup
But as you might already know, it isn\'t the case, the universe is getting colder, then where is the heat going to?
Someone in my class pointed to expansion. Then second law of thermodynamics proves that the universe is expanding?

here's an interesting read on the 2lotd
www.talkorigins.org...

Specifically for what you are talking about, since the universe is expanding, , its tempurature should decrease. Its unrelated to the 2nd Law. The heat isn't going anywhere, its being distributed. The 2nd law does say that things heat up.

The reason is as follows:

According to the Kinetic Theory heat is nothing more but the random movement of Atoms and molecules. Yes this always increases within a closed system.

The universe is getting colder because the large majority of it is nothingness. Meaning their are not atoms or molecules to move around and produce heat.

Originally posted by BlackJackal
The reason is as follows:

According to the Kinetic Theory heat is nothing more but the random movement of Atoms and molecules. Yes this always increases within a closed system.

The universe is getting colder because the large majority of it is nothingness. Meaning their are not atoms or molecules to move around and produce heat.

Yes, this is what I tried to explain in my earlier post. When all elemental particles in a very distant future are scattered and frozen to a halt, and the black holes has finally "vaporized", then the temperature will reach an absolute zero. It's the end of our universe, unless there are enough dark matter in the universe to stop the expansion and trigger a "Big Crunch" instead.

everything i have to say on the subject has been already said by those quicker than i, but heres a truly great short story by isaac asimov on the subject of entropy, namely, reversing it.

The Last Question

www.panspermia.org...

Google is your friend.