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00:00 This is a Triple J podcast. 00:02 Hello, welcome to another episode of Science with Dr. Carl. My name is Lucy Smith. This week I learnt that our guts have a circadian rhythm. I didn't know that. You're going to find out why in this week's episode. Plus, there is a TikTok trend that is yet to come across my feed, but people believe that our third eye, or that region, is magnetic. And they've been testing the theory. Does it work? Is it true? Dr. Carl will explain all. That is all on the way. Let's get into it. 00:30 Dr Karl is joining us from Perth this morning. Dr Karl, you've made a new bestie, an underwater bestie. Can you tell us about them? 00:38 It's my friend, the cuttlefish. And I love it to pieces and it loves me. And there's five of them in this tank. So we're doing our TV series, How Things Work. This is our third series. Doesn't quite outrate our good friend, Bluey, but it's still pretty good. 00:52 And they change colour. And finally, I've worked out how they change it. And they've learned a few different things along the way. So firstly, their skin is not just boring skin like ours, but it's actually a remote control, electrically driven, optical display with its own local smarts as well as being controlled by the central brain and it's got at least three different ways of making colour and for making the brown colours, the way it does that is that it has little tiny balls of brownish dye, you know, yellow, orange, red, etc. 01:25 And they're too small to see with the naked eye. They're in things called chromatophores. They're little balls that are too small to see with the naked eye and then it flattens them out into a large disc and suddenly you can see it. And then there's a different mechanism for the blue colours and they also make white stuff. And you can see the patterns rippling across their body. And this little guy was pushing up against the glass and we were just bonding, man. It was like a cosmic moment, man. I've got besties now. 01:48 Really? So did you look each other in the eye? 01:51 They've got a W-shaped eye, so our eye has sort of a roundish aspect. This sort of goes up and down. And what that means is that if you look at it from any angle, it can see you. And the weird thing is they've got all their hands coming out of their head, which is different from us, but I still am bonding to my friend the cuttlefish. 02:11 Your new bestie, the cuttlefish, just beautiful. And if you want to watch the series, How Things Work, you can do so anytime over on ABC iview or on ABC Australia's YouTube channel. Let's get into your questions. Dr. Carl's besties from across the nation. We'll start with Roseanne in Naar, Melbourne. Roseanne, you've got a question about music. 02:31 Yeah, hi, doctors. I'm just wondering, I listen to all types of music and, you know, there's supposed to be only about eight notes. Are we ever going to run out of a combination of musical notes at all? 02:46 This is a thing, Roseanne. A lot of people will kind of, because you see these copyright cases and these different things pop up where people feel like songs are too similar or maybe they're, for lack of a better term, ripping each other off. And a lot of the justification is often, well, there's only eight notes in a scale. Like how much can we really – we've been making music since the dawn of time. How different can it possibly be? Dr. Carl. 03:11 Okay. So you've got your classic eight notes in an octave, but actually there's 12 notes altogether. And when you start off at the beginning and you go to the end, you've doubled the frequency. So each note is the 12th root of two. 03:25 bigger than the note before it. But then in the 1700s, Bach and all those other people came along and they came up with the well-tempered clavier, which means that, okay, mathematically, that's what we want to have, but it doesn't sound right. Let's just change it a little bit. So that's called tempering. So imagine you've got your 12 notes and you make something that's 10 notes long. You've got 12 possibilities. That's 12 to the 10th. That's about $62 billion. 03:51 just for 12 notes, for 10 notes, and if you make it 20, you're up to about three or four, followed by about 21 zeros, and that's before you even bring in the rhythm, the note, the duration, where you have a rest, a long rest or a short rest, and then that's only in one octave. Then you can go to, you've got about, how many octaves are there on a piano? Eight or something? 04:10 Oh, yeah, yeah. 04:12 And then you've got the volume and the dynamics and the tempo. And I remember one famous musician said, look, I don't hit the notes on a piano any better or any different from anybody else. But in between, when I don't hit the notes, that's what I do better than everybody else. So there's the timing and the instruments and the articulation. There's just so much. You're heading up into... Way more possibilities than there are humans on Earth. We've already got to that by the time we just make 10 notes, 62 billion, because there's only 8 billion on planet Earth. 04:42 So, yes, we could run out, but then on the other hand, there are similarities and people do like stuff. 04:47 Well, why do we only think there's only 8 notes? 