Dr Karl Podcast

00:00 This is a Triple J podcast. 00:02 Hi there. My name is Tanya Bunter. I'm filling in for Lucy Smith, and I was very lucky to join Dr. Carl for some of your science questions. On this episode, you're going to hear what's the story with why some tracks are so good at being earworms, why tickling only makes us ticklish when done by another person, and how long is too long for those leftovers in the fridge. It's time to absorb some knowledge. It is Science with Dr. Carl. 00:30 Hi, Dr Tanya. Lovely to be with you. 00:32 So nice to be with you. Just before we jump into this, 0439757555 is the best way for you to get in touch with us. And then we'll give you a buzz if you have a great question. Dr Carl, what's been happening with you this week? Any new learnings from your life? 00:48 Ah, Okagasama day, which I will explain to you in just a minute. So ask me how I've been going. 00:54 How have you been going? 00:56 I am better, Tanya, because I'm standing in your shade. 01:00 Oh, that's so sweet. 01:01 And that's a Japanese term, which means not your shade where you're denying me room to grow, but you are protecting me. 01:11 And that means that we're all part of a society. So if I can walk through a door, somebody has oiled the hinges and somebody has swept the carpet and somebody has cleaned the glass. And it really came to me when I had my near-death experience this week when I got killed by a shark. 01:25 Whoa, whoa, whoa, whoa, whoa. Pull it back. There's a lot to unpack here. 01:29 Okay, I'm exaggerating a little bit because we're on radio. So I was at the north end in Maroobra on my little surfer plane and I foolishly was trying to get out to the sandbank where people were in the water up to their waist and I went through some water that was beyond my height and that's where the rip was and suddenly, I was such an idiot, I found myself getting caught by the rip and washed in the general direction of New Zealand. 01:54 And I knew enough not to try to swim against it. I tried to swim across it, but it was swimming that way. And I was just out of my control. And then suddenly, something about a metre in diameter, I could see it under the water, a metre in diameter and really firm, but with a soft surface brushed against my leg. Oh, no. And I thought, oh, my God. It's a great white shark that happens to be brown in colour. And for about two seconds, I thought... 02:17 Um, okay. Everybody's got to go. Um, this is it. And then suddenly I realised I was lucky enough to be brushing up against a rock. 02:25 Oh my God. 02:26 Which had vegetation on the surface. And then the waves were just taking me and I got rolled across the surface of the rocks and I didn't want to lose my surfer plane so I got all these cuts and bruises. And then this teenager about, this bloke about, I don't know, 15, 18 or something, gave me a hand up because I didn't want to give him a surfer plane, instead I wanted to get bruises. And he said, are you okay? And I said, i am better thanks to you oh and he gave me and he helped me so um this is our feel good start of the segment let's all be nice to each other because we're all part of the society even if we've never met we're all helping each other in some way there are is that enough of a good feeling oh my goodness yes that's perfect it's very sentimental love that and shouts out to that teenager who helped you out let's get into some science questions we have dr dan from chatswood what is your question for dr carl 03:17 G'day doctors, how are we? 03:18 Good mate, what's your question? 03:20 So I use a thermal imaging camera for work and basically I was just using it before and I'm looking at a mirror or a window and I can see my feet of my body radiating off it except I'm not physically at the actual window or mirror. I'm just wondering how that kind of works. 03:38 How far were you from the window? 03:40 I actually tested it out. I was right up against it. I was a little bit hotter, and then I walked away five metres, then ten metres, and then it was a little bit less hot, so... 03:49 Right. 03:50 Okay, so the thing to realise is that in the land of astronomy, everything in the electromagnetic spectrum they call light. Gamma rays, X-rays, microwaves, they call it light. What we call light, you and me, average citizens, is the stuff that stimulates our eyeballs. Right. 04:08 So that's everything between red and, you know, violet. 04:15 or if you want to get technical, 400 to 700 nanometres in wavelength. Now, there are some animals that can actually do imaging on infrared. The sidewinder snake in the USA is one of them, but we can't. All we feel is just a general feeling of warmth on our skin, but that is electromagnetic radiation. And in your smartphone, it can pick up electromagnetic radio... Sorry, the infrared, but also the thermal camera is much better at it. So... 04:42 it was basically just light that you can't see. So heat was coming from the world around us. It originally came from the sun. 04:50 One square metre picks up one kilowatt of power, half of that heat, half of that light. And then you're warm. Everything is radiating heat. and the heat radiates on the glass, your eyeballs can't see it. And then that glass turns out to be a bit of a mirror in infrared. And so your camera, which can see the infrared, sees it. So it was basically just you getting introduced to the concept that electromagnetic radiation exists outside what your eyeballs can normally see. And it'd be interesting if you could try that. 05:21 Can you do the experiment of trying it on the outside of a train window? 