Why Your Body Needs Gravity

11:29Hannah Fry:Yeah, because this is the whole point about space time, right? That space time is only according to your particular perspective. So that whole like speed is distance over time calculation only works when you're standing on Earth and it's like, all right. It's a good approximation.

11:44Michael Stevens:Okay, not to be the Newton flag bearer guy, but like most of the time I can go ahead and assume that the universe has depth. Yes. And it works. And it works. I'm able to sink my baskets. Yeah. Because I'm really good at basketball. Yeah. It's just a humble bragging. You can reach out for a handshake and expect the person's hand to be where you thought it would be. It is where I want it to be. And it's not like, whoa, my hand moved so quickly. My hand is like so much younger than me now. Suddenly the distances and the time.

12:10Hannah Fry:Anyway, anyway. Right. Here's the point about the Einstein thing. It's like once you get up to really fast speeds, once you're traveling long distances close to the speed of light, everything goes a bit woo-woo. Right. Everything goes a bit strange. All is dilated. It's all problematic. Your twin on earth is older than you. That's the key point I want you to remember. It's bizarre. OK, so NASA being NASA, we're like, guys, we can sort of try this. Why don't we just give this a go? We've got Mark and Scott Kelly. Let's just pop one of them in a spaceship, see what happens. Tiny problem, small, is that unfortunately getting a spaceship up to towards the speed of light and traveling 10 light years away.

12:53It's just it's just beyond their capabilities. Right.

12:56Michael Stevens:An appreciable amount of the speed of light not going to be reached anytime soon by any space agency.

13:02Hannah Fry:So they went for the next best thing, which is they put Scott on the ISS for a year almost. OK. All right.

13:10Michael Stevens:And how fast does the ISS go as a percentage of the speed of light?

13:14Hannah Fry:OK, so it orbits as well, it orbits at about 7.66 kilometers a second. I mean, that's fast. That's fast. That's fast. That's not light speed. fast it's not like speed fast it's about 0.00256 percent of the speed flight that's fewer knots

13:30Michael Stevens:than i expected yeah just two zero zero two wow okay so i mean that's small but i was expecting

13:41Hannah Fry:like 12 zeros right okay but the iss is fast look seven kilometers a second are you kidding me that's super fast you blink your eyes and you're traveled across london wow you're not quite half of london All right. Blink your eyes slowly. So NASA did this twin experiment in real life. They did. Here's the thing about it. Rather than it being a factor of two, which is what it was in the example I can view, they're aging twice as fast as you. Instead, one twin will be aging 1.0000000000003275 times faster than the other. There's all the zeros I was expecting. it's about 3.3 parts per 10 billion basically that's um that's how much faster okay say that

14:26Michael Stevens:again three parts per 10 billion yeah okay so for every 10 billion seconds yeah your twin on earth lives you only live 9 billion 999 997 exactly that's exactly that's still pretty cool it's

14:46Hannah Fry:pretty cool once you put it all in once you do all your calculations over 340 days which is how long scott kelly was was in the iss for in total one twin is between five and eight milliseconds older than his brother five milliseconds what can even happen in five milliseconds i mean not much not much if you want to pump it up there you can if you if you went up there for like three years Right. If you wanted to get a second on your brother, you just need to do a simple 110 years in orbit. Aye yi yi. We got to get those numbers up, NASA. You know what, Dave? You would come back and be like, wow, that's what I'm going to look like when I started this sentence.

15:29Hannah Fry:Yeah, right. My gosh. I'll tell you what, let's have a break and I'll do more when we come back. Excellent.

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17:58Michael Stevens:All right, we're back. So is this graph of like time dilation, it's not linear. Correct. So if you go half the speed of light, you're not halfway to not experiencing time at all. Correct. It's probably the graph's probably like that or something. Yeah, it's called the Lorentz factor. The Lorentz factor. That graph is probably shaped where it's like, oh, if you're going 0.002 % the speed of light, basically no change. But once you get up to like 80 % or beyond, then it's just like, whoa, now you're going to notice it.

18:30Hannah Fry:And then it flattens off as you go further on. Yes, you're basically at one, you're a factor of one, essentially, up until about half the speed of light, that's when it starts picking up.

18:42Michael Stevens:Really?

