Fire

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Today we'll start with one of the most beautiful introductions to a science lecture, and it's from Michael Faraday's Chemical History of a Candle.

He said, There is not a law under which any part of the universe is governed which does not come into play and is touched upon in the chemistry of a candle.

There is no better, there is no more open door by which you can enter into the study of science than by considering the physical phenomena of a candle.

Which is beautiful, but it's not right.

You have to spoil everything, don't you, with your evidence-based thinking.

There's always something, isn't there?

It's not his fault.

He didn't know about nuclear forces.

So you need nuclear forces to understand how stars shine, for example.

Just so you know, by the way, evidence-based thinking is very 20th century.

We're not doing that in the 21st century anymore.

Haven't you been looking around at the world?

In today's show, we'll be talking about fire.

What is it?

How did we learn to harness it?

And why is it so hard to control?

To guide us through the science of fire, we're joined by three people who have studied the chemistry of fire, the physics of fire, or at the very least, waved a lighter around while REM played Everybody Hurts.

And they are.

I'm Adam Rutherford, and I'm a geneticist, and you know me from Inside Science and the Curious Cases of Rutherford and Fry.

I've written about the role of fire in evolution, and I want to take this opportunity to apologise to my father because, as a teenager, I pretty much burnt everything.

So sorry, Dad, for the whole Pyromania thing.

I'm Neovnick Dade.

I am a professor of forensic science at the University of Dundee, and I'm a director of a research centre in forensic science.

I'm also a fire investigator.

Why do I like fire and what do I most like about fire?

I like having an open fire in my living room in the right place, obviously,

because I just like the comfort of it.

It gives us great comfort and great, I don't know, whimsicalness when you look into its flames.

My name is Ed Byrne.

I am a stand-up comedian, except when I'm on shows like this, when I'm a sit-down comedian.

And my favourite use of fire, apart from having it as an open fire, and I find it very comforting as well, but I find most comfort comes from its use for destroying evidence.

This is our panel.

What does it go down?

See, Niamh, you thought you'd come here actually just to a show as an expert.

In fact, you've come here to solve the crime.

And it was much easier than we thought.

He's given it away already.

It was him what done it.

But I have to say there's a misconception that fire destroys all evidence.

It did destroy all of it.

So, Ed, let's just work out then.

So, what have you tried?

And then Eve will tell you what you've done wrong in trying to destroy your evidence.

This is going down a very different way than we'd originally thought, by the way.

After joyriding, torch the car.

Yeah, always.

I don't know.

So, as in, can we just find it?

I didn't have to

have my feet held to the flames over this.

He said, when you did it.

So, what do you reckon would have been the best thing for him to have done with that car?

Drive it into a lake.

Or a quarry.

Better, quarry.

Quarry's better.

Nobody's going to be able to do it.

Oh, you mean a flooded quarry?

Okay, right.

Not an obvious age.

Are there still going to be fingerprints after a burnt out?

You can recover fingerprints, yes.

In actual fact, soot will enhance fingerprints.

You can see them easier because the soot sits in the pores of the fingerprints, so you can visualize them.

So, anyone who's trying to work out who Father Christmas really is, oh, this is great.

Anyway, so

anyway, we've covered the crime, that part of the just general hints there for people hoping to commit crime.

But also, another thing is

we always start with a definition, and this might seem strange when we're talking about fire, but we actually want to know what is fire?

What do we mean when we say fire?

So, I thought I'd show you, because you can't, as a fire investigator or people who like fire, you can't have a fire, a talk about fire without having a fire.

So, I've got a candle, so I'm going to light the candle with my match.

There we go.

So, what is fire?

Fire is a chemical reaction.

So, it's a reaction when you've got a fuel and you heat that fuel up, which is what I just did by putting the match to the wick of my candle.

And you heat that fuel up in the presence of oxygen.

And as you heat the fuel, you cause it to turn into a gas.

And it's the mixture of the gaseous fuel, volatile gases, and oxygen in the presence of an ignition source that produces this chemical reaction, which you can see in front of me.

