Viewers asking about a game called Portal to Viewers have been asking whether physicists here in Nottingham might be interested in commenting on the game because it's quite science.

He quite quite physics.

So this morning I downloaded portal to What's cooking a very long time on dhe.

I've been playing it for the last couple off hours.

It's been a long time since I've played video games a long, long time since I've played.

Video games were Mel's solutions to Einstein's equations.

In 1959 staying developed his theory of general relativity, in which he was able to show how space time could be curved by the influence of matter, and that the curvature of the space time told the matter where to move and it's used every day.

General relativity is used to explain things like the orbits of planets around the sun.

Fact.

What I found is that as a complete newbie to this there, I got overwhelmed.

I must admit by the plot, because it's portal to So it's a sequel to Portal.

But in a nutshell.

What you are.

You're a character called Shell.

You've woken up in the same.

A megalomaniac computer effectively called Glad Does, which is a portal gone on the portal.

Go on is the most important aspect of this entire game, and hence than the important in that it allows youto blast effectively portals wormholes in space Time and the wormhole is a solution, which allows you to connect one part of space time to another part of space time simply through the curvature of space.

It's been put forward in science fiction as a way of transporting vast ist distances across the universe.

There are interesting science e concepts in here, the wormhole idea.

First of all, that's a that's a staple of science fiction that something of very many scientists, physicist, particle physicists come up.

Cosmologists have looked at very, very seriously in terms of Can we create wormholes in space and time?

Perhaps not in this context that really thought about traversing very large distances late years.

In this case it's over much smaller distances, but the overall concept is the same is that you're sort of moving from war.

True space and time true are completely different.

Route than is usual.

They are.

We don't know if they exist.

They, uh there are solutions.

They could in principle exist.

The 1st 1 it was actually discovered by Einstein, I think, in Einstein and Rosen in 1935 it's called the Einstein Rosen Bridge that linked to regions of space time together.

But as an example of the problems they face their very unstable.

And so, uh, in the 19 sixties, another mega star of general relativity, John Wheeler on, demonstrated that that solution of Einstein's was actually unstable.

So as soon as the bridge reformed connecting these regions, it would pinch off again so that a light ray couldn't proper get through from one end to the other before the bridge collapsed.

So for a physicist, I guess what's most exciting about this game is that you've got these these wormholes, that you complacent different locations allow you two to solve different types of puzzles t to move from space to space in in in a very novel where which after away gets quite intuitive.

Andi, the reason so many 60 symbols viewers are interested in This is because I guess I'm just well is this type of thing possible.

Could we actually do this on Dhe?

Another megastar of general relativity, Kip Thorne, along with Morris, came up with conditions that you need.

And basically, what you have to do is this bridge that forms this tube, if you like, that connects the two regions.

This has to be stable against collapsing and the way you have to do it.

It turns out you have to have some form of very exotic matter on it.

It's got negative energy effectively or negative mass.

So this is like having particles with a negative mass.

We don't know such particles.

No, I'm not a particle physicist.

I'm not a cosmologist.

I'll get the disclaimers of the way, first of all, but from my reading of my understanding of wormholes, you need huge amounts of energy to actually create these type of things we're not talking about, you know, sort off of levels off terrestrial energy.

We're talking about Billy the vanity of billions and billions and billions of stars.

Direction be ableto warp space time in this fashion so you can move through true space time like this.

So this is not gonna happen.

But again, as a thought experiment as an interesting way of looking at some unique physics or strange physics in a different environment.

This is really, really interesting for a physicist, but But the general idea is you have to do something a bit unusual in order for them to exist.

And then and then you in principle, can particle could traverse from from one region to another.

But that opens another problem.

Potential problem on DDE.

That is because it's linking space time.

These these these wormholes could either connect one special region to another special region, or it could connect one time to another time.

On duh, it opens up the possibility of time travel.

