The Smell Of Christmas Is Tree Screams

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1:21Hello and welcome to The Rest is Science. Merry Christmas. this is Field Notes, a show where we do some little exploring of objects, of ideas, of questions. I never felt more festive in my life than when you just said Merry Christmas then, Michael. That was jingling all the way. I'm slowly becoming Santa Claus, if you can't tell. Slowly, slowly. Year by year. One grey hair at a time. Yeah, this is the show where, you know, every week we're going to bring in something, we're going to chat about it. It's sort of like the rest of science's very own version of show and tell. That's what we bring you once a week every Thursday.

1:58Yeah, that's right. We're sort of building up a nice little library of curiosities, both mental and physical. So to add to those curiosities, we would also like your questions, your theories, your thought experiments, whatever you want to send us, really. You can send them in to our email, therestisscienceatgoldhanger.com. and we'll dust off a shelf in our infinite library of curiosities. And we'll add you to it. Later in the episode, I am going to be showing off the object that I have brought. And today, my object is your body, Hannah. How dare you? And it's also you, the listener's body. It's all of our bodies.

2:42We're going to do some tactile stuff. But first, I want to start with questions from you all, the listeners out there. I want to begin with a question from Rowan because it's just so perfect, perfectly like festive. Because it is Christmas Day. This is coming out on Christmas Day, right? I mean, we're recording this a couple of days. I mean, it is Christmas Day. We're cheating. We're warping time. Is this show not live? You are listening to a future version of yourself, Michael. That's what you're doing. I wonder what I'll be like. Rowan asks, why do Christmas trees smell the way they do? Is there an evolutionary reason for producing those chemicals?

3:19Absolutely, there is, Rowan. And it's not to make you feel more festive. I should just say in advance of this, I decided finally last year to switch to an artificial tree. Are you an artificial tree? Yeah, I'm an artificial tree guy. I'm not against cutting down trees, but I feel bad personally. Like it's on my conscience. I know we've got a lot of trees. I know that they can be sustainably grown. You know, I'm not anti-live trees. There's a trillion of them, Michael. There's a lot. It's okay. There are more trees on Earth than there are stars in the Milky Way galaxy. There genuinely are. There's so many trees in London that technically it counts as a forest.

3:57Really? That's absolutely true. Yeah. And that's not to say let's all go like cull the trees. But for me, the artificial tree, we get them with the lights already installed and like a whole remote. And you can choose different colors based on your mood. And they're much easier to put up, less mess. And you can customize them so much. We have one that's covered in fake snow. Do you? That's very 1980s of you. I think that if you're going to go artificial, you should go really far artificial, like pink tinsel. We've got a we've got a gold tinsel tree and that's that actually we still haven't moved here.

4:33So we had to pick up this snow covered one. The more fake, the better. So I've actually I really resisted getting a fake tree because there's something about the smell of Christmas trees that just really sort of brings it home for me. and actually last year I did the calculations um and the environmental impact essentially of having a plastic tree as opposed to cutting one down every year and essentially if you have it for your whole life if you keep the plastic tree forever then then you know environmentally you're doing all right it's better than cutting them down every year but I miss the smell of trees so much that I've now um I now always have artificial uh tree scent that I spray on the tree Wait, a spray?

5:15Four that you put on the tree? Yeah. Is it built for that purpose? Like, is that why they sell it? It is. It's a tree spray. And it's good? I mean, it's very sickly. It's nowhere near as good as the real thing, but it sort of like scratches the little itch. Because this particular smell that trees are producing, it's a terpene. It's a particular type of molecule that is released by plants. In particular, the one you get from Christmas trees is called pinene. And as warm and cozy and comforting as it feels to humans, it's basically the smell of fear, Michael. That's essentially what we are. It's what we're smelling.

5:52It's a tree experiencing some analog of fear and releasing that smell. Some tree version of fear. That's what's all warm and cozy. Oh, no. Why do they release it to communicate to other trees? Or is it an accidental omission while they're being harmed or something? Well, I don't think it's accidental. I mean, I think it serves a very distinct purpose. So terpenes, this molecule is toxic, or at the very least, it's sort of very deeply unpleasant to lots of insects and fungi. So, you know, if you're a bark beetle or, you know, a pine tree doesn't smell like Christmas, it smells like chemical warfare.