05:27 Because in Australia, the train windows are normally covered with a thin coating of gold. And it's an incredibly good infrared reflector. So much better than glass. So if you tried the same experiment on a train window, you'd probably get a really good reflection of yourself. Can you do that for us? I can do that. 05:46 Yeah, give us an update. Thank you so much, Dr. Dan. 05:50 A little experiment. And just one last thing. 05:53 I've got one of these infrared cameras and when you walk around the suburbs at night, stupid little cough there, and you aim your camera at night at the house windows, the house windows are just pouring out like crazy. And we've put in double glazing and our house windows are dark. 06:14 But everybody else is just sort of trying to heat up the rest of Australia. 06:17 Have you noticed that as well in your work, that houses just pour out heat through the windows at night? 06:23 Yes, correct. Absolutely. I have noticed that for it. Because we do floor heating, so it's... We're there, especially night time for the coldness around as well. Ah. 06:33 Beautiful. Thank you so much, Dr. Dan, for your question. We've got Ben on the line from Mianjin, Brisbane. Dr. Ben, what is your question for Dr. Carl? 06:43 Hi doctors. Um, I have a question regarding Coca-Cola. So I was listening to my Coke the other day and it was fizzing different than normal. And it reminded me that for a long time, um, I've wanted to know why Coke tastes different coming out of a can, a plastic bottle and a glass bottle, because I'm adamant that it tastes better out of glass. 07:04 Ah, okay, you've got a few different variables there. Firstly, glass is incredibly inert. So it's really good at preserving the gas and the flavour. 07:15 And with a normal drinking glass, you're drinking from a wide opening. 07:20 So now you're getting a big fat bunch of aromas coming into your nose, mostly carbonic acid, but it may be a little bit of phosphoric acid, but that might be Dr. Pepper's. 07:30 With a can, it is aluminium, but they've got a barrier, which is excellent. So the carbonation stays in there really well. You do get a very nice metallic cold mouth sensation, but you're not getting the aromas. 07:45 And then finally the plastic bottle, or normally it's PET, polyethylene terephthalate or something like that. 07:52 It's a great barrier, but it's not perfect. It's not as good as glass. And so there will be changes in the carbonation and the flavour during storage. So there are your three variables. 08:05 But a lot of your taste sensation comes from the breathing, so the open glass probably gives you the best flavour. 08:12 Oh, excellent. 08:13 Do you have a favourite, Dr Carl, a favourite vessel to drink your beverages from then? 08:20 I tend, well, right now, I've got a wide mouth container and I'm drinking some sort of hippie placebo to stop me from getting a sore throat, which I've already got anyways, you can tell. 08:32 And apparently Mariah Carey has it to help me hit the high notes. I can't mention the name of it, but I do add some stupid manuka honey. Okay, here's a question for you without notice. Are you ready for it, Dr Tanya? 08:42 Yes. 08:43 You can buy this sort of manuka honey stuff in a little container for maybe eight bucks here in Australia. Guess how much they charge in shops in London? 08:51 Oh, I don't know because I know they're like security wrapped at the shops here, right? So quite expensive, I imagine. 08:57 Up to $500. Extortion. 09:02 It's irrational, all right? Okay, I'm fine with that. And so I know it's a placebo, but I'll still do it. 09:08 Well, thank you for that hot tip. And thank you, Dr. Ben, for your question. We have another question on 0439 757 555. Gaynor has sent us a message from Palm Cove. What is your question, Dr. Gaynor? 09:22 Good morning, doctors. I've got a tricky one. I've got scoliosis in my spine. And when I wake up first thing in the morning and wiggle mine at the bottom, it makes this horrendous crack, enough to actually wake up the dog. And I'm just curious, is that air? 09:37 releasing or is that the bones knocking together or it's rather loud but um yeah just curious as to what that sound actually comes from so um let me get this straight so with regard to your spine which runs from your buttocks up to the back of your neck normally it's a straight line but if i were to stand behind you and look at your spine it would go left to right like a figure s like a shape of an s 10:04 Yep, twists around the hips and then comes up towards the shoulders and twists the opposite direction. Right. 