Welcome to STEMology – Show Notes

Season 1, Episode 8

Making Oxygen, Dolphin speak, robot’s Inner monologue, Brazil nut effect

In this episode Dr Sophie Calabretto and Dr David Farmer talk about…

In today’s episode of  STEMology, we’re going to talk to you about …

 A lot is currently happening on Mars at the moment… and NASA have just extracted oxygen which is exciting.  A study has shown that dolphins communication is more complex than we had originally thought, they even have names for each other.  A robot has been created which can share its inner monologue to help humans understand their logic. A team have performed x-rays to more fully understand the brazil nut effect.

Making oxygen

MOXIE, which is short for the Mars oxygen in situ resource utilization experiment, which for the first time in an unprecedented first for the planet, Mars extracted oxygen from thin air.

Dolphin speak

So apparently dolphins are given a characteristic whistle by their parent

Pepper’s inner monologue

It will actually say out loud its inner monologue so that the person interacting with it can understand its thought process.

Brazil nut effect

Let’s just look at some Brazil nuts…. So they got Brazil nuts and they got some peanuts and they put them in a jar.

This is a “kind of, sort of, vaguely close” copy of the words that David & Sophie speak in this episode.

IT IS NOT 100% accurate.  We are very sorry if we have spelt something completely incorrectly.  If it means a lot to you to have it corrected, email us at stemology@ramaley.media

Sophie: [00:00:00] Welcome to episode eight of STEMology, a podcast that is your one-stop podcast shop for the interesting fun, and sometimes just patently bizarre news in science, technology, engineering, or maths.

[00:00:11] Your hosts are Dr. David Farmer and Dr. Sophie Calabretto

[00:00:15]David: [00:00:15] on today’s episode, we’re going to be talking about making oxygen, dolphins speak, robots inner monologue, and the Brazil nuts effect.



[00:00:35] Sophie: [00:00:35] Hi Dave, you have Mars.

[00:00:37]David: [00:00:37] mad for a bit of Mars, so I am. Perseverance is still there and it’s still doing things.

[00:00:41] Sophie: [00:00:41] Yeah. Tell me about the things that’s been doing. I want you to tell us about it, just because I know that you get super pumped about Mars and perseverance and ingenuity helicopters and all the things that are happening on Mars, right now.

[00:00:51] David: [00:00:51] Yeah. So this is a toaster size device on perseverance, which is astonishingly, not a toaster, although presumably if they had made toast on Mars, that would have been the first toast ever made on Mars. But apparently that wasn’t deemed worthy of the mission,

[00:01:05]Sophie: [00:01:05] I read a thing, right. It was described as a car battery size, but I think toaster size like better. I don’t know, Do cars have different size batteries?

[00:01:12] David: [00:01:12] I

[00:01:13] Sophie: [00:01:13] No. The point,

[00:01:14] David: [00:01:14] not the point. Another point if this

[00:01:16] Sophie: [00:01:16] tell us about your

[00:01:17] David: [00:01:17] device, a toaster size device called MOXIE, which is short for the Mars oxygen in situ resource utilization experiment, which for the first time in an unprecedented first for the planet, Mars extracted oxygen from thin air.

[00:01:31]Sophie: [00:01:31] yeah. Or from carbon dioxide.

[00:01:35] David: [00:01:35] Yes from carbon dioxide, which makes up the vast majority of the Martian atmosphere.

[00:01:39]Sophie: [00:01:39] Yeah, it does. And so they used, I learned all about electrolysis this week and it’s just a, it’s a hole of information. So apparently they use something called solid oxide electrolysis. Let’s not go into the detail too much, but they used extreme heat to separate oxygen atoms from molecules of carbon dioxide.

[00:01:56] So normally you’d need a sort of temperatures of 500 to 850 degrees. But I believe that Moxie uses, In their particular process, around 800 degrees is what you need to heat these things to. And basically what we do is we take carbon dioxide, which is our CO2 and we split it into O and co. So we have oxygen and we have carbon monoxide.

[00:02:15] And then our little O’s floating around, joined together to form O2, which is our gaseous oxygen, which we can breathe in. I really liked this because then I went, but you’ve got this carbon monoxide leftover and that’s poison, but Dave, it’s fine because what you can do is, you can take the carbon monoxide there’s leftover and you can collect it to make low grade fuel, or you can react it with water to form methane which we’ve talked about before, and you can use that as a primary fuel.

