Invisibility Quest

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BBC Sounds, music, radio, podcasts.

You're about to listen to a brand new episode of Curious Cases.

Shows are going to be released weekly, wherever you get your podcasts.

But if you're in the UK, you can listen to the latest episodes first on BBC Sounds.

I'm Hannah Fry.

And I'm Dara O'Brien.

And this is Curious Cases.

The show where we take your quirkiest questions, your crunchiest conundrums, and then we solve them.

With the power of science.

I mean, do we always solve them?

I mean, the hit rate's pretty low.

But it is with science.

It is with science.

Today in Curious Cases, we're on the hunt for things we cannot see.

The perfect topic for radio.

Isn't it?

Isn't it?

Yeah, it is an invisible medium on which we will be discussing invisibility.

People do say that radio paints the best pictures.

It'll have to do a hell of a job on this one.

This going to paint.

We need the radio to paint a picture of things that are literally unseeable.

Yeah.

This is not our fault, by the way.

This is the fault of a listener called Dylan.

Hello, my name's Dylan, and I'm from Epsom.

I would like to know if anything in the universe is truly invisible, and if so, what and how?

I think that is a spectacularly good question.

I think there's going to be hardcore physics here.

What I will say, though, is as a general trend, I don't think using the word

to people who are sending in questions is

that might preclude people from wanting to send them in.

Please send in your questions.

I won't blame you for it if it makes the show technical or difficult or filled with science.

You're right.

That is actually the whole point, isn't it?

Or double down.

Let's go on to who can anger us the most.

In fact, you want something invisible?

My ire.

My...

Just until it erupts, it's there bubbling away.

And oh my god,

what do we have to answer?

So yeah, so we're going to...

The disdain, the disdain that you have for Dylan.

No, I have no disdain for Dylan.

That's a genuinely brilliant question.

And he's cut to the nub of a really, really interesting topic, you know?

I mean, and we're going to keep it physics.

It's not going to be about, you know.

But can we truly see love?

It could be.

I mean, who knows?

Yeah, or

maybe these visitors are going to come in and say, yes, there is something truly invisible.

And it is.

You, the Nordic spirit of Kufufawal, who comes out every winter into the winter landscape and arranges the snow on the trees.

If that happened, if one of the physicists went suddenly, wow, that'd be amazing.

Or the other way, if we went that way, when they come in with a sheaf of paper about black holes, you know, and they've done all their study in this, and we're going, but what is it?

What about, you know, just happiness?

Is that immeasurable?

Is it?

I mean, look, I think the chances of this episode going in that direction are low, but not zero.

Okay.

In the studio with us to reveal the hidden universe, we have Andrew Ponson, Professor of Physics at Durham University.

And Matthew Bothwell, the public astronomer at the University of Cambridge and author of The Invisible Universe.

I mean, sounds like you're the man to

just hand it over to you.

If simple question starts off, then what do we mean by invisible?

Well, it's not one of these words that you need to sort of break down the etymology, right?

I mean, invisible just means not visible, anything you can't see with your eyes, I guess.

I mean, in this studio, there are invisible Wi-Fi signals and there's invisible heat radiation bouncing around and yeah we live in this whole invisible world.

Okay so why is air invisible?

I mean it's still made of matter.

Well it's just because so light waves that we see with our eyes, the optical light waves can just travel through it like pretty unimpeded.

If we could see with different wavelength eyes then air would be very very visible.

Like if you could see with infrared eyes for example then the atmosphere is a brick wall.

Like the atmosphere is completely opaque in the infrared.

So if we had infrared vision, the sky would be black.

Who figured this out first?

Who was the first person

who noticed these spectrum outside of our vision?

Well, it's a long scientific detective story.

I think the infrared was discovered by a guy called William Herschel, very famous astronomer, discovered all kinds of stuff, including the planet Uranus.

He was playing with the spectra you get from sunlight, you know, doing the famous Isaac Newton light through a prison thing.

And he noticed that beyond the red end of the spectrum, there was some sort of heat.

And so he was like, aha, there must be some sort sort of heat.

You know, there's some invisible aspect to sunlight that's heating this thermometer up.

Can you repeat this yourself?

Okay, so you know how sometimes you get like light coming through the window, there's a bit of a rainbow on the, that it, that it casts.

Can you do this yourself?

Can you like put a nice, a good thermometer?

You know, I've never tried it.

I think you probably could, right?