10:09 And then you're saying that in the morning when you wriggle, you get this loud cracking noise? 10:14 Yeah, really loud. Yeah. 10:16 Okay, I don't know what's happening there but I can tell you what's happening in your finger joints when you pull on your finger and make that cracking noise and I'm guessing it could be the same thing happening. 10:29 So imagine that you've got two cylinders kissing up against each other and around them you've got a strong plastic membrane and then you pull them apart so now you've got a bit of an empty space. 10:44 We'll fill it with fluid. So you've got a cylinder and then you've got some fluid and the fluid doesn't flow away because you've got some strong plastic and then you've got another steel cylinder. So you've got two cylinders and there's some fluid in between them and that's like the joints in your finger or in your spine. Have you got that sort of mental image? 11:00 Uh-huh. Now, it turns out by doing experiments with listening very carefully with microphones and then timing it, the crack of your fingers, when you're pulling your fingers, there's actually two sounds. 11:12 One is when you pull your finger joint apart, and I'm guessing this is what's happening in your spine, with your scoliosis, you pull it apart and little bubbles come into existence and they go pop. 11:26 Okay. That's the first sound because you've got a lower pressure. Okay. 11:31 Then the bubbles collapse and at the same time as they collapse, suddenly the volume decreases and the plastic comes inwards. 11:40 The side walls, the flexible side walls of that space holding the liquid, in other words, the space between the joints in your finger or the space between the joints in your spine, the... 11:52 the thing that's keeping them in there, the ligaments, the membranes, that collapses a little bit and that gives you the second sound. I'm guessing that's what's happening, but you'd really get a good answer from an orthopaedic surgeon, but your GP should know that as well. If there's any orthopaedic surgeons who have the answer, please ring in. What's the magic number again, please, Dr. Tanya? 12:11 0439 757 555. And Gaynor, a question. Did you have pain with that or is it just sort of like a similar thing to your fingers cracking? Is it the same sort of sensation as that? 12:22 Well, it's the thing, I can lay in bed and wiggle my bum back and forth and it will just click constantly. Interesting. And then after a while, I'm like, maybe this isn't such a good thing. I mean, it's fine, it feels good, but I'm pretty sure I'm doing damage. But inadvertently, I've managed to work out how to get rid of hot flushes. 12:39 Wow. 12:40 Tell us more. Yeah, I got sick of everybody saying, oh, it's a girly thing, you know, you just grow out of it. And because you wake up three, maybe ten times a night with hot flushes and you're not getting any sleep, which makes you cranky. My GP's been giving me B12 injections and my hot flushes are gone. 12:57 Interesting. 12:59 Is there some science behind that, Dr. Carl? 13:01 I don't know, but if it works and it's cheap and the side effects are zero or minor, I'd go for it. If it's working for you, wow. 13:13 Well, thank you. And the more I question my GP, she's like, get the girls to do blood work, get their cortisol levels checked, get vitamin B12 injections, job done. 13:22 Well, we're learning something very interesting from Gaynor as well. Thank you so much for your question. Dr. Carla, are you ready for some more? 13:30 Drew, I am ready and the answer might be, I don't know. 13:34 Let's roll. 0439757555. That is how Drew from Frankston South got in touch. What's your question for Dr. Carl? 13:41 Hello, Dr. Carl. My question is, I have epilepsy and they seem to increase during a full moon. I'm just wondering if that's magnetic field, changing tides or something like that, creating extra pull on something. 13:58 Or whether or not it's just bad luck. 14:02 Well, as you know, the Mythbusters did say the difference between science and screwing around is writing it down. Do you have some sort of record of it for us? 14 years. Okay, tell me about this 14-year record and good on you for trying. Yeah, go on. 14:16 Yeah, every time I have a seizure, we write it down on a list. And we've gone through the list many times to try to understand why. And it guaranteed on a full moon, I will have a seizure. My wife's a nurse, so she takes a pretty good look of what's going on. And, you know, my doctor has said that he has met other people that have a similar thing on a full moon, as in the way of a seizure. 14:46 Really? Yes. So you've got these 14 years of records and you and your wife have looked at it. Have you had a mathematician look at it? 14:54 No, I have not. Okay, look, I'm just saying that to be extra obsessive, but I'm going along with the fact that it does appear from the two of you that it does happen on the full moon and I got nothing. 