Original subtitles

Space.

It's vast, mysterious,

and sometimes just plain weird.

It keeps us up at night asking the big questions.

Will I be on time? Hmm.

But what is time, anyway?

Where am I even going?

Tonight, we're teaming up with two other curious minds,

Hannah Fry and Dara O Briain,

to tackle the space mysteries that have you scratching your head.

So, the main thing about Wolverine is where do the blades go?

- Yeah, I know, and is he just not uncomfortable all the time? - Hi.

- Hello. How are you? - How are you doing?

- Nice to meet you. - Hi. - How are you? Thanks for having us.

I think we're currently on your show.

- But then you're really on our show. - I see, OK.

- There's more of us, though, aren't there? - It's not a democracy. - Yeah.

Buckle up for a cosmic chat about the weird,

the wonderful, and the possibly extraterrestrial.

After you, George.

We had a long discussion earlier as to whether this was

a Sky at Night meets Curious Cases,

or Curious Cases meets The Sky at Night.

There was some fisticuffs backstage. I think you won.

Look at that.

Welcome to The Sky at Night.

Well, hello and welcome to a special edition of Curious Cases,

where we're going to do things a little bit differently tonight,

because Dara and I are currently in the BBC Radio Theatre at London's

Broadcasting House, and we have an audience.

CHEERING

Look at that!

We are going to tackle quite a few

of your questions on one single theme, space mysteries.

And to help us out, we have called on some people

who know their way around the universe.

The presenters from The Sky at Night.

Yes, the longest running science programme in the world,

older than Blue Peter, Coronation Street and Doctor Who.

68-years-old, The Sky at Night is now.

Wow, what an amazing guests for this evening. Welcome to all of you.

Do you know how special The Sky at Night is, Dara?

They had... They had an asteroid named after them, after their show.

What was it called, your asteroid?

It's Asteroid 57424 Caelumnoctu,

which is sort of Latin for The Sky at Night.

But the number was the broadcast date of the first episode,

and it looks like a dot, I've seen it in a telescope.

Caelumnoctu, that sounds very fancy, doesn't it? I looked

- up what Curious Cases would be if it was in Latin. - What is it?

It's curiosa casibus.

- I've got one named after me. - Have you? - Yeah, I do.

- Am I the only one? - Trying to pull rank in the room!

So, yeah, it's Asteroid 4901,

and it's just called O Briain, which is Latin for Dara O Briain.

AUDIENCE LAUGH

What does yours look like through a telescope?

Mine is a binary system.

Oh, you're just showing...

I mean, I was kind of forced into it, but it is very much my brag.

Yeah, it's a really interesting system.

- There's actually papers about mine. - OK, well...

I got a pretty good one.

And also, it's not going to wipe out life on Earth.

And that's kind of... That's an upside to have.

- Yeah. That's also a flex. - Yeah.

"Dara O Briain's coming in,

"he's going to wipe out the Earth," is not good.

You'd get one really good week of publicity out of it.

- After that, it's downhill. - You know, honestly, I'd be on everything.

Booked on everything.

Graham Norton finally returned my calls.

OK, over the past few weeks, we've been asking you to send

in your questions about space mysteries.

And we're kicking off with Arianne in Ireland who asked,

"What sound do stars make?" Right.

Big shout out to the literalists who'll go, "Oh, it's space.

"There's no sound in space." Like, whatever.

George, why is this a brilliant question?

It's totally a brilliant question. Because stars make sounds.

So they have sound waves travelling through them,

and we actually detect these sound waves on the surface of stars.

And the field of study of this is called asteroseismology.

So, yeah, it's really, really cool,

because we can look at the waves as we detect them,

and it tells us something about how big a star is

or what it's made of, or how dense it is.

Unfortunately, though, because of the vacuum of space,

and all the... Those sound waves can't travel to us as sound waves.

But, you know, we can detect them still by looking at the light.

It makes the star wobble. It makes the starlight wobble.

And do we ever turn those measurements

into a sound wave we can hear?

