In short
Defines fire as a self-perpetuating combustion process (not a single substance), explains the fire triangle/tetrahedron and how extinguishers work, traces fire’s origins on Earth and early human use, then argues that humans “like staring into fire” because it creates “soft fascination” that restores attention and supports social conversation.
Guest backgrounds
No guest appears; hosts are Hannah Fry (science communicator) and Michael Stevens (science educator).
Key claims
Fire is a verb/process driven by fuel, heat, oxygen, plus a chemical chain reaction involving free radicals. Candle flames have distinct zones: dark inner vaporized wax/radicals, blue chemiluminescence from radical-oxygen reactions, and orange/red soot from hot carbon particles. Fire likely became possible only after Earth’s oxygen rose due to early life. Humans maintained fire through labor and working memory, potentially fostering cooperation and fairness. Watching fire is psychologically “soft fascination” (attention restoration theory), unlike “hard fascination” (e.g., high-stimulation feeds).
Notable examples
Fire triangle extinguishing (remove fuel with clearing, remove heat with water, remove oxygen with smothering/CO2 foam); halon disrupting radicals; Neanderthal fire pit evidence in Suffolk (~400,000 years ago) using iron pyrite; earliest wildfire evidence in Wales (~420 million years ago); opportunistic fire use by Homo erectus in Israel (~1 million years ago); Australian birds using existing fires to smoke lizards.
Written by AI. May contain mistakes. Listen to the episode to check what was said.
Chapters
Tap a time to open that second in VODefining Fire
1:39 to 2:30
Exploring the definition and nature of fire beyond common perceptions.
“Queen Carvania stood haloed by the morning sun.”
Fire Triangle Explained
2:30 to 4:25
Understanding the three essential components for fire to exist.
“I mean, let's just begin with like what fire is.”
Extinguishing Fire Methods
4:25 to 7:55
Methods for putting out fires and the role of each component in fire behavior.
“OK, so you need fuel, you need heat and you need oxygen.”
The Relationship Between Fire and Life
7:55 to 13:19
Discussion on how life is necessary for fire, including the history of fire on Earth.
“But I remember in chemistry lessons, there was this talk about the states of the electron, right?”
The First Fire and Human Interaction
13:19 to 14:00
Exploring the origins of fire and early human interaction with it.
“Once that reached about 13%, which was more than 2 billion years ago, which is like halfway through Earth's life.”
The Origins of Fire
14:00 to 18:17
Explore the history and evidence of early human fire use and wildfires.
“Yeah, and that evidence, by the way, was found in Wales.”
Understanding Fire Chemistry
18:17 to 19:29
Learn about the different components of fire and how it produces light.
“So we've got the dark inside of the flame where you just have gases, vaporized wax, primarily.”
The Dynamics of Flames
19:29 to 26:54
Discover how flame colors change and the science behind blowing out a candle.
“And once it cools down enough, it becomes just the regular smoke.”
Fire Suppression Techniques
26:54 to 28:00
Understand how fire extinguishers work by interrupting chemical reactions.
“But initially blowing it out is about interrupting the flow of fuel.”
Transitioning to Fire and Humans
28:00 to 28:35
Discussion about the need to understand the relationship between fire and humans.
“And when we come back, we will visit the relationship between fire and humans.”
Show all 20 chapters
Transitioning to Fire and Humans
29:39 to 30:15
Discussion about the need to understand the relationship between fire and humans.
“Hear the story in every heartbeat with Apple Watch Series 12.”
The Evolution of Fire Use in Hominids
30:24 to 36:19
Exploration of how fire usage may have changed the behavior and cooperation among early humans.
“It takes a lot of work and it takes a different kind of work opportunistically using it.”
Attention Restoration and Soft Fascination
36:19 to 42:00
Discussion on the concept of fascination and its mental health benefits, including the role of fire.
“And exactly how it all happened is a tough thing to figure out.”
The Nature of Fascination
42:00 to 44:20
Explore the concepts of soft and hard fascination and their effects on our thoughts.
“This is something that's interesting that asks for like no effort.”
Wholesome Experiences vs. Digital Distractions
44:20 to 46:58
Discuss how natural experiences differ from modern digital distractions and their impacts.
“But it doesn't leave the door open for the the social and the the pleasant thinking, the creative thinking.”
The Importance of the Hearth
46:58 to 49:44
Examine the cultural significance of fire and communal spaces in human connection.
“This argument about our connection to the fire, I mean, it's only really recently that we've lost it.”
Television Programming Insights
49:44 to 52:44
Learn about the historical approach to TV programming and its relation to human attention.
“people have danced around for a really long time.”
Finding Balance in Attention
52:44 to 56:00
Discuss the need for balance between directed attention and moments of soft fascination.
“Instead, I'm just watching like TikTok on my own.”
The Importance of Mindful Engagement
56:00 to 57:50
Explore how mindful activities can balance rumination and directed attention.
“Rumination is specifically when it's like bad.”
The Importance of Mindful Engagement
58:18 to 58:45
Explore how mindful activities can balance rumination and directed attention.
“Apple Watch Series 12 measures your heart rate every five seconds with the most accurate heart rate sensing in a wearable.”
Transcript
Automatic transcript. May contain errors.0:00Michael Stevens:Welcome to The Rest is Science. I'm Hannah Fry. And I am Michael Stevens. Today, I want to talk about fire. Yes, please. Okay. A lot of people ask, what is fire? And today, I'm going to argue that it's not a gas. It's not a plasma. It's not a liquid. Fire is the great grandmother of social media.
0:24Hannah Fry:Michael, you are genuinely one of the best people on earth.
0:29Michael Stevens:Wait until you listen to the episode before you make any kind of judgment.
0:34Hannah Fry:All right, deal.
0:39Michael Stevens:This episode is brought to you by Cancer Research UK.
0:42Hannah Fry:As if they weren't cool enough already, some astronauts have now added cancer scientists to their CV. They are making use of microgravity conditions in space to carry out experiments.
0:52Michael Stevens:That's because the same thing that lets astronauts experience weightlessness also affects how cancer cells grow. behave, and respond to drugs.
1:01Hannah Fry:And back down on Earth, Cancer Research UK is working with astronomers to explore tumors with technologies that are typically used to map the Milky Way, which I think gives you an idea of just how complex this disease is.
1:15Michael Stevens:That's right. There are over 200 different types of cancer, but by pushing boundaries and embracing the latest technologies, Cancer Research UK has helped double cancer survival in the UK over the past 50 years.
1:26Hannah Fry:And today it is continuing to save and improve lives around the world. For more information about Cancer Research UK, their research and breakthroughs, and how you can support them, visit cancerresearchuk.org slash rest to science.
