Reply #61: I seriously doubt it's an alien

[krispos42]

We would have seen them coming, absent of some sort of mythical (but entertaining) hyperdrive. Solar sail, nuclear fusion, antimatter... the energy required to slow down a spaceship from near-light speed would be visible for light-weeks or more. And the time to drag a ship down from those kind of velocities, even given plenty of energy, is measured in months.

I kinda like to think that if a giant spaceship capable of generating megawatts or gigawatts of energy was pointing that energy at us for the better part of a year, we'd, yanno, notice. Or something.

If you allow things that are currently theoretically impossible, things like hyperdrive, warp drive, superluminal drive, jump drive, Alderson drive, gravity polarizers, impulse drive, or whatever, then it all goes out the window and you can pretty much do what you want.

But much as I'd like to allow it, I can't. So... that means I don't know what it is, but I know what it isn't.