What does that mean?

So super liminal means above light so faster than light motion.

This is not possible.

Everyone knows that.

I'll show you a picture.

Would you like to see a picture of some super liminal motions?

Here's a picture.

So this object, the 83 h monos are artists in about 2000 to suddenly went into outburst.

And then there's a series of pictures from the Hubble Space Telescope, and as you can see, it's expanding.

And this is kind of as ever when you take a picture, you're kind of measuring the angular size of it.

But because we know how far away the subject is, you can translate that angular size into a real size and see how fast the object is actually increasing in size over time and it works out.

It's expanding it about a light year per month now, given that this cosmic speed limit is the speed of light, which is a light year per year kind of.

By definition, Ah Lightyear per month is about 10 or 12 times the speed of light.

It's a very bizarre object.

This is a very uninspiring star have to say.

What used to be a very uninspiring star in that's Omanis or tress is means it's in the constellation of Mon a Saurus, which is the unicorn, which is no consolation.

Many people have heard off because it's not a particularly exciting consolation.

Ahn Drea, 838 means this was the 838 variable Star found in this particular constellation.

So again, it's not exactly top of anyone's list of anything until 2002 when all hell broke loose.

It brightened up incredibly quickly.

In a matter of days, it was 10,000 times brighter than it had been at the point where it brightened up.

It was about a 1,000,000 times as bright as the sun.

The classical thing that does this is a thing called an over on there.

It's kind of a probably a thermonuclear reaction happening on the surface of a white dwarf or something like that.

This doesn't fit the bill.

It doesn't have the properties of an over something else.

Very peculiar happened to this star.

It's likely that it ate something, so it likely that another star merge with it or a planet merged with its or something fell into the star, which really stirred it up and heated up and made it very bright for a fairly brief period of time.

But pretty big incident in the history of this star system.

It is.

I mean, that's the interesting thing is that the stars still there, So nothing totally catastrophic has happened it, But somehow it managed to get incredibly bright for a little while.

Then after dinner, just calm down.

It's faded back down again to kind of the level it was at before, and the other thing that sort of became clear is it's Actually it's a binary star in the middle here.

So again, it might be something to do with the properties of the fact that it's a binary star in the middle.

But no one's really quite clear what made it do this catastrophic brightening.

There is this thing that that appeared around it, which was indeed expanding faster than the speed of light.

The natural way people think about these things is what it's going to be explosion.

So it's just the stuff going out from the explosion.

That clearly can't be the case because the stuff going out for the explosion is restricted by this speed limit of the speed of light.

So it can actually be a physical thing, which is expanding and what it actually is, a thing called a light echo.

So it's not actually a physical object expanding at all.

It's just that, in some sense, it's an optical illusion.

Let me give you a kind of simple example of the same sort of thing which I could do here in the in the room.

Okay, so if I take a laser pointer, if I shine the laser at the wall and then just move my wrist back was avoids a little bit.

The being moves back and forth on the wall.

Now if I moved back further away from the wall and do exactly the same thing, so move my wrist by about the same amount.

You see that the dot moves a lot further on the wall, just a geometric effect that one further away from the wall.

So, actually, although the angle that is moving through it's the same the distance the dot moves on the walrus further now, you could imagine if I would have a powerful enough laser pointer as I move further and further away eventually reach a point where just moving that little bit would actually make the doc move along the wall faster than the speed of light.

Because it's just gonna keep going faster and faster.

There's nothing to stop it.

And we're not breaking any laws of physics by doing that because, actually, you know there's nothing physical going on there.

It's not like there's a particle moving along the wall faster than light.

It's not like this.

Any information moving along the wall fast on the light, But nonetheless, you can have something which you know where the appearance of the dot actually moves faster than light.

It's possible tohave things that appear to move it will actually do move faster than light like that.

Don't really wouldn't be moving faster than life.

We're far enough away, but again, you're not breaking any of the speed limits, and that's kind of what's going on in this object.

Here, let me draw you a picture.

It's easiest thing to do.

Okay, so here's the story.