And it produces light, it produces heat, it produces products like water and carbon dioxide and carbon monoxide and other stuff.

So, fire is a chemical reaction.

So, what is the I need an equation?

Oh, good.

You gave me an outline.

I don't know that easy as catchphrase as a physicist.

Just one more thing.

I need an equation.

I'm a chemist, I'm not a physicist.

So, but do you have it just roughly what's the outline equation?

So, you mentioned there.

So, you've got, usually, fuel contains carbon and hydrogen.

So, you've got something with carbon and hydrogen with it mixing with oxygen, with O2, and you introduce heat and it turns into water, H2O, carbon dioxide, carbon monoxide, and other products.

What sort of things burn?

So we are looking at a candle there, there's the wax, there's obviously the wick.

What is it that's actually burning?

So what's actually burning, there are a couple of really important components to causing a flaming combustion.

So you see a flame.

You need to have a fuel, and the fuel can be anything really that contains carbon and hydrogen, but it contains other things as well.

You need the presence of oxygen in the air, and you need the presence of heat to start the reactions occurring.

So what the heat is doing, and what you can see, well you see it in a moment, what the heat is doing is it's taking a solid fuel and it's turning it into a gas.

So solids don't burn, liquids don't burn, you have to turn them into a gas first.

And it's a process called thermal decomposition.

So you're breaking the bonds in the molecules of the particular material that you're setting on fire, whether it's wood or plastics or whatever it is.

So you need to put heat energy in, and as that heat energy evolves a gas and you mix that gas with oxygen in the air, and you introduce an ignition source, my match, then you'll get that chemical reaction occurring.

So it's always the gas?

Yes, yeah, yeah.

So if you, okay, if you touch lava in a vacuum, it'll still hurt, but could you technically not say that you were burnt?

Would there be other issues as well?

Because as well as the burning, you're in a vacuum.

So you may also be preoccupied with other.

Is this another of your crimes that you're working out?

Because I'm seeing there may be flaws in a lot of them

obviously i was speaking hypothetically you know the uh were you the kind of kid who played with matches are you someone who

i'm obsessed with fire now i am a massive fan of it as a as amy i spend an enormous amount of time chopping sawing wood logs moving them about building storage facilities for wood stacking it admiring it, moving it into the living room, admiring it again, setting it on fire, and sitting and staring at it.

And I'm sure Adam will tell us about the evolutionary aspects of fire.

And I wonder,

when you sit and you stare at fire, because fire has been such an important mover in our evolution, is there genuinely an evolutionary...

Do we enjoy looking at fire in the same way that we enjoy looking at a prospective sexual partner, say?

You know what I mean?

The same urges, that primal urge you have to recreate.

No, come with me on this.

The crimes, the crimes.

How many more crimes?

Sex feels good because it's an evolutionary imperative, okay?

That's why it feels not a logical reason why something so filthy should feel so good, but it does.

And I just wonder if this...

We can enjoy watching a fire far more than you enjoy watching a soap opera, right?

So is there an evolutionary aspect to that, our enjoyment of it?

Yeah, well, I mean, the first thing is I hope that you don't look at fire in exactly the same way that you look at a prospective sexual partner, because in which case you're doing both fire and sex wrong.

This program goes out at 4.30 on a Monday on the school run.

Just

remind you of that.

Adam,

the question is evolutionary.

Yeah, so from an evolutionary perspective, fire is an absolutely essential part of human evolution.

It's been with us for, well, since before we were Homo sapiens, there's evidence for fire associated with Homo erectus up to a million and a half years ago.

We look like we've got it under control by about 100,000 years ago, possibly a bit longer than that but from a from an evolutionary perspective it fire does so many things and we have evolved alongside fire for all of that time so for example it allows us to keep warm so we can move north from the equator so our expansion around the earth is dependent on our ability to control fire but also it allows us to cook food and this is an essential part of our evolutionary development because it means that we have to spend less time foraging less time eating because fire is effectively like pre-digestion before we put it in our mouth.