04:51 Well, because you've got that word octave. 04:54 And then you've got – they're the white – are you filming it on this? I think they're the white notes. Is that right? 04:58 The white keys. The white keys. If you look at the white keys on a piano, those are the octave notes. And then the black keys are the sharps or the flats. So they're kind of – I think it's a semi-octave above. I'm getting into some music theory here for you, Rosanne. Yeah. Thank you. And I could be wrong about – Not a semi-octave, a semi-half above. 05:17 Yeah, and I could be wrong about each note being the 12th. 05:20 Semi-tone, semi-tone. Semi-tone, yes. Sorry, Rosanne, you're unlocking years of, yeah. Really? 05:27 So did you do that stuff, Dr Lucy? 05:28 Yeah, I had to, I had to. When I played the flute, you've got to do music theory alongside your grades, yeah. 05:34 Wow, so we could see you in a different career further down the line as a flautist. 05:38 Maybe, maybe. So you go up by tones or semi-tones, yeah. 05:42 Or down. Yeah, or down, absolutely, for sure. Yeah. So there's many, I think, many combinations to take us. Is that, yeah, yeah. 05:51 We haven't run out of all of them yet. 05:52 All right. Does that help, Rosanne? Oh, yeah, absolutely. I've just learned a new thing that we have 12 instead of 8. There you go. We've got Matt in Jindabyne right here. Now, Matt, you've got a question about earthquakes. 06:03 Hey, yeah, morning, doctors. I want to know the difference between an earthquake and an aftershock. 06:09 In general, an aftershock is a lot weaker than the original earthquake, but not always. So they're the same thing where you've got the crust pushing. So we have these dozen or so tectonic plates. 06:23 Australia is way from the edges. Way on one side, we've got New Zealand. Then above us, we've got New Guinea. And then halfway to Antarctica is the bottom of it. And then it goes into the middle of the Indian Ocean and it runs into Tibet, into the Himalayas. So we're in the middle. But even so, it's not like a solid lump of steel. And as they move around at roughly the rate your fingernails grow, at a couple of centimetres a year, they build up stresses. And so when you relieve that stress, it goes bing, bing, bing, building up, building up, and then suddenly releases. That's an earthquake. But then... 06:52 Afterwards, you have little baby earthquakes. They're called the aftershocks. And in general, they're usually weaker. But sometimes they can be really quite strong. And also they get further apart. This is called Omori's Law, O-M-O-R-I. So they're less frequent, they're weaker, and they get further apart. And they can continue on for weeks or years. But sometimes it can be a magnitude 6 earthquake which followed by a magnitude 7 aftershock. And so the geologist goes, say, OK, you got us there. 07:24 We'll just call the magnitude 6 one. The first one, we'll call that the foreshock. So you can have the foreshock, the actual earthquake, and the aftershock. They're sort of playing it both ways. 07:34 So would an aftershock have to be, like, centred exactly where the earthquake originated? 07:41 Roundish within – now, I'm weak on my geological knowledge. Please ring in geologists on 0439 757 555. But I'm guessing within, like, 20 or 30 kilometres. And normally in the crust, which varies between roughly – 10 kilometres thick on land to, sorry, 100 kilometres thick on land and then 10 kilometres thick on the ocean, but it varies. So the earthquakes happen in that relatively solid bit. And then underneath that, you've got gloopy molten rock kind of halfway down to the centre for another 3,000 kilometres. 08:14 Cool. Matt, does that help? 08:15 Yeah, thank you. 08:17 Crazy. Dr. Carl, my boyfriend lives in New Zealand and there was an earthquake at Milford Sound and then they could feel the shaking, you know, that's four and a half hours away from where he lives in Wanaka and there was moderate shaking that they felt even that far away. Why does that happen? 08:35 Because the distances – the earth is relatively small, I'm guessing, and the forces are great. They're of the order of many times the strength of nuclear weapons and so they can transmit over huge distances. I'm guessing on that one, but I do remember the very first night I went to New Guinea, I was trying to get – I was going to get into my bed and I had one foot on the ground and I built my bed and I had one leg up and then suddenly I fell to the ground and that was what they called a guria. And the house was built on iron sticks and you could park your car underneath like a Queenslander. 09:08 And every day we'd get little tiny gurias. It was just like common. 09:12 My gosh. Okay. Layla in the gong. You were camping recently and you noticed something in the sky. What did you see? 09:18 Hey, doctors. How are you? 09:21 Very well. Thank you, Dr. Layla. Welcome. 