1:40Michael Stevens:Queen Carvania stood haloed by the morning sun. An army hung on her every word.
1:47Hannah Fry:My champions, I have sold my chariot on Carvana. Twas a lovely SUV, an inexplicably queenly offer. They're even coming to the castle to collect it. Tonight, we feast.
2:03Michael Stevens:An offer you can feast on. Sell your car today on Carvana. Pick up fees, mail, buy. Push your limits, train with precision, see the results. At Equinox, that's high-performance loving. Everything you need to lock in and unlock your potential at Equinox. Start today at Equinox.com.
2:30Michael Stevens:I mean, let's just begin with like what fire is. I've made a lot of shorts about fire, and this is my chance to really clarify, solidify, and calcify my stance on fire. First of all, what would you say fire is? Like your daughter asks you, one of your daughters asks, what is fire? Is it a gas? Is it electricity?
2:53Hannah Fry:No, I mean, I think it's the energy given off by a chemical reaction, essentially.
2:58Michael Stevens:Yeah, it's a chemical reaction. So it isn't like one thing the way gold is one thing. It's one kind of atom. Fire is a whole lot of stuff going on. And what exactly is in it depends on what's burning. So that's kind of the key. I think asking what is fire is like asking what is...
3:21Hannah Fry:Like foaming or fizzing?
3:23Michael Stevens:Yeah. Like when you mix vinegar and baking soda and you shake it up and you look at the whole thing and you say, what is that? We don't say, oh, that's blooba. You know, we don't need to give it one noun. We say that it's a process. It's a thing that's happening. We've got bubbles of gas and we've got the vinegar and the baking soda mixing and then there's some water being produced, whatever. And everyone leaves it at that.
3:45Hannah Fry:But fire is a verb rather than a noun.
3:47Michael Stevens:That's right. But we see fire as a noun. It fire is a noun. It can also be a verb. You can fire something. You can fire someone. You can. OK, let's walk through the steps. OK, because fire is is is at least two different things, depending on where you think the fire begins and ends. For those of you that aren't that haven't watched every single short I've ever made or don't already know what what the fire triangle is. It's the three things fire needs to happen because fire is a chemical reaction known as combustion. And you need to have three things for there to be a fire. Or do you? We'll get to that later.
4:25Michael Stevens:OK, so you need fuel, you need heat and you need oxygen. Take away any of the three, just one of the three, no combustion. Which is how putting out fires work. Exactly. So you've got some fuel. Let's say it's your house. It gets hot enough. There's oxygen around. There's a house fire. How do you put it out? Well, you need to get rid of one of those three points of the triangle. You get rid of the fuel. We do that when there's a wildfire and we start like clearing the brush and creating a perimeter around the fire where the flames just are going to run out of fuel because they're going to hit like dirt.
5:00Michael Stevens:If you want to get rid of the heat, water is perfect for that. That's why we put water on fires because the water absorbs so much heat. The fuel goes, ah, there's not enough left for me to react with oxygen. Guess I'll stop burning. So that's what even hot water will put out a fire. But remember we talked about like wet water.
5:19Hannah Fry:And wait, unless it's like many thousands of degrees hot. Let's just let's put limits on this. Yeah.
5:25Michael Stevens:So steam, if you had if you put used steam that was at a thousand degrees Celsius, it wouldn't put out the fire. Thank you.
5:35Hannah Fry:Worth clarifying.
5:36Michael Stevens:Carry on. Isn't this the most practically useful podcast you guys have ever listened to?
5:41Hannah Fry:Guys, guys, guys, your house is burning down. Right. Let me don't use steam a thousand degrees. Yeah.
5:47Michael Stevens:You can also get rid of the oxygen. You can do that by smothering a fire in sand with a blanket. Stop, drop and roll. You can also use fire extinguishers that shoot carbon dioxide foam on the fire. Carbon dioxide is heavier than oxygen. It's going to go down low. It's going to starve, suffocate the fire. But there's actually a third way to stop a fire. Wait, the fourth way? There's a fourth way. There's a fourth point on the fire triangle.
6:14Hannah Fry:You're going to try and tell me now that this is actually a fire square and has been all along.
6:17Michael Stevens:It's never been a square because squares don't have the beautiful geometric property where every single vertex touches.
6:27Hannah Fry:Sure.
6:28Michael Stevens:So instead, they call it the fire tetrahedron.
6:31Hannah Fry:Oh, much nicer.
6:32Michael Stevens:Okay. The fire pyramid. And so before we talk about this fourth point on the fire pyramid, the fire tetrahedron, let's talk about what happens when something burns like a candle. OK, so strike a match. Now I've got a big source of heat. I bring that towards the candle and the candle is a source of hydrocarbons and they're in this like solid ish form. Right. It's a wax. And when that heats up, the hydrocarbon breaks apart. It chemically breaks apart into what are called free radicals. These are basically if you're familiar with molecules, when you look at these, you go, that's not a molecule. That's like it's incomplete.
7:12Michael Stevens:It's like half a molecule. It is ready to combine with stuff. So we've got diatomic carbon, just like two carbon atoms. Give me a break. They've got free electrons. They need to combine with something, but they aren't yet. You've got things like, I don't know, carbon and hydrogen, just those two atoms bonded together. They're extremely reactive. They're radical.
7:33Hannah Fry:Don't you think that sort of, I always think the phrase free radical describes, I don't know, people in San Francisco in the 1970s, you know?
7:39Michael Stevens:Yes, very similar. So whichever analogy is going to help you, just grab on to.
7:44Hannah Fry:As I've mentioned before on this podcast a number of times, chemistry, my chemistry knowledge is that it's pretty limited, right? Like maths and physics, I'm all there. Biology, I can make my way around. Chemistry is ropey at best. But I remember in chemistry lessons, there was this talk about the states of the electron, right? That it's like you have these shells, which I think is actually an incorrect model.
8:12Michael Stevens:Yeah, but I think it works for kind of understanding and explaining chemical reactions.
8:15Hannah Fry:That the electrons are at different levels, energy levels, some farther and some closer in towards the nucleus of the atom. And when the electrons move between those states, move between those energy levels, that's when they start emitting certain colors of light.
Read the full transcript
8:32Michael Stevens:Yeah, when they absorb electromagnetic radiation, there's a lot of ways to describe what's happening. They're vibrating more. They go up an energy level. My chemistry, my atomic chemistry, is also pretty limited. But when they fall back down, they usually emit something like a photon.
8:50Hannah Fry:Okay.
