Answers to Your Science Questions

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

We demand to be home.

Winner, best score.

We the man to be seen.

Winner, best book.

We the man to be qualified.

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

Suffs.

playing the Orpheum Theatre, October 22nd through November 9th.

Tickets at BroadwaySF.com

BBC Sounds, Music, Radio, Podcasts.

Welcome to the podcast of BBC Inside Science with me, Marnie Chesterton.

The show was first broadcast on the 17th of April, 2025.

Humans are curious creatures.

I'd say it's the key to our success on this planet.

This This fundamental desire to ask why, what and how, what's beyond this mountain, how can I preserve my milk supply?

Why are my feet cold?

It's how we spread across every continent on the earth and invented cheese and socks.

And what is science but a systematised desire to understand, to scratch that curiosity itch in a methodical manner that gives you reliable, evidence-based answers.

And since Inside Science is your hub for science on Radio 4, it's no surprise that some of you have contacted us with questions about how the world works.

And yes, knowing that today was coming up, I have actually also been asking you to email insidescience at bbc.co.uk with anything science-flavoured that's been puzzling you.

Today, we've assembled a panel with decades of dedicated study between them and we'll be tackling a selection of your questions on everything from the cosmos to the direction of snail travel.

Let's meet them.

Hi, I'm Professor Catherine Haymans.

I'm a professor of astrophysics at the University of Edinburgh and I'm also the Astronomer Royal for Scotland.

I'm Professor Mark Mazzin and I'm a professor of Earth system science, which usually people go, what's that?

So basically I study climate change in the past, the present and the future.

And I'm Dr.

Penny Sarche.

I'm Managing Editor at New Scientist.

Great.

Well, welcome, gang.

Good to have you with us.

This is a discussion, by the way.

So I'm going to pitch a question to one of you.

But if anyone else wants to join in, contradict anything else, pick a fight, then you can do so.

Catherine, we're going to start with a short question about the cosmos.

Philip wants to know, why are planets round?

I'll give you a short answer, Marnie.

Gravity.

Do you want me to expand?

Yes, please.

No, moving on.

We've got a lot of questions to get through.

So gravity is the force that pulls you down after you've jumped up in the air and it always pulls you to the center of the earth, no matter where you might be jumping around on the surface of our planet.

Now, about 4.5 billion years ago, when our planet formed, it was a hot, liquid rock, and there were no people jumping around on the planet, obviously, but gravity worked in exactly the same way, pulling everything towards the center in all directions.

And if you do that, if you've same force pulling in all directions, you end up with a sphere.

But there wasn't a center.

Hang on, there wasn't, you say, towards the centre of the Earth, but there wasn't an Earth.

Well, so in the very early universe, we've got lots of stuff swirling around the solar system.

We don't really completely understand how planets form, but there would have been a clump of matter with more gravity than the rest pulling things towards it.

And it keeps pulling and pulling and pulling, and that's in all directions, and that's how you end up with a sphere.

Okay.

But there's a bit of a twist because planets also spin, so there are more forces involved than just gravity.

And so they're not perfect spheres.

And you can see this particularly with the planet Saturn.

That's spinning so quickly that it kind of squashes at the poles and bulges out at the edges.

But yeah, planets definitely round thanks to gravity.

Is there anything that doesn't fit the formula?

I'm thinking of, you know, I mean, it's not planet size, but the comet 67P that hit the headlines.

I mean, that notoriously looked a a bit like a rubber duck.

So

comets, asteroids, things like that, they're much smaller.

They form in different ways.

They don't have so much gravity to pull everything towards them.

So you don't get that nice round shape.

They also tend to sort of collide into each other in the asteroid belt.

So they get all sorts of strange shapes because of that.

So no cubes, no cube-shaped planets lurking in there.

No cubes.

No cubes known of as yet.

And if you do see any cubes, they're probably aliens.

There we go.

Moving on from planets to life on this planet, and Mark, I'm batting this one your way.

Take a listen to this from Jeff.

I've got a question for you, which seems simple, but I'm struggling to get my head round it.

How do trees grow?

When I look at a cross-section of a tree trunk, the annual growth rings are generally uniform in thickness along their length, just with some variation between rings in good or bad growth years.

How does the tree manage the growth of each ring in a consistent manner?

Also, the amount of material a tree has to manufacture increases each year as it gets bigger.

Does that mean trees have to work harder every year?

So what is an Earth system scientist doing knowing anything about trees, Mark?

Oh, so I hide in the geography department.

So again, I've been sort of like bombarded with all the physical sciences.