09:23 Thank you. Yeah, I was camping out the back of Mudgie a few months ago and it was a really bright night with a full moon and there was sort of a really thin veil of clouds over the whole sky. But then when we looked around the moon, there was like a perfect ring around the moon where there were no clouds at all. And we sort of came up with some hypothesis, but didn't land on one that we liked. So I was hoping it could help us out. 09:49 Hypothesis, you say? Scientifically trained. Oh, my gosh. Woo-hoo. Big it up for you. Fancy words. Hypothesis. You said a guess. Good on you. Okay, so there's a bunch of reasons, but the main one is that the moon's glare... can overcome the faint cloud. So the cloud is lit up by the moonlight and it scatters it and very close to the moon, the contrast and the glare can make the cloud difficult for your eyes to see because the moon is really bright. 10:21 And your visual system is attuned, is set up to look at contrast. So if you've got a brightness... big difference between something bright and something not bright. So the cloud in the way of the moon, whereas the cloud off to the side, the glare of the moon overcomes that. So you tend to get a perfect circle. And by the way, the number is roughly a half of a millionth. So the amount of sunlight reaching the Earth's atmosphere, or the amount of moonlight is roughly 1 400,000th, call it half a millionth, of the sunlight. 10:54 So that's how weak it is, the full moon, compared to the full sun. So that's the first thing, the contrast thing. And then there's another one that you can have an actual cloud hole, and this is very uncommon, but clouds can sometimes make circular holes. And another one is that you just simply have, it's the brightest... thing in the sky and that sets up other visual pathways. But the main one is the contrast brightness between the sun, sorry, the moon being so bright and going straight through the cloud and then off to the side, it doesn't see it. And did you see little rainbow effects as well? 11:27 I can't quite remember, but if I see it again, I'll look out for them. 11:31 Yeah, if you let your eyes adjust and switch off all the other lights, you can see a really weak rainbow sometimes. And this one, I learned this when I was a TV weatherman, is due to, wait for it, here's the magic phrase, high altitude hexagonal ice crystal. So just practice that and you can sort of roll it off like you really know something. 11:51 That's awesome. Thank you. Thanks for your question, Leila. Thank you. 11:55 In the midst of science with Dr. Carl, answering your science questions, which is sending in on 0439757555. We've got Kwame in Darling Point, Sydney. Now, Kwame, have I missed something on TikTok? I've had a few questions about this. 12:10 Good morning, doctors. How are you both? Good. 12:14 How's your game? So, yes, there is something that's blowing up on pretty much all social media platforms at the moment. And it involves people taking what I imagine to be a metal-ish object and putting it in the place where I suppose people say is the third eye region and it sticking and grabbing hold like there's some sort of magnetic pull. 12:40 Are you able to explain or debunk what's actually occurring? 12:45 Okay, so how is electricity and magnetism, how are they made? And we discovered with Faraday you get three different things and any two will make the third one. And the three different things are firstly a magnetic field, so you're talking about that between the eyeballs, right? Between the forehead, the eyebrows. You get a magnetic field or... 13:05 you get electrons moving along some sort of wire, and it can be metal or biological, and then finally that wire can move. And any two will make the other three. That's the basis of our electrical society. So presumably you're manufacturing a magnetic field between your eyes. No, you're not. Now that part between the eyebrows is called the glabella, G-L-A-B-E-L-L-A, And in third year medical school, you learn what's called the glabella tap. And if you just come up to anybody and you say, I'll just tap you between the eyebrows, every single time they'll go, blink, blink, blink, blink, blink. 13:39 Unless they've got Parkinson's disease. 13:43 and then they won't blink. Okay, that's nothing to do with magnetism. So the amount of electrons in your body is equal to the amount of electrons that you can suck out of the electrical grid, about 100 amps. That's a huge amount of current. It'll make a skinny wire get very hot. But is that a very low voltage? 0.08 of a volt instead of 140 volts. 14:05 And we can measure magnetic fields. So you definitely do have electrical currents in your brain generating tiny magnetic fields and hemoglobin does contain iron, but it does not make your forehead a magnet. And the third eye thing, yes, with lizards or some sort of reptiles. And if you do get a very sensitive magnetometer anywhere on your head, You can pick up a magnetic field. But something special about between the eyebrows, I'm kind of guessing, but I haven't read a study on this, that it's purely just the fats sticking in the skin. 14:36 I was going to say, like, you know, have people been sticking bobby pins to their head? Is that something I've seen maybe? Yeah, yeah. Yeah, is it just the bobby pins sticking to the skin and the oil? Yeah. 14:50 Ah, and I've got a little experiment. So get some metho, which is going to be terrible. Methylated spirits is going to be terrible from your skin. But with that, you can pretty effectively remove all the oils off your skin. 15:01 I don't think people should do that. 15:02 I don't think people should do that. But if you want to debunk it as a science communicator, go over and beyond duty. And with a bit of luck, suddenly they won't stick anymore. 