I mean, he was able to do it in like the 1770s, so

with a state-of-the-art thermometer.

I would guess the artist.

So if you go beyond the red of a rainbow on the floor from whatever glass, like, and stick a thermometer into that empty space, it'll start heating up.

Yes, you will notice a tick upwards in heat because there is some infrared light being diffracted by the prism that your eyes can't see, but your thermometer can pick up.

I have an infrared camera with me.

Do you want to have a play with it?

Just looks like a phone.

It does not.

It does.

No, yeah, it's an infrared camera.

Oh, you can actually see.

Sorry.

You have a very red nose, by the way.

Do you know what?

Every time.

Every time.

I mean, don't be all Rudolph about it, but that's not a nice thing.

I know, it is.

Yeah.

Oh, no, actually, sorry, I'm thankful.

You all have have A-red nodes.

Does infrared pass through materials?

It depends on the material, right?

So yeah, it can travel through sort of the air around us reasonably easily.

It can't travel through sort of 100 miles of air in the same way that optical light can.

And so

this is seeing a wavelength of about 10 microns, about 10 micrometers, and that wavelength just does not come through the atmosphere at all.

But yeah, but something thin like a plastic bag or something.

So if we were to take it, for example, and thank you for building up to that, if you were to build a series of glasses that contain either ice or water, so different temperatures, obviously, same thing at different temperatures.

You would be able to see them from behind plastic, yes.

Thank you very much.

So just before we move on, just before we move on, I'd

just like to tell you that you are red all over, apart from the tip of your nose.

Wow.

Old Johnny Cold nose over there.

Oh, that's interesting, though.

Between us, we make one warm birthday.

Okay, so

we have five glasses of water which are being lowered behind, I think, what looks like a bin bag, a very scientific piece of equipment.

And with the camera, we should be able to see which glasses are warm and which glasses are cold.

So, obviously, optically, we can't see anything at all.

We can't see the glasses at all, exactly.

But can we hold up the camera then?

We can.

Should we do this together, Hannah?

Let's do it.

Oh, look!

Oh my gosh, that's incredibly obvious.

So, there are, you can see all five glasses appearing on the infrared image.

I mean, very clearly.

Two of them are bright orange with sort of a yellow glow around them.

And then the the other three are like these dark blue spots so okay it's it's the ones so from from left to right it's ice hot hot ice ice correct

as if by magic as if by magic but all the things that we have in the strong image in our head about how light travels that notion of an up and down your wave traveling along and it's also the same for infrared absolutely yes it's the same for any kind of electromagnetic wave so from x-rays all the way down to radio waves with everything in between microwaves infrared optical light it's all electromagnetic waves, right?

Like the optical part of the spectrum that our eyes are sensitive to is quite narrow.

If you put it in terms of a piano keyboard, if we see one octave on a piano keyboard, how many octaves are on that keyboard?

Yeah, one octave is right, because it's about a factor of two in wavelength, right?

So a middle C up to a C, one octave higher is about a factor of two in wavelength, and we see visually about a factor of two in wavelength.

Right.

So the entire, you know,

all of the light, or all the electromagnetic radiation coming down from the universe is something like 65 octaves from the highest energy gamma rays all the way down to the lowest energy radio waves.

It's about 65 octaves.

So about eight or nine grand pianos side to side compared to our vision, which sees one little tiny octave in the middle.

We're useless.

We see it.

Yeah, we see almost nothing.

Well, then, so almost everything is invisible to us.

Andrew, most light we don't see.

And that's just an evolutionary trick.

That's just the way we have developed.

Yeah, absolutely.

I mean, the key thing is that the sun emits light of particular colours and generally speaking most of most of the energy from the Sun does come out around about the kind of wavelengths that we are sensitive to that our eyes are sensitive to and also that the atmosphere lets those wavelengths through so

we're sensitive to the things that are easiest to see if if you like I think we've got to be careful about the definition that we're using here then because okay if it's like invisible as in you just can't see it with your eyes that feels like a quite a kind of not quite the right definition here.

So maybe we just need to say that invisible is stuff that you can't detect.

Yeah, I mean,

that would be a perfectly good definition.

I mean, the trouble is that then you start coming into the question of, well, what does it mean to detect something?

So there are loads of examples where people sort of detect things in very indirect ways.

I mean, if we go to astronomy, the discovery of the planet Neptune, for example, was not done by pointing a telescope at the sky and seeing that Neptune was there first.