18:43Hannah Fry:Once you get up to 0.8, 0.9, that's when you're doubling, right? Right. So you traveling that fast are aging half as quickly as someone who's stationary. Correct. That's when your factor is two. But, you know, you get really close to the speed of light. You can have 10, a factor of 10. I mean, you can have any number you like. you get super duper duper close yeah you could you could be like 100 if you want right i just i just spend just a year up there and i'll come back and be like oh no everyone you love would be dead dead yeah yeah maybe don't do that but that's the theory anyway that's like einstein's theory of how one would age compared to the other but nasa aren't stupid right they sort of knew that they wouldn't be able to go fast enough yeah actually measure the difference of five milliseconds But what they did do, and the reason why they did this twin study, was to look at the impact of physically being in space.

19:38Hannah Fry:Not just because of general relativity.

19:40Michael Stevens:But all the other things. All of the other things. That have much bigger effects. Right. Like no G-force on your body for a year. Right. Between the two brothers. Probably more radiation. Right.

19:51Hannah Fry:And let me tell you, Michael, the effects of being in space are mental. Right. completely insane all right tell me what happened okay so one of the big things um one of the astronauts i got to meet he is not allowed to be in space anymore because being in space has changed the physical shape of his eye because of the way that the pressure changes so on the iss they have to have loads of spare pairs of glasses oh up there floating around your prescription changes

20:25Michael Stevens:Why do your eyeballs change? Because surely the air pressure inside can be made similar to Earth's.

20:33Hannah Fry:Right. It's not just about pressure, though. I mean, so your optic nerve swells. You get all these folds that appear. You get it's sort of like wet wallpaper, basically.

20:43Michael Stevens:Yes, because there wouldn't be gravity keeping the blood away from your eyes. The blood just is like, I'm going to be here. So, I mean, the whole shape of it changes.

20:52Hannah Fry:Yeah. And then and permanently so in some cases. There are some astronauts. There's one guy called John Phillips who went up, had 20-20 vision when he went up. And then when he came back, it was 20 out of 100. I don't know loads about how those numbers work, but I think that's not good.

21:06Michael Stevens:That means that what a person with normal vision can see from 100 feet away. Right. He'd have to be 20 feet away to see. OK. Yeah. Which is, I would say, bad. Which is worse than 20-20.

21:18Hannah Fry:So there were all these theories about why, what is it, what's going on? And I mean, something's definitely increasing the pressure on astronauts' eyes. But what is it? Is it to do with lymphatic fluid that's moving around in microgravity? And NASA calculated that the equivalent of two large plastic bottles of Coke shifts from your legs when you're in space towards your head. Wow. You've got a lot of fluid. I mean, that's sort of why they look a little bit like they're being choked.

21:49Michael Stevens:That's one of the main reasons I wouldn't want to go up. I think that if my face got all puffy and it was all congested, I would just feel so grumpy. They wouldn't invite me back anyway.

21:59Hannah Fry:No, I mean, you wouldn't do 340 days up there, would you? The thing is, is that they did a study into this in 2015. And they were looking specifically at people on the Vomit Comet to work out how much pressure was in their heads in that moment. And they were actually surprised to find out that intracranial pressure, right, intracranial, so inside, actually dropped during the periods of lower gravity. Okay. so the the current theory about why is all of the stuff going on in your eye so even though your face is getting puffy and your lymph is up in your face it's inside your head you're actually okay okay so the current theory is that it's your uh cerebrospinal fluid oh that is floating around this is the stuff that helps to cushion your brain yeah by the way and when you are not in in an upright position when you don't have gravity assisting you, that pressure is like all over the place and your eye ends up changing as a direct result of it.

23:00Hannah Fry:Jeez. Not good, is it? Why does your face change? Because of the lymph. Because of the lymphatic fluid.

23:07Michael Stevens:Your eyeball is harmed by this cerebrospinal fluid stuff because the optic nerve goes right into the brain. Exactly. So you're like, wow. Yeah, not good.