15:09 Right? So the thing about the full moon is that your body is between the moon... 15:16 and the sun. So you're on the earth and on one side, so you're on the dark side of the earth in the shadow, the sun is shining on one side and then you're on the dark side and then in the sky straight above you in roughly a straight line through the earth out there is the moon and the amount of gravitational change caused by the moon being out there It is heavy, but it's a long way away. It's roughly equal to a fully loaded passenger jet flying above you. 15:48 Oh, yeah, not very much. So the change in gravity is microscopic. The magnetic field wouldn't come into it. There are other things that we haven't considered. 15:58 Yeah, the tide. Sorry to jump in. The tide seemed to change on a full moon as well. I'm just wondering. 16:04 Yeah, so you do have that, but the fact that the tides are made of water and your body is made of water, but even if the Earth's oceans were made of liquid iron... We'd still have the tides. It has nothing to do with the fact there's water. It's the gravity pulling on them and the fact that they've had a long time to set this up. 16:24 I'm suspecting that this effect is real. Have you gone looking in the literature, in the peer-reviewed literature on Google Scholar to find out more about this? 16:32 Yes. Yes, we have. We've looked everywhere possible. My wife being a nurse is actually thinking of doing a course on it. 16:40 And what did you find in Google Scholar? Did you find that there was a link that other people had reported on this? 16:45 Yes, my doctor has said it's not an unusual thing and this is coming from a very well-known doctor and he says it's not completely unusual that he has experienced this before. 16:59 The only thing I can think of is that because the full moon throws more light, You might go out more at night or might alter your circadian rhythm by staying out later at night. That's kind of it. But really, it doesn't make a difference nowadays because we have artificial lighting. So it used to be that people would go out and party and have meetings specifically on the full moon because they could walk from here to there or drive a horse and knock their light and still see. But that's not so much thing. 17:26 Sleep deprivation is well known to be involved with being a trigger, but I'm guessing that might not be happening to you. 17:33 No, definitely not. I don't drink, I don't do anything and I don't really go out much just for the fear of having an epilepsy out in the public. 17:43 All I can think of is that we need a mathematician, a third party, to go and have a look at your data and then do a search. Maybe this would be a fun way of getting a paper up for the Ig Nobel Prizes. 17:57 Absolutely. As I said, my wife is thinking of doing a degree. 18:01 She's just done a finished one and she's thinking of doing another one because it's such an unusual thing. 14 years of guarantee that it happens. 18:14 She's thinking of trying to do some sort of course on what is going on. This is why I'm calling this morning. 18:22 Medical statistics. 18:23 Beautiful, Drew. Thank you so much. And keep us in touch on the text line 043975755. With any more of your full moon things, we're getting a couple of messages. Chrissy from Redcliffe saying, my kids go crazy the day before and the day after a full moon. There's definitely a strong connection to all of that. Yes. Yes. 18:44 Because it is well known among medical people and hospital people and people in psychiatric wards that there are more events happening on the full moon until you actually go and check it out. Oh. And so when they've gone and checked it out and they've looked at not just what people say on a night, typically, hey, it's really busy here in casualty. Ah, look, it's a full moon, therefore one caused the other. That's called confirmation bias. But the studies have been where you've looked at every admission to a hospital or psychiatric ward or everything on the police input, you know, the notepads that they take, and you compare that, you do that over a 10-year period for an entire country, and you've got hundreds of thousands of records, you do not find a peak on a full moon. 19:26 And yet, medical doctors and people in psychiatric wards and police will say there's more activity on a full moon. So it's the internal confirmation bias. The easiest person to fool is yourself. We need an external statistician to look at it. 19:39 We have a very interesting question from Dr. Lisa. On a full moon, do a parasite cleanses, her recommendation, worms are most active then? True or false, Dr. Carl? 19:49 Definitely don't know. Let's check it out in the peer-reviewed literature and be careful of checking it out on the AI. The AIs, I use them as a really good search engine, but always I'm sceptical. And sometimes you say, can you tell me more about that? And I say, oh, sorry, that was a mistake. 20:08 And all you have to do is ask him to tell you more and I'll admit it was a mistake. So you have to do the proper search and the peer-reviewed literature. 20:14 Beautiful. Thank you for that, Dr. Carl. 0439 757 555. It is the Science Hour. We're getting your questions answered by Dr. Carl. We have Dr. Ben on the line. What is your question? 