15:12 Very interesting. Kwame, thanks for shedding some light on this, bringing this to my attention. We've got Hayley in Eora, Sydney. Hayley, you've got a question about the moon. Now, we just heard about the ring that potentially appears around the moon. Hayley, what have you noticed? 15:26 Hi, doctors. So my question is when the moon is going through its phases during the month, so waxing and waning, I've noticed that sometimes it does this horizontally and sometimes it does this vertically, and I wanted to know why that is. 15:42 Ah, so you've got three major options where the crescent moon, the fingernail moon, either you have the fingernail part, the lit bit, either above or below, or roughly on the side or somewhere in between. And it's not the... what's happening is that you're going around, the moon is going around the earth and you're going around the sun and you're looking, your local horizon is tilted. The earth is not vertical. If the earth was vertical relative to the equator of the sun... 16:14 you wouldn't see this. But it's actually tilted at about 23 and a half degrees. It varies on a 41,000 year cycle between 23 and 21 and a half and other things happen as a result of that. But the point is the earth is not vertical. So sometimes you're looking at the moon over to the left horizon, the right horizon, and it can be a fingernail moon at that time. And so it depends on your season, your latitude, which is how far you are from the equator, and the time of night and also whether the moon is waxing or waning, getting bigger or smaller. So you can have a crescent moon being the fingernail being almost horizontal at one time of year, not in the same month, but one time of the year, and an almost vertical several months later. 16:52 That's great. 16:53 Thank you. And there's an extra Australian thing. 16:56 Because you're in the southern hemisphere, you see it differently from what people see in the northern hemisphere. So you can use the viewing thing on your phone to contact your bestie on the other side of the equator and see what they see at the same time of day or night. 17:08 Oh, yeah, that's interesting. Thank you so much. Great. Thanks, Hayley. Let's go to Jindermine with Tim. Tim, you've got a question about scented candles. Yeah, nice. 17:16 Hey, doctors. Yes, I wondered why does the smell of a scented candle be stronger when it's extinguished versus when it's lit? 17:26 And only for a few minutes? 17:28 That's right. 17:29 Right. Okay, so you can do the experiment, and this is a great experiment to do with the kitties, where you light a candle and you let it burn for maybe 60 seconds, two minutes, and then you have another candle on the side, you're just burning away happily, and then you blow out... the main candle. And then you'll see a thin stream of something looks like smoke. 17:52 And then you bring your second candle to that rising stream of thin smoke, maybe two or three or four or five centimetres away, and the flame jumps downhill. 18:03 So what you've got is something that can burn but hasn't been burnt. 18:12 So when a candle burns, and Michael Faraday wrote a whole paper on this, and he taught us so much about the burning candle. 18:19 When a candle is burning, you're turning the wax, firstly from solid into a liquid, then into a gas. And in that gas rising up, you've got the hydrocarbons and you've got the fragrances. But the hydrocarbons and the fragrance are not being burnt. They're not being destroyed by the flame. They're present in that thin column of rising kind of smoke and they're not being burnt. So temporarily, if you put your nose to it, you'll get this whole, oh, different fragrance molecules. 18:51 Yes. 18:52 Yes. 18:53 Tim, do you have a favourite scented candle flavour? 18:57 I must admit I'm talking on behalf of my girlfriend. Okay. 19:01 All right. And hey, Christmas presents sorted for life, am I right? Yeah, exactly. Hey, the ladies love a scented candle. Tim, thank you so much for asking this question on behalf of your partner. 19:11 Thank you. 19:12 Dr. Carl, do you have a favourite scent? No. 19:15 Now I'm going to do a bummer, man. 19:16 What? 19:18 You know, you go into a church in Europe somewhere and they've got all these burning candles and incense and stuff. 19:23 Yeah. 19:24 The air pollution is higher inside the cathedral from the burning candles than it is out on a six-line highway outside the church. Oh. 19:34 You're joking. 19:35 On the other hand, they smell nice and they're fun. 19:38 I kind of like that smell. 19:39 I like that smell. Look, a little bit every now and then is surely fine. 19:44 I'm a sucker for jasmine. Can you get jasmine scented candles? I think you can. 19:47 Absolutely, yeah. 19:48 Oh, man, I love jasmine. 19:50 So when I was a hippie, I used to wear jasmine flowers in my hair every time the season came around. 19:54 Oh, beautiful. 19:55 Of course you did. Thank you. Of course I did. 19:56 Yeah. 19:59 We are doing science with Dr. Carl. He joins you live to answer your questions. Sophie in Avalon, what's your question? Morning, doctors. 20:08 I have a question about immunity to stomach bugs. 20:12 So it's almost like a riddle, this story. 