23:16Hannah Fry:there's more you're going to tell oh there's oh there's more not everybody is affected in the same way with their eyes it affects some people worse than others but we're talking we're talking the whole of the body is essentially like really not happy when it goes into space i can see that this

23:31Michael Stevens:would be a big challenge for long space flights very definitely we've got to come up with some artificial gravity yes maybe some more stuff you tell me what else goes wrong because this is the

23:41Hannah Fry:thing you just don't expect that gravity would make that much of a difference but it turns out that that the earth is the reason why our bodies function in the way that we do we are we are of

23:53Michael Stevens:this planet right we really are we really are this is our womb and our crib and our world and our grave and we think oh it would be so cool to have no gravity around and then our bodies tell us actually this is what i was built for what are you doing okay so let me give you some

24:13Hannah Fry:examples about the ways in which our body is built for this body temperature is so much harder to control when you're in space is it really than it is when you're on earth because if you're on earth right you lose most of your your body heat through through convection you've got air that's moving around you you've got cooler air you've got that sort of movement turning on a fan on a hot day all of that kind of thing. But on the ISS, there's no convection. Right. Because there's no buoyancy.

24:41Michael Stevens:Warm air doesn't rise. Warm air stays kind of around as an envelope around your body.

24:47Hannah Fry:So sweat sticks to your skin as well. And astronauts' temperatures when they're up in space rises by about one degree C. You're constantly hot and puffy. Yeah. And you can't see. Hot and puffy. A fan would help. A fan would help. agree because then you're mechanically moving the air humans have sort of outsourced a lot of our thermoregulation to the planet which i think is a kind of crazy idea there's also our circadian rhythm our sense of time our sort of concept of days and nights just goes completely all over the place when you're up in space because because that again is tied to the orbit of our planet around the sun right and the rotation of our planet um on its own axis so there have been lots of studies

25:35Michael Stevens:into this okay in the iss they can control their lights but they've got what 17 sunrises and sunsets a day so you have to just rely on the artificial lighting in the iss for night and day you do i want to write this down or a couple of things down because i i'm obsessed with the ways in which we offload our mind to calendars and computers and notifications and alarms. But you're right. Even before technology, our bodies were offloading functions to physics in general. Right. I need to dump heat. Luckily, convection exists. Thank you very much. I need to not have my eyeballs get all fricked up.

26:20Michael Stevens:Luckily, gravity will keep those fluids at bay that's the closest i've ever heard you get to swearing i can't believe that if my mom hears that i said fricked i said it again i'm gonna have to go to space

26:36Hannah Fry:just to get away but also this idea of like when to rest you know our bodies automatically know when to rest and that is something else that we have completely outsourced to the planet we have in the form of our circadian rhythms and daylight being the the primary driver of it There have been much longer, older studies into this about how messed up we get about the passage of time when we don't have those cues. One that I really like was in the 60s, a 23 year old geologist got put into a cave and then just sort of left there. This is in the Ligurian Alps, about 130 metres down. I would say not a nice place to spend some time.

27:19Hannah Fry:So it's like it depends on how introverted you are.

27:24Michael Stevens:Not really. No, it depends on how much you treasure your sanity. Yeah. Yeah.

27:28Hannah Fry:It sends you completely wild. So there's a one way phone line. He could call up and the team would not call down, but they were instructed to never mention the time or the date whenever he called them. And every time he woke or he ate or he prepared to sleep, he would ring them so they could log it. So they had a little clock that he wasn't allowed to see. And he just had the freedom to eat when he was hungry and sleep when he was tired and so on. Anyway, when he eventually came out, he had been down for 63 days. Would you like to guess how long he thought he'd been down for?

28:05Michael Stevens:Yeah. Hold on. My guess is that he thought he'd been down for, gosh, I don't even know, longer or shorter. i i'm gonna say he thought he'd been down for 90 days right which would have been my guess as well

28:19Hannah Fry:i would have i would have assumed that it was torture and that it just felt like time had stretched in the sense of psychologically actually he thought he'd only been down for 35 days whoa right half as long yes i mean it's the factor of two again it's the same as if you send your twin in a spaceship but except you haven't actually aged for real which i think is wild But basically what happened is his circadian rhythm stretched a little bit day by day by day by day. Right. Until he was living not 24 hour days, but sort of 30, 40 hour days and just not even realizing that that was what was happening.

28:55Hannah Fry:Wow. But the same thing, if you're not careful, without the like cues, without sort of the sense of time and like cues, you just cannot keep track of time. I mean, I think clocks sort of help this as well. As you say, you sort of outsource this to a clock.

