Professor Geraint Lewis

If you fly off in a rocket and keep accelerating, in about 99 years to your own time, you would reach the edge of the universe as we can see it now.

Billions of years would pass on Earth, but to you it would be a long lifetime.

So, yeah, we do get this contraction.

Everything feels closer the faster and faster we get to the speed of light.

That makes me sick.

Well, I was just going to mention that if you look at a modern warship, they have these systems on board which are all automated because the threat is missiles these days.

So they are bristling with, I think they're called Vulcans, and they basically have loads of them over the ship

And you just need to fill the sky with lead to take out these missiles.

And it's potentially what they're doing in the expanse as well, is you just chuck as much stuff out there as possible that you try and hit everything that's coming in.

Well, it's an excellent question.

So to a physicist, there's really not much difference between air and water.

They're both fluids, and they follow the rules of fluid dynamics.

And in the same way, you can imagine if you dig a big hole in the Earth that the oceans would flow in there.

If you dig a hole big enough in the Earth, the atmosphere would flow in there as well.

So the atmosphere responds to gravity.

And if there's a hole, everything will just flow in.

So you could end up with the situation that all the atmosphere is in the hole and there's nothing left on the rest of the planet.

So yeah, definitely if you start digging big holes, you'd have to worry about the atmosphere that you've got out there.

Yeah, you could end up with no atmosphere over the surface of the planet and everything in the hole.

Yeah, I got caught up in a sort of multi-car crash in the US.