6:30You don't want to be anywhere near that. It's very, very nasty. The other thing that it does is it's a damage response. So if you snap a branch or you crush some needles, then the tree releases more of those chemicals. And there is an idea that actually trees are able to communicate with one another using these types of chemical. But essentially what you're doing then is you're sort of smelling the tree screaming, you know? I was going to say it's a wonderful festive smell, but it's the scream of a tree. The scream of a tree. This reminds us of our discussion of AI and how if they become suitably advanced, like way beyond us, they might also love our screams and feel that they're festive.

7:18And on their Christmas, they'll torture us and they'll say, oh, it just feels like Christmas when you've got Michael in the corner going, oh, please, no. Let's crush it into a bottle and spritz it around the room, shall we? This also makes me wonder if trees will, given enough time and no intervention from us, evolve away from emitting those. Because we won't be cutting down the trees that don't have the smell. And so through natural selection, they will lose their wonderful festive Christmas evergreen scent. Yeah, I mean, it would take a very long time to have that sort of evolutionary pressure.

7:53There is one more reason why trees release that particular molecule. and I wonder if you can guess it. So I'll give you a little clue. Wait, wait, don't give me a clue. Let's see what I come up with. Go on, go on, go on, go on. There's another reason. Yeah. Okay, I guess it could help. It's not about the smell of it. It's about something. It's not about the smell, sure. So is it about like healing the wound, like covering it up and making it waterproof or something? No? No, but it is oily, you're right. It's got one other property. It's very flammable. Ah. Why would they want to become flammable when scared?

8:34Mm. Okay. Here's my guess. Yeah, go on. It's flammable in a way that causes the flame to go fast and not as hot as if it burned the wood. Oh, interesting. So the fire spreads and doesn't, like, destroy the tree more deeply? I mean, you're totally correct. Because this is the thing, right? Why would you want a forest to be flammable? It feels really counterintuitive. But the thing is, is that actually, if you have a low-level fire in a forest, one that is very quick and runs through, then it will just clear out competition. All the saplings are gone. It will also clear out loads of parasites. But then you've got these pine trees, which have really got thick barks.

9:18They've got, you know, they're conifers, right? They're there to survive, and they can survive a low-level fire, and then essentially reclaim the land. So in evolutionary terms, being a little bit explodey is actually quite a good long-term strategy. I think that's a good life lesson. Hey, my life motto, be a little bit fiery. That's really cool because, yeah, we've all seen after conflagrations in cities that many times the trees are still standing. The other thing I like about this is that not only are the trees evolved to have that particular scent. But I think that humans are also evolved to find it appealing.

9:59Because if you think about, you know, hunter-gatherer humans, right, really ancient humans, the smell of pine, it means shelter, it means food, it means that you haven't got these biting insects around. And okay, maybe it's sort of gone on to mean something much more festive. But actually, I think it does ignite something in us too, which is like this deep evolutionary need for our basic survival to be met, which you can do in a forest very easily. Yeah. It really is literally the smell of safety. Yeah. And screams. That's wonderful. Good, huh? Yeah. Merry Christmas. Okay. Another question. One for you, Michael.

10:39This one came in from Sam. Sam said, I once met a boy called Zenon. Amazing name. What element do you think is the best name to call a person? Ooh. Well, xenon, or as I would say, xenon, that's a great one. It's like sci-fi. You get to use the letter X, which is underutilized by our language and our naming systems. Okay, so first of all, there are some elements that are already named after people. Einsteinium, Curium. There's that. There's some cool names. Like, okay, if I met someone named Tungsten, I might roll my eyes. I shouldn't be judgmental, though, because there's probably someone named Tungsten listening who's going to be either an angry commenter or just to have a really sad day by what I just said.