And, you know, time you spend eating is time you risk being eaten because our mouths are quite near our eyes.

So we can't, it's hard to look out for predators if you're, you know, chowing down on something on the ground.

Is that why a lot of mafia hits take place in restaurants?

There's a lot of crime coming from Ed Byrne here.

What was it?

You said 100,000 years ago.

How do we trace that point where human beings, their ancestors, had control of fire?

What is the kind of record that we see left behind?

So earlier than that, we do see clear evidence of fire, although it's quite sparse and it's quite difficult to account for.

What we also think is that it might be naturally occurring, as in it's been started by lightning.

By 200 to 100,000 years ago, we have evidence of hearths, you know, centralized cooking areas, kitchens in caves.

We also have evidence that Neanderthals had control of fire as well.

So there's one dig site in Tuscany where some wooden clubs

have been excavated.

And of course, wood doesn't preserve very well over tens or hundreds of thousands of years.

So this is quite rare.

And it's boxwood, which is particularly hard, but it's quite clear that the outside of it has been deliberately burnt in order to take away the small twigs.

So it's not just Homo sapiens, it's humans much more broadly, maybe as far back as Homo rectus, but definitely Homo neandotilensis.

So there are a lot of points you made there, so I can see an interesting idea that to move out of the Rift Valley and certainly to move into Europe, you need fire to keep warm.

But you mentioned about digestion.

Fire is the eucophytes pre-digesting the food.

Could you elaborate on that?

Yeah, well, we spend time chewing food, and we chew food, which helps break it down and release chemical bonds.

And there's enzymes in our saliva, which does the same thing.

And then when it goes into our stomach, the whole process of eating is just extracting energy from food, from the stuff that we consume.

What cooking food does is make that process happen before we put the food in our mouths.

So we spend a way disproportionately small amount of time eating compared to almost all other animals, especially our closest relatives like gorillas and chimpanzees, who spend an inordinate amount of time eating.

So we spend a lot less time eating food and a lot more time watching television programs about preparing food.

That's what we've been able to do.

That's our use of our evolutionary gain for us.

But you shouldn't underestimate the importance of the length of time we spend eating, because loads of other animals do that as well.

So we know that vervet monkeys in South Africa spend much less time foraging in areas where the grass has already been burnt down.

And meerkats, you know, meerkats when they stand up on their legs, they're not just doing that to be super cute.

Let the records show he's doing the meerkat hands, listeners.

Because it is impossible to say the word meerkat and not do the meerkat hand.

Yeah, I now realize I'm actually doing the meerkat impression.

Meerkats stand up on their back legs not to be super cute, but because they're actually looking out for predators.

But when you time meerkats eating in high grassland, they spend a lot more time on their feet looking out than they do in areas which have been burnt down.

And they know this.

And loads of animals know this because they can simply see further.

So it's just another example of many animals that have quite a sophisticated understanding and dependence on fire.

And I suppose, Adam, in terms of we talked about human evolution and the pressures or the advantages that taming fire can have, I suppose in terms of using it as a technology, that step, you know, we all think of Stone Age to Bronze Age to Iron Age and so on.

In a sense, it's a step of learning how to make higher temperature fires and furnaces, I suppose.

Yeah, absolutely.

But more importantly, it's about just control.

And I think that we are, this is something that Darwin spent a lot of time thinking about in The Descent of Man, the things that make us uniquely human.

And tool use was one, language was another.

But he put fire as separate, a sort of subset of tool use.

And says that it's, you know, equivalent to our ability to

speak, to communicate with each other in terms of its significance.

There certainly aren't any other animals that have the level of sophistication of dependence and control of fire that we do, although, as I said, we now know that Neanderthals also had controlled use of fire.

There aren't any animals that can start fires from scratch.