Yeah, absolutely. So you just take any wave and you say,

"This is what it would sound like if it was a sound wave of the same

"kind of shape and frequency."

So, yeah, sonification of stars is definitely a thing.

What's also really cool is that, like, they work...

The stars work really similar to instruments. So, you know,

like, small stars are like flutes, and big stars are like trombones.

- Like an orchestra. - Yeah, exactly.

You've brought in some space sounds to play for us,

because you've picked different forms

of intergalactic audio to play for us.

Maggie, what were you... What did you bring in?

I wanted to actually go for something that is actually a sound.

- Yeah. - And the Cassini-Huygens space mission was a mission to Saturn,

and Cassini went into orbit around Saturn,

got some great data, but Huygens was a little probe,

made by the European Space Agency.

And it actually landed on this moon, Titan.

And as it actually fell through the atmosphere,

because there was an atmosphere,

and there was a medium to carry the sound,

we could actually listen to it.

And I think this is a small section

of the end as it actually sort of lands.

I am, as always in these situations, wary of building it up too much.

I know.

- I know, Dara. - Let's take a moment.

I've not heard this,

but I'm taking a wild guess that everyone's imagination

is probably imagining

something maybe more majestic than we're about to play here.

- Come on. - It's OK. - Yeah. OK.

So this is the sound of the Huygens probe landing on Titan.

Manage your expectations, everybody.

WHOOSHING

POP

That was very good. That was very good.

- Can we turn this into a competitive thing? - Ooh.

Giving that a seven out of ten...

All right, George, what sound did you choose?

So can we hear mine first,

- and then see if you can figure out what it is? - Oh.

- Oh, twist. - OK. OK.

- All right. - OK. Here it is.

UNDULATING RUMBLE

- Was it a space elephant? - No. - Was it a buried choir?

So to me, that sounds like utter despair.

- Yeah! - It's not... - Not an upbeat noise. - Right?

This is actually a sonification of

a black hole at the centre of a galaxy cluster.

And so, like, if you can

picture those really cool images that we have of black holes,

and what they've done is kind of like swept around

and, like, made the profile of the wave into a sound.

So this is the sound of kind of sweeping around a black hole,

and it just sounds like the despair at the end of the universe.

- Mm-hm. - I love it. - Absolutely. - Yay! - Yay.

Hey, you know what, George? Nothing says light entertainment

like the impending death of falling into a black hole.

So, you know, I'm going to give you an eight out of ten.

So did I!

LAUGHTER

Damn. Upbeat and cheery never wins!

Sorry. You went for the kind of big smiler -

- it doesn't work. - Yeah. - The actual...

The sense of existential despair that we got from that was too good.

- Chris, what have you brought? - Well, I have spared no expense,

and I thought we'd go for the grandest

and most important sound of all.

So just after the Big Bang,

when the universe was in a hot, dense state,

there was enough matter around that you could have

sound waves propagating through the universe.

And we could still see the effects of this in something called

the cosmic microwave background,

which is the oldest light of all.

So that means we know what sound waves were there,

and we can work out what the spectrum is.

- And so that is the big sound. - He's built it up.

He's built it up. Go on, then.

So this is the whole universe as an instrument.

RUMBLING

- Good, isn't it? - It's sort of space ASMR.

So the reason it sounds terrible is that you had

all these frequencies at once.

So the point is, the universe didn't just have one note playing.

It was all of them. So you get this sort of white noise.

But that was the whole universe.

- Well, ten for honesty. - Yeah.

For sound, I think you oversold it.

Do you know the bit on the M25 where it changes from tarmac...

Yes!

- No, I think George wins that round. - I think George wins.

Do you agree everybody? Yeah. There we go!

APPLAUSE

Well obviously we are not going to do

a show about space mysteries without talking about aliens.

And this is a question in from Richard, in Whitley Bay.

Venus and Jupiter are deemed unsuitable for life.

But aren't there points in the upper atmospheres where the temperatures

and pressures are similar to where life is found on Earth?