20:28 Good morning, doctors. Every time it's sort of summer and a car's been sitting for a while and I get in a hot car, I have a habit of sneezing just from sort of getting into that really hot environment. 20:39 Can you give us a time frame? Is this like immediately when you jump in? 20:43 Within probably 10, 15 seconds. Get in the car, sit down, sneeze and know it's coming now. So it's But yeah, something about it. But it has to be sort of 30 degree plus kind of day, like hot car kind of environment. 20:55 Dr. Carl, what do you reckon? 20:57 Almost certainly. 21:00 It's been caused by the change in temperature. If it happened after a few minutes, and especially once you've got the heater or the aircon going, then you're talking about nasal irritation and some sort of allergy thing. But instead, what you've got is your nose is firstly responding to the rapid temperature changes because it's a lot hotter in the car. And the nerve supply to your face is supplied by something called the trigeminal nerve and the nose is packed with branches of the trigeminal nerve and they are also involved with sneezing. 21:37 And then having the hot, dry air, and it is really quite different from outside to inside, immediately it irritates the nasal mucosa. Just as a little bit of a background here... 21:48 When air comes into your nose, it's the outside temperature and whatever humidity is. But by the time it gets to the back of your throat and about to enter your lungs, it's at 100% humidity and 37 degrees C. And so there's special little... Did you know there's erectile tissue in your nose that swells and contracts to force the air to go around corners to do maximum exchange with your mucous membranes? And so your nose... 22:17 can pick up this sudden thermal change and that can activate the sneezing reflex. So I'm reckoning that that's the problem. How do you get around it? 22:26 I've got an old hybrid about 20 years old, I just sold it, 15 years, and it had a little air conditioning system running off the solar cells in the roof that would keep the inside of the car okay, otherwise leave the windows open a little bit more, otherwise just enjoy sneezing. I like a good sneeze. Does it bother you? 22:41 I love a good sneeze. Everyone loves a good sneeze. 22:43 Bit of relief. Thank you for that, Ben. 22:47 Thank you. 0439 757 555 is the way you can get in touch with your questions. Send us a message with your name and we'll have you chat to Dr. Carl. We have another person on the line, Christy from the Gold Coast. What is your science question? 23:01 Well, I've got an interesting one. I'm an educator in long daycare and also outside of school hours care. And that age bracket is really into tickling like that's their repertoire. And they've been asking me why can we tickle each other, but we can't tickle ourselves. 23:20 Ah, it seems to be related to the cerebellum. The cerebellum is part of your brain that's involved with coordinating your activities and involved with balance. 23:32 And if you are a little bit drunk... your cerebellum stops being so good at coordinating your balance and you'll see people, when they're walking, have their feet further apart. We call this the wide-based gait. Now, the cerebellum coordinates your bodily activity so you can put your finger on your nose So it knows where your body parts are at all time. And when you're tickling yourself, on one hand, you are stimulating those areas of the body that can be tickled. 24:02 But on the other hand, it's saying, oh, come on, you're just doing it to yourself. Just stop bothering us. We don't care about this. So the experiment has been done where you can make a little glove and it's got a time delay built into it. I can't remember exactly. I think the time delay is 0.2 of a second. And if there's a 0.2 of a second time delay between when you move your finger and the glove actually tickles you, you can tickle yourself. And I'm suggesting this as a possible stupid Christmas device that will be sold in vast numbers and make somebody very wealthy for one Christmas and afterwards end up in cupboards which people throw away. 24:39 So you can tickle yourself with a time delay involved of about 0.2 of a second. The rest of the time your body says, ah, I know it's you. I don't care. 24:49 Thank you so much for your question, Christy. Yeah, does that answer? Thank you so much. Beautiful. 24:53 Thank you. I can tell the kids that they can just use a glove and tickle each other and tickle themselves and that'll be fine. 24:59 A little tickle in disguise. Beautiful. 25:03 We've got Ian on the line that has a question that fits in that little box. What's your question? 