Last week we were in the Greek islands with our wonderful undergraduates and we were taking tree course to actually look back to see how trees grow but also how they reflect the climate change of the region.

And to answer the question, trees don't grow at the same rate through their lives.

Interestingly enough, when they're young they grow very rapidly, but the tree rings aren't necessarily distinct even though they're thicker.

And so what our eyes are drawn to are the beautiful regular sort of layers that are produced when the tree is matured.

And they seem to look similar in size, but as the listener absolutely correctly said, we have thicker rings for good years and we have thinner rings for poor years.

But why do we have these rings?

So the first thing is in a temperate climate like the UK,

Trees grow with two rings.

The first one is a lighter ring, which occurs in spring and early summer, and then there's a darker ring that represents wood in the late summer and autumn.

Now, trees always try to add as much wood as they can, but remember they're limited by the amount of sunlight, the amount of water, and nutrients.

But they also have a balancing act, which is yes, they want to grow as much as possible, but they also want to reproduce.

And so, the tree is constantly trying to balance: hey, I've got to actually produce fruit, I've got to produce acorns, I've actually got to reproduce at the same time as growing.

But as the tree grows and matures, you will see that the rings do get thinner, and trees get to that point where they get to an old age.

What's really interesting about trees is they constantly grow.

This is the way they avoid old age by growing and growing and growing.

And they do get to a point where suddenly old age and decay catches up with them.

I'll give you an example.

English oak can produce acorns by the age of 40.

Okay, so 40 is when they've hit adulthood.

They will then be very productive between 80 and 120 years old, and they can be productive for another 300 years.

They then go into this old age where they're still growing, so that keeps off the whole decay and dying for another 300 years.

And then that's the end game.

Whereas if you compare, let's say, rowan trees, they produce fruit and berries around 15 years, and maximum life is about 120.

Okay, round the table, I should say, Dr.

Penny Sasha has a PhD in plant genetics, so she's marking your work here.

Please say I got it right.

No obvious errors there, Mark.

All I would add is that yes, trees do have to, the bigger they are, the more they do need to work.

They need more energy, so that's why they have more leaves, a bigger tree naturally.

And also, it's not precise, but as a sort of rule of thumb, if you look at the mass of a tree above ground, that's approximately the mass of the roots underneath as well.

So the root system is growing and that really does power that growth and being bigger because yes, more energy is needed when it's a bigger size.

Sticking with life on Earth, Penny, we've had a question from Matt about some non-plant life.

Let's listen.

I have a question about the skeins of geese which fly over our house on their way to the local salt marsh at Martinmere.

They're very noisy, constantly calling to one another.

Can anyone translate what they're saying?

Is it follow me, I know the way?

Or wait for me?

Are they discussing last night's T V?

Whatever it is, it must take quite a lot of energy and that makes me think it must be important.

Can you shed any light on this?

It's a great sound.

I just want to grab my binoculars and head outside.

I think energy is a a really interesting way of looking at this actually.

We don't know exactly what they're saying, but clearly they are communicating.

And I'm sure there's a degree of which way are we going?

How fast are we going?

That's too fast for me.

That looks like a really nice feel down there.

But a lot of what we think they're talking about with all of those very noisy honks is their formation because geese and ducks famously they fly in this V formation.

And what's clever about that is it minimizes drag for those who are flying behind, but it means it's much harder work when you're the leader.

So they take turns.

And if you think about it, that's actually quite a difficult thing to coordinate in mid-flight, swapping.

I'm sick of this, I don't want to do it anymore, it's your turn.

So, there is some thinking that quite a lot of the loud honking is just required to keep them in that formation and make sure that it's fair.

So, sort of like, is it encouraging honks?

Like, come on, keep going, you can keep doing this.

Yeah, or maybe I like to think they're squabbling, like, no, it's your turn.

I've been doing this, you know, long enough now, and it's time for me.

I'm not breeding.

I love the fact that sort of like what you've got is somebody in the front going, oh, Bert, back left, it's your turn, get up here.

And the bird going, nothing to do with me, I'm happy flying.

Consistent with what the personality of geese seems to me.

Yeah, yeah.

Does anyone know where we are on sort of Dr.

Doolittle science of talking to animals?

There was a really good study the other week that found that some birds, I think it was a type of parrot, they have a mental map of sounds that is really similar to the ones that we convergently have.

So there's still kind of really foundational discoveries being made there, but the more we look, the more complex communication between animals, particularly birds, but all kinds of animals, is turning out to be.

I know I have colleagues who really do think AI is going to decode what whales are talking to each other about.