And

that was basically true and useful for us until about two years ago when it was discovered, or when it was written up in the scientific literature, that there are three species of raptor, Australian birds of prey,

who, well, they're called fire hawks by the Aboriginals who've known about this behavior for thousands of years.

But what they do is they hang around near the edges of savannah fires in Western Australia, and then they fly down and they grab a stick

in their talons or in their beak, and they fly over man-made or naturally occurring fire barriers like roads or rivers, find a nice dry piece of bush, drop the...

the flaming stick into it, set a new fire, they go and sit in a tree, and then they just wait.

And they wait because all of the little tiny mammals and lizards and animals run out of this burning inferno because they're going to get burnt to death, and then they get eaten to death.

So, this is the first and only other example of an animal that deliberately starts fires, even though they can't start it from scratch.

There is something about that image which you can't help, there is a kind of anthropomorphization that happens.

That is a kind of Hanna-Barbera or a successful wily coyote in that situation.

Absolutely, and in fact, so this is a really good example of what's known as indigenous expert knowledge.

So we write this up in the scientific literature in 2017.

It is part of the Aboriginal Jaralan ceremonies, dream time ceremonies, maybe thousands of years old.

There is speculation, it is speculation, but I think it's interesting speculation, that maybe the Aboriginal Australians learnt their ability to control fire from the birds.

Because in Western Australia, the savannah fires, the annual savannah fires, are part of the natural fire ecosystem.

And Aborigines have been controlling that for thousands of years.

There has been a suggestion that they actually learnt this ability from the birds.

I know

in your book you talk about a particular beetle that's evolved to use fire.

Yeah, yeah, the fire chaser, which gives you an indication of what its behavior is like.

So

this is a beetle that has two under its front legs it's got these these two infrared detector patches.

So they're a bunch of cells.

And they're pretty much the only creature that, when a fire is kicking off, will make a beeline for it.

A beeline is the wrong thing.

In remoteism, a beetle line for it.

And we know this, there's examples from the 20th century of there was in America, there was

an American football stadium that was burning down and everyone's running away from it.

There's this line of these beetles marching towards it.

And the reason they do this is because they lay their eggs in freshly burnt logs.

And so this is a food source for them.

And this is how they've evolved.

It's absolutely essential for their survival.

The most amazing thing about it is they appear to be able to detect fire from 80 miles away.

So they go in this line from tens of miles away.

They'd be able to detect using these infrared sensors fires.

And they're the only creature that

really burns towards them.

Sorry, that was not deliberate.

Semi-sophisticated relationships with fire.

None of them have the love-hate relationship the moth has, though, surely.

Can you explain what is a moth's deal with the fire?

Oh, don't look at me for that.

They're just idiots.

Something to do with it confuses the line of the moon.

So it's a distance thing where they presume that that's actually the moon.

In fact, it's right there and that's why they go straight into it.

Yeah, you would think that they would have learnt in the genetic system.

What happens during the daytime?

I mean, don't they just get massively confused by the sun?

Well, they would, wouldn't they?

Yes, fly towards the sun wouldn't they if that were the explanation?

Because that was a big thing in Australia with bougain moths flocking around the Sydney Harbour Bridge and it was because of the lights on the bridge just totally confused them.

They thought they were the moon.

You know starlight, lots of insects use starlight to guide them.

We know that dung beetles use the Milky Way to guide their trajectory home and we know that because very, very clever scientists decided to test it by putting hats on them.

I love those kind of experiments.

Neither, thinking about how fire changes the way that human beings can change their own civilization, what about our understanding of not merely controlling fire, but then what heat does?

Thinking of things like the Iron Age, the Bronze Age, the ways that we kind of start to use fire to adapt different materials as well.

Well, I think that

understanding of what the phenomenon of fire can do in terms of changing our, particularly our built environment, or as you said, in those kind of evolutionary spurts almost.

A lot of it is trial and error.

A lot of it is is people finding out by accident almost as to how

fire can modify things or how fire can be used to smelt things or to create other materials.

So a lot of that has evolved simply by people trying it out I think and by trial and error.