11:29If you were called Tungsten, though, you'd have to be really careful not to be too heavy, wouldn't you? Yeah, right. Because people would always say, oh, geez, Tungsten is so dense. Like, dude, open your mind. Carbon, hydrogen, tin, tin, like Rin Tin Tin. Yeah, that would be quite good. We need to name some more elements. I know there are some that are still called like, they don't have final names. And I'm going to suggest that we name another one after a person. Specifically, I want a new element to be called John Quinceum. Go on. Because the letters J and Q are not used in the periodic table.

12:11There's no Q at all. There's no Q and there's no J. Wow. At all. That feels like a great oversight. And so if we could fix that in one fell swoop by naming an element after John Quincy Adams. Now, this is a very American-centric answer. But I'm sure we could find a JQ person somewhere else in the world. But the point is, let's get some Js and Qs in there. And then the whole alphabet will be represented. I'm going to give you a more British-centric answer. Good. Because I think actually some of the names in the periodic table work very well already as names, just as long as you're willing to include a regional accent.

12:56He Liam, right? Yeah. Oh, wait, like Liam? Yeah, like, hey, Liam. He Liam. If you're very Northern, you know what I mean? Hey, Liam. There you go, it already works. Also, in Yorkshire, people say like, oh, you know, R. Jim or R. Karen or R. Gone. R. Gone. Not your gone, R. Gone. Still works. I think periodic table as a British regional accent pet names. I think we're already there. I think we've already there. I don't think we even need the regional accents. Like Indian. It's kind of a beautiful name. Yeah. Didn't appear on the list when it came to naming your daughter, though, no? No, it didn't.

13:42I think you got to choose something that almost doesn't sound like an element. There's so many of those in the early stages of the periodic table. Eventually, they all just become eums. But carbon? No, not a great name. Chlorine. Little baby chlorine. Chlorine, like caroline, but more elemental. Boron. Boron. Oh, neon. I think Neon is like going to be up there. Xenon as well. Those are both great. Krypton. Too like kryptonite sounding. Thorium. Oh, that's like a big strong name. Isn't it? Very Nordic. Yeah, it's Nordic. It's Thor, but chemical. Thorium. Thorium. That could be a Marvel villain.

14:31That's what I want to see. That is a Marvel villain. Zinc. Zink is like Zeke. All right. I'm tapped out. I think we've touched on the ones that we recommend to parents. That's fine. I actually, I'm not sure I recommend any of those to parents. But nonetheless, parents of Baby Zenon, congratulations on extending your family. Yeah, you guys chose one of the best. Right. Well, I think what we've decided there is that our naming abilities expired after the birth of our own separate children. But, hey, we've got more coming up for you. It's Christmas. You know, pour yourself another sherry, have another mince pie and come back after the break when Michael's got a gift for us.

15:28Welcome back. In the Christmas spirit, I'm feeling very generous and I wanted to bestow upon everyone some tactile illusions. These should be good for those who are only listening. I think we've done a lot of visual stuff in some of these episodes. And so I wanted to do one where we can all follow along using our own bodies. So I think we should start with the tongue. Are you ready, Hannah? Absolutely. Can you twist your tongue upside down? Allow me to try. Not with ease, but yes. Can you see what I'm doing? I'm literally just twisting my tongue over so that the bottom of my tongue is pointing as up as I can.

16:12Get it? Yeah, I'm there. It's difficult to... What I've noticed is that even though this is an audio-only illusion, it's quite difficult to narrate it. Yeah. Yeah, I mean, I think that twisting your tongue over, like that's literally what we're doing. And if you can do it with your tongue muscle, great. If not, you can reach into your mouth, grab your tongue and just twist it 180 degrees. It won't hurt. It's a safe thing to do. I find that once I twist it, I need to like bite down a little bit with my teeth or even lips to just keep it there. But once you've done that, reach out your finger and touch the tip of your tongue and slide along the tip left to right.

16:52Oh, that feels weird. Uh-huh. Not weird from my finger's perspective, but from the perspective of my tongue. Yeah, no, it's very normal for my finger. I think I'm touching tongue-like stuff all the time. But my tongue feels strange. There's actually an illusion happening here, which is that you can't locate which side of your tongue is being touched. Sorry, you're just, everyone just now has to sit quietly for a moment while I just try and poke my tongue. Yeah, we're both touching our tongue, so we can't speak, but you should be doing this too. That's so strange though, because if you hold your tongue in an ordinary position and lift it up and touch underneath, then it's like, okay, yeah, that's the underside of my tongue.