25:08 Hello, doctors. Hope you're having a great day. 25:11 I'm hoping this is not a basic question, but I just wanted to ask, is there a reason why songs get stuck in your head that you haven't listened to in years? Like the last few days, it's just been songs have been going through my head that I haven't listened to in a long time. 25:26 And I wonder if there's any science behind that. 25:30 Is this one in your head, Dr. Carl? 25:32 I should be so lucky, lucky that I can't get you out of my head. 25:37 Which songs have you been getting? Which is weird. So that's what I thought. Is there any science behind that? 25:42 Yeah, it's called an earworm and apparently it first appeared, the word, in a book by somebody called Desmond Bagley called Fly Away and the exact phrase was, and the chant was created in my mind, what the Germans call an earworm, comma something that goes round and round in your head and you can't get rid of it and you can get rid of it. So it turns out that people who are more likely to catch earworms when they were looked at in an MRI scanner, the parts of their brains devoted to perceiving sound and telling the difference between one note and another in terms of pitch and emotions and memory, they were all larger than normal. 26:21 And in many cases... Music has been a way to pass on myths and legends over many years. We used to think that the oral tradition could be carried successfully only for a few hundred years. But in Australia, we've had legends come down, which we know are accurate, describing the rising of the waters 14,000 years ago and 9,000 years ago, such as at Melville Island in the Northern Territory and off the coast of Perth and in the Spencer Gulf. 26:52 and in Melbourne and Botany Bay and all up down the coast of Australia. And these legends have been carried by a combination of music and rhythm over thousands of years. Getting back to the earworm, it's got a few things. Firstly, it has to be part of your culture. It generally doesn't cross cultures. But on the other hand, I am very fond of a few Tibetan throat singing riffs. Forgive me for that. 27:14 Sorry, you need to give us a little display of that. 27:18 What do you mean? I'll try and get the song up in the break. Yeah, we've got to do it. And then secondly, the music has to be a little bit faster than normal, and that's where Bad Romance fits in, and a certain amount of repetition, and being simple and having an easy-to-remember melody is good. And then thirdly, it's got to have a few unusual features. something unexpected like unexpected or large jumps in pitch and it's hard to get rid of it but it turns out you can get rid of it by chewing gum because it turns out that the pathways in your brain that replay music in your memory are the same as the pathways that program the muscles in your jaw to chew gum. 28:01 Wow. I know. So then you have to chew gum. Or you can just play it over and over until it goes meaningless. But in my case, I'll be trying to do some writing and then the family will be banging on the door saying, you've played that 4,000 times. And I'll look at how many times it's played and they're pretty close. So that's the history to earworms. What's your favourite earworm, Dr Tanya? 28:23 Ooh, I feel like I've got a couple of high rotation tracks. There's always like a Britney Spears. So interesting that like that pop music is also one in your head. Dr. Ian, what's yours? 28:34 So like yesterday I heard Sia clap my hands. 28:37 Ooh, another pop track. 28:37 And then this morning randomly I heard Kids in America. 28:40 Oh, a deep cut. 28:42 Yeah, exactly. So this is what I'm saying. 28:45 We need to do a shared playlist, I feel like, to do a collection of all of that. Thank you so much, Dr Ian. We've got another science question. Dr Nick from South Australia, what is your question for Dr Carl? 28:56 Yeah, good morning, doctors. Hey, so I work outdoors in the heat of Australia, obviously, and more of a question about hydration. So the electrolytes or the hydrolytes you can add to drinking water, is that worth buying them and using them? 29:12 Are you sweating a lot? 29:14 I'll read it on that, yeah, yeah. 29:15 Okay, if you're sweating, besides losing water, you're losing salts. So for somebody like you, in that case, the hydrolytes that have the salts in them, the electrolyte powders, that usually is going to help put those salts into you. But if you're just like a normal day sitting in an office and you're not sweating, all you need is water. 29:38 If you've got vomiting and diarrhea going on, these oral rehydration solutions are very valuable because they've got the mixture of sodium and glucose which helps bring it across the membrane from your gut into your bloodstream. It also carries the water through it. They discovered this some years ago when we had terrible cases of children dying from diarrhea and and you can keep them alive just by putting water through a bag and then into their vein and you just do that for a couple of days and then they're over the infection and they're alive. 30:11 But they didn't have the several hundred dollars and also the skilled medical care and then some doctors, I don't know if it was doctors or dieticians, I don't know what their field of knowledge was, they discovered that if you got some water and you gave it to them, it just went straight through. But if you got some water and added sugar and the salts, they would then cross from the gut wall into the bloodstream, carrying the water with them. And suddenly, instead of dying, they weren't. And so that's the background to them. So if you're sweating quite a bit, yeah, go for the hydrolytic type fluids. 