But also within the built environment into the modern era there are two branches

of

I suppose areas of study around fire.

One is fire science, which is understanding how things burn and understanding that once we burn things,

how much energy those things release, because the amount of energy is different depending on what it is that we burn, and harnessing that and using different mechanisms to harness that.

And that's what fire scientists do, mainly in laboratories, to understand those kind of mechanisms.

And then there's a whole area of discipline called fire engineering.

And fire engineering understands what does fire do within buildings.

So what are the stresses and strains that buildings can cope with if

a fire happens within that building?

Or again, how do you harness the energy that's produced by a fire such that you can create buildings that are safer to be in

if those buildings are affected by fire?

Because you said that all fires aren't equal, so there are things that burn hotter.

And I suppose if you're looking at the development of a technology, so to

bronze iron, cast iron, you need hotter and hotter fires.

So could you talk a bit about the different temperature ranges that you see in fires, the different sorts of fire?

What are the different temperatures?

So, what we've got in front of me, I'm putting my finger through the flame because I like doing that.

What is in front of me?

If I put a thermocouple, something that measures temperature on this flame, this is called a laminar flame, a single flame, then the heat that I'm producing within that flame and different parts of it, but on average, is about a thousand degrees centigrade.

So, a candle flame.

A candle flame.

It's about between 800 and 1,000 degrees centigrade.

Everybody has held their hand over a candle, and as you move your hand down, it gets hotter, and that's the hot gases that come off as a result of the

combustion happening.

If you're looking at particular objects and you're trying to melt those objects, so you're trying to burn them, cellulosic material like woods, papers, some fabrics like cotton will start to thermally decompose around 260 degrees C.

So within a condition, if I held a piece of wood, like a match, over this flame here for a reasonable amount of time, not very long, then I'll start to see the wood evolve gases and it will burn.

Plastics, it takes a much more heat to get them burning, so maybe about 400 degrees C, and that's simply because of the makeup of the material.

But then different materials, once they burn, will produce more heat energy into a defined space.

So if we burn polyurethane foam, what you're sitting on, the material that's in the chairs, polyurethane has a high heat release rate.

So once it gets burning, it produces itself a lot of heat.

That will then affect materials nearby and therefore increase the

amount of heat, if you like, that those materials, the surface of those materials are being affected by.

So it's a really complicated process.

And in the kind of job I do as a fire investigator, what you have to do is understand in the real world what that means.

So what are the circumstances that might be plausible to cause a particular thing to ignite and then for that fire to spread.

And that requires a knowledge of the materials and

how much heat they will release and what configuration they're in.

So

as you burn things like candles or other materials, our candle is burning in the middle of the table, well, on the table, in the middle.

If I put it in a corner, then I'm reducing the oxygen flow and the flame extends, it gets bigger.

If I put it beside a wall, same thing, it reduces the oxygen that can flow into that combustion and keep it going, so the flames extend and get bigger.

So the whole package together is quite complicated in understanding just how it works.

What's the most common cause of

fires,

residential fires, other than to if it's not arson, what's the most common cause?

The most common cause that's recorded is electrical.

So electrical appliances of one type or another, whether they're

overheating sort of washing machines, a good one,

not a good one, I mean a bad one, but it's one that's very common,

or other types of appliances like television sets and things like that.

So electrical cause

the most commonly recorded single cause of fire.

Other things are variable by time of year.

So this time of year candles are a potential significant cause because people like to use them for atmospheric purposes.

I have seen where people have, there's a product out many years ago who was a little like a little candle holder like for these little tea lights and you hung it on your Christmas tree.

So you put you light it, in it goes, you know, your Christmas tree's in a corner, wonderful configuration.

I think it was marketed as the accident waiting to happen.

It goes, you know, and you sit there and it burns away and Christmas trees burn really well because they've got a very high surface area and they're full of materials that will burn really well and they go up like nobody's business.