8:51Michael Stevens:And that might be a photon with a wavelength we can see or it might not. It might be visible light and we go, wow, it's glowing. Or it might be thermal light, in which case we can feel warmth and a snake can say, wow, I see it. But these radicals are coming out in kind of two main areas. One is right out of the wick where they actually don't have any access to oxygen. So when you look at a candle flame, you can sometimes see that right by the wick, it's kind of darker. It's like it's very beautiful. There's like this darker region in the flame. And that's where you've got this vaporized wax primarily made out of radicals that haven't combined with anything yet.
9:28Michael Stevens:Down near the base, those radicals combine with oxygen. and they have so much energy that they literally release light through a chemical process called chemiluminescence where their electrons are just like so energized they drop down release photons and it happens to be in the blue wavelength so so the blue part of a flame and the dark inner part of the flame are gases they're just a mixture of gases primarily gases that are vaporized radicals, vaporized wax. But higher up, you get the classic red-orange flame of a fire. And that is where the really hot radicals are interacting with oxygen, and they're finally getting a companion to share electrons with.
10:17Michael Stevens:And they're forming carbon dioxide, they're forming water vapor. That process creates a lot of energy. To break a bond, you've got to put in energy. But when you form a bond, energy is produced. That's why the flame is so bright. The heat produced by the radicals interacting with oxygen is a self-perpetuating process. That's why fire kind of like persists. You touch the match to the flame. That's enough heat to get it started. But then what happens to those radicals and the oxygen produces enough heat to keep it going. So it just keeps eating. It's almost like alive in that sense. It preserves itself.
10:56Michael Stevens:Right. Right.
10:56Hannah Fry:So this is what I was thinking as you were talking, because actually when you try and come up with a definition for what life is, consumption is a big part of it. Being able to sort of self-sustain is another part of it. And actually by a few different measures, fire sort of is alive.
11:17Michael Stevens:It's like an almost life. So if you really don't want fire to count, you can say life needs DNA. It's like wet blanket. Come on. Come on. But fire, you know, fire, a flame is made of totally different molecules every second. But I'm made of different molecules every five, six years. So, like, I'm just a slow flame. You're just a slow flame. We can discuss what life is in another episode.
11:44Hannah Fry:I mean, there's all sorts of chemistry going on inside you. There's all sorts of combustion even.
11:48Michael Stevens:There's slow combustion going on inside me.
11:50Hannah Fry:You're just a slow flame.
11:52Michael Stevens:Yeah. It's like Pyre was like, guys, let's just chill out. and become traditional life.
11:58Hannah Fry:I think it's the other way around. I think fire looks at humans like, guys, can we speed this up? Speed it up. What are you doing?
12:04Michael Stevens:Funny enough, when I say that joke, I realize that it's entirely not true because fire on Earth doesn't really predate life. Fire is able to exist. Combustion is able to happen on this planet because life was here first. There was a time before wildfires of any kind could even happen. Obviously, there was a time before there were plants on the dry land. But you need to have free oxygen. Those radicals need something to react with. Well, they need oxygen to react with to produce what we call fire.
12:35Hannah Fry:Hold on. Is that true then that you only get – I mean, of course, you only get fire when you have oxygen. Fine. But you only get fire where there is life. Do you not see fire in the rest of the system?
12:47Michael Stevens:You don't need life. But you do not see fire, except I'm sure in some crazy situations that are extremely rare. You do not see fire anywhere else in this solar system. There just isn't free oxygen on any other planet where a fire can just start happening. Even early Earth had no fire. We needed to wait until life, like very early algaes and bacterias came about that were like, hey, I'm going to poop out oxygen. And they gradually, over millions of years, put oxygen into the atmosphere. Once that reached about 13%, which was more than 2 billion years ago, which is like halfway through Earth's life.
13:26Hannah Fry:So for the last couple of billion years, there was no fire?
13:29Michael Stevens:There was no fire, yeah. Wow. So there were living things on Earth before there was fire.
13:35Hannah Fry:So hold on, does that mean that fire has a birthday? day.
13:39Michael Stevens:The possibility of the chemical reaction happening has always existed. And I'm sure fires were happening elsewhere in the universe. But on Earth.
13:51Hannah Fry:There would have been one day, one single day when the first fire happened.
13:57Michael Stevens:Yes. I mean, that's true. But it depends on how we define fire, because I'm sure we could find an isolated incident of combustion, very very quick combustion in the early days of earth there happened to be enough oxygen in some little environment that it happened but evidence for like a fire fire a wildfire is much harder to find the earliest evidence we have found of a wildfire was 420 million years ago right so actually much later yeah much much later because you needed you needed plants to evolve on dry land that could burn, that could be a fuel source. Yeah, and that evidence, by the way, was found in Wales.
14:37Hannah Fry:Really?
14:38Michael Stevens:Okay, right in this country, the United Kingdom. And then we're going to jump forward a lot just because this fact is also very cool. The earliest evidence we have of humans making fire on purpose were Neanderthals in Suffolk. They found this fire pit, not Homo sapiens, but it looks like Neanderthals had actually not opportunistically found a fire, like from a lightning strike and like brought it somewhere, but had actually made it because we found iron pyrite in this archaeological site. And the pyrite is not naturally found there. So it had to have been carried around. And sure, like you would carry around iron pyrite.
15:16Michael Stevens:It's fool's gold. It looks cool, right? But it also is great for striking a flint to produce sparks. And we find it just around this fire.
15:26Hannah Fry:Hold on, hold on. How long ago is that?
15:28Michael Stevens:Yeah, about 400 ,000 years ago.
15:30Hannah Fry:Okay. Right. You know what? Reasons to be patriotic. You know, Big Ben, the London Eye, the King, the Beatles, invented humans losing fire.
15:44Michael Stevens:I'm not going to say that you guys invented the making of fire. but there's no evidence to show that you didn't.
15:53Hannah Fry:Okay, but also wildfire, right? I know in California things get really serious and nasty, right? And wildfires really can be absolutely devastating. But we now know that Welsh people can be like, guys, we've got much more experience in this than you guys.
16:09Michael Stevens:Yeah, thanks for starting it, Wales.
16:12Hannah Fry:That's amazing.
16:13Michael Stevens:Now, yeah, I know, that really...
16:15Hannah Fry:Petition to change our logo to just a flame.
16:17Michael Stevens:You could do it. Our flag. Why not? Just make it a flame. Well, because the problem is that like next year we might find evidence in Ethiopia that fires were being made. So that was a huge discovery. It happened just a couple of years ago in December of 2025, this discovery. And a whole study was published about it. And that pushed back when we thought people started making fire by a lot. Earlier estimates were like maybe 50 ,000 years ago. You know, because maybe you've got to like make yourself a little bow drill where you have a stick and a string on it and you go back and forth.