It was actually done by measuring the way that other planets were orbiting around within our solar system and going, hang on a second, something doesn't look right here.

It looks like there's another planet that we've never seen that's pulling the planets that we can see around.

And that turned out to be absolutely right.

In the end, a telescope was developed that was sensitive enough.

If you pointed it in the right direction, you could find Neptune for real.

But at first, do you want to call it a detection or not?

I don't know.

Is it a detection?

Is it a deduction?

You start to get into language questions here.

But there was one point where people thought there was an invisible planet.

Well, yeah, I mean, they thought there appears to be a planet there, but we just can't see it directly.

I'm stretching the definitions of invisible here, to be honest.

Okay, here's what I want to know.

If you pop up to space, little spaceship, and then you start having a look around

using those kind of invisible lights, as it were,

do you see different things?

Yeah, 100%.

You see a completely different universe if you look at the sky with this invisible light.

But if you look in the far infrared, for example, so like super long infrared wavelengths just before they become microwaves and radio waves, and you look at our Milky Way galaxy, instead of the, you know, you can, listeners might be able to picture the Milky Way galaxy that they've seen sort of on hanging on walls and so on.

In the far infrared, the Milky Way galaxy looks enormously puffed up and dramatic and volatile, like the huge loops and sheets and whirls of dust being thrown up out of the plane that we can't see with our eyes.

It looks completely incredible.

You see this completely alien universe when you look in any other wavelength, but the ones we're familiar with.

And we have sent up

all manner of different things.

Now that we've known, now that the blinkers are off and we realize there's a lot more going on than we could possibly see, we've sent up telescopes in x-rays, in infrared, in ultraviolet.

We are constantly getting images of all these different.

Yes, to all of this.

Yeah, we've sent up, I think basically, if you can name it, we have sent up a telescope that can see it.

What's an x-ray of the universe looks like?

Oh, it looks amazing.

You see these,

like, the galaxy looks very dotty, and each little dot is a black hole.

Isn't the whole point of black holes that you can't see them?

Well, yeah, so black holes are called black holes because the gravity is enough to swallow light, right?

So there's what we call the event horizon, the outside edge of a black hole, and anything that goes past that, even light, is swallowed.

But we can see black holes because before things fall past the event horizon they sort of swirl around the cosmic plug hole a bit.

Um black holes are quite messy eaters so anything that falls in um sort of gets all kind of churned up into this what we call an accretion disk, this sort of swirling maelstrom of stuff being gobbled up by the black hole.

And because the gravity of the black hole is so strong, that swirling maelstrom goes incredibly fast and gets incredibly hot.

And at those temperatures you glow with x-rays.

So if you take an x-ray of the sky, you can see black holes glowing.

It's uh it's incredible.

Oh, I like that.

Can we get back then to what we can do with visual light in terms of making things possibly appear invisible?

Yeah, because if stuff can like become visible and then become invisible in space, can you do that on Earth?

Can you like trick stuff into becoming invisible?

Yeah, I mean,

not in quite the same way, but there's a lot of interest, you can imagine, from military circles in particular, in trying to make things that you would normally be able to see perfectly clearly invisible and by designing special types of materials people are making steps towards being able to do that like a sort of invisibility cloak that you can put round things it's very early days as far as we know unless there's any kind of very secret technology that nobody's told us about but as far as we know it's very early days very difficult to actually do this

but people are making developments in that direction but Matt you have an example of something that would trick the eye.

So, in fact, I have a very neat piece of plastic here.

It's a sort of translucent playing card type thing, and it's going to make a pen disappear.

An actual invisibility cloak.

Yeah, exactly.

And I think the word trick is right.

It is literally a magic trick you can buy.

So the trick is called Lubor's Lens.

I think that's how it's pronounced.

But it's what's called a Fresnel lens.

So there are tiny little scores.

I'm holding up a sort of translucent playing card size thing of material.

And there are these tiny little scores in it, which bend the light around an object.

And it's sort of direction-sensitive.

So so it will let you see vertical things.

Well, horizontal things become almost invisible.

Go on, give it a go.

Okay, so if you come over,

so you've laid out like pens, basically, a kind of a grid formation.

Exactly.

Yep.

So we have three vertical pens and one horizontal pen.

And if you hold up the lens like

the vertical pens are unchanged, and the horizontal thing just completely disappears.

And if you if you rotate it 90 degrees, I make the vertical disappear pen.

