# Is the universe thermodynamically open or closed?

1. Jun 15, 2005

### µ³

Googling reveals a bunch of information regarding to whether or not the universe is geometrically open or closed, but not thermodynmaically. Is it the same thing? So anyway, is the Universe open or closed thermodynamically speaking and what is the evidence behind it? Sorry if this has been answered before, I tried using the search feature and I couldn't find anything. Thanks in advance.

2. Jun 15, 2005

### Integral

Staff Emeritus
It has to be closed. If there was anything else to exchange energy with it would be in the universe.

3. Jun 15, 2005

### µ³

What if the universe was infinite (but with finite density)? Would it still obey the laws of thermodynamics then?

4. Jun 15, 2005

### Integral

Staff Emeritus
Let's see, it seems to obey the laws of thermo... Now just what is your question?

5. Jun 15, 2005

### µ³

Nevermind, I got it, thanks. I was just wondering if thermodynamics could be strictly applied to the universe because I wasn't sure if it could be considered closed or not. But thanks to your explanation I realized it would be nonsensical to consider it "open".

6. Jun 15, 2005

### Iraides Belandria

I think, this is , almost a phylosophical question. What is behind of all the galazies, beyond the limits of everything?. The quantum vacuum?, The nothingness?, what crossess the boundaries of the universe? work?. heat,?, cosmic rays ?. Subtle radiations? what is it beyond?. Anyway. it looks to me that sometihng flows.

7. Jul 4, 2005

### nvntr

Gravity Works

8. Jul 29, 2005

### FunkHaus

$$\mu^3$$,
I once had the same question. Here's what I assume you're curious about. If the universe has existed for an infinite amount of time, then by the postulates of classical statistical mechanics, it should have already settled into an equilibrium situation (ie a maximum entropy state with as many degrees of freedom as possible). However, this is not what we see. There are still very large scale motions present in our universe with few "degrees of freedom" (the Earth's orbit around the Sun is an example). So then one is tempted to say that the universe has only "existed" for a finite time. So then what was here before it?? But if it really wasn't here, and then just "appeared", this would contradict conservation of mass (which is in relativity conservation of energy).
This has bothered me for a while. Well not really bothered--more like "intrigued". I suppose it's possible that quantum effects in the early universe prevented an approach to "equilibrium" as suggested by classical statistical mechanics. Let me know what you think about this.