16:54Hannah Fry:And the way that they do in movies and stuff and in real life.
16:58Michael Stevens:But no, this discovery showed that like people were creating fires by their choice much, much earlier.
17:07Hannah Fry:So is that OK, because that's the distinction here, right, is that they were doing it deliberately and we can tell that they were making them themselves. Is there evidence of people using fire? I don't know, like caves with sort of blackened patches, but we're just not sure that they made it. Because you kind of indicated that yourself.
17:26Michael Stevens:The earliest evidence we have for what's called opportunistic fire use, where you just find some. There's a natural wildfire. There's a lightning strike on a tree. And then a creature like takes advantage of that is in Israel at least a million years ago. Right. Homo erectus in this case. We find that they had a fire and had been using it for a long time with some like shells around evidence like that, that they weren't just like, whoa, but that they were like, let's put this where it's going to be helpful. We don't know how to make it ourselves yet. We're going to wait for the Welsh to figure that out.
18:05Michael Stevens:But so, yeah, I mean, still, that's that's that's pretty incredible. And and fire winds up being an amazingly important part of human evolution, most likely. But we're going to we're going to get to that after we finish talking about what fire is. OK. OK. So we've got the dark inside of the flame where you just have gases, vaporized wax, primarily. That's it. In the blue part, you've got radicals that are so energetic, they're releasing chemical light. But up higher in the flame, there's a little bit less oxygen. So some of these radicals combine with each other to make soot. They just make big clumps of carbon.
18:46Michael Stevens:These are solid. These are little tiny pieces of a solid, but they're so hot, they glow with black body radiation, just thermal radiation because their atoms are moving so quickly. And that produces the orangish red glow of a flame. Okay. So that part of fire is an aerosol. It's little pieces of solid mixed into a gas.
19:10Hannah Fry:Okay.
19:11Michael Stevens:And that gas is the carbon dioxide, the oxygen, the water vapor, the products that are being made and the ambient air. So, you know, it's not true to say that fire is hot smoke, but the orange glowing part of it really is just hot smoke. I mean, it is hot smoke. And once it cools down enough, it becomes just the regular smoke. And the classic demo is to blow out a candle, watch that smoke trail come up and light the smoke trail way up here. Now you've put in enough heat that the soot particles start reacting with oxygen again. and now they're hot enough to glow because of that chemical reaction happening and that feeds back down through the smoke goes all the way back down to the wick and the candle is lit again.
19:54Michael Stevens:Okay, so basically if someone were to ask me what is fire, I would say it's a mix of a whole bunch of different phases. You've got gases and you've got solids. The solids are dispersed within the gases and they're all so energetic and hot they release light.
20:10Hannah Fry:Simple.
20:11Michael Stevens:Simple. Simple. One of the best videos...
20:13Hannah Fry:I would say it's a quicker human.
20:16Michael Stevens:You would say, yeah. And you know what? We would both be right. So there's a great video from Be Smart about what a flame is where he does this great demonstration of just having a candle flame and then taking a cold metal spoon and placing it way above the flame where you actually collect water vapor. Because that's one of the offshoots. Yeah, the offshoots. That's one of the products of the radicals combining with oxygen. H2O. Then if you put the flame in, sorry, if you put the spoon in the orange part of the flame, you get soot because that part of the flame is just carbon particles suspended in gas.
20:56Michael Stevens:And then if you put the spoon in the dark inside of the flame, the spoon will come out covered in solid wax, just wax that has cooled down from the vapor phase back into a solid. So it's all in there and it's all full of energy and it's self-perpetuating so um i in my house i have a
21:17Hannah Fry:i have a fire i have one of those wood burner things um it's sort of middle class trophy in many ways um having one of them in your house anyway the thing that's always really noticeable is the different colors that the flames take on depending on how you change the oxygen supply also depending on how how far into the burn process you are so right at the beginning very yellow flame if you try and like choke off the oxygen supply everything goes blue until it gets really really hot and then it becomes very red but what i'm hearing from you is that the different parts of the flame that you see all together in a candle you're pushing what's in your wood burner into predominantly those states.
22:06Michael Stevens:Yeah, that's right. So it's a really good point, too, because I'm talking about like a candle flame or a log burning, which is also what you're talking about. But it reminds me that there are different kinds of flames. There are like acetyl flames where the flame is actually so hot that it does contain enough plasma that you could call it a plasma. That's when a gas gets so hot, its electrons are like, bye, I'm free. Okay. That's like what the sun is made of. OK, but for the most part, a birthday cake handle, you don't get in plasma. You're getting you're getting some plasma. Like literally every gas contains some atoms whose electrons are more free.
22:41Michael Stevens:OK, so where exactly we say this whole thing is turned plasma. It's up whatever you want. I mean, that's not it's not my decision. Yeah. OK, you can what you should not. But you it is possible to microwave a flame to create a plasma.
23:00Hannah Fry:Go on.
23:00Michael Stevens:Okay, so don't do this, but if you light a little candle, like a birthday candle, put it on the tray of your microwave, and then you place a little glass dish over the top of it, not touching the flame, but a bit above, and then you microwave this whole apparatus, the hot products of combustion will get superheated. And in that little dish, that little glass bowl you've put above the flame, you will get a bright white glob. Look this up on YouTube. There are people who have done it. And again, don't do it because it will cause a fire. It will hurt you. It will break your microwave. But inside, there's like a cloud.
23:38Michael Stevens:It's not even a cloud. It looks like a lava lamp blob, but it's bright white. It's like and that's plasma. OK, that's cool. It's like predominantly plasma. The blue light, blue light in a flame means there's an incredibly clean combustion happening. There's a lot of oxygen and it's all, it's just all combining and you're getting that chemiluminescence.
24:02Hannah Fry:You haven't got floaty bits.
24:04Michael Stevens:You don't have floaty bits of solid carbon that are just thermally glowing because of their heat in orange or a yellow color. It's also possible to get something so hot it turns blue.
24:14Hannah Fry:Maybe when you're sort of like closing the oxygen supply, what you're actually doing is you're preventing, I mean, because you obviously still need some oxygen in there. But maybe what it's doing is it's not allowing there to be turbulence within the cavity. It could be something like that. Yeah. That makes the flame cleaner.
