# Vacuum energy

1. Dec 29, 2009

### Rubix

Let's say I have a 5m3 cube of air and right next to it a 5m3 vacuum. Does the cube of air have potential energy? According to that, the potential energy would be converted into kinetic energy when the cube of air and the vacuum were joined. Would vacuum energy be the initial potential energy of the air?

And apparently (I read in a thread here) that vacuum energy constant will double in 11 billion years? Does that mean that the cube of air in 11 billion years will have more potential vacuum energy? Doesn't really make a lot of sense in the big picture.

2. Dec 29, 2009

### edpell

Both 5m^3 cubes have the same amount of vacuum energy. The side with the air also has the energy of the air [E=mc^2]. Yes the potential energy of the air pressure will be partially converted to kinetic energy as the pressure drops in half as the two sides are opened to each other.

3. Dec 29, 2009

### edpell

As to the vacuum energy doubling in 11 billion years if it does it will do so in both cubes. I guess we could ask where does the energy come from? What about conservation of energy (or I guess in spacetime conservation of 4-momentum).

4. Dec 29, 2009

### LURCH

No, that is not what the term "vacuum energy" refers to. Vacuum energy is also known as " zero point energy" and, if you are doing a web search, you should also look for the term, " Casimir affect." Basically, vacuum energy is the result of a phenomenon predicted by quantum mechanics; the continual emergence and annihilation of virtual particles.

5. Dec 29, 2009

### Chronos

Vacuum energy is never having to say you are empty space. It is what remains when everything else is removed from a volume of space. It is misleading to think of it as 'energy' because you cannot actually draw any energy from it. It is the lowest possible energy state that can exist in the universe. As Lurch noted, it is a consequence of quantum physics.

6. Dec 29, 2009

### edpell

But it can produce a pressure that accelerates that rate of expansion of the universe.

7. Dec 30, 2009

### Blenton

Really? So you could not do work from it?

8. Dec 30, 2009

### edpell

I would say if it accelerates the expansion of the universe we are getting some work out of it. Though I agree I see no way to use the vacuum energy for human use (i.e. heating a cup of tea).