Also just a throw away line and I am sure people would call me a crack pot. And I am far from an astrophysicist, so you can take my niavity.
http://discovermagazine.com/2008/aug/18-nothingness-of-space-theory-of-everything
This article talk about temporary particles in a vacuum and dark matter. What if 100 years from now power can be derived from dark matte or capture the temp particles, would that mean you could produce and engine that used space as fuel?
This has been a common science fiction idea for years (for example Charles Sheffield's stuff). The problem is in the paragraphs about 1/3 of the way down the 2nd page - if you can pull energy from the vacuum, then that means the vacuum is unstable and can go into a different state, where the laws of physics would be different and we'd all die.
As an example of this, think about two populations of (fresh water) fish - "A" that's living in water that's 5 degrees C and "B" that's living in water that's -5C. In both cases, there's thermal energy in the water. In case "A" the fish can try to extract that energy by rearranging the water into ice. The problem is this doesn't work - the "water" state is the stable one. In case "B", it will work - you'll get energy out of the water by turning it into ice. The problem is that water
likes (energetically) to be in the "ice" state at -5C, and the ice crystal you just made will grow until the whole pond is made out of ice and the fish die because the physical properties of water are very different from those of ice. If you say "vaccuum" everywhere I said "water", then you've got the argument on the 2nd page....
CAVEATS:
1) Experts will notice that I was being a little fast and loose about energy vs. free energy above. The general argument remains the same, though.
2) There's always the very small chance that some of what we think are very basic physical principles (like the 2nd law of thermodynamics) might not apply at these small scales/high energies. If so, something weird might come out of it.
3) If the vacuum is "choppy" (think waves on water), then there might be a way to extract energy from the chop. I suspect it would be difficult to get much out, though.
John