OK, which is how exciting is that, but in particular it opens up the possibility of going back in time.

And then you have all these paradoxes, which emerged as soon as you have these possible scenarios where you can go back in time.

You could go through a wormhole, reenter a minute before you went through and shoot yourself, and then have you managed to shoot yourself because you don't exist?

And these air paradoxes and hawking and thought and many people think general relativity can't allow for these.

And in fact, Hawking has a chronology protection conjecture.

Hawking's idea of how it this effects wormholes is quite neat.

It's a feedback mechanism, he said that so this will prevent the wormholes from actually allowing this to happen.

But it could also be the demise of the wormhole.

That's why I'm telling you.

And the analogy is, Ah, nice one with sound.

So when you go to a rock concert, you often you hear the speakers go berserk and there's a feedback loop.

So what's happened is the sound has gone through the microphone.

Maybe from the singer Gone down, the wire been amplified.

Come out of the speaker, and as long as it goes out into the auditorium, you're okay.

But if some of that sound gets back into the microphone and then it goes through this cycle again, it gets amplified.

It gets louder.

Then it goes back through, and that's a feedback loop, and that's what leads to the horrendous screeching.

And, of course, you then can't hear what's going on on.

Hawking has said that a similar thing will happen in world holds for wormholes to be of any use in the sense of being able to travel through time.

It's got to at least be able to have light through it all particles going through it.

So it has to be a reasonable size.

But as soon as it becomes a reasonable size than it can allow radiation t go through it.

And once that radiation goes through it, in fact, it can create quantum fluctuations can create more and more radiation virtual particles.

You'll get this cascade that the radiation comes through and get amplified going through and through and through, and eventually will cause the wormhole to collapse or explode and disappear.

So hawking, actually, what thinks that wormhole may not survive because of this?

And there's a great debate going on us to whether they cannot account.

So with many of these games in particularly portal, too well, the computer Huster has to do the calculations on it has to take the laws of physics and the equations of physics on it has to solve them on what it's doing is basically solving what we call differential equations Now.

I don't want the entire viewership of 60 symbols to switch off.

The moment I see is the differential equations differential equation.

The simplest possible differential equation.

You're probably gonna cut this out pretty put out.

I need to get a marker.

I don't think people are actively looking for wormholes that what people have done have simulated what something would look like if you were looking at them through a wormhole.

So if you know, if they if we stumbled across a wormhole and that wormhole was connecting us to some different part of the universe, then you know the light get so bent and distorted as it goes through these large gravitational fields.

And people have simulated that because they are just solutions to Einstein's equation.

So one of the beauties of Einstein's equations is, once you've got this solution there, then you can do things like you can propagate light through it.

And you can say, Well, what happens to lights and you could be at the other end and you can simulate what you would detect.

What?

What is it?

It just looks like a mess to me Equations, That bed, the reality of the physics.

I mean, that translates to the computer game, and it feels real to you.

But it's mathematics.

It's mathematical physics on dhe.

We tend to avoid marts and 60 symbols, and Brady and I have talked about this quite a lot.

This would probably get caught, but with I've never heard of Portal till you mentioned it's really never Been portal to had never been heard of Portal and Pentagon.

Find out what it's about, but this is May I'm walking around.

This is character Chelan Agrium.

I'm moving back and forth.

I'm pressing this key down now.

The computer is making those calculations on the basis when I hold this key down.

What's the displacement?

What's the speed et cetera on then?

Calculating that and updating the graphics accordingly?

When we do something like this, something really neat like this, then you can see the gun recoils.

Gun comes back.

McCoy's conservation of momentum theirs.

To make that look, really, you have to have the physics and you have to have the maths underneath the physics, and you have to cold that to make that all look, really, neither the makers know the distributors of portal to have paid as any sponsorship for this.

I did this in my own time.

I did not waste university resources.

I'm a physicist.

I know nothing about council research, so no council research has been hindered by my playing off this game.