I had a friend who worked in the fire service and they had one that they actually started calling a student fire, which is

little tea lights sitting on top of an old TV, like a cathode ray tube TV, and

it just melts the plastic underneath it and just drops into the TV, and then the whole thing goes up.

Super common.

I used to be involved in a training course where that was my party trick.

I used to set televisions on fire with tea lights.

Yeah.

It was for training.

It was for training.

The greatest fire battle I've ever been involved with, and there's a long list, obviously, but this is get ready for a name-drop.

I once put out a fire with Eddie Izard.

Some candles set fire to a curtain, and everyone else ran out of the room.

But Eddie Izzard and I beat out the fire.

He used a pineapple and I used a watermelon.

And it had a proper slapstick kind of he was there, you know, the stalk of the pineapple, the watermelon, and it was.

If Eddie Izzard had done this as a routine, you'd like, oh, he's lost it.

Yeah, this is getting too

silly.

He never remembers anymore, but I think, don't you remember that day?

You had a pineapple, I had a watermelon.

Yeah, anyway.

I think you might have dreamt that.

Do you know what?

After some time.

We did a whole show about dreams once before, and I've heard they're as good as reality.

I believe it happened, and thus it did.

Does fire occur anywhere else in the universe?

And I have a reason for asking that because it strikes me that you need oxygen in an atmosphere, and the oxygen in our atmosphere came from photosynthesis.

So, my thesis I'm going to advance, because I thought about it about half an hour ago, is that given that, though, it is interesting that is there any other way of having fire emerge or exist without an oxygen atmosphere on a planet?

Flaming combustion requires oxygen, that's for certain.

You can have smoldering combustion, which is combustion almost at the surface of a material, but not everything will smolder.

The material has to be porous and it has to have other characteristics.

And that can be in a very low-oxygen environment.

You know why Shana Easton smoldered so much?

Was she constantly in a low-oxygen environment?

You're getting back to the vacuum now, aren't you?

So I would, you can have fires in zero gravity.

Fires in zero gravities don't look like the kind of flames we're used to.

The flame is completely spherical.

But I'm not sure that you could have fire in absolutely zero oxygen.

Or

what's the minimum oxygen level?

Say it's in a

well, in a room.

So in a room, fires transition

through a series of very

well-known states.

So you start with a small fire, that then the heat that's derived from it then starts to heat up materials around, and they start to gas off, as we call it, or produce thermal decomposition products.

And they go on fire, and that then generates more smoke and more heat.

And in a room like the one the studio we're sitting in, that smoke would rise because hot gases rise, it would hit the physical barrier of the roof, and it would spread out across the roof.

And then it radiates heat back down into the room, and everything starts to evolve gases.

And it comes to a point, so all of that happens, and it becomes fuel, it's a fuel-controlled fire, so it depends on what's in the room.

And it comes to a point where everything becomes so heated up that it's evolving all of these thermal decomposition products.

You've got a fire burning away, so you have an ignition source, and the whole fire evolves into, so the whole room evolves into fire.

It's when a fire in a room becomes a room completely on fire, and then it becomes ventilation-controlled.

So if, because it uses up a huge amount of oxygen, and fires like that, developed fires like that, will maintain at about 5% oxygen, at about, but it depends on the size of the room and other things.

But that's when you see things like materials like doors failing or windows blowing out, and that's associated with this event where a fire in a room becomes a room on fire, which is called flashover.

So, unless that fire

gets

an input of oxygen, it will die down, but it'll just be a superheated room until somebody or something

lets air into it.

And then you get a phenomenon called backdraft, which isn't the way it happened in the movie.

But then you don't.

It never happens to be a movie.

I know, I'm sorry.

So

it's a very complex relationship in terms of the amount of oxygen that's required, and it depends on what goes on fire, so what's present in the fire.

Yeah, because what I think is interesting is that we don't have an oxygen atmosphere until about

more than about 5%, until about what, a billion years ago or so, something like that.

We should give some context to the reason you're asking this question, because basically, I had written in my book that fire predates life.