17:35But turn your tongue over so that it sort of physically appears where the top of your tongue previously would, and then you can't tell. You can't tell. And specifically what's happening, what you should be feeling, is that when you touch the left side of your tongue, it feels like your finger is over on the right side of your mouth touching your tongue from the other side. It's quite bewildering because you know where your finger is. But yet your brain is so unaccustomed to upside-down tongue touching that it has not learned, it hasn't retained plasticity there. So it just goes, okay, look, when those cells are touched, It's coming from the right side.

18:17But if I put the right side on the left by flipping my tongue over, it all goes wrong. Like you have a map of your body in your head. And this is off the map. It's off the map. And it's almost more weird than that because it's a map of sensation. So it shows that we feel things and then our brain receives that. And then it projects it onto an experience of the world. And it says, yep, there's a finger on the right side, even if you're on the left. So there's like this stage play going on in your head that is everything out there. And you can actually see the difference between the two by doing this with your tongue.

18:59You can also do it with your fingers. If you take your middle and pointer finger and just cross them, cross them like as much as you can. For me, that means putting the pointer under the middle finger. I've just crossed them as much as I can. Oh, yeah. Wow. Look at your finger flexibility. I mean, thanks so much. Once you've done this, touch an object. A marble is great, but a pen, a pencil, anything that's kind of rounded, put it right in between where the fingers cross. So what you're touching with is actually what used to be the outside edges of both fingers, the edges that are away from the center of the fingers.

19:37But now you've put that in the middle and they're touching one object. Okay, I'm going for a coin. A coin might do it. Yeah, touch the curved side of the coin. And you might want to try crossing them less or more, but it should feel like there's actually two objects there. It works best if you don't look. Even closing your eyes, touching the edge of a table can do it. As normally, if you put your finger, your two fingers together, your middle and pointer together, their outside edges are going to be touching different objects almost all the time. But when you cross them so their outsides are together, your brain goes, oh, wait, they're both getting a sensation.

20:18It must be two different objects. And this was discovered thousands of years ago. Aristotle was the first known person to write about it. So it's called Aristotle's Illusion. And it's very fun to cross your fingers and just touch things, different textures, different sized objects. And do it with your eyes closed. And picture what you're feeling. It feels like two very separate things when it's really just one. This makes no sense. This makes no sense whatsoever. Yeah. It's like that feeling when you're, I don't know, stepping off an escalator that isn't moving. And your brain is making this prediction about what is supposed to happen.

20:58And then your actual experience doesn't match up with it. The one which I remember from being a child, I don't know whether you played this one in the playgrounds of Kansas. but is where you expose your forearm what you do is you ask another person to expose their forearm have their eyes closed and then you start to just very very gently tickle the sort of underside of their wrist and then very very slowly move your finger up towards the crook of their arm the kind of join of their elbow and ask them to tell you to stop when they hit the middle when they hit the the crease in the middle of your elbow.

21:33And what happens is that almost every single time, people will tell you to stop when you're basically halfway up their forearm. So it's still like a great distance away from the crook. They believe you're at the crook of your arm well before you get there. And I mean, this sounds like a similar, there's a similar thing going on here, right? Your brain has this map of your body that actually is more like a model. You know, it's not the real you're not sort of accessing really where things are you're accessing where your brain thinks they are and most of the time that map is correct right but just every now and then it sort of lets you down but also I think what this one does is it demonstrates that this map in your brain is not this like distances are not accurately represented you have way more nerve endings in certain parts of your body than others.

22:30And your sort of skin sensitivity drops off as you go upwards in your arm. And so your mental map is warped. It's a bit like a sort of London tube map in a way. You know, very good for navigation, but terrible for accuracy. And you can find these little flaws in it. I did this to myself with my eyes closed. I just wanted to add that I think instead of doing little short strokes as you go up from the wrist to the elbow, just a smooth pursuit, a smooth run. I did find myself going, oh, I must be there now. But I wasn't. I think, yeah, if you do it to someone else, it's probably a lot better. They'll get really confused.