24:32Michael Stevens:Yeah. Yeah. Now, you can also get something that's blue hot because it's just so hot. That's not what's happening in a candle flame. If something is blue because of thermal radiation, it's about as hot as it. Well, it's not as hot as it can get, but it could be. because for a reason I actually don't understand, even though I made an entire CuriosityBox product about this, there's a limit to what color things can change as they get hotter. As they warm up, they stop predominantly reflecting light, which is how we see most stuff. And they start just having electrons that are so excited, they thermally radiate heat out.
25:08Michael Stevens:At a certain temperature, things will start glowing red, like no matter what they're made out of. They will become red. Then they'll become like orange and then yellow and then white and then blue. But after blue, it stops changing because of physical reasons and because of human perceptual biological reasons. We just don't see a change after that. So there really is a color of absolute hot.
25:32Hannah Fry:So wait, after that point, it leaves the visible light spectrum?
25:36Michael Stevens:Nope, it stays at blue.
25:37Hannah Fry:Okay.
25:38Michael Stevens:Yeah. Well, I mean, it stays at, in terms of what we can see, it stays at blue. Every black body is releasing all different types of radiation. There's X-rays coming out of it, but like not a lot. But for reasons I don't know, but Planck understood and explained, there's this big bump in the visual region for a hot body. Oh, yeah. I wanted to also say that this kind of description of combustion, of fire, also helps explain why you can blow a candle out. I used to think that when you blew a candle out, it went out because blowing on it maybe cooled it down. Yeah, I think that's what I would have thought.
26:20Michael Stevens:Yeah, because I'm just, again, thinking about that fire tetrahedron. What am I disrupting? But you're actually not cooling it down. Maybe a little bit you are. But primarily it goes out because you've disrupted the fuel source. By blowing it, you're causing that stream of vaporized wax to separate. Oh. So that the chemical process can't jump to the next batch of vaporized wax. And then once that fuel source again becomes a straight line of smoke, you can put heat back in and it keeps going. But initially blowing it out is about interrupting the flow of fuel. I also want to say that the fire tetrahedron gives us another way to fight fires.
27:02Michael Stevens:If we're not going to lower the temperature, we're not going to get rid of the fuel or we're not going to get rid of the oxygen, we can also interrupt it at the chemical reaction stage. Because when combustion happens, you've got these free radicals. They combine with oxygen. We've got ourselves a flame. We've got this. Yeah, and we've got a lot of heat energy released. But if we can slip something in there that's more reactive than oxygen, and yet when it combines with the radicals, has like a much weaker bond that puts out less energy, we can stop the fire. That is how halon fire extinguishers work.
27:41Michael Stevens:They introduce these chemicals that contain like bromine and stuff like that. I don't know their chemical makeup, but they're more reactive with the free radicals than oxygen. They say, get out of the way, oxygen. I'm combining with this diatomic carbon. Boom. And also, our marriage is crap. There's no heat coming off of this. And so the whole thing just goes out. All right. So let's take a break. And when we come back, we will visit the relationship between fire and humans.
28:36Hannah Fry:Alex, you've got to ask yourself if you want to play or not. You're the Prime Minister. You've done nothing! We would need to understand the policy context. All the relevant context will be structured as a framework today. Kill the President of Russia. Yes. Who is going to be able to pull this off? Sergeant Tom McDuff! Devised as a technically rigorous geopolitical action thriller. Where Britain plays its strongest hand against its strongest fold. Bear Hunt. Available now in full wherever you get your podcasts.
29:17Michael Stevens:Push your limits. Train with precision. See the results. At Equinox, that's high-performance loving. Iconic spaces that inspire. Personal training backed by real data. Unlimited group fitness classes from yoga and Pilates to strength and conditioning. elevate your post-performance ritual with saunas steam rooms cold plunges and more everything you need to lock in and unlock your potential at equinox start today at equinox.com
29:47your heart can tell you a lot about your health apple watch series 12 measures your heart rate
29:53Hannah Fry:every five seconds with the most accurate heart rate sensing in a wearable so your vitals app now with heart rate variability can tell you when something is off and your readiness score can let you know when to rest and when to push. Hear the story in every heartbeat with Apple Watch Series 12. The features described are for wellness purposes only and not for medical use. iPhone 11 or later required.
30:12Michael Stevens:Based on Apple conducted study of heart rate accuracy, August 2026. Visit apple.com slash Apple Watch Series 12.
30:22Michael Stevens:Even the opportunistic use of fire was a big change for hominid creatures. It takes a lot of work and it takes a different kind of work opportunistically using it. You don't even need to be a hominid to have done that. There are birds in Australia that will take advantage of an existing fire to like move a burning twig or a smoldering twig around to create an environment where they can like smoke out lizards and stuff. Yeah. To eat them. To eat them, not just to like say hello or prank them. It's for food. Yeah. when humans started to not just temporarily take advantage of something that was burning, but try to maintain it because of its usefulness, that might really represent one of the, maybe not one of the first, but one of the key turning points in history that led to us today.
31:17Michael Stevens:Maintaining a fire is something that takes quite a lot of labor and quite a lot of working memory, meaning you kind of have to remember what you are doing and why you're doing it and this is something we don't see in a lot of other animals the ability to say you know what today i've got to go out and find this thing that i did not instinctively evolve to want the way like a squirrel wants to collect nuts it's like a new idea you have i think if i get more wood and just put it on this fire it'll keep going let's go find that and we don't have axes we don't have chainsaws so we're gonna have to collect wood and also we learned yesterday that the drier it is it works better like the longer it's been on the ground and not wet so find that kind it's like a very complex cognitive thing because i'm not talking about modern human cognition i'm talking about Homo erectus, a hominid that whose ancestors did not do this.
32:20Michael Stevens:So you got to go out there and you've got to collect this wood. And guess what happens while you're collecting wood? There are problems. There are cool things like, oh, my gosh, that's a root vegetable I could eat. There are things that you will find that will distract you. And like every other animal gets distracted okay and kind of more lives in the moment but what we see with like later hominids is that they do a lot of things where it's like you had to stick with that you had to use directed attention and working memory to keep reminding yourself no no i'm doing a different thing again animals don't need to be reminded to do the things that they instinctively do like breathe or care for their children or hunt or hunt but collecting firewood is this literally like an invented behavior and you have to stick with that then here's the other problem you put in all that work where you were not um collecting food you were you were not uh being safe you could have just not been out in the woods looking at stuff where there could be bugs and predators and whatnot where you could trip and fall.
33:31Michael Stevens:And you create a fire and it's awesome. OK, it produces warmth. It produces light. It also like might scare away predators. There's all these benefits. But like anyone can kind of take advantage of those benefits, even if they didn't help build it. Right. That's true. Terrence Toomey has written at least a couple articles, at least that I've read about early human use of fire and how that may have facilitated the emergence of cooperation amongst members of our species. Okay. Because you've got to sort of keep track of like, did you help with this fire? Are you like, are you going to use, are you going to use this?