30:44 Also... Sorry, what is the actual hydrolite in those? So I'm using those little pouches that you tear and you tip them into a litre of water and they've quite often got a flavour in them, like a raspberry or a lemon. Should I be worried about taking those flavours and stuff? 30:58 I know water's the best thing, but... 31:03 I would check that with your... Does it taste terrible? Is that why they put the flavours in them? 31:09 The flavors do help you take them down more, which is why they had them for the kids to add a little bit of sugar into it because it tastes nice. I don't think they're necessarily bad for you, but the thing is that there are so many products appearing on the market. So I was talking with somebody about... 31:28 the weight loss drugs and they ordered some weight loss drugs online and it turned out that what they bought hadn't been properly certified. They took eight times the dose and they ended up having such slow movement through their gut that they burst their esophagus. 31:44 Oh my gosh. 31:45 And then had to go into hospital and they just managed to survive. So on one hand, it used to be that if something came into the country, you could trust that it had been tested and certified. But now we've been finding that even devices such as medical devices have just been rubber stamped and have actually killed people. So I don't know what to say about the particular brand that you're using. 32:06 I feel like it's probably recommended that we just take the recommended dose, right, is what you would probably say and feel what's going on in your body first and maybe don't push it. And look at the colour of your urine. 32:17 Yeah. The best thing is to make sure that when your urine is coming out, it's the right colour, you can buy these colour charts. And at many of the tradie sites that I've been to, somebody has printed one of these off and then covered it in plastic and then stuck it to the toilet wall and then that way you know what colour your urine should be. Not too dark, not too light. 32:36 Beautiful. Thank you for answering that, Dr. Carl. And we're going to keep in the gut. We're having another question from Liz in Eora, Sydney. Liz, what's your question for Dr. Carl? 32:47 Hi, doctors. I'm wondering why it's always been said that you shouldn't reheat meat more than once. 32:53 As a meal prepper, this is a question for me. I'm scared. 32:58 Providing you... Okay, so you can get food poisoning from bacteria two different ways. 33:06 One is that you take the bacteria into your body and then in your body they make the toxins. Or two, they make the toxins anytime they're awake. 33:18 And so they can put the toxins into the food. And so that even if you eat the food, you put the food into the fridge and you keep it cold, the toxins are still physically there. Those molecules are there. So the normal recommendation is that when you're getting raw meat, it could have bacteria in it. So you cook it to a certain temperature, at least 70 degrees C, and that kills the bacteria. And then if you eat it straight away, you're normally pretty safe. We'll forget about the bacteria that can survive above 100 degrees C, the ones that cause Botox, that's a whole different class. 33:50 Then when you take it out and reheat it, there's a brief window during which it can get invaded by bacteria And then if it's below 70 degrees, I think is the magic number, between say 40 and 70, they can grow really well and increase in numbers. But if you were to heat it up and then immediately put it back into the fridge, that would slow down massively the growth of those bacteria. And so if they were going to be putting toxins into the food... 34:17 they wouldn't be doing that because their activity would be slowed down by being at around 4 degrees C, which is the temperature in the fridge. So if you were to take them out of the fridge and put it in, out, in, out, in, out a few times, more than once, and immediately cool it down as fast as you can, you could probably get away with it. And I'm thinking that's the thinking behind it. I personally have heated up meat maybe twice. There are some meats that are especially prone to it, like some, I think in chicken you can get certain bacteria that love to grow there, I would tend to go just to be ultra safe with just heat it up once and chuck it. 34:51 But on the other hand, I do break the rule myself. What about you, Dr. Tanya? Do you ever break that rule and heat it more than once? 34:56 I've got to be honest. Like, my mum's African, so the rules have been blown out a little bit. Like, I reheat rice. I reheat beef. I do put it in the freezer if I know it's going to be a few days, though, to be honest. 