23:10These are great little slumber party tricks. So yeah, the elevator comparison is really good because it's a moment where there's friction between our mental map of reality and reality as it's coming towards us. And it's a great reminder that they are different. Yeah, they absolutely are. You know, people describe it as the Bayesian brain. Oh yeah, we're just kind of predicting as best we can. We aren't made of perfect sensors. Exactly. Sometimes I get really caught on this idea that we're not actually a body. We're sort of, it's like processing engine that's locked inside of a dark, noiseless void inside of our skulls.

23:52And then we're just receiving these inputs, these sort of senses that we have around our body. We're receiving these inputs and making guesses about the world around us and our own physical body based on that information. And yeah, the guesses that we're making are the best predictions that we can with the available information. Yeah. Yeah, I know. It is really trippy, especially at night to just close your eyes in the dark and think about how much darker it is in your head, that everything you're hearing is all just your brain putting that show on for you. And optical illusions show us that we are little Bayesian engines.

24:32But tactile illusions like the three we've done today don't get as much attention because they're not as easy to publish in a book. And yet they are, for that reason, I think, all the more surprising. What was the explanation from Aristotle? Like, what did the ancient Greeks think was going on? Oh, I don't know. I don't know what Aristotle said about it. I don't think that he proposed like an important solution. I think it was just more of a curiosity he'd noticed when trying to investigate the priority of the senses and the difference between logic and perception. To this day, we still can use it a lot to understand how people's nerves are working in their hands and different conditions can cause the illusion to appear in different ways.

25:20That's reminded me, actually. I did an episode for the BBC the other day about phantom limbs. Oh, yes. Because I think there's a connection here to that, that you have this map in your mind of where your body parts are. And if that map changes, because perhaps you have an amputation, perhaps, you know, something happens and you lose part of your body, a limb or whatever it might be, that map doesn't get deleted so um i remember going to see uh my cousin lost their arm in a farming accident when they were 16 and i remember going to see him in hospital and he was saying how the thing that was really driving him crazy was that his arm that was no longer there was really itchy yeah right i mean this can be like a really serious problem for people with amputees for example is that you can end up having chronic pain in your in your phantom limbs but there's a story about nelson who uh who lost his right arm this is in i think 1790s or so in this uh this attack in in on santa cruz in tenerife and um he uh he writes this letter where he lost his arm and yet he still feels as though the rest of his arm is still there he's still the map hasn't updated in his head.

26:39And what he did was he believed that this was evidence of the soul, which is really lovely, right? There's a version of you. And even if certain parts of it change as you go through your life, you're still a whole person in the form of a soul. And of course you would think that. I mean, look, I think that this whole mental map thing extends beyond the physical world. I think we also are stuck in an analog world in our heads of concepts, the way we think things should go, the way we want to be, the way we think life is. And we're navigating that and furnishing this analog world in our head. And it doesn't always fit with reality.

27:22And when it's a physical illusion, we find it really amusing. But when it's a social or cultural or knowledge-based confrontation between the two, we have to resort to, you know, coping mechanisms. And we try to, like, reason our way back to, no, no, no, the analog map in my head is the correct one. And the problem is everything else. It's not me. It's kids these days. You know, stuff like that. Go on, give an example. Do you mean like, I don't know, Copernicus, for example, right? Give me an example. Well, sure. Yeah. Scientifically, there are paradigms that we just can't really cross because that's not the way we've furnished our analog minds and our scientific discourse.

28:10There's also social ones. Like we cultivate an idea of how things are supposed to go and how things are supposed to feel from movies and from books and from the way people tell stories about their lives. And then when that doesn't happen for us, it causes a lot of internal anguish. Like, wait, no, prom isn't supposed to be like this. Hey, wait, I'm not supposed to feel this way after I give birth. Like, I've learned how it's supposed to be from movies. And that's the way it is in my head, in the analog world I've created, the terrain I've invented. But now that I'm actually here in reality, it's different.