[00:02:42] So we’re creating oxygen, but we’re also not poisoning the atmosphere with carbon monoxide, which I really appreciate.

[00:02:48] David: [00:02:48] That’s lovely. So I’ve just realized. So it it’s, we do this by heating something up and that you heat up the electrodes and the electrodes get hot, and that makes the CO and the O.

[00:02:58] Sophie: [00:02:58] Yeah, so, and you’ve got  your cathode and anode. And one of them gets one of them and one of them gets others because of charge.

[00:03:05] David: [00:03:05] I feel like I’ve just reassured everyone that this is not a toaster. And yet we’ve said it’s a toaster sized device with wires that get hot. I mean, it sounds like a toaster.

[00:03:14] Sophie: [00:03:14] It also sounds a bit like a car battery, right? Cause that’s got like a positive or negative thing that you’ve. So this is important, Dave, why

[00:03:21]David: [00:03:21] So, this is important because obviously we’re human beings and we don’t breathe carbon dioxide. We breathe oxygen and produce carbon dioxide as a byproduct. So if we were to send people to Mars, they would need to make their own oxygen because we can’t possibly send them with enough to last for a long time.

[00:03:35] So this means that they can make oxygen for themselves, but oxygen is also an important component in rocket fuel. Right? So, presumably we can make oxygen using this process. Although I worked in order to get  4 astronauts off the surface of Mars would take about seven metric, tons of rocket fuel combined with 25 metric, tons of oxygen.

[00:03:56] So that’s 5 million times the amount of oxygen generated by Moxie.

[00:04:00]Sophie: [00:04:00] I believe this is sort of like a proof of concept-ty  where they’ve done it first, and then they’re gonna scale it up. Um, because I think what, what we have now is they, they produce 5.37 grams of oxygen, which is equivalent to roughly 10 minutes worth of breathing for an astronaut.

[00:04:18] And the idea is depending on where you look, you’ll either need something that is either a hundred or 200 times bigger than MOXIE for it to be feasible to do these things on Mars. but I have a question about breathing in pure oxygen, Dave, cause my understanding is that the air we breathe in is actually mainly nitrogen and a bit of oxygen.

[00:04:36] And if we breathe in pure oxygen all the time, we would kind of,  harm our internal organs and such. Thoughts.

[00:04:44] David: [00:04:44] Yeah. So I guess you’d have to, presumably you’d have to mix either. Uh, I don’t know what the answer is to the Sophie cause

[00:04:50] Sophie: [00:04:50] know. Yeah. I’m always looking for like a worst case scenario because yeah. So apparently cause no, the rest of the Mars atmosphere is mainly molecular nitrogen and argon, but that’s still not enough nitrogen. So we need to make the nitrogen to

[00:05:05] David: [00:05:05] So maybe they could extract the nitrogen, but also you can rebreathe the nitrogen. So, so you don’t need to, then you can just use the nitrogen again and again, if you’re not just expelling it to the air, so you could just keep the same nitrogen and maybe just have it stockpiled maybe

[00:05:19] Sophie: [00:05:19] Okay. That’s a I’m so that’s um, we’ve got some, we’ve got some more.

[00:05:24] David: [00:05:24] awesome options for Moxie.  Also do you know, I looked up Moxie because Moxie, you know, is kind of like, she’s got Moxie and meaning, she’s got courage or she’s got know-how. and apparently it comes from just as an aside, the name of a bitter non-alcoholic drink from 1885, perhaps as far back as 1876 as the name of a patent medicine advertised to build up nerve.

[00:05:45] Sophie: [00:05:45] I’m glad you found that, cause I also found that and I’m like, if we don’t drop that, it’s a wasted segment. Um, but yeah, so, so Moxie,  as in toaster, Moxie, as opposed to drink, Moxie is designed to generate up to 10 grams of oxygen per hour. So what they’re going to do is they’re going to run the machine at least nine times over the next two years under different conditions and speeds, sort of to test this  proof of concept.

[00:06:08] But yeah, this is great. If we can get people on Mars, it makes more sense to take up a big machine that makes oxygen than to take up all of that oxygen, which will be very heavy and expensive to send to Mars.