Could airship drones be sent to look for exotic, simple forms of life?

So there's two parts to this, obviously.

George, what exactly are airship drones,

and why would we be sending them to Jupiter or Venus?

So airship drones, think "a balloon" but you can...

They're kind of robotic, and you can operate them like drones, remotely.

There have been, previously,

kind of balloons dropped through Venus's atmosphere,

and they want to do it again because they want to measure what's there.

I think the issue, though, maybe

with sending something like this to Jupiter,

is that it very rapidly, like...

The pressure gets out of hand.

So, you know, the whole thing would just...

SHE BLOWS A RASPBERRY

- That's the technical term. - It is the technical term, yeah.

And I think for Venus, you've also got to be careful.

There's a lot of sulphur. It's a bit acidic.

So, yeah, you've got to design your airship drone pretty carefully.

I mean, you're basically trying

to float a hot-air balloon over a death planet. That's...

A little bit. Yeah, yeah, yeah. Little bit, yeah.

So, like, you know, think, like,

weather balloons, but maybe more high-tech.

There is an exciting history, though,

of the series of Russian probes that attempted to land on Venus

with almost hilarious misadventures.

Yeah, they send out one picture and then they melt.

- Yeah, I think the temperature pressure... - Just melts?

Yeah, it's so high. I think it was 23 minutes

that it survived on the surface.

So one picture...

SHE WHIMPERS

Just melted away because it's horrendous.

OK. These exotic life forms that we're...that we're describing.

I mean, what do you think? Do you think that there could be

some, genuinely, on Venus or Jupiter, or elsewhere?

There is this layer in Venus's atmosphere,

which is about room temperature and pressure.

It's still acidic, as you say. And that's... What's interesting

is that's the layer that, our mate Jane Greaves,

a few years ago announced that she'd found

a chemical called phosphine in.

And phosphine on Earth is made mostly, frankly, by penguins.

It's a biosignature.

It's made by life. It's in penguin poo,

amongst other things.

And so the fact that we found it on Venus,

maybe it's the product of some volcanism,

or some weird chemical process,

but it could also be life hanging on in this...

- Venus penguins! - Venus penguins. Very, very small Venus penguins.

Venus penguin fart, specifically.

We always talk about life,

but we put conditions of "life as we know it."

And I think that's the...

Life could be so varied or so different from what we anticipate.

Just to name drop,

I did have this conversation with David Attenborough once.

- Sure, sure. - Yeah, yeah. - As you do.

Well, you know, Dame, Sir, I imagine

- you all have dinner together every week. - We all stick together.

It was a number of years ago and I was having a debate.

I feel terrible because I was having an argument

with our national treasure,

and saying that I don't know if we actually need water for life.

Life as we know it, yes, but maybe not...

Maybe life not as we know it. And so how do you define life?

There might be a whole variety of life that we just don't anticipate.

I don't want microbes, though. I want little green men.

Luckily for Hannah, our friends at BBC Ideas

have been looking at two approaches to finding them.

- Hello? - Can you hear us? - I can hear you.

- Can you hear me? - Hello? Is there anybody out there?

Well, that's the question, isn't it?

Has been for as long as anyone can remember.

Are we alone?

It might sound like science fiction, but the universe is so vast,

many scientists think it's unrealistic

to imagine we're the only form of life in it.

The universe is full of natural radio waves generated

by stars and planets and galaxies,

but that emission is really very smooth.

That's Mike Garrett, an astrophysicist,

an active member of SETI, the Search for Extraterrestrial Intelligence.

Artificial radio waves are very spiky

because they convey information.

So we're looking for anomalies, signature of potentially

other intelligent civilisations out there broadcasting to the universe.

What SETI assumes is that

the aliens are very motivated,

that they're going out of their way

to send us intentional signals for our benefit.

And that's Douglas Vakoch, the founder of METI,

which stands for Messaging Extraterrestrial Intelligence.

They think listening is not enough.

Maybe we should do the heavy lifting by reaching out first.

Someone has to make the first move.