34:14Michael Stevens:Are you going to like do something tomorrow for me? And we see this kind of concern over fairness with like very young human children, you know, three, four years old. But we don't see it with chimpanzees. OK, if if you reward a couple of chimpanzees for their activities and you give one of them a much better reward, the one that got the better reward is like, great. But if you do this with young human children, they go, well, you can have some. Right. And so his argument, which I'll let you read to really spell it all out, is that fire use, which was this communal benefit that also required communal work may have been one of the earliest times that our species had to kind of develop and exercise that and also that people who were good at it individuals who were good at it had an advantage because they could stay in these communities and be accepted by them and reap the advantages of the fire they could for example eat cooked food right which is so much easier to digest i love this stuff i love this stuff i mean look
35:23Hannah Fry:on the one hand i think that when it comes to sort of this type of anthropology this type of sort of evolutionary history it's really hard to know concretely one thing follows another you know these aren't falsifiable things that we're saying here these are looking at the evidence and drawing connections between it however that said if you do take this story at face value these examples of where the existence of something in our environment changed our behavior changed the direction in which we evolved in i really love this stuff it just goes to show how we are not this isolated entity right we are we are of this earth right which is like a phrase that they say in the yurok tribe say, in North America.
36:10Hannah Fry:It's so clear when you describe it like that, that we are a direct result of everything that exists around us and everything that we use.
36:18Michael Stevens:Yes, we are. We are the children of our experience. And exactly how it all happened is a tough thing to figure out. That's why, you know, anyone can sit in a chair and go, well, you know, we like the color blue because of, I don't know, here's the thing. You can't design an experiment to test that. So the field of cognitive archaeology, which is studying how people thought in the past or and by people, I mean really any kind of hominid, anything that thinks really is is a difficult field. And actual like evidentiary statistical conclusions are hard to get at. But you can do things like you can study how a certain kind of stone tool could have been made by hand and compare and have living humans try to make different designs that we know were made in prehistoric times and compare how long it takes and the benefits and can this be used to cut, what's the best way to cut meat off of a bone with this kind or this kind?
37:22Michael Stevens:And we kind of test it today and we do actually learn quite a bit. It's almost more right now about asking the right questions. so anyway cooperation came about and as far as we know today one of the first arenas it could have been practiced in in a very approaching modern form would have been around a fire and and in maintaining and then much later making a fire but there's something else about fire that's very fascinating and it's the fact that fire is fascinating we can sit by a fire and look into it and feel quiet feel fine just sitting next to someone else and looking at the fire it's relaxing relaxing watching the ocean is similar people watching can be the same watching fish in an aquarium watching birds you know it's there's something strange about it and i i'm not gonna pretend that anyone knows where this began you can do you can do those like made up stories uh i like to call them metonymic explanations where it's like well okay because fire is so useful we came to like looking at it and it's like i don't know what we do know from from modern psychological research is that humans have had for a long time, and we have this pull between sort of two types of use of our attention.
38:56Michael Stevens:One is directed attention, where I voluntarily will my attention onto something, solving a problem in front of me, doing work, solving problems on a worksheet at school. And that's pretty tiring. It's not tiring in the way that like running up stairs is tiring, but it seems to probably tire us because it uses a lot of our brain's inhibitory processes to stop distractions. Like I can't do what I'd rather be doing. I'm doing this. And that is actually metabolically quite taxing. So that might explain why after a lot of directed attention, you're just like, oh, I'm so tired. And like all I did was sit in a chair and do a podcast all day.
39:40Michael Stevens:Why do I feel tired? It's because you've got a lot of directed attention. Now, on the other end, there's the involuntary attention when you're just sort of left alone to your own thoughts. This is what you might feel when you're not able to fall asleep, but you're just in bed and you're kind of like spiraling, thinking about things that you did and negative thoughts and fears. And did I do that wrong? And what is this person thinking? And that's called rumination. Now, both of them have benefits, which is kind of strange to say that rumination does. But there's this growing body of evidence that even depression had this benefit towards forcing us to face complex problems.
40:21Michael Stevens:You can't ruminate on them forever. Sometimes there's no solution. Sometimes it creates a situation where you're not able to then be social and think and cooperate and be with other people. So there's this tug of war between directed attention, which is outwardly focused on like a problem on a task and you will it. And then rumination, which is unwilled. It's focused on inside personal things and emotional fears. But then in between them, there's what it's literally called this fascination. And that's when you're interested with like no effort. Oh, and that's how we use the word today. That's fascinating.
41:04Michael Stevens:Yeah. It usually means, yeah, I'll keep watching this. Right. But I don't have to do anything.
41:09Hannah Fry:You're kind of passive in the process.
41:11Michael Stevens:Yeah. So a couple of psychologists, Stephen and Rachel Kaplan, they've developed a theory called attention restoration theory, which focuses on the benefits we get from what they call soft fascination, which is what you are experiencing when you just sit and look at a fire. When you sit and look at the ocean and listen to the ocean. it busies up the mind in just the right way that you don't ruminate but you're not also having to direct your attention you're able to sort of restore a lot of your cognitive concerns and you're ready to talk to other people now soft fascination has a lot of health benefits and like we do this it's called self-care today like I just need to turn on my pink noise machine and I need to read a gossip magazine.
42:05Michael Stevens:This is something that's interesting that asks for like no effort. And it's not inwardly about you and your concerns, but it's also not like a task you have to do for work that's really directed in taxing. It's like just right there in the kind of like, I'm getting something, but it's nothing.
42:21Hannah Fry:I'm seeing where you're going with this. I'm seeing where you're going with this. Keep following.
42:25Michael Stevens:Okay, so let's upgrade this a little bit. What if we made soft fascination more fascinating to the point where I don't actually have any more room for talking to other people and thinking about like nicer, less ruminating thoughts but just kind of like being creative? What if instead of looking at the fire, I played a video game or I got onto TikTok and I just scrolled through stuff? That's also fascinating. And it protects us from being alone with our thoughts, but it also protects us from the cognitive load of directed attention and like work requirements.
43:04Hannah Fry:It also protects you from sometimes the torture of ruminating on something.
43:09Michael Stevens:Exactly. Just like watching a fire, it's something, but it's kind of nothing too. However, the something is so loud, it kind of blocks out that chatting by the fire feeling. For me, in my more modern life, I get this when I'm on airplanes and I have nothing to do. There's like no movie looks good and I just kind of am sitting there, maybe glancing at what movies other people are watching. And maybe just staring at the pattern on the seats or the ceiling. And I started thinking about like, hmm, I'm not ruminating. I'm thinking good thoughts like, you know what? I could run for president. Yeah, I know who I would choose to be my campaign manager and I could do this.