And when I arrived here tonight, Brian's first sentence to me was, your book is wrong.

Social decorum normally is, hello.

Quite a lovely idea, social decorum with a physicist.

The reason, though, it is interesting, isn't it?

Because I'd remembered a graph that I'd seen, I'd used somewhere, which shows the oxygen concentration of the Earth's atmosphere.

And it's really very low until about a billion years ago.

And in fact, there's no oxygen essentially in the atmosphere before photosynthesis, right?

It's

down well below a percent, way below.

So it's an interesting idea that you cannot have fire without life, it was the question.

Yes, and I sort of have to concede now on national radio that your opening salvo to me, your book is wrong, is in fact correct.

I was more generous.

You know, department.

Like, so stars we think of as burning, but are they not?

Are they just hot gas?

Well, it's nuclear fusion, which goes back to our definition.

So yes, you don't need oxygen, it's hydrogen, fusion, it's helium, it's a nuclear reaction which releases energy.

Whereas fire, I think we've decided the definition, it's a chemical reaction, which is basically oxidation.

So it requires oxygen.

And that's why I said, you know, anywhere in the universe, it's kind of of course I expect there'll be life out there in the universe.

But there may be very few planets where photosynthesis operates.

And therefore, there may be very few places where fire exists in the by our definition you know i think that is probably right i'm sorry to say but but the implications for this conversation are really really profound because if you're right brian and i think that you are what that means is that life created fire not the other way around or not in any other formulation you only have fire because life existed so not that the mythological idea that the gods you know you steal fire from the gods or yeah it's kind of the other way around plants created the gods we we gave gave, or life itself gave fire to the rest of the universe.

This is some really deep philosophical stuff.

Anyway, the main thing is, Adam's book, you don't need to buy now.

It's a very, very shoddy book, but he's got a new one out in February, and that's meant to be better.

Brian's going to proofread that.

This is the point of a great book, that it raises interesting questions that we haven't got.

A lot of the great science books are deliberately wrong.

I never thought of that before I read Adam's incorrect sentence.

Thank you, I think.

Well, as we've, right, because we're very near the end and I wanted to make sure we got onto the hard science.

Spontaneous combustion.

Because you're an expert, right?

Because when I was brought up in the 1970s, anyone listening, 70s, 80s, if you were brought up, and you read things like The Unexplained magazine, and there was this terrifying picture of kind of a hole in the floor and the remnants of a leg, and that was it.

And this was another case of spontaneous combustion.

So now we have a proper expert on fire.

Can you explain that?

Is it unexplained or is it explainable?

Firstly, I love to

say the phrase expert on fire.

I just want to say that I'm not

an expert on fire, but thank you for the sentiment.

Well, you are in this panel.

You're doing very well.

Thank you.

Spontaneous human combustion does not happen.

So, what is it in those cases?

What's happening?

So,

what we have shown to happen by experiment, not with people,

not doing well now, not with people, is it's a thing called a wick effect.

So it's like

the scenario,

and it's a bit gory, but the scenario would be somebody who might

be incapacitated.

It's usually someone who might have had a heart attack or something like that, or somebody who's incapacitated, but sitting in the environment of a fire.

So sitting beside maybe an electrical fire or something like that.

And as they are beside the fire and stay and remain in contact or close contact with the fire.

What the fire begins to do is render down the areas of fat in the body.

So the middle of the torso, and those in particular, and those all the audience are now grimacing at me.

So those areas, and they render it down a little bit like a candle is rendered down.

And they soak into the clothing of the person, and then

it's the clothing of the person that acts like a wick in the same way as a candle wick does.

And so the fat in the middle part of that person starts to slowly burn and render away.

So fires, as you're describing, so what's left are the extremities, the legs, the arms, the head, often, but the whole torso can be burnt away.

Adam's laughing.

The whole torso can be burnt away.

So

it looks like it's the source of the fire.

It looks like it's the source of the fire, but in actual fact it's not.