Making the first move in any relationship has its risks.

Opening oneself up to rejection, or worse.

Stories of alien fleets visiting Earth

with the sole intention of wiping us out

are common ground for science fiction. But there is a theory

that, if we're not careful, this could become science fact.

I think one of the things that Stephen Hawking,

famous cosmologist, said about this idea

of transmitting signals is

that it might not turn out very well for us here on this planet,

just like it didn't turn out very well

for the Native Americans when Columbus first settled there.

But Meti is amongst those

who see this argument as a red herring.

It's too late to hide. We're already known in the universe.

Douglas and his colleagues believe

that, through TV and radio broadcasts,

not to mention mobile phone towers, Earth has been leaking

radiation into space for decades.

This leakage is exactly

what SETI looked for as signs of life elsewhere.

So it stands to reason that, if aliens are listening,

they could probably already hear us.

Though not against communicating per se,

Mike argues that we need to think much more carefully about

what we want to say and how we want to say it.

Who speaks for Earth and who has the right?

When I see a lot of these signals being sent,

they don't represent all of this planet.

You know, just arbitrarily sending

signals out into space is not very democratic.

The first message sent into space

for the benefit of aliens was in 1974, more than 50 years ago.

It became known as the Arecibo message.

And so far we've received nothing in return.

Which returns us to Enrico Fermi's question - where is everybody?

There is a conundrum, though, right? That when we turned on

the opportunity to listen into space,

it was strange that there wasn't a cacophony of sounds.

Yes, I think the space age was a bit of a disappointment.

That we found that Mars just had craters,

that Venus was this hellhole, and so on.

And I think people just expected it

to be obvious that there was life in the cosmos.

And it's not. But the universe is a big place.

Actually, this is just a tiny sort of diversion.

Last time I met David Attenborough, um...

THEY LAUGH

..I was, um... No, no,

because we were both doing the pre-Christmas,

selling books on radio interviews,

and I had some kids book out about space. And I...

When he sat down, we're chatting away, and I said,

"By the way, I should tell you - the book I've written, yeah?

"It has some stuff about animals in it."

And Attenborough genuinely leaned in and went,

"You have planets, I have animals."

LAUGHTER

APPLAUSE

That's good.

Meti will continue reaching out to those planets

that orbit within what's known as the Goldilocks Zone.

Not too hot, not too cold, just right for potential life.

Meanwhile, Mike and SETI will keep an ear to the sky,

advancing techniques to pick up signals from other worlds.

And maybe one day, just maybe...

If we detect a signal and we know

that we're not alone in the universe,

I think that should make people happy.

If we discover another civilisation and they're very different from us,

we'll realise, actually, how similar we are to our neighbours.

Next up, we've got a question from one of our younger listeners.

See what you make of this.

Hello, my name is Marlon. I'm 11 and I live in Croydon.

My curious question came to mind

when I was watching a video about the edge of space,

and I thought, "What is the edge of space?

"What's it made of and how can we perceive it?"

Space must have an edge, if it's expanding, right?

But then how can it be infinite?

- Hmm. - Deep, deep. - Yeah. - Yeah.

- OK. - Marlon is already the boss level of this particular....

I know. All right, Maggie, give us, like,

at least a rope barrier and a bounce.

- Yes. - You know what I mean?

- That's what I want. - The answer is - we don't know. There. So I think,

because it's trying to understand, sort of,

the concept of the universe.

And so our current understanding of the universe

is it began with something called the Big Bang.

So it's sort of a singularity

expanded out to create space and time. And so if you ask,

"What is beyond space and time?"

It's a very hard concept to grapple.

We don't know where its limits are.

With things like the James Webb Space Telescope,

we look at, sort of, light coming from the early universe,

but we can't go beyond that because

the light won't reach us, if you see what I mean.

So, yes, we are limited in what we know and what we can see,

and we interpret that,

but we believe it began and it's expanding outwards.

Any guesses though, Chris?

Well, we do have this edge to the observable universe.