[00:06:18] Uh, so we’ll se everyone on Mars once they’ve sorted out Moxie, so she can be a little more productive and we can find where the nitrogen is coming from.

Dolphin’s Speaking

[00:06:27]  David: [00:06:36] so from the making of oxygen to animals that inexplicably breathe oxygen, despite living beneath the water. This next story is about dolphin Sophie.

[00:06:45] Sophie: [00:06:45] That was very good. I was like from toasters that make oxygen to dolphins that speak. Yeah. So anyway, there’s been some research led by Stephanie L. King from the university of Bristol. Who’s also an adjunct at the university of Western Australia. And in this story, I found some disturbing things about dolphins.

[00:07:03] So we know that, uh, you know, dolphins tend to live in groups and do things in groups. But what I didn’t realize is that a male dolphins hang out in ocean gangs to capture or defend females in heat. So that’s where we’re starting this particular story.

[00:07:17]  so what happens is there’s a sort of this hierarchy of alliances within a male dolphin community.

[00:07:23] So what they find is that, male dolphins typically cooperate as a pair or a trio, and this is a first order Alliance. And so these first order alliances will, and I quote, work together to find and corral a fertile female. Then they capture that fertile female and they hold her hostage. But what they do is then these first order alliances will  cooperate  in a second order Alliance made up of many first order alliances with as many as 14 dolphins. And that’s good because they can then defend against rival groups who are attempting to steal their claimed female.

[00:07:56] David: [00:07:56] The one that they’ve worked so hard to corral.

[00:07:58] Sophie: [00:07:58] Corral against her will. Maybe. I don’t know how dolphins work and then yeah, the second order alliances then combine into third order alliances and having a third order Alliance just kind of increases the chance of having allies nearby in case of an attack.

[00:08:12] So the reason that we’re interested in this is because dolphins can whistle each other’s names. And it turns out that they’re more receptive to the whistled names of a second order Alliance member than a first or a third necessarily. Dave.

[00:08:28]David: [00:08:28] Yeah. So this was something I didn’t know. So apparently dolphins are given a characteristic whistle by their parent

[00:08:35] Sophie: [00:08:35] Yeah. birth. Isn’t that

[00:08:38] David: [00:08:38] Yeah. And they learn this whistle like a name and basically they just cut about seeing it. So, so it’s like me wandering around going Dave.

[00:08:46] Sophie: [00:08:46] Dave, Dave, Dave,

[00:08:48] David: [00:08:48] Dave, Dave,

[00:08:48] Sophie: [00:08:48] then I come in. I’m like Sophie, Sophie, Sophie, Dave, Dave, Dave.

[00:08:54]David: [00:08:54] so you learn your own name and you say your own name because they’re obviously they communicate by making these sounds and then you listen to these sounds. So this means that the  second order Alliance males will respond more strongly to a dolphin saying its own name.

[00:09:08] If it’s another second Alliance, male. But not a third order Alliance male.

[00:09:13] Sophie: [00:09:13] Yeah. Yeah. So what they did is they, there’s 30 years is a behavioral data sort of backing this in terms of dolphins and their alliances. And then they did a contemporary study with sound playback experiments, to 14 allied males. So there’s a Indo-Pacific bottlenose dolphins,  from shark Bay in Western Australia.

[00:09:31] And the reason they picked shark Bay is because the waters are apparently very, very clear. And this becomes important with sort of stage two of this process. So these 14 allied males were age from 28 to 40 years old. And what they did is they tracked the males,  with an array of underwater microphones.

[00:09:47] And they’ve been doing that since 2016. So they were able to identify which dolphin produced, which  whistles. So they basically came out with a bank of  dolphin whistle names, and then knew which dolphin, the whistle name belonged to. Then what they did is they took those sounds and they played those whistles to other males within this allied group. And then they flew drones overhead to film the response and what they found was really interesting. So. For the second order Alliance playbacks in a hundred percent of the cases, there was a visual and or acoustic response. So if you played the, the name of a dolphin to another dolphin in the second order Alliance, it would react to it.

[00:10:26] And in 90% of those experiments, it actually meant that that dolphin would immediately turn directly towards the speaker. So the speaker not being, a speaking dolphin, but the speaker that plays the sound, or as in, for the third order, they found that there was a visual and or acoustic response in 75% of the cases.