And

the type of evidence that's left behind in a room where such an event can occur, or it has occurred, is very low-level burning.

So it's all centered around the body and it doesn't spread to other parts of the property or the room or whatever.

I've waited 40 years for that.

Well there you are.

So there was a set of experiments done using pigs as a model

to show that this kind of this was the phenomenon that was occurring.

And it happens over long periods of time so it might be many hours before I bet that was tasty when it was done though.

There were some hungry scientists at the end of that experiment.

In the Radio Times this was going to be listed as a show called called What is Fire?

And now it's a show called Why Adam Rutherford's Book Is Wrong on

totally different.

I'm going to be educationally completely different.

How do we feel?

It's Rethean.

It's Rethian

Before We Get Abolished by Boris.

Ed, you've got away with it, by the way.

Your first question, which we never got to, was, Ed, you studied horticulture at the University of Strathclyde.

So our question for you is, slash and burn method of land cultivation.

How do you feel?

So anyway, you've got away with that.

And is it the best method for creating a Sweden?

Do you know what a Sweden is?

I don't know what a Sweden is.

If you looked it up on Wikipedia,

I think it's that burnt area of grassland that you use when you cultivate

a field by burning it and then the thing that's left, I think.

Yeah, that's commercial horticulture.

I was going to be a gardener.

Oh, fair enough.

Anyway, so we asked the audience a question.

Good job we didn't ask him then.

Yeah, thank heavens that never came out.

So anyway, we asked the audience, far is one of the many things that public information films used to warn us about.

But we'd like to know, what would you like to see a public information film warning us about?

So, first of all, cardigans, which is very specific to me, I presume there, Nick.

Thank you.

And also, overpriced Canadian face cream.

Many of you won't know about this, but this is the one time with Brian where basically science goes out of the window.

His selection of face creams, none of which have any evidence base whatsoever.

But when I picked him up on that, he went, I know, but you can't take any risks with this, can you?

And rubbed his shiny cheeks.

Yeah, and the answer is that he should use them as well because he's actually younger than me.

Anyway, go on, what's your one?

What are you up there?

It says D-Ream 25th anniversary heavyweight vinyl re-release of things can only get better.

There's someone here from Catherine texting while in charge of a sleigh.

That's actually technically.

Santa and the chimney collision.

I'd like to see the bicycle proficiency test resurrected and publicised again.

I like these.

These have been taken very seriously by people, by the way.

Infectious diseases, viruses, and genome editing.

Yep.

We've moved a lot.

It used to all just be ravis and water, but now it's genome editing, the new world of public information films.

Thank you very much to all of our guests, Ed, Niamh, and Adam.

Next week, we're going to be dealing with quantum worlds.

Well, in some of the worlds, we're going to be dealing with quantum worlds, but in other worlds, we're not going to be dealing with quantum worlds, are we, Brian?

Well, it's a matter of definition, as we'll find out next week.

Will we find that out next week?

Or will we find it out in, I mean, which next week?

Because other people are going to get a different week, aren't they?

It's a matter of definition.

We'll find out next week.

Are you sure?

We might find out but what about the other weeves that don't find out in another quantum world?

Oh I think I've collapsed the wrong wave function.

Anyway, bye-bye.

Hello, I'm Clemmy Burton Hill from Classical Fix, the podcast where we try out classical playlists on classical newbies.

I just wanted to tell you about a very special episode we've just made with the brilliant writer and comedian Rob Delaney.

That one or so minute of music that we just heard was the strangest cacophony.

I think it might be a healthy part of mental and emotional hygiene to listen to sad music in a world that says don't be sad.

If Beethoven had a dial where it could be, you know, from zero to ten, this would be some five Beethoven.

So it's totally amazing.

If I didn't know it was Beethoven, I'd be like, oh yes, lovely.

But with this, I'm like, come on, Beethoven, show me what you got.

Rob Delaney on Classical Fix.

Download it now on BBC Sounds.

I can't wait to get my fix again.

This is wonderful.

Thank you.

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