So as long as you're a practical astronomer,

this question is easy to answer, because the edge of the observable

universe is the bit whose light is only just reaching us.

So we could see the bit of the universe which,

in the last 13.8 billion years,

has had time to send us light.

And that's... You can put a line around that.

If we froze the expansion of the universe, we could say

what part of the universe that is. It's a guess.

But the guess is that we live in this tiny fraction of the whole.

So we've got this little bubble

that we can see, and that has an edge.

But the whole thing, well, that could easily be infinite.

And the thing that's impossible to get your head around,

I think, intuitively, is the idea that our universe

could have started in this Big Bang, this point in time,

but it could have been infinite then,

it could still be infinite now, and it's expanding ever since.

I don't have an intuitive answer to it.

- It's just the maths tells us that. - Wow.

- Great question, unsatisfying answer. - Yes, I know.

LAUGHTER

We have a lot of cosmological questions,

a lot of questions about the shape of the universe.

This one is from Stephen.

When everything was created in the Big Bang,

it all exploded outward and is still going.

So why is the universe not shaped like

a big doughnut with nothing in the middle?

There's no central point, presumably.

There's no one central point that we've pushed away from.

Because I think the idea of an explosion

is a bit of a misunderstanding.

You have been saying explosion

- for 80 years now. You've been going about... - Big Bang.

- Big Bang. - Rapid expansion, not explosion.

Because explosion.. Pow!

And, sort of, matter starts here

- and then it's thrown outwards. - Yeah.

But I think this is sort of the singularity,

but it expands rapidly, but it expands outwards.

So it isn't like an explosion,

where all the matter that was there is thrown outwards,

but it's the matter itself is expanding outwards.

And so I think, getting... So, then, it's less likely

to be a sort of a doughnut or a toroid.

It's more likely to be sort of a continuum,

but sort of expanding outwards.

But on the name, actually, the BBC is to blame for the name,

the fact it's called the Big Bang.

In this very building, Fred Hoyle in 1948, I think, who...

Fred Hoyle was the Cambridge astronomer

who didn't believe in the Big Bang theory.

And he gave a talk about modern cosmology on the radio.

and he wanted to disparage it.

So he said, "this Big Bang theory,"

- and the name stuck. - So it was an insult.

So it was actually named by the theory's opponent.

So it's his fault. But it's so memorable, so it stuck.

In the '90s, American Astronomy magazine got so fed up

of this explosion problem that they had a competition

for people to suggest other names for the Big Bang.

- And about... - Bangy McBangface.

Yeah, yeah, that's what would happen now.

But 10,000 people wrote in and,

at the end, they had an expert panel judge them,

and they decided that Big Bang was the least worst name.

And so Big Bang won.

"Horrendous Space Kablooie" was second,

which still has the explosion problem.

- Yes. - Yeah. So it's not an explosion, it's a stretching of space,

- and that's how you should think about it. - Nonetheless,

a doughnut is different to a sphere because its curvature is different.

We can estimate the curvature of space? Is it doughnut-shaped?

Like, there is a theory about this, right?

Because, like, you know, so,

the four-dimensional fabric of spacetime

people do actually research, you know.

"Is it flat? Is it curved?

"And if it's curved, is it like a saddle? Is it open? Is it closed?"

And some people think that it might be shaped like a doughnut, a torus,

which would be kind of like, you know, like going around like that,

which is pretty cool, because then it means that, like,

as you travel through the universe,

eventually you'd come back on yourself.

Like if you're inside a video game and it's like,

you know, you can kind of go in a loop.

But it's important to say that we know that, if it's a doughnut,

it's a very big doughnut,

and we live only on a small part of the doughnut.

- So we're not ruling out the doughnut? - We're not.

But we see that the bit of the universe we can see is pretty flat.

And so, therefore, for it to be on a doughnut,

we have to only have a tiny bit the doughnut.

The same way that, if you stood on a football, you'd notice it was round.

You stand on the earth, you have to do a bit more work.

If you stand on something a billion times the size of the Earth,

it's very difficult to tell that you're on a sphere at all.

