Can we extract energy from the Cold?

Dave - That is a very interesting question. You can't gain energy directly from cold, but what you can do is get a lot of energy by moving heat from somewhere which is warm to somewhere which is cold. And that's essentially what a steam engine does or a car engine, any of the heat engines work exactly like that. However, the colder you get that cold into the system, the more efficient the process is. So if that cold end is absolute zero, then if you move a kilojoule of energy from something warm to there, then you've got a kilojoule of useful work out of that. If it's hotter than that, then it gets a lot less. So, once you collect energy from cold directly, you can get a lot of energy by transferring heat to somewhere very cold.