You get the opposite effect.

It's very surreal, isn't it?

It really works.

i would

i want to say so does that want to

oh my gosh that is really it's kind of it's it's it's uncanny how well it works wow

wow you can make your own finger disappear

that is genuinely really impressive as long as the military want to hide pencils from their adversaries you could attack people if you attack if you if you stayed horizontal the entire way and then we're against a vertical grid that's that's remarkable how effective that is yeah i mean yes obviously, in incredibly specific circumstances.

So it bends...

Sorry, explain to me again, it bends the light.

So it takes the light from the sort of the edges and redirects them towards the middle.

Because your eyes are expecting to see this horizontal pencil in the middle.

But where the light would be coming, you actually see the light from the edges that have been redirected.

Which is why you need the vertical light, because it gives you a sense of you can see a similar strip.

Exactly.

If you take the vertical things away, you just sort of see a smudgy blur and the illusion doesn't really work at all.

Well, actually, interesting, there is in fact a whole area of physics that's dedicated to making special materials called metamaterials that bend light in fancy ways like you showed us there but could one day produce a better invisibility shield.

Here's Dr.

Mitch Kenney from the University of Nottingham to tell us more.

When everybody thinks about invisibility their mind goes straight to Harry Potter.

So essentially what he's got is a magic sheet that he can wrap around himself and what this sheet will do is allow light to come from behind him through the cloak into your eyes, and vice versa.

And there's a field of physics called metamaterials, and these metamaterials are hoping to achieve something very, very similar.

If you were to place an object in the middle of these metamaterials, you could guide light around them.

It's a bit like water flowing around a post or something like that.

It's all about the flow of waves and recombining the waves on the other side so that what you see is the thing that's behind the object.

You don't actually see the object itself, it's cloaked.

So a lot of the time the building blocks used for invisibility cloaks consist of small metal C-shaped rings with a little opening on one side.

They're probably about one or two microns in size, a thousandths of a millimeter I guess you would say.

When the light gets absorbed, because of these properties of these metal rings, you can reshape how light leaves so you can control which direction it leaves and how much of the light is also absorbed.

To my knowledge, no invisibility cloaks have been made for visible light yet.

So the best that we've sort of done at the moment is a little block that is a few inches across or you know maybe a few centimeters and what would happen is that it only works from one direction.

That is the problem.

It works for one wavelength or sort of one color you could say of light.

Not a colour that we can actually see though.

So you would actually see the metamaterial just sat there and you'd be wondering well what's that there for?

So we'd see the cloak.

We wouldn't see

the

perfect.

So it's really far from perfect.

The military application thus far is you can have very, very skinny, one-dimensional soldiers, or really, really tiny ones that are

a couple of inches across and approaching from only one direction, as long as they were not visible in the visible light spectrum from the first place.

So, I mean, I think in the long term, there's a hope that you'll be able to do this with visible light.

The reason that it's a bit easier to do for this sort of longer wavelength lights, so infrared microwaves or radio waves, is because basically the way that you are redirecting the light is instead of using the properties of atoms and molecules, which is how light normally gets manipulated in everyday life, you're actually trying to create little structures that are on a similar scale to the wave itself.

And those little structures are the things that kind of redirect the light and get it to do crazy things.

So you need to be able to fabricate those structures,

physically make them on a similar scale to the size of the wave that you're trying to redirect.

So if that's radio waves, no problem.

You can easily make something sort of centimeters, meters scale.

But if you're talking about visible light, where it's actually more like a millionth of a meter, the thing that you're trying to redirect, your structures also need to be a millionth of a meter or smaller.

And you need to fabricate, obviously, lots and lots and lots of those structures in a very precise way across something that's really big if you want to shield something really big.

So that's where the technological challenge is.

But I think in terms of the sort of basic physics of it, the cloaking could be applied even to visible light.

I have to say my go-to is not Harry Potter on invisibility.

My go-to is James Bond, who had a car that took a picture of the opposite side and then projected the picture on the near side.

So that's what made the car look invisible.

But that could only ever work from one angle though.

Whereas these metamaterials, at least in principle, you can engineer them to work from multiple angles.

And of course, that's really important if you really want to cloak convincingly.

So I was able to see a very good Halloween costume that was based on that premise, though, of like two phones, one strapped to the front of someone's stomach, one strapped to the back, and they were basically video calling each other so that you could, it appeared as though you could see through this person's stomach.

