David Kipping

potentially yeah potentially depends on i think you know the properties of whatever the spacecraft is um i mean one one problem with warp drives is there's all sorts of problems with warp drives but when like the start of that sentence one problem yeah there's just this one minor problem that we have to get around but uh when it arrives at its destination it basically collects this vast uh

It has an event horizon almost at the front of it, and so it collects all this radiation at the front as it goes.

And when it arrives, all that radiation gets dumped on its destination and would basically completely exterminate the planet it arrives at.

That radiation is also incident within the shell itself.

There's Hawking radiation occurring within the shell, which is pretty dangerous.

And then it raises all sorts of exacerbations of the Fermi paradox, of course, as well.

So you might be able to explain why we don't see a galactic empire.

I mean, even here it's hard.

You might be able to explain why we don't see a galactic empire if everybody's limited to Voyager 2 rocket speeds of like 20 kilometers per second or something.

But it's a lot harder to explain why we don't see the stars populated by galactic empires

when warp drive is eminently possible because it makes expansion so much more trivial that it makes our life harder.

There's some wonderful simulation work being done out of Rochester where they actually simulate all the stars in the galaxy,

or a fraction of them, and they spawn a civilization on one of them, and they let it spread out at sublight speeds.

And actually the very mixing of the stars themselves, because the stars are not static, they're in orbit of the galactic center and they have crossing paths with each other,

if you just have a range of even like five light years and your speed is of order of a few percent, the speed of light is the maximum you can muster, you can populate the entire galaxy within something like 100,000, about a million years or so.

So a fraction of the lifetime of the galaxy itself.

And so this raises some fairly serious problems because

if any civilization in the entire history of the galaxy decided to do that, then either we shouldn't be here or we happen to live in this kind of rare pocket where they chose not to populate to.

And so this is sometimes called fact A, Hart's fact A. The fact A is that a civilization is not here now.

An alien civilization is not in present occupation of the Earth.