Could aliens travel through wormholes?

One thing that’s certain about aliens, if they exist and are visiting us, is that they must have access to technology that enables them to traverse vast distances across space, presumably, by resorting to various tricks, at very high - possibly faster than light - speeds. If so, how? Theoretical physicist from Imperial College London, Toby Wiseman...

Toby - Well, the conventional way might be some kind of super fast rocket that they have developed with their brilliant civilisation technology. They might have also come across the idea of a warp drive, and made that a reality. And perhaps even more strangely, they’re able to slingshot themselves around the universe using black holes. Possibly even wormholes that they can just pass through to traverse huge distances. So those would be the exotic ideas.

Chris - The first of those - a really powerful rocket - that’s technology or physics that Isaac Newton gave us hundreds of years ago but we know that works and we know that’s plausible. But is it really going to cut it? Because the sorts of distances we’re talking about here across the universe, what sorts of distance would the minimum distance be? If there is life that is not in our immediate vicinity in the cosmos, what’s the minimum distance that Mr or Mrs alien has got to traverse to get here?

Toby - Well, if they're coming from inside our galaxy, we're talking probably tens of thousands of light years. But if we're talking outside our galaxy, it might be millions, even billions of light years that they would have to travel to get to us.

Chris - So that just would not be possible with a rocket, presumably.

Toby - I'm not sure that's true. If we're able to just go by the laws of physics. One of the things that Einstein told us is you can't travel faster than the speed of light. And I believe him, I don't think you can, but he did also say that if you can travel very close to the speed of light, the way you perceive time and space is changed. And so in fact, if you can travel very fast close to the speed of light, you are able, in principle, to travel vast distances in an arbitrarily short time.

Chris - What that means then is that if they're going very, very fast, that for them time continues to tick at the rate my clock ticks at. But for everybody else, their clock goes incredibly far into the future. So basically if you were traveling close to the speed of light, time would carry on at the normal rate for you. But I would age far faster than you is what you're saying. And so therefore you would get places without much time passing for you, but huge amounts of time for everyone else.

Toby - That's exactly right. So for example, our nearest star is roughly four light years away. If you could travel very, very close to the speed of light in some clever rocket and I was watching you from Earth, I would see it take about four years for you to get there and another four years for you to get back. I'd have aged eight years in that time. But for you, if you could get very close to the speed of light, you could do it in a few hours.

Chris - Gosh, that's quite mind bending stuff. The other thing you mentioned is wormholes. Now these crop up in science fiction quite a bit and the analogy that's given about this is they say, well, instead of going along a whole sheet of paper, if you roll the paper up so the two ends meet, then you can jump from one end of the paper to the other over a very short distance. Now is that bending the rules of physics for artistic license purposes or is there some kernel of truth in that?

Toby - So the sort of scientific history of wormholes and explorations goes back a way. Einstein's theory of space and time is pretty weird to be honest, and it is in principle possible for space time to be bent and curved in this sort of way you describe. So like with the piece of paper, there can be the conventional route along the piece of paper between two points, but there might be some new shortcut route that doesn't lie in the paper, a sort of tunnel joining two points. That in principle is possible in Einstein's equations. And indeed solutions like that have been mathematically written down. But the sort of matter that we think would have to be required to support a solution like that we don't think exists so that it could really be a shortcut. What we think is that wormholes might be possible, it might be possible to join two points in space time through some strange little wormhole tunnel, an alternate route between those points. But it seems like that route will always be longer than the conventional route. So it is not very useful as a way to travel large distances.

Chris - It sounds like the London underground because when I go on the underground, I always lose touch with reality on the surface and I discover that what's a long journey on the underground, I could have just left the station and walked one street <laugh> and I'd have been where I wanted to go.

Toby - It's exactly like that. So with the London Underground, of course you've got points A and B, you can walk on the surface. Most people don't think to do it. But actually the distances are not that great, certainly in Central London. If you go down into the underground, you've got a completely new route. And if you couldn't take a train and you had to walk that route would actually be longer than typically you could do on the surface. So it wouldn't be a very good way to get around. Perhaps people will invent wormholes with some fabulous rocket that travels through them, and use them that way. But as far as we understand so far, wormholes are possible, but they're not going to be a shortcut. It's going to take you longer to go through the wormhole. It's also unclear how you could create the wormhole. So if they're preexisting, perhaps you could use them in some useful way, but we don't know how you could create two wormholes, or a wormhole with ends at very far separated points.

Chris - You're not making a compelling case for aliens being able to do this in a practical way that they'd have to really, really want to do if they were going to do it. Which I guess leads me to my next point, which is why would they want to come here in the first place? Surely if they can do all that and achieve all that, would they not already have the ability to reach out and learn everything about us without actually having the bother and the faff of coming here?

Toby - I think you're right. What probably modern physics tells us is that whilst in principle people could travel vast distances, it would require super enormous amounts of energy. Maybe vast amounts of anti-matter sort of to make a rocket. And that sort of technology is so far beyond anything we have. They would be a tremendously advanced civilization. They're not going to look anything like us in terms of their capabilities. And so why they might want to come here and look at us now, of all times, is a very good question, I think.