20:15 I live interstate and I went to see my family over the weekend and my kids both got a stomach bug and they cleared it within the night. My brother's family, his wife got the stomach bug. My dad's family, my step-mom got the stomach bug. 20:33 My partner got it too. But anyone with my last name or from my full family didn't have the bug. Now, I slept in the bed two nights in a row with two spewing children and I still didn't get sick. 20:50 So I'm wondering, is there a genetic blood thing... 20:55 or is it just pure luck? 20:57 They're both, true. So my daughter Lola is a third-year-out medical doctor, and up in the Hunter Valley, this bug came through the hospital, and about one-third of everybody got knocked over for two days at least. When I say knocked over, they could not work, and they were really sick and vomiting and painy for either two days, three days, four days, or five days, and then it got better. And they decided to test it, and they tested, you know, 20 different bugs, nothing, 50, nothing, 1,000. 21:23 they didn't get anything. So something came through that we didn't know about, knocked over one third of the people and then went away and we still don't know what it is. And in the same way, we don't know the different immunities you can have. So the bacterium or the virus that comes along and calls the stomach bug, we don't know which at this stage, it can be in different varieties in different people and it can mutate in that person and then change into a different form. So with regard to the norovirus, which is the one they hate on the ships, There's definitely some degree of resistance to it depending on your family, but there's so many different types of norovirus that can go out at the same time. 21:59 So I'm just saying that we don't fully understand it. If in a hospital we have the ability to test for a thousand bugs and we still couldn't find anything, we definitely don't have the capacity to do it for people in the street because it didn't kill anybody and we've only got a certain amount of money that we can spend. 22:16 And we will get more knowledgeable about this in the future. So what were the symptoms you had? 22:23 They all had vomiting and diarrhea. Sophie didn't have any. No, I was sweet. 22:26 You were sweet, but they had vomiting and diarrhea. 22:28 Yes. 22:29 And you had nothing. 22:30 I had nothing. My brother had nothing. My dad had nothing. 22:33 Wow. 22:34 So in that case you'll say – And it's also gone into a friend's we were staying with. They've gone down too. Wow. 22:40 So with norovirus, there's something called FUT2 and that's the name of a gene. It's kind of an immunity gene, kind of. And the reason they worry about it is because it can just take off. It is incredibly infective. And there was a case where there was a big wedding in New Jersey and there was something like 20 tables each with 10 people and somebody vomited at one corner of the room and they immediately swept it away. And on the other side of the room... 23:10 Yeah. 23:10 Other people got infected. Right, it really spreads. So there's a whole lot of factors and I'm sorry it's adding up to a don't know, sorry. 23:18 That's all right. Sophie, I hope everyone's feeling better. Yeah, everyone's way better in my house, but yeah, it was interesting. Damn, that sounds good. A fun trip to Melbourne was had by all. I know, and you're right, it does sound like a riddle, doesn't it? If so-and-so got sick but other person didn't, yeah. Yeah, how many actually got the virus? Zane in Melbourne, you've got a question about shift work and your gut. What's going on? 23:43 Hey, doctors. 23:44 Yeah, just so I've been a shift worker for last sort of 10-ish years now as a nurse and now as a fiery. 23:52 And myself and my colleagues have noticed that when we've been like up all night working, we, myself and a few of the others, we seem to get gut symptoms similar to that of IBS. So like frequency, some cramping, you know, Sorry for the content warning, but, you know, liquidy consistency. 24:12 Hey, same with your chest, Zane. 24:14 Oh, you're talking about the squirts, I believe. 24:16 Yes, and I was just wondering whether that has anything to do with, like, staying awake all night when you should be sleeping, so, like, when your gut should be resting and, you know, wondering if there's any relation between staying up all night working and sort of IBS symptoms. 24:31 Zane, I can attest to this. When I had to get up real early for breakfast radio or when I was doing the overnight shift in radio, I felt like I was way more prone to getting indigestion and reflux and also constipation. 24:46 Yes. 24:46 Yeah. And I didn't know if it was an anxiety thing or an increase in cortisol at that time. Dr. Carl, can you speak to this? Yeah. 24:55 Yeah, the basic phenomenon going on is that besides your brain having its own circadian rhythm, circa means about, diem, day, so you've got a rhythm about a day long, so does your gut. 25:08 Not just the gut wall and how it compresses and pushes food along in peristalsis, but the bacteria. And so your gut's motility, you know how it moves, follows a daily pattern and you eat at regular times and your gut gets used to that over time. And you mentioned hormones like cortisol and melatonin and they're all involved. 