29:09Michael Stevens:Yeah, yeah. Yeah. So if we lived in like this room with no natural light, but we had a clock, we could still say, oh, I think it's bedtime now. But I spent three days in an isolation room with no clocks. And the lights were on, weren't they? And the lights would never go off. Oh, and no meals were delivered because I didn't want to ever get any clue. So all the food was there with me. and I didn't ring anyone up because I was afraid that even if I rang up to be like, oh, hey, I've decided to go to sleep, that I could tell what time it was based on how groggy the person sounded. If it was like the main producer answering, it's the middle of the day.

29:43Michael Stevens:If it was some younger production assistant, I'd be like, it's the middle of the night, okay. And I had them surround the whole chamber with loud fans because I didn't want to be able to hear, that sounds like someone who's doing some maintenance work that wouldn't be happening at night. It's not night. So but I got immediately confused by the next day. I thought it had been two days or something. But that was only a three day isolation. So you thought it was longer? Yes. I thought, OK, it's definitely Sunday by now. And then down on screen, they're like, it's Friday at 11 p.m. Like I was just way off.

30:21Michael Stevens:I would take little naps and wake up and think, oh, man, it's been a whole night. But I couldn't turn the lights out. Did you have an eye mask? No, no. But I used like the pillows and the bedding. And I had a little there were cameras in there the whole time, too. So I had like a kind of a private ish toilet. But I just meditated. I didn't have I started playing with my sock. And I said, no, this is about nothing coming into my brain. And it felt like it whizzed by looking back. At the time, though? At the time, it felt like, is this ever going to end? Are they going to leave me in here? But I have no memories from it because nothing happened.

31:05Hannah Fry:Yeah. Oh, my gosh. I can't. I would worry that I would permanently psychologically damage myself in that situation. You are much braver. I hoped I would.

31:13Michael Stevens:The opposite of worry. But I'm fine, as it turns out.

31:18Hannah Fry:As it turns out, we think. Still too early to tell.

31:23Michael Stevens:Is it? Is it? All right. So circadian rhythms. Yeah. Your set of time anchored to the planet.

31:29Hannah Fry:Your bones also, by the way, another thing, extremely anchored to gravity. And what's happening is astronauts, they're losing bone at this unbelievable rate. They just don't need it. They just don't need it because you shouldn't think of your bones as though there's this storage unit. You should instead think of it as almost like a bank, right? Sort of like making deposits and withdrawals all the time. And when you stop requiring these withdrawals, it just sort of decays away, right? Just stops like remaking itself. The thing is, is that the way that your skeleton exits your body, do you know this?

32:06Michael Stevens:No.

32:06Hannah Fry:You essentially urinate it out. Oh, really? So it's put into the liquid waste. Yes, you're pissing out your own bones.

32:16Michael Stevens:That sounds kind of fun, actually. Not going to lie.

32:20Hannah Fry:But kidney stones are a really big problem in space because that's essentially one of the things, right? As you are urinating your bones away, they collect in the kidneys. Exactly, they're crystallizing in your kidneys. And the thing is, once you get back to Earth, you're still in trouble from all of this. So there was one study in 2022 which looked at astronauts a year after they'd been in space. And if they had been for six month missions, they still hadn't recovered a year after. Essentially their shin bones looked a decade older than they would have been had they stayed on Earth. We need that gravity.

32:59Hannah Fry:We need that gravity. Blood also, by the way, you are breathing out your dead blood cells as you're in space. You can tell because every time a red blood cell dies, it releases one molecule of carbon monoxide. Oh. And so you can tell how much blood is decaying in somebody by giving them a breathalyzer, essentially, by testing. More CO2 in their breath. Right. More blood cells die. And space anemia is a really well-documented thing that people are losing blood cells in space at a rate of one and a half times what you would be getting on Earth. Wow. One and a half times. Right. It's a lot. isn't it?

33:36Hannah Fry:So you're urinating out your skeleton, you're breathing out your blood, you can't see anything unless you've got the glasses that they've got on the ISS. You can't really sleep. You can't really sleep. You're hot. It's hot and you're sweaty, but your sweat's not going anywhere and your face is all puffy. I mean, this is like, frankly, doesn't sound that great, does it?