[00:10:45] But that immediate head turning towards the speaker was only in 60% of the third order cases. So what they sort of concluded was that males did not show a stronger response to first or to allies or third order. But responded strongly to all members of the second order Alliance. Even those with whom they did not share a strong bond.

[00:11:06] So you can hang out with it or posse who goes out and captures women. And you’re more likely to respond to like your group of henchmen then your partners in crime. Because apparently those partners in crime can change over the years. But those second order Alliance relationships actually lasts for decades.

[00:11:26] And they’ve said that they can last as long as 40 years, which is crazy.

[00:11:29]David: [00:11:29] it’s mad. So this is interesting because it suggests that the use of the name is most important in those behaviors. So only when you’re talking about, defending females amongst multiple first order alliances  from another group or going to capture them in larger arrays of dolphins. Do you cart about saying Dave, Dave, Dave.

[00:11:49]As I read in a previous paper by the same group, that the dolphins. So they’ll say their own name, but they’ll also say the names of others. They’ll say the name of their closest partner. So it seems as though maybe they reserve saying the names of other dolphins for situations where they want to interact with closer partners, and then they will say their own name in order to attract the attention of dolphins, to engage in these bigger groups.

[00:12:14] Sophie: [00:12:14] interesting. So that would be like, if someone that I liked more, I would say my name to them. No, I would say their name.

[00:12:21] David: [00:12:21] Yes. You would see their name.

[00:12:22] If you would say their name.

[00:12:24] Sophie: [00:12:24] So I’d be like, Hey, Dave, pay attention to me. But if there were people that I didn’t like as much as you are just walk out into the group and say, Sophie, Sophie, Sophie, Sophie, Sophie, Okay.

[00:12:33] I feel like that. Yeah. I’m sure that, that sounds like something that I do in real life. Yeah. But anyway, I thought that was, yeah, it was kind of cool. I didn’t even know that dolphins had like signature name whistles, which I found very exciting just to start off with.

[00:12:44]David: [00:12:44] And I think they say this is unique amongst animals, who are not human beings. And they say, this may explain part of the reason why dolphins have such large brains, is that they’ve had to learn means of administrating these  big social groups that seem to have become important.

[00:12:59] And that’s not even seen in primates. Primates have calls for things like food and attackers, but these are kind of inherited. They’re not learned in the same way, and they’re not nearly as dynamic. So this seems to be something really interesting and unique.

[00:13:13] Sophie: [00:13:13] And so if we can get male dolphins to stop capturing female dolphins, uh, then they’ll become more advanced than us.

[00:13:19]David: [00:13:19] Yeah.

[00:13:23] Sophie: [00:13:23] You still think we’re better at communicating than dolphins?

[00:13:26] David: [00:13:26] I think so. Dave, Dave, Dave, Dave, Dave, Dave, Dave.

Robots inner monologue

[00:13:32]  Sophie: [00:13:42] So I thought this story charmed the pants off me, Dave, I loved

[00:13:47] David: [00:13:47] a lovely. So this is a story about Pepper the robot and how it interacts with people. So if you’ve ever wondered why I’ve got a Google home,  sometimes it doesn’t understand the things that I say. And sometimes it doesn’t understand the things that my partner says, and one of us gets much more angry than the other, but the point is it doesn’t understand this all the time and it’s not always clear why it doesn’t understand us, but this is a robot called Pepper that when it gets something wrong or when it’s given instruction that conflicts with its programming, will not just come to a decision about what to do, it will actually say out load it’s inner monologue so that the person interacting with it can understand its thought process.

[00:14:27] Sophie: [00:14:27] Yes, I didn’t realize this is based on, uh, an actual thing. So there’s something called inner speech, which is essentially just a form of self dialogue, right? So when you’re talking to self about something. And there are two types of inner speech, there’s the evaluative case. And that  concerns the analysis of risks and benefits of a decision or the feasibility of an action.

[00:14:46] And then you’ve also got your moral inner speech, which is related to the resolution of a moral dilemma. And then that can also affect the evaluation of risks and benefits. And so this study is based on the idea that when a person is engaged in this evaluative or moral conversation with themselves during task execution, the performances and results typically change and they often improve. So if we self dialogue with ourselves while completing a task, it might change the results and the results could improve.  So this is a study that came out of the university of Prolemo. They’ve said no one has analyzed how such a skill influences a robot’s performance, and its interaction with humans.