25:28 And then when you're out of sync, when you're sleeping, normally you'd be awake, you can get what's called an exaggerated gastrocolic reflex. Gastro meaning eat, colic meaning colon. So you eat and then straight away you go to the toilet. And if you happen to have caffeine and, God help me, a large cigarette or a large meal, that can improve that. 25:49 But also when you're a fiery and we did a show on fireys and I'm just so impressed. You know, I had no idea that fireys actually do rescue as their main work. Did you know that, Dr. Lucy? 25:59 Yeah, we talked about it with that fire guy last week who was talking about and you mentioned as well getting people out of cars. 26:06 Yeah. 26:07 Yeah. 26:08 Yeah, we do that a lot. Yeah, and that was amazing. So the thing is that you're not just simply being awake and resting, you're being awake and under potential stress. Sometimes working and sometimes having just worked and sometimes being ready to work. So this interferes on top of the fact that your microbiota in your gut, they've got their own timing. And fireys have an extra one. because you're not just sitting quietly awake. You've got the sleep deprivation and the sudden adrenaline and fireys are so physical. 26:38 Like trying to hold the 35mm hose, I can barely hold it. 70mm, forget it, I'll get tossed aside. And then you get the heat exposure or the dehydration and then you think, I'll have a cup of coffee and irregular meals and then trying to sleep during the daytime, that's almost the perfect recipe for upsetting your gut, which might feel a bit like IBS, inflammatory bowel disease, but it's basically you're just interfering with a natural supply of the gut. On the other hand, you're essential for our society. You are keeping us alive and safe. You are doing the work of the angels. 27:08 And nurses as well, having that adrenaline as well. Zane, thanks for the work that you do firstly and thanks for your question. 27:14 No, thank you so much. Thank you for the answer. I'm glad to know that there is something behind it. 27:18 Yeah, it's not just you. 27:21 Nathan in Brizzy, you've got a question about our brain. What do you want to know? 27:25 Yeah. Hey, doctors. My question is pretty basic, although maybe complicated. What's the storage capacity of the human brain? 27:36 Ah. Okay, so we went a bit through this last week, so I'll go through it quickly. There's sort of four phases ranging from short term to long term memory. So in the short term, you increase the number of molecules that go across the gap between one nerve and the other. In the median term, you then increase the sensitivity of the receptor system that can pick them up. And then the third stage is you kind of rewire it to work at this higher level. And then the fourth stage is you rewire whole parts of your brain. Then, to put some numbers on it, you've got 43 million nerves on one side of your brain and 43 on the other side, and they're joined by a tiny bundle of only a couple of million nerves. 28:14 They seem to work just like one brain, but the magic number is 83 billion nerves. But here's a big difference. In a computer, each nerve-thinking element transistor is joined to two other transistors. In your brain, it's a thousand of them. So if you just go for the simple, you join to one other thing or two other things, you're talking about one and a half, yes, they call it two petabytes, which is 2,000 terabytes. But then when you start factoring in the possibilities of all those thousand things, it goes way extraordinarily high. 28:45 And then the other factor is you can't remember everything. And so a while ago I was thinking... Am I losing it? Because I can't remember what I read four days about the exact numbers on blah, blah, blah. And I've always had this phenomenon that a thousand units of information come in and then that pushes out one unit of information out the other side of my head. And I'm still able to remember stuff and heavens for that. So... 29:08 I think it's because I'm using it. It's kind of like on the outside I look like a badly packed sack of potatoes, but on the inside my brain is like Arnold Schwarzenegger in his prime. And you don't fill the brain like a hard drive. You're just reorganizing the bits to give you different memories. It's not as though you write one and lay it down. But we still don't fully understand it and you won't, as you get older, eventually run out of space. 29:30 You can continue to form new memories. And part of the problem is that when you access a memory from the past, you don't look at it like it's a paper, like written words on a page. It's more like it's something written in dye on water. And if you look at it too hard and interfere with it, you can change the memory. So suddenly on your fifth birthday, it was raining. You made up that memory or somebody told you. And so you change your memories. So you don't seem to run out of memories. But on the other hand, we've got Alzheimer's disease, which is a terrible thing of itself, which is completely separate. 30:01 Does that help, Nathan? 30:03 Yeah, yeah, definitely. That's great, guys. Yeah, so as potentially human life gets longer, our capacity to remember will still be retained. 