33:56Michael Stevens:No.

33:56Hannah Fry:One good thing is your DNA is all right. You're okay. Your DNA is okay. And we know this because there was an experiment where they took some mouse sperm, freeze dried it, popped it up to the ISS, left it there, you know, just sitting in storage for a little while, brought it back down to earth. Thawed it. Thawed it, used it for IVF, put it in a mouse. Absolutely, totally fine. Happy mouse babies. Congratulations. Grandchildren, mouse babies. Absolutely fine. Your DNA, fine. If it's in a sperm cell, no big deal. Happy. Okay. In your body, however, slightly different story. So while your DNA is, it's like a recipe of how to make the whole of you as a human, the way that those genes are expressed changes in your whole body, changes all of the time, right?

34:45Hannah Fry:When you sort of, I don't know, do a lot of exercise or even going back to the bone thing, right? When you're under gravity, there'll be certain expressions that are dominant over others. When they did the testing during the twin study, when they were testing Scott's genes in space and then Mark's genes on Earth, so they described it as like a set of fireworks going off in Scott's body. Scott was the one in the ISS. You would definitely expect to see some of these changes if you take a human and you put them in a really stressful situation. There's like lots of changes that the body is adapting to.

35:20Hannah Fry:But what was really interesting was just the sort of the scale of the magnitude and the speed of this. But also that when he was brought back down to Earth, about 90 % of these changes reversed, but 10 % of them lingered. They didn't go back. They didn't go back. The suggestion for why this might be the case is that he's exposed to so much more radiation than his brother was. and this matters because these systems are things that are involved with immune function with dna repair with like you know inflammation with oxidative stress with like bone formation all

35:57Michael Stevens:of this stuff and this was primarily they think because of radiation damage potentially right

36:03Hannah Fry:because the thing is is that mark kelly who was on earth his gene expression has changed too but because he'd lived a year sure so he also had this giant atmosphere uh protecting him right Right. From radiation. Right. Which is brother up in space, more exposed, much more exposed. And that brings us then to the biggest change of all. Oh, everything is like, OK, yeah, sure. You put your face is puffy or whatever. Your bones are pissing out your bones. Big deal. Big deal. Who cares? I call that Tuesday. But this one is like really dramatic. Do you know what a telomere is? Yeah, it's like the end of the DNA.

36:42Exactly.

36:43Hannah Fry:It's sort of, it's best described as the cap on the end of a shoelace. Okay, yeah. That protects it. When DNA is replicating itself, you know, when cells are dividing and replicating themselves, this thing gets shorter and shorter and shorter over time. And it's actually a really good way to assess how old somebody is. So their epigenetic age, as it were, as opposed to their chronological age. Right. You want long telomeres. Got it, yeah. You want nice and long. It means you're nice and young. You've got plenty more replications to go before you lose more and more of that shoelace. When Scott Kelly was in orbit, his telomeres got longer.

37:18Michael Stevens:Right? I was just going to ask, what can I do to lengthen my telomeres? Are there any like snake oil salesmen selling, you know, telomere lengthening cream? Yeah. NASA. Go to space and it's NASA. Whoa. NASA. So, okay. Do we have any ideas why?

37:36Hannah Fry:Why that's going on? Wow. Okay. I should also add, it sounds really good while you're in space. You've got nice long telomeres. Isn't that lovely? Kind of makes up for all of the other horrible stuff. When he came back down to Earth, the length of his telomeres collapsed and were then shorter than they would have been before.

37:54Michael Stevens:What a rug pull. What a rug pull. You had me ready to buy my ticket to the moon. Because this is it.

38:00Hannah Fry:Then it's like Einstein was right. You live longer when you go into space. As long as you don't come home. Oh. Ooh, I like that. I should say, it wasn't like all of them were suddenly way short, but he had an increased number of critically short two minutes. It sounds painful. It sounds critical, frankly. It does sound critical. It sounds bad. It sounds bad. Okay, so the question as to why this might be the case, there's another twin study where they took two pairs of twins and they took them to Everest. Two of the twins, right, from different families, went up the mountain. their brothers stayed down the bottom of the mountain and they did the same thing they were like doing all of this testing on them they had to like draw blood from them while they're at the top of the mountain which i think was apparently quite dramatic i bet yeah um anyway they saw the same thing that the telomeres elongated when they were at the top of the mountain the same thing as you get if you're on board the iss which is like a really strange thing but once again once they came down it didn't end well right so the suggestion as to why this might be the case There's only two ways that the human body can lengthen their telomeres.