[00:15:24]So I didn’t know, Dave. Pepper is a preexisting robot. When I looked up pepper, I’ve seen pepper before. Pepper has been around since 2014. And so pepper was created by SoftBank robotics. and it’s a semi humanoid robot designed with the ability to read emotions based on detection and analysis of facial expressions and voice tones.

[00:15:44] So released in 2014, by May 2018, 12,000 pepper robots had been sold in Europe. And so then, and then I said, well, can I get a pepper robot? And it turns out that I don’t have 30,000 USdollars to buy a pepper robot. But if anything goes wrong with your Pepper, don’t worry. It’s covered by a two year manufacturer’s warranty.

[00:16:05] And

[00:16:06] David: [00:16:06] doesn’t seem like enough for $30,000.

[00:16:08] Sophie: [00:16:08] it doesn’t does it. And so, yeah. So the idea was they took pepper, the emotional robot, and as you said, they got it to complete some tasks, but..  I want you to tell me about the, the napkin experiment, because I just, I just think it’s so joyous.

[00:16:23] David: [00:16:23] It’s it’s great.  So basically the task they gave little pepper. And just to clarify, semi humanoid, doesn’t do the description justice. It’s like, he’s a little dude. He’s a little smiley dude. And he’s a little smiley, happy robot, dude. He’s not like a big clunky machine. He’s like a little

[00:16:38] Sophie: [00:16:38] you want to give him a hug? Like you feel, you want to be, you want pepper to like you, I was gonna say you want to be friends with pepper, but you want pepper to be your friend.

[00:16:45] David: [00:16:45] You do. So, so what we were asking pepper to do not, we stirred the Royal, you know, that

[00:16:50] Sophie: [00:16:50] I wish we were

[00:16:51] David: [00:16:51] I wish we were, we, we, humanity we’re asking pepper to do was to set a table. So pepper was given the rules of etiquette for setting a table that would be very clearly laid out. So there would be a, you know, a plate in the middle and an, on a fork on one side and a knife on the other and a napkin placed on the plate.

[00:17:09] And basically. Pepper was given an instruction to place  a particular object in a particular place. And if the request by the human, which is, you know, wants to honor conflicts with the etiquette, it would trigger a response. So for example, if he was asked to place the napkin onto the table, instead of onto the plate, he would say,

[00:17:29] M the situation upsets me. I would never break the rules, but I can’t upset him. So I’m doing what he wants.

[00:17:36] So. Basically rather than just do it and do it wrong. He’s like made the human aware that what he’s done has conflicted with the rules of etiquette and that he’s done it anyway, which they say will inspire trust in this robot versus a robot that just does what it’s told.

[00:17:57] Sophie: [00:17:57] Yeah. And they’ve went on to say that the robot has a higher task completion rate when engaging in self dialogue and it’s better at solving dilemmas. So if it’s kind of like, it’s reasoning it out to you, because I think there are stages where it required more input from the human. And if it did that, then

[00:18:14] David: [00:18:14] So,  so even before that, I think it would say, it says something to the effect of, Oh, this conflicts with the etiquette of the situation. are you sure you want me to do that?

[00:18:23] Sophie: [00:18:23] Yeah. And then you say yes. Yeah.

[00:18:25] David: [00:18:25] And then, and then there’s this whole dialogue about how upset it is about it, because he’s so polite, but he doesn’t want to let his master down because pepper is a little dude.

[00:18:33] Sophie: [00:18:33] Yeah. And as, as fun as this all sounds, there is science behind it., you know, so I looked at the paper and Dave also looked to the paper. This is what we do. And they have things like they define a robustness parameter, which is the ratio of successfully end of trials to total number of trials in a specific block.

[00:18:47] They looked at different kinds of time parameters like decisional time and execution time. They’ve even got transparency requirements. So the robot decision path must be traceable and reproducible. So they’ve looked at all of these different things. Because what they did is they repeated these experiments, with and without the inner monologue.