And so we know that our universe appears to be flat.

So you can have these exotic shapes,

your doughnuts or your crumpets,

or whatever it is that you want the universe to be like.

But we only see a tiny bit of it.

Are we eliminating what you hinted at there?

That it would be enclosed.

So, I mean, like Chris says,

we can't fully rule it out, but it's really unlikely.

It looks pretty flat. So, you know,

either the universe really is so much bigger than

we can even imagine, and everything that we can see

for billions of light years is only a tiny bit.

Or it's flat as a pancake. So we should go for "Pancake Universe."

I really like the idea that in maybe 100 years' time,

people will be sitting in this theatre and going,

"Now, they call it a Pancake Universe because the BBC..."

"It was an insult, actually."

OK, so maybe a doughnut, maybe a pancake.

Definitely some sort of baked good. All right.

That is almost all we have time for.

Have we solved anything, do we think?

- No, no. - That's astronomy. - Do we ever?

Do we ever really solve anything?

No. But look, they've been going for 68 years.

They need to go for another 68, so that's fine by me.

While the cosmos remains mysterious, the skies never fail to inspire.

So he can't finish up without

Pete taking us through some of the upcoming sights.

Since the clocks went back last month,

darkness arrives an hour earlier,

and that gives us some great opportunities

to enjoy the night sky.

Early evening, we've still got the stars of summer,

including the Summer Triangle,

which includes the impressive constellation of Cygnus the Swan.

Now, in the core of Cygnus the Swan,

you've got an asterism called the Northern Cross.

Later in the evening, you've got

the stars of winter beginning to appear,

and that also includes the magnificent

constellation of Orion the Hunter,

which is a great navigational aid.

And from Orion we can find other constellations,

such as Gemini, the twins.

To find Gemini from Orion,

identify the two brightest stars in Orion,

Rigel in the bottom right, and Betelgeuse in the upper left.

Extend the line they make up and left for twice the distance...

..and you'll arrive at the pair

of stars which represents the heads of the twins, Castor and Pollux.

Gemini is one of those unusual constellations

that actually looks like what it's supposed to represent.

Well, with a bit of imagination, at least.

From the UK, it gets to its highest position in the sky

between mid-November and mid-December,

in the early hours of the morning.

Now, that puts it in a position which lifts it

well above any turbulent atmosphere,

which you'll find lower down,

which makes it perfect for stargazing.

Gemini is currently home to the gas giant Jupiter.

It's easy to find, being the bright,

star-like object located just below Castor and Pollux,

and there is a treat starting to come into view.

Due to a Jovian equinox approaching in December 2026,

Jupiter's moon Callisto will be seen appearing

to cross Jupiter's disc for the next two years or so.

A great time to watch is in the early

hours of the 21st of November, when you'll be able to see

the shadows of Io and Callisto

crossing Jupiter's disc at the same time.

Another treat coming at the end of

the year is the Geminid meteor shower.

As its name suggests, the shower's radiant is in Gemini,

the radiant being the small area of sky

that associated meteors appear to emanate from.

The shower is active between the eighth and 16th of December,

the peak occurring on the night of the 13th into the 14th of December.

With the moon passed last quarter,

and 12 hours of night sky darkness,

it has the potential for a great show this year.

The night sky is something which all of us can enjoy.

So whether you're just looking up at beautiful stars above you,

or you're out in the early hours with a telescope and camera,

I hope you get some great, clear skies.

As ever, there is an extended online star guide which

is available on our website,

which is at www.bbc.co.uk/skyatnight.

We love seeing any images you've taken.

These are some of the highlights from

what you've recently sent in via our Flickr account.

Well, that's all for this year's series of The Sky at Night.

We've had a fun-packed trip across the cosmos,

covering everything from potentially-hazardous asteroids,

to the expanding universe, and all our

episodes are still available on the BBC iPlayer.

We'll be back with all the latest astronomical news

in spring next year but, until then, happy stargazing and...

..goodnight.