And the Force is stronger than this?

[acroyear]

Built on Facts : The Physics of the Death Star:

Now let's say you wanted to take apart the earth. Yes, the whole thing. You want to grab each bit of dirt and pull it out of the earth's gravity and move it out to deep space. How much energy in total would it take? There's some practical reasons for wanting to know. The engineers who built the Death Star would need for their superlaser to deliver at least that much energy. And what could be more practical than that?

But figuring out exactly how much energy requires some finesse - figure out how much energy it takes to remove a kilogram worth of earth, and suddenly the earth has one fewer kilogram worth of gravity. So the next kilogram won't take quite as much energy to remove, and so on. We're going to have to do some thinking about how to get around this.

Lots of fun math in there...