And the laws of physics say they pretty much can damn well stay out there.
While the laws of common sense say they'd have no reason to come here when they don't know there's a here to come to...
I think the real reason we haven't seen any proof of aliens is going to be much more interesting than either of those statements.
Um, I doubt it. Really, I doubt it. Space is just *so* damn big, you see, that that damn lightspeed limit buggers everything up...