I think that is potentially possible.

I'm excited about that.

I'm excited about that.

There's a thing called Project SETI, which is funded by Silicon Valley Money, and they claim that they're going to use large language models to try and decode whale language.

And they've put 2026 as their

soon, I know, as their deadline for a conversation between a person and a whale.

But how do they train the data?

Because you need a truth.

With AI models, you need a truth.

Yeah.

And so how do they know?

You need at least a starting point of what the communication is about.

I imagine we must have decades of people out on boats making observations and recordings, I suppose.

And can we just feed this into an AI to process them all?

Our next question takes us back up to the stars.

So, Catherine, this one's definitely for you.

And it's from Tricia.

When we look up at the stars, why are we always looking into the past?

Surely, if the Earth is revolving, at some point we should be looking at where we are going, the direction we are travelling in.

So, a lot to unpick here.

Catherine,

why is looking down a telescope like looking back into the past?

Let me try and explain.

So I want you to imagine that we've built a road between Earth and the Sun and we're going to drive along this road at the speed limit set by the British government for motorways.

So we're going to drive along it at 70 miles per hour and at that rate it will take us 150 years to get from the Earth to the Sun.

Now the sunlight as it comes back to us on planet Earth, it's effectively going along our imaginary road as well.

Now, its speed limit is governed by the universe.

So there's a maximum speed limit in our universe, which is 300 million meters per second.

And that means that the light from the sun takes eight minutes to make that journey from the sun to Earth.

So on a sunny day, if you could look at the sun, don't directly look at the sun, but if you could, you would be seeing...

an image of the sun as it was eight minutes ago.

And so astronomers can use this phenomenon in our universe that there's this maximum speed limit for light

to time travel.

The further we look away in our universe, the farther back in time we're looking.

So when we get out our telescopes and we look at our nearest neighbor in the universe, Andromeda, the galaxy of Andromeda, we're seeing an image of it as it was two and a half million years ago, just because it's taken the light that long to travel across the universe towards us.

And we've got fantastic new technology now.

There's a brand new telescope up in space, the James Webb Space Telescope, that's allowing us to look incredibly to far distances in the universe.

And we're seeing galaxies as they were when the universe was just 300 million years old.

300 million years sounds like a long time, but in astrophysical terms...

It's nothing, is it?

It's nothing.

It's the very, very early stages of the universe when galaxies were first forming.

So astronomers can time travel back in time by looking really far away.

But Tricia was wanting to to know can we look into the future because we're she's she's right that the earth is spinning around once every 24 hours that gives us night and day and we're also moving around the Sun

but the reason why we can't see into the future is because of that that maximum speed limit again if we wanted to look into the future we would have to travel faster than the speed of light so we could kind of get ahead of it to to look at what's happening in the future and unfortunately Einstein with his theory of general relativity says that that's not possible.

Our universe has a maximum speed limit, and that means we can look back in time, but not into the future, no matter how fast we're moving.

There was an experiment recently where people said, Well, we think we've broken, we've found something faster than the speed of light.

Yeah, as with a lot of great claims like that, unfortunately,

it was neutrinos, and unfortunately, it boiled down to just a problem within the instrumentation.

Oh, a coward.

Because that would have been well cool.

It would have.

It would have.

It would have been so cool.

All those headlines.

Einstein was wrong.

I try,

in my day job, I do experiment with different theories of gravity to try and explain all the dark stuff out there.

And I skip up Blackford Hill in Edinburgh, up to the Royal Observatory each morning thinking, will I prove Einstein wrong today?

And I can't.

It's really, really good theory.

It's so hard to find any problems with it whatsoever.

So alas.

Time travel only to look to the past, not the future.

Are we going to carry on, Catherine,

finding older and older things to look at?

How far back in the universe can we go?

Yeah, so the James Webb Space Telescope was designed to look back, to look really far away in our universe, to look incredibly far back in time, to see the birth of the first stars and the galaxies.

And it has, oh, what a Christmas present that was for astronomers across the globe because it has delivered a huge number, a surprising number of really massive galaxies in the very early universe.

And it's really making us scratch our heads of how did these very bright massive galaxies form so early on in the universe and that's one of the the biggest questions in in astronomy at the moment is what on earth is going on in the early universe and and it's thanks to this new technology that and this time traveling trick that allows us to to peer back in time to see what was going on then and we don't understand it at the moment but that's the way science works isn't it we'll think about it and scratch our heads and build a big telescope and then we'll have a better idea.

Just ask someone for more money for an even bigger telescope.