39:09Hannah Fry:One, when you're born, there's this thing called telomerase. It's an enzyme that you find in embryos. You also find it in stem cells. I mean, it does exist, but just not in the normal run of things in the adult body. The other way that you can lengthen your telomeres is something called ALT, which is alternative lengthening of telomeres. And this isn't rebuilding. It's more that it's using a sort of DNA trick. It's like copying the sequence from another chromosome. it's extremely rare and you really only see it in certain types of cancer cells oh so why would that be happening to people in space and at the top of everest like who honestly who knows sort of seems as though what is happening is this ability for your cells to lengthen their telomeres is switched off but kind of remained dormant unless you push that human into a really extreme environment.

40:06At which point your body sort of starts acting like it's cancer cells. Or it starts acting like it's being born again.

40:14Hannah Fry:Like it's being, well, although it's a different, it's a different mechanism. It's a different mechanism.

40:18Michael Stevens:It's alt, not telomerase.

40:19Hannah Fry:That's a really important point. In both the Everest and the twin study when they were in Scott and Mark Kelly, it was the alt mechanism, not the young, cute little baby one that you get in embryos.

40:33Michael Stevens:Bummer for them.

40:34Hannah Fry:Bummer for them. This raises this really interesting question, because it means that we know that humans can lengthen their own telomeres. And this is like a very important thing if you're talking about lengthening people's lives. It's been demonstrated that you can force people into a situation where their telomeres lengthen. You also then, everybody ended up worse off, right? As soon as they had this happen to them, they ended up worse off. But going back to Einstein's idea of who ends up being older, the one on the spaceship or the one on Earth, this telomene thing, while you're in space, you maybe have a longer lifespan, but get back.

41:11Hannah Fry:The one who went to space is worse off. It's the opposite way around to what Einstein said. So to them, less time has passed.

41:20Michael Stevens:They may have aged visibly on the surface less. but deep in their dna they might actually be older might actually be older right if you actually put them on the rocket ship that went away from 10 yeah so who would you rather be the twin on earth or the twin in space on earth thank you very much much rather stay on it you mentioned earlier

41:43Hannah Fry:how are we going to get people long distance space travel if all of this stuff is going on yeah maybe they just need to be born in space yep maybe they just need to not have the history of

41:55Michael Stevens:of gravity in their midst okay all right so right if we start delivering babies in space they will be prepared for it yeah i mean there has been a bit of delivering babies in space just not human not human yeah they've done like rat babies i think fish as well oh fish or in the case of the telomeres we maybe maybe the change we kind of like but coming back we don't i mean yeah i think the only solution to this is that we we do some pregnancy we've got to do a lot more reproduction

42:28Hannah Fry:in space we need we need a maternity ward in space yeah get on it guys um and we started this episode by saying that astronauts are willing to uh to give themselves over for the study of science i think a newborn astronaut let's not be on the realms of what humans can achieve the newborn can't consent to being an astronaut it's all right they're doing it for humanity

42:48Michael Stevens:we can thank them later we can thank them later we'll find a way to lengthen their telomeres back yeah it's okay so those of us on earth have a lot to be very very grateful for and we have a lot to be grateful for to those who go out into space for us because they're living through time differently and they're changing their DNA for us.

43:15Hannah Fry:Thank you, astronauts. And thank you, listeners.

43:18Michael Stevens:Yeah. Whereas we do this show for you. And we love doing it. So thanks for being with us today. Be sure to subscribe to us on YouTube or follow us on whatever platform you're using to watch or listen.

43:33Hannah Fry:And field notes later in the week. We'll see you then. Bye-bye. Bye.

44:07We'll see you next time.

44:18I didn't like what you said, Odin pauses, about the future.

44:24Michael Stevens:This is the love story of real hinge couple Odin and Edward, written and read by me, Curtis Garner. Listen to the free audiobook now.