Oh, that's very smart.

Isn't it?

Yeah.

I mean, if you want to get competitive about Halloween costumes.

Which I totally do.

Okay, Van, but so we're not, we're not close, which is, I know, is probably what Dylan is really asking.

We're not close to creating something that'll allow you to cloak yourself.

No.

Okay, well, let's go back to the universe then, because I'll be honest with you, Dylan, it's not looking good for you.

If we've got all of these different telescopes, though, right?

You know, infrared and X-ray and microwave and so on, and you're seeing in Advertising Commerce all of this stuff out there in the universe, then is anything really invisible?

Well, yes.

So over the last sort of century or so, astronomers have come to this sort of conclusion that actually most of the universe is completely invisible at every single wavelength.

There is this very strange stuff that we call dark matter.

And you shouldn't be tricked into thinking that we know what it is.

Astronomers use the word dark to mean I don't really understand what's going on here.

But there is some sort of the universe is mostly made of some sort of strange invisible substance that is truly genuinely invisible.

It doesn't shine at any wavelength at all.

Not on the piano.

It is.

However, many grand pianos.

Exactly.

It is not playing a note on the piano.

Okay.

And so how do we know it's there?

Well, it's so what Andrew was saying before actually about the discovery of Neptune, I think, is a nice key up for it.

So we didn't see Neptune itself.

We noticed Uranus behaving strangely, and that clued us in that there was this mysterious planet pulling Uranus around.

And we discovered dark matter in a similar way.

When we look at how galaxies move around the universe, whether it's sort of galaxies orbiting inside clusters or even individual galaxies spinning around,

everything is moving as if there is a lot of invisible stuff around.

Like we're seeing the gravitational footprints, if you like, of this weird invisible stuff, and we just can't see it at any wavelength.

And that's not the only one of these things.

I mean, dark matter doesn't solve all of the unusual behavior that we've seen in the universe.

It only partially solves it.

Well, yes, there is a lot of weird stuff going on in the universe, you're right.

So, dark matter, on sort of quote-unquote small scales, as big as a galaxy, dark matter appears to be around and sticking stuff together and making everything move around bizarrely.

But when we look on the biggest scales of all, look out the other side of the universe, and we measure how fast the universe is expanding, it seems to be speeding up, which no one really understands why.

So we've known the universe is growing for about 100 years now.

Then about 20, 25 years ago, astronomers did an experiment to measure exactly how fast the universe was expanding.

But then the answer was, it's speeding up.

Like something has its foot on the accelerator pedal of the universe.

There's some sort of energy pushing the universe apart faster and faster and faster.

We have no idea what it is.

We call it dark energy, but yeah.

And again, it makes it doesn't play any notes from the piano, it doesn't register on any of the no.

The only evidence we have of it is the fact that we can see the universe speeding up.

Right, this dark matter stuff, is it in the room with us?

Yeah, absolutely.

It almost certainly is just suffusing the entire universe.

There's not very much of it in the room with us because, although there's a lot of it in the universe at large, here on Earth and in the solar system in general, there's an awful lot of normal matter.

So, the normal matter vastly outweighs the dark matter in this room to the point where the dark matter is just entirely negligible in this room.

It's only when you look out to the scale of, say, galaxies, where, in terms of the normal matter, there are sort of vast empty spaces, and the dark matter is sort of able to just fill up those spaces, and that's how, in the end, dark matter comes to outweigh regular matter across the universe.

But, yes,

in the universe at large, it's roughly speaking 5% of the entire universe is sort of regular material that we know and love from humans.

Of which we can only see one octave of 60 something.

We are pathetic.

We're really, really bad pathetic.

But we're not pathetic because we figured these things out.

And so I mean, that's the amazing thing about the human mind, of course, is that we can reach beyond just what our senses tell us.

5% exists on the scale, on the piano.

How much of the universe exists as dark matter?

About 25 thereabouts.

And then the rest would possibly be as dark energy.

Yeah.

Exactly.

And it's not, by the way, that there is a sort of ghost other universe where they exist and do radio shows where they go, where they describe us as dark matter.

Almost certainly not, because everything that we know about dark matter shows that it behaves in a very simple way.

So, although it's very mysterious, in some sense, it's very simple, that it only seems to experience one force, and that is gravity.

It generates gravity, and it feels gravity, and so

it can get pulled around, and it can pull us around through gravity.