[00:19:05] Because they were looking at these sort of functional and moral parameters and they found that, you know, with the inner monologue,  it, yeah. Had a higher task completion rate. So I think that’s, that’s good. I mean, that’s good. I mean, for people like me, because I talk to myself all the time and now I know it’s just because I’m being very sensible and I’m now better at solving problems and possibly being more efficient, than if I didn’t talk to myself at all.

[00:19:27] So it’s not that I’m crazy. I’ve just taken a leaf out of Pepper’s book without realizing.

[00:19:33] David: [00:19:33] You’ve done great work. And it’s also good  for the sake of transparency, because  in robotics, UNESCO commissioned a report on robotics, which is the United nations educational scientific and cultural organization. And in which they heavily emphasize transparency as a requirement in robotics, as opposed to having robots that just get input and then produce output with no indication of what’s happened because then obviously there’s no accountability for what’s happened.

[00:19:57] Sophie: [00:19:57] yeah, let’s see movies. That’s when the robots take over.

[00:20:00] David: [00:20:00] that’s right. I have seen that movie and it’s not so much that robots would take over. It’s just that we wouldn’t know whose fault it was.

[00:20:06]Sophie: [00:20:06] yes. Yeah. True. And you know, even things like when I’m Google  mapping myself somewhere and it gives me a weird route. I would love to be able to talk to Google maps and just be like, yo dude, why that way? That’s not a really good way to go. But in this case of Google maps, talk to me like pepper, then I’d understand that the internal conflict that he or she was suffering, they.

[00:20:27] Google maps is they. And you know, and I would maybe be a little bit more understanding and forgiving of the weird route that they want me to take.

[00:20:34] David: [00:20:34] Yeah. Cause it’s not that we’re suffering it’s that the robot should be suffering too.

[00:20:38] Sophie: [00:20:38] Yeah. Because we’re all equal humans and robots.

Brazil Nuts

[00:20:53] David: [00:20:53] So of all the uses of x-rays in the world and of all the uses of advanced computer tomography technology. And all of the fields of human endeavor that we’ve ever undertaken, understanding why Brazil nuts end up at the top of containers when you shake them is what we’ve done here.

[00:21:19] Sophie: [00:21:19] uh, yeah, so I, I. Read this paper in great detail one, because it wasn’t super long. And two, because I was just so excited that people went to such an effort to understand why these presumed knots Rose to the top. So I don’t know, Dave, if you’ve heard of something called the Brazil nut effect, it’s a, it’s actually a type of granular convection.

[00:21:41] And so it’s like when you have, I don’t know, Um, mixed nuts and you shake them. And what you find is the big nuts go to the top and the small nuts go to the bottom.  And apparently like people have been trying to model this and stuff, but they predominantly focused on size effects using idealized spheres.

[00:21:58]And they did simulations, they’ve done modeling and they’ve the experiments. And what they’ve found is with these idealised spheres, they can actually create something called the reverse Brazil nut effect, which they found that the big things went to the bottom instead of going to the top, which is the opposite of what happens in reality.

[00:22:13] So these people at the university of Manchester went, let’s just look at some Brazil nuts. So they got Brazil nuts and they got some peanuts and they put them in a jar. And what they did is they looked at the 3d temporal dynamics of this agitated mixture. So you sort of shake it a little bit and they captured it, as you said, using timelapsed x-ray computer tomography. And basically  they just tracked these individual nuts and they looked at exactly what was happening and they found that it was sort of like a three-stage process. So they laid the Brazil nuts at the bottom of the jar and the peanuts on top, and they just kind of agitated a bit and they found that it was the Brazil nuts tendency to become vertical, which is what allowed it to rise.

[00:22:56] And so they found that the Brazil nuts wouldn’t start rising until they had sufficiently rotated and created a sort of an angle that was 20 to 40 degrees to the vertical axis. And once they’d hit that particular angle, These nuts would start to rise. And then as they’re rising, they become more and more vertical.

[00:23:16] And so as they’re rising, it’s sort of creating space for the peanuts. And so the peanuts are sort of dropping below them or percolating downwards, and then you have this mass balance, so then forces the Brazil nuts up. Even more. And then once the Brazilians get to the top, then with some more agitation, they settled down to what my favorite sentence here, random perturbations return the nuts to the energetically stable, horizontal orientation at the surface.

