Are you nervous about?

Answer any questions?

Moderately, You never know what you're gonna get from the public.

Someone has asked.

Can you explain stream theory in a way that I can understand?

That's very easy to answer.

No, no, no.

Yes.

I'm not sure I understand or believe in string thief.

We're used to the idea of particles and we're used to the idea of forces.

One big goal in science is to unify all of this and a one and umbrella.

The thing that's proved most difficult to incorporate has been gravity.

One possible way of doing it is through what's known a string theory, because string theory is where you replace a particle of point like object with a small strength.

That's it.

Okay, Every time you think of a party, you have a small strength on that string vibrates and the vibrations, the modes on the string, the frequencies, if you like of this vibration correspond to different particles when you get down to the very, very tiniest scale in the universe.

So you're talking in a very sub atomic sub elementary particle scales, you need some way of explaining the properties of matter on one of the ways of trying to explain the properties of matter.

Use that it seems to behave a little like a wave on a string and usually is a little loop of strings.

They've got like a standing wave, so it's a useful way of just thinking about the properties of matter.

The beauty of string theory is that there's a There's a a closed loop of string that conform on that closed loop.

A string can contain gravity.

It sort of comes down to a philosophical question as to whether that really is fundamentally what's going on, whether that's just a convenient mathematical description of what's going on because you never see it.

It's too small to see what is the speed of gravity, I think, referring give the idea of gravitational wave gravity travels at the speed of light.

A gravitational wave would have a speed on dhe.

People are tryingto detect gravitational waves.

It was very important for cosmology, and my feeling is that they must travel at the speed of light.

Anything that's massless travels at the speed of light, and Einstein told us that nothing can travel faster than the speed of light carrying information and gravity being massless.

It's called the massless particle, if you like.

It's called the gravitas and that shoot from one place to the next and the speed of light so it actually propagates at a finite speed.

If another huge planet mystically appeared somewhere else in the solar system, we wouldn't know about it straight away.

Wouldn't know you'd have to wait for the light travel time so you'd see the planet appear at the same time that you would start feeling its gravitational influence as well.

What its magnetism.

How does magnetism work?

Magnetism arises from electrical currents was very closely associated with electricity.

On dhe.

Electrical currents normally arise from electrons.

Electrons are small.

Fundamental particles carry charge on the atomic level.

You have atoms with electrons whizzing around in circles.

On.

Whenever you have a charge going round in a circle or in a close orbit, coming back to the same place that will create a magnetic field around the magnetic properties of, say, something a piece of iron, it could be a permanent magnet.

This is probably not a permanent magnet.

Can be a permanent magnet.

That's due to the fact that a lump of iron, their arm or electrons were there, which they spin.

Pointing up was the spinning in this direction than there are where they spend pointing downwards.

Spinning in the opposite direction should get them all lined up in the same direction.

So all these little whirling electrons are going around the same way and pointing in the same direction.

Then you get a magnetic field out of bed of iron.

Well, it in a piece of wood or in our story or a water that, of course, the electron spins in that case, that the bonds between the atoms that form up the molecules or the material in that case, all the spins air sort of paid off well, he's anti parable each other like this, but I and you could have.

If you make a small piece of I in the right way, you could make it a permanent magnet so you can get up to about half a Tesler or a bit more than that, with bits of clever metal that everything's lined up.

If you want something of about 97 Tesler 10 times larger.

You're much better off taking a superconducting cylinder, so you have a bit of metal, which is super conductor.

You set a permanent current going around it the other way to Bruce.

A magnet, of course, is a solar oId magnet.

We get a copper wire or super correctly wire.

You wind it in the coil, and then you flow electrons through it.

You pass a current through it on that can also generate a magnetic field.

So that's then generating a field by passing a current through a superconductor, a piece of copper wire.

And that's how you create a big magnet.

But you wouldn't want to do that at home.

What would happen if a car was travelling at speed of light and then turned on its headlights?

Yeah, that's a good one.

It was the same question, more or less than Einstein asked when he said, I'm traveling on a moonbeam or a Sunbeam on What would I see?

How would the world exist if I could travel at the speed of light?

Well, first of all, you can't get a calf to travel at the speed of light because you need to take all of the energy in the universe handsome or to get up to the speed of light.

So then the next question is okay, So supposing the car was going very, very close to the speed of light and turned its headlights on.

And then there's this weird property that, at least from the driver in the cars point of view, he would see the light from his headlights streaming away from him at the speed of light.

And the strange thing about special relativity is that somebody who is just standing next to the car as it went whizzing past would also see the light heading out of the speed of light.

This is very different from our everyday kind of experience of throwing things.

You know, if you throw something from moving train, then the ball that you throw is traveling at the some of the speed you through it, plus the speed of the train.

Light doesn't work that way.

Like always travels at the speed of light.

It is completely crazy, and you know that.

You know, there's a very fine line between crazy, ingenious, and Einstein was a genius because it's a crazy idea that turns out to be true.