But in order to have life and discussions in a studio, you need other forces, and especially electromagnetism, which is the thing that enables you to have basically molecules and atoms, and in fact light and radio waves and all the things that we've been talking about.

It's because it doesn't experience electromagnetism that it is so, so hard to pin down.

But that also means there isn't a sort of shadow universe with alive creatures that are wondering what we are.

Hold on though, because

a few minutes ago you were saying you had only a vague understanding of 5%

of the entire use.

How do you know that there aren't other forces that they're experiencing?

Maybe they think that we're only experiencing simple forces.

Yeah, I mean, I think the remarkable thing about dark matter is that it's been very predictive as an idea.

So although we haven't captured it, we haven't seen it directly, it has made astonishingly accurate predictions.

So for example, it's made predictions about the cosmic microwave background light.

This is the sort of leftover glow from the Big Bang.

It made very, very precise predictions about what you ought to see.

there because of the way that dark matter would have pulled that around.

And all of these are based on one assumption, which is that dark matter is as boring as can be, that it just experiences gravity and no other forces.

The moment that you try introducing any other forces into the picture with dark matter, it suddenly starts behaving in a different way and it messes up all of those predictions that were so successful.

So although we haven't captured it and we haven't seen it directly, it's an astonishingly predictive and therefore successful scientific theory.

But if it experiences gravity, would it not all pull together?

We not clump like planets?

Could there be planets of dark matter?

I mean, no,

it does clump, but there can't be planets.

And so it clumps because of gravity, as you say.

But if you want to create a planet, you need to do more than just clump.

You really need to compress.

You know, a planet is so much denser than the universe around it.

It's just, you know, mind-bogglingly dense compared to space at large.

So you not only need to have gravity sort of pulling stuff together, you also need to have a way to actually start sticking bits of things together.

For that, you need the other forces.

So, gravity will get you so far, but it will not get you down to the scale of a planet.

Do you think Dylan expected the conversation to go in this direction?

And I think that the overall conclusion is, Dylan, we can only see 160-something of 5% of the universe.

Stop trying to lose more.

Also, the main thing is,

what are we regarding as invisible?

Because we can detect the behavior of a lot of things, like whatever.

Similarly, if you did actually have a Harry Potter invisibility coke, you'd still be able to smell the teenage children who live in a boarding school as they walked around.

There is still a residue of actually of other stuff going on here that you would spot.

So I think we can safely say it's not happening.

It's not a perfect thing.

Going to go with the note.

Well, thank you very much to our guests, Matthew Bothwell and Andrew Ponson.

I mean, so no is the answer to Dylan.

Nothing is truly invisible.

Well, it kind of depends how you're defining it, isn't it?

Yet another curious case without a positive answer.

Yeah, but I mean, but we can take comfort in the fact that if we were recording this 200 years ago,

we would have seen a far more dollar universe and it also wouldn't have gone anywhere because we hadn't discovered radio waves.

Excuse me, the town crier would have had an absolute field day with this one.

But also, they didn't know that they lived in a dollar universe.

They thought they were like the kings.

They were like, we know everything there is.

We have seen colours from red all the way to violet.

We know all of the universe.

But no, it turns out there was a way more going on.

Will Dylan be happy with that though?

Do you know what?

I think any simple seeming question that ends with dark energy is all right by me.

He wants to make things disappear.

Should we just send him the...

Oh, that's a good idea.

We'll send you the little lens thing.

Yeah, there you go.

So you can pretend that, yeah.

In the very specific conditions of a horizontal pencil against some vertical pencils, yes, we've got you in the visibility cloak.

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I'm Nicola Cochlan and for BBC Radio 4, this is History's Youngest Heroes.

Rebellion, Risk and the radical power of youth.

She thought right, I'll just do it.

She thought about others rather than herself.

12 stories of extraordinary young people from across history.

There's a real sense of urgency in them.

That resistance has to be mounted, it has to be mounted now.

Subscribe to History's Youngest Heroes on BBC Sounds.

Sucks!

The new musical has made Tony award-winning history on Broadway.

We demand to be home!

Winner, best score.

We demand to be seen.

Winner, best book.

We demand to be quality.

It's a theatrical masterpiece that's thrilling, inspiring, dazzlingly entertaining, and unquestionably the most emotionally stirring musical this season.

Suffs!

Playing the Orpheum Theater October 22nd through November 9th.

Tickets at BroadwaySF.com.

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