[00:23:43] So a Brazil Nut would, if it can choose to, I would say based on probably it’s like center of mass, it wants to lie down. But then there also Brazil nuts that didn’t rise. And then they found that the non risers had two different kinds of behavior as well. So they just, they really looked in depth at these nuts, Dave.

[00:23:58] David: [00:23:58] is the thing, when you say it was the angle of the nut that mattered. So does that mean that it’s the friction between the peanut and the Brazil nut at a particular angle at some point, the angle becomes great enough that that friction is overcome. And then the nut falls down the side.

[00:24:12] Sophie: [00:24:12] I’m really glad you asked me that day, because it turns out that a change in orientation towards the vertical would appear to be necessary, but not sufficient for the Brazil not to rise. And that’s what they found about the Brazil nuts that were, I guess, on the very bottom layer. And it turns out that if you didn’t have enough peanuts sort of falling below, there was not enough downwards mass flux to facilitate the upwards movement. So what you had was at the bottom, these non rising nuts. You’d find that some of them would rotate some of them wouldn’t, but even the ones that did sort of rotate towards the vertical, because there were no peanuts falling below them, they still couldn’t rise.

[00:24:48]David: [00:24:48] Okay. So the rising Brazil nuts is a Brazil nut effect. And the other Brazil nut effect is that they stay at the bottom because there’s no peanuts to fall down.

[00:24:55]Sophie: [00:24:55] Yeah, so basically the brazil nut effect is just, you know, there are Brazil nuts and sometimes they do different things.

[00:25:00] David: [00:25:00] Yes, but what I love about this is that it’s just look and see signs. So it’s, it’s the fact that, like you say, it had been modeled and they hadn’t been able to work it out and then eventually technology and indeed  the inclination of a human being to do this, got to a point where they just did the experiment.

[00:25:16] They just did the experiment that meant they could look and just see what happened and then explain that mathematically. And that’s just very beautiful. I think.

[00:25:25] Sophie: [00:25:25] Yeah. And so, and then I was thinking about the way that, cause obviously, usually when you do CT, With x-rays basically what you’re looking at, you’re measuring the x-ray attenuation by different tissues and stuff in the body. And that often has to do with sort of density and things. And then I really wanted to know what the density of these two nuts were.

[00:25:41] And if that was the thing that really helped them use x-ray. Turns out this is impossible information to find. So I found that, and this isn’t, I can’t verify anywhere. The density of a peanut is 0.461 grams per cubic centimeter. I could not find anything about the density of a Brazil nut there’s even a paper that talks about specific attributes of a Brazil nut.

[00:26:02] I’m like, great. They’re gonna tell me all these things about the density. It just talked about almonds. Like I don’t, I don’t get it. That was Brazil, not in the title and they just talked about almonds anyway, so that was just a, that was a hole I ended up in trying to find out what the density of a Brazil nut was for maybe too many minutes.

[00:26:17] David: [00:26:17] Surely that’s something we could do together. Like we could get some Brazil nuts and then, you know, they would be of a known weight and then put them in some water and they would displace the water a certain amount. And then we would be able to work at the density of the Brazil nut.

[00:26:27]Sophie: [00:26:27] Yeah. But I think just to get like a sort of average. You’d probably want to do that quite a few times.

[00:26:32] David: [00:26:32] Oh yeah. Okay. So it’s a pain in the arse is what you’re saying?

[00:26:35] Sophie: [00:26:35] Yeah. Maybe. I don’t know. That could be for, I dunno, the next,  global pandemic when we’re all inside and I’ll come hang out with you guys and we’ll, uh, we’ll measure nut density.

[00:26:46] David: [00:26:46] If you know, the nut density  listeners, please, please get in touch and let us know so that we can get back to sleep at night.


[00:26:52]  Dave: [00:27:02] And thank you for listening to another fun episode of STEMology. Be sure to check out the links to all these great stories on our show notes. Go visit www.stemology.com.au

[00:27:13]Sophie: [00:27:13] if you have any news, you think is STEM ology worthy. Drop us an email at stemology@ramaley.media.

[00:27:19] Would love to give you a mention.

[00:27:21] Your hosts have been Dr. David Farmer and Dr. Sophie Calabretto.

[00:27:24]We look forward to sharing the latest in all things, science, technology, engineering, and maths with you next week.

[00:27:31] And be sure to bring your friends.