Why do you think the galaxy in the solar system lying flat, plain conservation of angular momentum?

Eso, in fact, the first person who figured out the answer to this somewhat irritating he wasn't actually a physicist or an astronomer at all.

It was a philosopher guy called Immanuel.

Kant was most famous for crazy bits of political political philosophy, but actually, in his spare time, kind of messed around with natural sciences as well.

And he wrote a book which explained this.

As Galaxies form, they formed from a big cloud of gas, and as that glass starts to collapse under gravity, it starts to spin.

And it's the same thing with solar system, just on a much smaller scale.

And it collapsed on the gravity, and in the middle of it, the sun formed, and then the rest of it kind of collapsed down on because it was spinning.

It ended up not collapsing in that direction, but collapsing in that direction.

So you ended up forming a thin disk of the guests, and then that gas and other junk turned into the planets.

And so the planets kind of remembered that an original disk of material from which it formed.

And the neat thing is just it's kind of a throwaway line in this book of natural history of the heavens that he wrote he just said un presumably things like the Milky Way, the same thing on an enormously larger scale that presumably they formed from some big blob of gas that collapsed on and the stars formed out of that gas and ended up just orbiting around in this nice, orderly fashion.

Well, it doesn't have to be spinning much.

That's a neat thing, if it's just spinning it.

So presumably you have some big trouble gas and another big bopper gas near it, and they flew past each other, and they just kind of twisted each other a little bit and set themselves spinning very slightly.

And then, just as you know, the when the skater pulls their arms in and they end up spinning faster and faster.

So as this thing as it collapsed down, it conserved its angular momentum, which meant as it collapsed, it ended up spinning faster and faster and faster until it was kind of just this rotation we supported disc.

Is there a common misunderstanding about physics, astronomy, that noise you there is something that gets May.

I'm getting a little bit serious now.

Bread was things that annoy me personally, and this thing's just annoy me at a professional level.

The one that annoys me personally is when people refer to me as an astrologer.

Uh, the thing that drives me mad is when I get mistaken for being an astrologer.

And then, you know, they asked me to do their styles for them.

That's not what we astronomers do.

Astrology is one of my bugbears, and it drives me mad that so much energy is put into talking about and referring to what star sign someone is.

It's ridiculous.

You would say that your policies.

I'm a Tory.

Actually, I think we're meant to be old geeks on that irritates me.

There's a general feeling that's the kind of areas that I work in.

And my colleagues here working blue skies, the particle physics, the astronomy has no application, so we should just effectively stop funding at them in.

We should stop supporting certain eso and we should pile all our money into practical aspects.

Is a the Engineers Roll It Roll Academy of engineers recently put out statements basically saying, We should stop funding on DDE.

That really bugs me, because these these are academics who know about the benefits of science and physics in particular.

But what's wrong with knowing stuff?

What's wrong with actually spending your time studying and then leading a normal life elsewhere on being really interested in passionate about?

So I love physics because I want to know how the world works.

Who knows what benefits will come out of Sun?

Who knows what benefits will come out of?

The techniques are used in astronomy.

They could have revolutionary effects, the Internet.

The fact that a ll these viewers can come watch these videos is because of particle physics.

It's because of what went on at CERN, and that wasn't forcing 2020 odd years ago.

And yet there's this.

There's this mindset which way must cut things immediately, especially those that don't have obvious immediate benefits.

And that bugs me because some of the people that are saying that I think should know better that the media image of us he's probably Sheldon off the Big Bang theory on There are people in physics.

I mean direct was shown who are so literal minded that they can't inter relate with other people at all.

But you've talked to my colleagues.

We're not really like that at all.

There's a very strange misunderstanding, which is to do with the phases of the moon, which is so basic and fundamental that it's a bit worrying that so many people don't get it in.

A lot of people think that the reason why there's a dark side of the moon light side of the moon is because of the earth gets in the way.

And so it blocks out some of the sun's light, and that's a That's a thing called an eclipse, and it does happen from time to time.

But it's not the main thing that goes on the thing that most frustrates me about not too much physics, but the physics and science and culture and physics and science and society is the abuse of physics term.

So particularly energy and energy fields and negative energy and positive energy, and how this is coupled into mysticism.

That's the thing that really gets my goat.

The main reason why half the moon is dark and half of it is like it's just because just like your there's a day side on the night side and sometimes we can see just the day side of moon, which is when you see a full moon.

Sometimes you just see the dark side, the night side of the moon, and that's when you see a new moon and sometimes in between the two and you see a bit of day side in a bit of night side, so that that's probably the misunderstanding that worries me the most.

And there's a lot of pseudo science where things are dressed up on.

Products are dressed up with pseudo scientific science in terms.

My biggest annoyance is this email that continues to get forwarded every year.

That says, the more that Mars will look as bright and as big as the full moon in the sky.

It will happen in mid August or something, and every year it gets forwarded, and every year people believe it, and it's totally wrong.