43:59Michael Stevens:And it's like it's like exactly the kind of pleasant thing that we usually share with other people at like a campfire. So this kind of thing happens. But once you up that stimulation level, then you start getting what's called hard fascination. And that's and that we're not totally sure what the effects are, but it definitely protects us from directed attention and and rumination. But it doesn't leave the door open for the the social and the the pleasant thinking, the creative thinking. It's just a fantasy world. so one of the big differences I think anyway this is again I'm into speculation territory here
44:42Hannah Fry:but sitting on a beach watching watching the ocean being in a forest laying under trees looking at their their branches swaying in the wind or sitting around a fire and watching the flames lick up into the sky all of those feel very wholesome very nurturing experiences sitting on my phone in bed flicking through instagram does not feel wholesome i do not end up feeling good at the end of it and i sort of always wondered whether a big part of although having said that i do recognize that my brain is in a very similar state of not really doing anything and passively allowing information to wash over me yeah i mean you're feeling the difference between soft and hard fascination right okay that's interesting because i also wondered whether there was something about it can't be a coincidence that all of those examples that i that i just gave the forest the ocean the the flames are all sort of like very embedded in nature they're all situations in which our ancestors if they found themselves you know in a forest or by the ocean or you know in front of a fire would have felt safe and you know that that's how you live right Like there's this riverbed in France, which I take my daughters to and took them there the summer.
45:59Hannah Fry:And as soon as you get there, there's this thing that washes over you that's like, oh, this is where I'm supposed to be. You know? Yeah. And I do think that there's something about that with fire that it's like it's I look, I don't have any evidence for this. But I do think that there is something about sitting around a fire that you are, you know, generation after generation after generation. if we go with what you said earlier our bodies are the way they are because of our relationship with flames and I think that there's something about your body still remembers right? Maybe you're getting a bit woo woo but your body still remembers because so much of your history, so much of your past was spent around a fire Exactly
46:44Michael Stevens:so I don't know enough about it but you can look into the biophilia hypothesis which is exactly what you're describing that we evolved to love nature and that it produces this calming effect because it's what we're supposed to be looking at.
46:58Hannah Fry:This argument about our connection to the fire, I mean, it's only really recently that we've lost it. So the ancient Greeks, they had all of these gods of everything you can imagine, right? There was like the god of the sky, the god of thunder, the god of the ocean, you know, there was the god of olive trees, there was the god of whatever, but there was also a god of the hearth, right? And I think in the modern day, that sort of feels a bit like oh well what have you got a god of the doorstep as well like come on but actually i think what that demonstrates is just how fundamentally important the hearth and the fire was to society and to culture up until extremely recently because this would be the place that you would sit around and you would have conversations and you would discuss your day and you would tell stories and sing songs and like this was the place where we were the social species, not just the cognitive one.
47:50Michael Stevens:Exactly. It really is a fundamental part of what made us humans in the sense of what that means today. Because, I mean, we still have it today. I think the hearth today is still, you know, all cooking together. Cooking is one of those activities that doesn't necessarily require super direct attention. You've chopped these vegetables before, you know what pot you're going to use. So you're not using directed attention that isolates you from the world, but you're also too busy to be ruminating negatively within your own thoughts. So what are you doing? You're chatting about like what Susan next door did with your kids.
48:27Michael Stevens:You're talking, you're talking. And that's where conversations start happening. Look, don't get me started. Let's go look tonight. Let's go cook up some marinara sauce. I'll tell you all about Susan. But this is where conversations happen about Susan, about what should we do about timmy okay should we i have this idea guys it's called laws what do you think i think i think that the the king bad idea okay those conversations happen when we're being soft fascinated better because otherwise it's awkward we're distracted we're scared just yesterday one of our producers was saying yeah whenever there was something pretty serious to talk about my dad would take me for a drive.
49:07Hannah Fry:Right. Absolutely. You know, so doing something, but you're not it's not requiring your attention. Or I think doing crafts with my girls is like if we're sitting in drawing, doing Lego or something. So we sort of we're doing something. That's when we get the best conversation.
49:24Michael Stevens:Crafts, Lego, building, cleaning. They're all they're all soft fascination beds that we can lay in to have these conversations. But when that bed gets too fun and it becomes hard fascination, we don't have those conversations about the big topics. And this is something that people have danced around for a really long time. I want to talk about Paul L. Klein's 1971 TV Guide article. I actually, I love this article so much, I own a copy of the TV Guide it appeared in. So who was he? He was an executive in audience measurement at NBC back then. And he basically just lays out like his like executive strategy.
50:06Michael Stevens:And it turns out to be this really mind blowing piece of insight into human nature. He's like, guys, all right, my job is to make sure that people watch our TV shows. And here's the problem everyone's everyone's making at all the networks. They're trying to make a show that people want to watch, but people don't want to watch a good show. They want to watch television.
50:28Hannah Fry:Right. Okay. They want to sit around as a family And they want to be soft or hard fascinated.
50:35Michael Stevens:They just want something to watch. And watch is like they want to watch a fire. They want to watch the TV set. And so we're just providing that to them. And the key, if you want to win as a network and have the highest ratings, isn't to make the best show. Because that's what we think is a good show is like directed attention focus. This is a show where we're going to discuss religion and politics. He's like, no, no, no. Just like softer. Make it softer. And you do that by creating what he called the least objectionable programming.
51:11Hannah Fry:Wow.
51:12Michael Stevens:Give them, because this is why networks lose. People turn it on and they go, I don't like this. This is not good for my kids to see. And they go. And they go until nothing's objectionable anymore. And now it's a fire in the fireplace.
51:24Hannah Fry:That's so interesting. You know, I think there's a podcast as well, by the way. I think there's a podcast too, because I used to make radio programs that were trying to be the directed attention version of this, where it would be like, right, the narrative needs to be completely crafted from the top to the tail. I need to like seed ideas throughout. It needs to be taking people on a journey and so on and so on and so on. And I think the thing about podcasts, the like modern world of podcasting is, actually people just want something in the background. Right. People just want something to vaguely listen to while they're going for a drive or doing their laundry or like, you know, mowing the lawn.
52:03Hannah Fry:And like their brain can wander in and wander out and not necessarily listen to every single word of it.