30:12 It will just shift around a bit. Oh, no, then you go to read the book Disturb the Universe by Freeman Dyson, who reckons that the correct shape for a human is not this biological meatbag that evolution gave us with all the problems, but rather a cloud of iron vapour. 30:27 weighing 50 kilograms, the diameter of a planet floating through space. And yes, don't worry, you could still have sex because as Frank Zappa said, your brain is your main sexual organ. So the storage capacity could go much, much higher and we could learn technologies to start putting it onto electrons. We can't do that yet. 30:46 Right. Amazing stuff. Thank you. 30:48 Thanks, Nathan. And we've got a text from Maisie who says, Hi, doctors. Important reminder to wash your hands with warm, soapy water after going to the toilet and before eating. The number one way to prevent stomach bugs for the average healthy individual. Regards, an ED nurse that's terrified of stomach bugs. 31:06 She's so right. And the thing is that on the ships, because they're worried about the norovirus, they give you this alcohol wipey stuff, the norovirus has a coating. It ignores the alcohol wipey stuff. They should get everybody to wash their hands if there's any hint of an outbreak. But on the other hand, you've got customers to deal with and they don't want to wash their hands. 31:22 Maisie added that, saying hand sanitiser does not effectively kill stomach bugs. 31:27 Depending. 31:28 Dome bugs can transfer through gloves. Yeah. 31:32 All they want is to have babies and we just happen to be in the way. We're the carriers for bacteria and viruses to have new babies. Enjoy the role that you're just in an intermediary stage. 31:42 Gosh, wash your hands. Thanks, Maisie. Thanks for the PSA. 31:47 We've got one last round. Casey in Winston Hills. You've got a question about vitamin D. Talk us through it. 31:54 I do. Morning, doctors. 31:56 Dr Casey. 31:57 Hi, I've got a three month old breastfed baby and I have to administer her oral vitamin D because she's not allowed in the sun. So I was just wondering how does our body produce vitamin D and does the UV level contribute to how much we produce? 32:12 Yeah, you're stuck between the devil and the deep blue sea. I mentioned my wife went to a lecture in the morning once as a medical doctor and she got convinced by the dermatologist to put on sunblock before she even fully dried getting out of the shower. And then she went to a lecture by the orthopedic surgeons in the afternoon called slip slop. You know, put on your sunblock and crack and break your bones. So, you know, there's a delicate balance. So there's different types of UVs. It begins at 400 nanometers, that's the wavelength, and then it goes down. UVA runs from about 400 to 290 and that's not involved with making vitamin D. It's the next one, UVB, which is 290 to 320 and that makes a chemical based on cholesterol and then that changes the molecule into something called pre-vitamin D and then... 33:03 Your skin has to be hot. And if your skin is hot, that rearranges it into a different form of vitamin D called vitamin D3 and then it goes to the liver where it turns into another form which then goes to the kidneys. So then finally you have the active vitamin D. So it goes through a whole bunch of changes. How much do you need? They're really vague on that. Anything from a few minutes to maybe 20 to 30 minutes. 33:27 And I think, did you get your vitamin D for your baby from the bottle that has a picture of a man with a huge codfish on his back? Or do they have a more attractive form of vitamin D nowadays? 33:38 No, this one's 400 international units per drop in a purple bottle. 33:43 Ah. So when I was a kid, all the kids used to have that and we were told to stay out of the sun, but all the kids went in the sun, everybody got sunburned. Wow. So, and is your baby otherwise hella and wealthy and everything else? Healthy? 33:53 Yes. Yes. She's wonderfully healthy and well, but yes, we know we need to prevent rickets by ingesting the vitamin D. We've actually had rickets. 34:02 in Queensland with people who, for various religious reasons, stay out of the sun and cover themselves up fully and don't get any sunlight on their skin anywhere, apart from the back of the hands, and they tend to cover them. And so we've actually had a few, a very small number. So you need a little bit of sunlight. It is possible to get rickets, but you've got to work at it. 34:26 Good to know. Thank you so much. Thanks, Casey. Alex in Canberra, you got a question about knees, kneecaps. 34:33 I do indeed. It's a baby mafia related question. Morning, doctors. 34:37 Baby mafia. 34:39 Well, in a sense that babies are not – can I just say also, Doctor, huge fan, only Carl I'd ever listen to. You know, if I heard the R from your dulcet tones to my eardrums, I'd be a king and then some. 34:52 Oh, shucks. Just to butter you up. But, yeah, babies' kneecaps aren't formed for several years and they start out as cartilage. But then obviously babies start walking from the age of about, I don't know, six months, eight months – Not my hazel and ivy, but I do hear that some babies do walk early. 35:10 Do you know why this is? Yeah, so they have a kind of kneecap, fancy name is patella, and it's basically for mechanical leverage. 