35:08 Right. So with rice, they're worried about a bacterium called Bacillus ceruleus, which is a Latin word meaning blue. And I know people who refuse to reuse rice when they've cooked it. They think that somehow this bacteria is there and even if they put it in the fridge, it will grow and kill them. So they just toss out all the rice. Yeah. Whereas I'm happy to, you know, put it in the fridge. That makes me feel better. Yeah. 35:34 I'm like, yeah, it's such a touchy one. Yeah, we do. 35:38 Okay, I'll give the standard advice of chuck it away, but I know that I keep it maybe, I might hit it twice. Okay. That's a hard area. 35:48 That's all right. Liz, I hope that helps. 35:52 We've got a 12-year-old on the line. Oliver from Melbourne, what's your question for Dr. Carl? 35:57 Hi, doctors. I'm Oliver, and I'm wondering, how can some people hold their breath longer underwater than other people? 36:04 It is amazing. I'll just look up the record. There was a Croatian freediver, and I think they're crazy. I mean, I love breathing air. Why on earth would you deny yourself that simple pleasure? And it was reported on the 18th of August in 2025 that Vitamir Maricis took one gulp of pure oxygen, so he'd been breathing pure oxygen for 10 minutes, and then went into a pool and lay on the bottom of the pool, wait for it, for 29 minutes and 3 seconds. 36:33 How is he able to do that? 36:35 Well, that's where it gets kind of messy and complicated and tricky. So people have got different reactions. So firstly, the reason that you decide to have another breath is not because you're low in oxygen. There is a sensor in your neck one on each side at the junction of the where the carotid artery comes up your neck and then splits into the internal and external and it measures the oxygen level and also the carbon dioxide the reason you breathe is because you're high in carbon dioxide not because you're low in oxygen. 37:08 So that's the main thing. 37:09 And different people respond differently. Now, secondly, there's something called the diving reflex, and these people are able to do it without being in water. But the diving reflex is that you, and we do this in Physiology 101 in university, you've got a bucket of water, you put your face in it, and immediately... your heart rate slows down and your hands and feet become colder because you've closed down the blood vessels. You're not wasting your blood supply by sending it to the stupid old skin. You're keeping it for the brain and the heart. 37:41 And another factor is the relaxing. If you're doing nothing as opposed to swimming, you can last around a lot longer. And then there's individual difference in lung volume and haemoglobin. But there's another thing, which is the spleen. So if you're looking at populations of people... I think there's some Japanese female populations who do a lot of deep diving for sponges. They've got huge spleens. So you've got your lungs and on the lower right you've got your liver but on the lower left you've got spleen and they've got genetically larger spleens. 38:14 over many hundreds of thousands of years, which store more oxygen in it. So all of these things put together and being able to ignore the signal from the carbon dioxide. So these people can ignore the carbon dioxide saying, you've got to breathe, you've got to breathe, and they just say, I don't have to, I can stay alive. So on one hand, they can stay underwater for an increasingly long time. The guy who broke the world record by five minutes, by going from 24 to 29 minutes, he said that he saturated his tissues You can't really put that much extra oxygen into your tissues. 38:48 I think you might have a large spleen, but we didn't have that information. And the thing is that every year in Australia, over the warm period, in backyard swimming pools, you have some kids when the parents are looking at them and they have breath-holding competitions underwater and always one kid dies and it doesn't have to. So don't try and hold your breath for too long underwater. 39:08 Oliver, I feel like you might have already tried that before. How long can you hold your breath for? 39:15 Is that pretty good, Dr. Cole? 39:16 It's about what I can do. But if you just ignore the screaming in your brain saying to breathe and you just hold it. 39:25 On one occasion, I did go to a minute and a half and it was really scary. But these people, they push past that screaming in their brain. 39:33 Well, it's a big mental activity. Thank you, Oliver. Good luck, but be careful. Thank you, Dr. Oliver. And thank you so much, Dr. Carl, for hanging out with us and asking all of these questions and answering them with us as well for you listening. We will be doing this again next week. 0439 75755 is how you can get those questions in. I'll be checking the text line across the week. Thank you so much, Dr. Carl, for hanging out. 39:59 Peachy Keen. And look, thank you for talking me through it. And thank you, lovely audience. And catch you next week, Peachy Keen. 40:03 Thank you so much to Dr. Carl for getting us across some of these niggling questions around science. Also, thank you to Ella and the Triple J Ops team for getting this episode into your ears. We'll catch you next week with more answers to your science questions. 40:18 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.