So here's us over here with our telescope pointing up into the sky, and he is the thing which suddenly went extremely bright, distant object that suddenly brightened enormously due to whatever this peculiar phenomenon is.

The extra bit we have to add to this picture is that before it went incredibly bright, probably in some previous explosion of some kind it throughout a shell of material which is now just hanging around in a kind of a sphere.

So this is a shell which is light years away.

So it must have been something that happened a long time ago.

Nothing at all to do with this present explosion.

It might even be left over from the formation of the store in the first place, but it's just some shell of material hanging out.

The thing suddenly brightened up in 2002 and it basically lit up.

That sphere is like a lamp shade lit up around it, but we didn't see the lamp shade all lit up at the same time we saw it.

The first bit that was lit up was a bit that had the shortest part of us, then another bit a bit further out and so kind of ring of material in this in this debris field and then 1/3 and so on.

So over time you'll see this expanding ring of material.

Of course, the material it's always in expanding at all.

It's just this fear of material sitting there, but it's because it's being lit up in the sequential way.

You'll see it expanded this expanding ring of material that's getting lit up, and that's really all that you're saying here.

Now it's a little bit more complicated cause you can see there's lots of structure in this thing, So probably there's actually a whole series of these spheres of material around it.

But the basic pictures the same.

It's just a whole series of things or getting lit up in this sequential fashion justice with the laser on the wall.

You know, it's just down to the geometry of the situation.

If you set things up, you know, the difference between this path and this party isn't actually very big.

And so, actually, the time delay between the direct route and the next root out isn't actually all that long, and so that you know the time for it to Togo, from lighting up just the central bit to lighting up this much bigger ring can actually be quite short.

And just by playing around with the geometry, you could make that speed anything you want it to be, including force and the speed of light.

If you're here on a pointing a really powerful laser pointer at the moon, you could presumably create this effect on the surface of the moon, where the laser point is moving across the surface of the moon faster than light.

Does that mean if I was standing on the moon, this point of light on the surface would come towards me and then pass mate faster than the speed of light?

It would.

But of course, but there's no it's not like it's a physical thing.

It's not like it's a particle or a car or a rocket going past you fasten the speed of light.

It's just a series of like lighter rivals that shoots past you, falls on the speed of light.

So if I replaced that powerful laser pointer with a really big metal road, then you can do it because then there's a physical entity which is actually traveling, and that you can't do.

If you were trying to accelerate the end, you're tryingto.

By doing that, you're trying to accelerate the end of the road force on the speed of light and the laws of special relativity say, actually, in order to do that, you'd need an infinite force to do it, so you wouldn't need just a strong wrist.

You didn't need an infinitely strong wrist in order to do it.

So So where it falls down is the mass becomes so great.

It really is.

Yeah.

I mean, it just it.

So the inertia of the thing becomes so great they actually the laws of physics guarantee you can't do it with a physical thing the way you came with a beam of light.

Does this optical illusion this'll?

Deception caused problems For astronomers, that seems like something that could catch you guys, that you've got to be careful right in that if you were to, you know, you might try and do a naive calculation of trying to figure out how far away these object was If you didn't have any other constraints as to how far it was by saying, Well, I know that this thing can't be expanding faster than speed of light.

I can see how fast it is expanding on the sky.

That then tells me how far away the object could be.

So you could get completely confused by making the wrong assumption that you're actually seeing a physical thing expanding and using that to infer something about the properties of the object you're looking at delight.

Echoes occur anywhere else other than in gas shows, surrounding styles or binary stars.

I think they're the main place.

You see them, so we've seen them.

So for supernova 1987 8 for example, they're seeing light echoes still from the explosion from supernova in 1987 8 But you really need something which produces a pulse in order to get a kind of unidentifiable echo from different directions on the main things that produce those kind of pulses are exploding stars in one form or another.

So that leads nicely to the issue of second generation moon trees.

I'm sure you can figure out what they are.

These are the sons and daughters of original moon trees are first generation moon trace.

Just take the seeds, plant them somewhere else.

Okay, We don't know exactly where the trees were planted it with somewhere here at the Space and Rocket Center.

So in order to figure out what the whole scrambles like writing space shot.