35:21 So if you do a bit of physics 101 in high school, if you have a little pushing out of the force away from the pivot point, you get more leverage. And so it starts off being flexible and resilient and cartilage. There is a kneecap there, but it's not bone. It's soft, squishy cartilage, but it still has strength and it's really useful if you've got a rapid-growing baby. Then they go from being paralyzed to being able to roll over. You had the thing where you leave the baby on the bed and suddenly you come back and it's lying on the floor and you hurt her thumb. Yeah. 35:51 Yeah, definitely, definitely. 35:53 And then they start crawling and in what we've seen with our little babies around the place is that for some reason they discover reverse gear first. And so they work there, they crawl their way underneath the furniture and they're bleating at you because they don't know how to go forwards, they can only go backwards and the kneecap is important there. So the kneecap is doing huge changes. 36:13 in the rapidly growing baby of a body. And then when they start to stand up, when they're standing up, you see them standing and, you know, juttering around for about 20 seconds and they'll fall. It's like you pumping iron to the maximum until your muscles fail and then instead of saying, well, that's it for the day, you do it again and again. So they are pushing themselves to the maximum all the time. Yeah. And so... 36:37 The kneecap works well as cartilage and as bone, but evolution has to keep it soft and squishy so it can adjust to the height of the baby. So you can have two people the same height and they can have their hips... at different heights. And so there are adjustments you have to make. 36:56 So that was your first question. 36:58 We do the reflex. We do the reflex walk when they're born. And so all babies have that reflex to already walk the moment we're born, which I think is just fascinating. Yeah. Like every other mammal. 37:08 Yeah, it's there, but we don't have the musculature, but also we don't have the neuromuscular innovation for being able to speak and all the other complicated things that make us human. 37:16 Okay. 37:17 Thank you, Dr. Carl. 37:17 Thanks, Alex. Woohoo. We got Tanya in Perth. Dr. Tanya, what do you want to know? 37:23 Good morning. I just want to know why ears produce wax. 37:27 Ah, okay. So if you look at the eardrum, on the other side of it is a little bone. But you're looking at the eardrum, you can do the little tube. Doctors and nurses know how to do this. And it's got a layer that doesn't shift. And then above that is a layer that does shift. And if you get a tiny bit of Indian ink and you put a tattoo on the eardrum, don't do this experiment at home, folks. It's a really fragile area. Mm-hmm. 37:53 You'll see it do a clockwise circle around the center point in the eardrum and then hit the side of the ear canal and then migrate its way outwards. So earwax is a mixture come out of specialized glands. And the earwax has a fancy name called Cerumen, C-R-U-M-E-N. So there's oils and waxy stuff and fatty substances and dead skin cells. And what it does is it can fight... microbes there are chemicals in there that actually stop bacteria they slow them down it won't kill them but it'll slow them down also anything that goes in there gets carried out by the migration and it tends to keep the skin healthy and waxy i guess if you wanted to you could prove that your ear canal was also magnetic if you want to go down that pathway and also got the protective coating from water and mechanical irritation and it carries the old stuff out with it so in most cases you do not need to change the earwax or to remove it. 38:48 And there seems to be a genetic difference between China and the rest of the world where they have dry, flaky wax and moist wax. I can't remember which part of the world has which. I've forgotten. 38:59 All right. Thank you. Thank you. Oh, Dr. Carl, thank you so much for taking us through our science questions. 39:07 And thank you, audience, for making me think about stuff I hadn't thought about for a long time and dragging stuff out of the recesses of my brain where they've been lurking away to stop them from mouldering because I refreshed them. Thank you, lovely audience. 39:17 That's it. We'll do this again next week. Dr. Carl, I'll catch you then. 39:20 Peace you, King. 39:21 And that's it. Thank you so much for listening to this week's episode of Science with Dr. Carl. If you have a question that you want to send in early, you can actually do that. We've got a Google form in the show notes where you can pop through your question for Dr. Carl, your name, your number. We'll give you a call and get you ready to go for an upcoming episode. We would love to have you on. Next week, we're going to have Laura Dreesen on. She's an astrophysicist and will be answering all of your space-related questions. This week's episode was produced by Byron Smith and Ella Carter. I'm Lucy Smith. 39:52 I'll catch you next week. Bye. 39:54 Dave Marchese here from the Triple J Hack team. Hey, if you love Dr. Carl's podcast like I do, you might enjoy the Hack podcast as well. Each day we bring you the news that matters to you, from the latest science on climate change to what's happening in politics and news around the world. The Hack podcast. It's your daily fix of the news you need to know. Get it wherever you're listening now.