52:09Michael Stevens:That's exactly right. Their brain can wander the way it wants to wander, not in a negative loop on personal emotional problems and not in a directed taxing, like problem solving loop, but just in a free form human creativity way. But today, something really dramatic has happened where you don't need to produce the least objectionable programming anymore because we all watch alone. So if I'm – I don't even – this isn't even my life. Like there isn't broadcast TV that I turn on with my family that might make me go, oh, my wife won't like that. Oh, my daughter shouldn't see that. Instead, I'm just watching like TikTok on my own.
52:49Michael Stevens:And if I see something really disturbing, I just watch it because this is me. you know if I like there are objectionable things like things where I'm like I've seen it before or this is boring what's the point you know but otherwise I'm I'm I'm just kind of able to watch anything and so I've shifted towards watching content that is hard fascinating because it's okay those hard points aren't causing me to change the channel because of the other people around I just get stuck in this thing that like captures all of me and I don't worry about tomorrow but I also don't hope about tomorrow. I'm just stuck in this hard fascination feed.
53:26Michael Stevens:And you need other people looking at the screen for you to go, I'll soften it up. Fine, fine, fine. And that's where you get back into a social civilization building human experience.
53:36Hannah Fry:And that's the thing I feel like we're all missing. Yeah. Well, I feel like I'm missing anyway. That is so interesting. That is so hard fascinating. It is, isn't it? It isn't it?
53:50Michael Stevens:So, you know, we'll try better next time to be softly satisfied. Yes, we will. Softly fascinating. Or maybe we won't. You know what? Well, maybe that's your job. You know, you guys go out there and get us some get us the modern version of a fire to look at. That's the thing. There are so many soft, fascinating things you can do, but they often feel like a waste of time. Like looking at a fire is it's just it's classic enough that we all do it. But like during the day, we don't have enough, like we got to peel a lot of potatoes. So let's just do this for like the next three hours. It's more like, well, no, I bought them already peeled.
54:26Michael Stevens:So like we don't have any soft fascination activities. So we're going to have to just be direct about it and like find a new thing to do. Or we're going to have to like sit here and just think about our problems. I think it was Alan Watts who was like a lot of people think that zen is about like contemplating truth while you peel potatoes he's like no no no zen is just peeling potatoes right is that the actual quote that's the actual quote yeah he's like no it's not about like oh and everything i do i contemplate the the big things or god or the godhead or no it's like I just I'm just mowing the grass because that's where it happens just this morning I watched a reel uh where a guy's like oh here's here's what it's like to cook as a full-time job like in the olden days and he's like it takes a long time to make a honey-baked ham like I worked on this for two days and but I also had to make this dough and I had to make jam and I had to bottle it and da da da da and people are all like this is ridiculous and I'm like I know but it shouldn't be it shouldn't be and not that not that we all need to be doing that I think there is definitely room for directed attention, please.
55:40Michael Stevens:And we need to ruminate to a certain extent healthily. But we need all of them. And we need that anchor in the middle that brings us together that's not one or the other. But it's just fascinating.
55:50Hannah Fry:Yeah, absolutely. I really, really enjoyed that. Thank you very much, Michael. Thank you. No, thank you. I'm going to ruminate on that quite a lot.
55:58Michael Stevens:Well, don't. I mean, consider it. Rumination is specifically when it's like bad. In like a psychiatric language form.
56:06Hannah Fry:I think that you've tapped into something that has really been bothering me a lot in the last few months about my own life. About, and I didn't have the vocabulary to describe it until you just have. Which is that I do feel like I spend my entire existence switching directly from rumination to, what do you call it? Directed attention. To directed attention to rumination. And maybe I get a little bit of an escape for it when I'm asleep. and then if I have any social media on my phone I'm just like become extremely addicted to it I have to delete it doesn't make me feel good but you're you're absolutely right that like I know sort of instinctively that I'm searching for the moments when I'm just doing embroidery or just putting a lego set together or just you know doing some cooking but it's like trying to find space for those moments I didn't have the vocabulary to know exactly what it was that I felt like I was missing until you've just described it.
57:04Michael Stevens:Yeah, there you go. It's helpful to me too, researching this, because it shows why I enjoy and it's okay to enjoy. Like, you know what? Today, I'm just going to find all my dust jackets and put them on the books and put them on the shelf.
57:18Hannah Fry:Oh God, you're talking, absolutely talking my language. I'm just going to empty out a drawer and organize it and put it back together.
57:24Michael Stevens:Yeah. And it's not just about the tidiness. It's not just about having an organized home. It's about participating in an important human.
57:32Hannah Fry:connectivity yeah and and i think you know if fire changed our bodies i think not having fire might be changing it too do you know what i'm gonna do tonight even though it's like the second of september when we're recording this i'm gonna light a fire that's what i'm gonna do it i'm gonna do that do it all right thank you very much we will be back later this week with an episode of field notes. Until then, see you later.
58:02Michael Stevens:Push your limits, train with precision, see the results. At Equinox, that's high performance loving. Everything you need to lock in and unlock your potential at Equinox. Start today at equinox.com.
58:17Hannah Fry:Your heart can tell you a lot about your health. Apple Watch Series 12 measures your heart rate every five seconds with the most accurate heart rate sensing in a wearable. So your vitals app, now with heart rate variability, can tell you when something is off. And your readiness score can let you know when to rest and when to push. Hear the story in every heartbeat with Apple Watch Series 12. The features described are for wellness purposes only
58:40Michael Stevens:and not for medical use. iPhone 11 or later required based on Apple-conducted study of heart rate accuracy, August 2026. Visit apple.com slash Apple Watch Series 12. I see you. Avatar Fire and Ash is now streaming on Disney+. It's the film critics are calling the best Avatar yet.
58:56Hannah Fry:Go, go, go, go!
58:57Michael Stevens:A true epic and completely jaw-dropping.
59:00Hannah Fry:This is the only purest thing in this world. Return to Pandora on Disney+. It will be an adventure for the whole family. And watch the Oscar-winning phenomenon at home. This is sick!
59:13Michael Stevens:Avatar Fire and Ash Now streaming on Disney Plus Rated PG-13
From the publisher
What is fire, and why does watching it hold our attention in a different way from scrolling on your phone?
Hannah Fry and Michael Stevens start with the science of a flame: why it glows, what its different colours reveal, and why fire is a series of chemical reactions rather than a single substance.
Then they travel back to a time before wildfires could burn on Earth, and ask how early humans learned to use and make it.
Could keeping a fire alive have helped our ancestors learn to plan and cooperate? And what happens when we replace the quiet pull of a hearth with the endless pull of a phone?
From candle flames to early human history and the psychology of attention, this is the story of fire, the space it occupies in our history and lives.
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