Wow, you can't go wrong with a bigger telescope, honey.

Thank you, Catherine.

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Suffs.

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

We demand to be home.

Winner, best store.

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.

You're listening to Inside Science with me, Marnie Chesterton, and this week we've turned the whole show over to listeners' curiosity and helping to provide answers.

We have Penny Sachet from The New Scientist, Catherine Haymans from Edinburgh University, and Mark Maslin from University College London.

Mark, next question, definitely a Mark question.

Andy wrote to ask, I remember hearing that if we hit four degrees of warming, we will inevitably hit 10 degrees of warming because we will hit so many tipping points they will effectively trigger one after another.

Is this true?

And if so, do we know any more details about the tipping points and which ones we're likely to hit at lower levels of warming?

So we're unlikely to hit four degrees warming.

With the current policies, we're looking at about 3.1 to 3.7 degrees warming.

That's nearly four.

That's nearly four.

But if the pledges that were made at the climate conferences come through, we're looking at 2.4 to 2.8.

So that's bringing it down.

So those disasters that we were talking about 10 years ago, when we were looking at five or six degrees or beyond, those have receded in science because of the changes in policy and economics.

and basically because renewables are just so much cheaper than fossil fuels.

But having said that, we are worried about tipping points because we have a target.

So the Paris Agreement 10 years ago said we should hit 2 degrees maximum with an aspirational target of 1.5 degrees.

Now, last year we hit 1.6 degrees warming.

So we've already pushed through that limit once.

And if we say there consistently, then there are four four tipping points that we are particularly worried about which is the collapse of the Greenland ice sheet the collapse of the western Antarctic ice sheet the die-off of tropical corals and boreal or temperate sort of permafrost abruptly melting and and sorry what is a tipping point what defines that as a tipping point so a tipping point is a place in the climate where things irreversibly change and so therefore you have a Greenland ice sheet, it's melting, and we know it's melting quite rapidly.

But there is a tipping point where that melting becomes inevitable, i.e., the whole ice sheet will go.

Now, it may take a couple of hundred years, but the processes have started and cannot be reversed.

That's a tipping point.

So, these are quite big, scary thing.

The interesting thing is, those ones that we're worried about, they will increase sea levels with the melting of those ice sheets.

They will cause local regional warming.

So you'll have more warming in certain regions, particularly the Arctic, but they're not going to double glowing warming.

They're not going to suddenly emit so much carbon that they're going to double and go from four degrees to 10 degrees.

So the tipping points are worrying for other reasons, not the actual doubling of climate change.

And again, I think this whole worry about 10 degrees, I'm really sorry.

Things that are happening now around the world, all those extreme weather events, are scary enough.

If we get to two degrees, there's a brilliant report by the IPCC that says, look at all the things that are going to happen at two degrees, which is scary enough.

So we don't need to even be scared by four degrees.

We need to be scared by one and a half to two degrees.

What's going to happen?

Brief summary?

Brief summary.

So you're looking at more extreme weather events that are going to occur more regularly.

So look at the Californian wildfires.

Everybody seemed to be surprised, even though though climate scientists have said when this will happen in the future.

Not if, when.

I mean, let's go back and be really selfish and look at, say, the UK.

In 2022, we had a heat wave that hit 40 degrees Celsius in July.

Now, as a climatologist, the peak temperature in July for the last 10 years is 24 degrees.

This is why we go on holiday.

Okay.

This is 16 degrees warmer than it should have been.

Let me repeat that.

16 degrees warmer.

Okay.

So this is something we were predicting for 2050 and occurred in 2022.

So the real effects of climate change are already here and impacting.

And so therefore, we should be worried about one and a half to two degrees.

Again, if we ever go near four degrees, that will be hell and earth.

Forget actually going beyond four degrees.

I saw the UK has recently committed quite a lot of money into setting up like an early warning system for predicting if tipping points are kind of if we're heading towards setting them off.

By that logic, then we should actually already be really worried about what's happening now rather than worrying about these much more catastrophic things that are potentially weigh in the future.

Oh, absolutely.

And I have to say, a dear friend and colleague of mine, Tim Lenton, at Exeter University, has been really leading the charge into understanding the science of tipping points because it's one of those things which we can model the future given sort of like emissions.

But what what we want to know is about the chaos in the system.

How will these systems actually hit thresholds?

And that's really difficult to do.

But we need to understand.

We need to understand: are we in a position where we're going to collapse the circulation of the North Atlantic Ocean?

Are

AMOC.

AMOC.

Oh, yes, AMOC.

And again, most scientists will look at that and go, the science says not in this century.

But you then have some studies that go, no, it happened in the next 10 10 years.

And you have to be very gentle about sort of like understanding the likelihood of these tipping points.

For me, climate change is scary enough.

What's happening around the world and what's going to happen around the world in the next 10, 20 years is very, very scary.

We don't need to add onto that the horror stories of tipping points.

We need to be aware of them and look at the science, but actually we need to reduce our emissions now.

Moving on from the big Anthropocene shaping questions to the smaller queries, science puzzles lurking in your own backyard, Eric Johns got in touch with this question.

At night, garden snails climb up the side of my house.

The house is rough cast, so it's not an easy thing to do, and they get at least as high as the first floor, perhaps higher.

What on earth are they trying to achieve?

It doesn't seem to be a particularly useful thing for them to do.

Thank you, Eric.

So, Penny, I've decided that the plant scientist on the team, your remit includes garden pests, too.

Any answers to Eric?

It certainly does in my spare time, I have to say.

Forget dark energy.

This is like the real mystery.

What are they doing?

There are so many theories about this and not enough evidence.

Really?

Yeah.

So there are some really obvious ones like snails climb so that when they rest they don't get stepped on or they climb to avoid predators.

Also when it's quite warm, if they climb up it's cooler.

None of that really explains to me why they climb so high.

There's also a theory that maybe they're going up to the guttering to lay their eggs up there.

That seems eminently observable and testable but I, to my knowledge, no one has tested that yet.

To me I think it immediately makes me think of a lot of snails sort of evolved in shoreline maritime environments where they are climbing up hard rocky faces.

So maybe it's just they have this exploratory vertical behavior, and for some reason, they're just doing it on your house.

But there's also some quite wild ones out there.

One suggestion is they might actually be eating the wall, especially if this is pebble dash.

They might be getting calcium from the cement.

And I don't know that we know that the snails we have in this country do it, but some certainly do do that.

African land snails, apparently.

But my favourite one is some kind of parasitic fungus has taken over the snails and is driving them up to the top of the house so that the spores can be released and its evil life cycle can continue.

But what strikes me with all of these ideas, which are quite fun to unpick, these are all testable.

And this is a perfect undergraduate summer project.

So if anyone wants to go out there and solve this question for us, I'm sure they can.

Thank you, Eric, for that question.

Moving on, just squeezing in one more.

And finally, we've received this question from Amanda.

Dear Inside Science Team, please could you find out and explain why when I put a duvet cover in the washing machine with other items they all end up inside the duvet cover when the programme finishes.

Is it because of some identifiable hydraulic or fluid dynamic characteristic?

I'd love to know and even try to understand.

Right, so

thank you so much, Amanda, for the question.

We have a plant scientist, a climatologist and an astronomer.

So who's taking this?

I'd like to argue this might be a little bit like cell biology.

Okay, bear with me.

Penny, floor's yours.

So I have thought about this on a weekly basis for as long as I can remember.

And I think what might be going on here is obviously when you've got a duvet cover and if you haven't sort of buttoned it up before putting it in the wash, you've got a very wide opening.

So that's easy statistically for things to enter it.

And then as it twists around in the wash, it's actually harder to leave.

So what you've got is kind of a difficulty gradient.

Things are more likely to go in than they are to come out.

And my reckoning is if that keeps happening for a long enough period, enough cycles, eventually everything ends up inside.

And the reason I kind of try to claim that's like cell biology is sometimes certain substances, it's much easier for them to get into the cell through the cell membrane because of the way it's made than it is for them to randomly diffuse out again.

And that's a really sort of clever, not kind of actively driven way of creating order or something really weird like you observe in your washing machine.

That's my theory anyway, and I'm sticking to it.

I've got an alternative hypothesis, Penny.

Uh-oh.

I just think the duvet cover's hungry.

But I'll defer to you on that one.

I mean, so there's your astronomer's answer and

your cell biologist's answer.

Thank you so much, Amanda, for the question.

That's us out of time.

Thank you to our panellists, Dr.

Penny Sachet from The New Scientist, Catherine Haymans from Edinburgh University, and Mark Maslin from University College London.

Thanks to our listeners for getting in touch.

A reminder that if you have a question, the email address is insidescience at bbc.co.uk.

And I hope everyone has a lovely Easter break.

Until next time, bye from me.

And that's it.

You've been listening to BBC Inside Science with me, Marnie Chesterton.

The producers were Dan Welsh and Debbie Kilbride.

The show was made in Cardiff by BBC Wales and West.

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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.