How exercise shrinks tumours and starves cancer; Weird molecules found on comet 3I/ATLAS; Einstein v Bohr on the nature of light

0:01This episode is brought to you by Google Chrome. You think you know a browser, but Gemini and Chrome? That's new. It can help you with practically anything on the web, like restoring a vintage motorcycle from a 50-page restoration block, or finally break down that long article you've had open for weeks. Gemini and Chrome is here for it. Ready to make anything online make sense? There's no place like Chrome. Check responses set up required, compatibility and availability varies 18+. On the show this week, we are learning about how exercise slows the growth of cancer. Yeah, it's real news you can use this week.

0:32It turns out that when you exercise your muscles, they start growing faster and their demand for food outcompetes the demand from cancer cells. So cancer grows more slowly when you exercise. In mice at least. But it may be the same in humans and we're going to get into that. We also hear about some molecules discovered on the comet 3i Atlas and we've discussed what this means or what it doesn't mean for the origin of life. If there are things like methanol, which is this by-product of lots of the chemical reactions that are needed for prebiotic molecules, then maybe that suggests that other star systems have more of these pre-bartic molecules than even our own solar system and maybe increase the chances for life.

1:06And we're also getting into the details of an extraordinary quantum experiment that settles an old argument between none other than Albert Einstein and Niels Bohr. Just those two. Just those two. The fact that we're actually able to do it now, I think that really would blow Einstein and Bohr's minds.

1:25Welcome to The World, The Universe and Us from New Scientist. I'm Dr Rowan Hooper. And I'm Dr Penny Sarchet. we know that regular exercise can reduce our risk of developing cancer and also that it improves survival among people who have cancers but it's only now that we're starting to really unpick why the various mechanisms that kind of underpin that effect but this is big deja vu vibes coming because we did discuss this a few months ago yeah we did and that study that we were discussing then was all about the gut microbiome which seemed to be key in this effect so to recap back in july A team in Pittsburgh found that when mice were sedentary and had aggressive melanomas, they had bigger tumours and worse survival rates than more active counterparts.

2:09But that was not seen, that sort of beneficial effect was not seen in exercising mice that had been given antibiotics or raised in sort of sterile germ-free environments, suggesting that it's the gut microbiome that mediates that good effect you get from exercising. and what they found in that experiment that was quite intriguing was that there's this molecule called formate that's made by bacteria the levels of it rise in the body with exercise and that formate seems to boost the power of an immune cell that then targets cancer so that was really exciting this kind of mechanism okay I do remember this now yeah because it was the first time that we'd seen a direct mechanism for linking how exercise benefits the positive outcomes for cancer.

2:54Yeah and just to show that things are really straightforward especially with cancer scientists have now found another mechanism that seems to play a role here and this one involves muscle cells almost kind of out-competing cancer cells for glucose during exercise and glucose is this key energy source we need it when we exercise to fuel our muscles but also it's really gobbled up by cancer cells it's essential for tumours to grow and Alexandra Thompson is here to tell us more. Alex, what did the study involve? So it involved scientists at Yale injecting breast cancer cells into 18 mice, 12 of which were obese, which can worsen the progression of certain types of cancers.

3:33So half of the overall 18 mice were free to run as much or as little as they wanted to on an exercise wheel. And then four weeks later, the scientists looked and they saw that the obese mice that chose to exercise had tumours that were 60 % smaller than in those that didn't have access to the running wheel and they were also slightly smaller than those in the non-obese sedentary mice. So regardless of whether the mice were obese or not exercising was a really good thing. Correct. And how did they determine how glucose comes into it? Well they observed that just 30 minutes of exercise is linked to an increase in the uptake of glucose in the mice's skeletal and cardiac muscles and a decreased uptake in tumours.

4:16Right so there really does seem to be competing for the resource between the muscles and the cancer. But how do the muscles, why do they win over the tumour? Well, in another part of the experiment, the researchers analysed the mice genetic activity and they found that more than 400 genes in key metabolic pathways change as a result of exercise, making muscle tissues metabolise glucose more. And what's more, exercise was also linked to a downregulation of a protein called mTOR, which is involved in cell growth. So that might also be limiting tumour growth as well. And so we always have to stress that this is a mouse study.

4:55And it's actually quite a small one as well, isn't it? Yes, but having said about the mice, the researchers say that these metabolic pathways are very similar across mammals. So they probably also similar mechanisms going on inside us. And also similar changes in gene activity have been reported when people with cancer exercise. And so seeing as metabolism happens in all tissues and is affected by the microbiome, these two mechanisms that we've been talking about, you can sort of see them maybe interacting, being synergistic. Yeah, I think there's probably multiple mechanisms that cause exercise to have this effect.

5:29I think what's most exciting here is that it feels like the activity that the mice had is quite achievable, providing if somebody has cancer, they need to be well enough and strong enough to do that activity. And it should probably be signed off by a medical professional. But about 10 years ago, there was another study in mice that described how exercise boosts the immune system's attack against cancer. But they were running up to seven kilometres a day, which is like marathon mice. Whereas in the latest trial, they were free to run as much or as little as they wanted to. And we still saw this great effect.

5:59That did strike me that when you said earlier that the obese mice that chose to exercise, like what was behind that choice? We don't know. We don't know. What was going on in their heads? But the running wheel was mobile. Well, they hadn't locked it, so they just chose to hop on. So some were intrinsically thought, I fancy doing some exercise, and some were less so. Clearly. I do worry, though, the 30 minutes, it sounds achievable, but that's for mice. What would it be if you scaled it up to a human? Many hours, potentially. Yeah, OK. We're probably going to scale it up a little bit, yes. It did make me wonder that, you know, this characteristic of cancer cells, they're so glucose-hungry.

6:37I wondered if that might be why obesity, or one reason why obesity is linked to cancer. Hmm. Is it? Well, so I don't know. There are several more established mechanisms. So, for example, fat cells can produce hormones that can drive cell division. Fat can lead to inflammation that can raise the risk of cancer. And there's things like mTOR. But there is a link between obesity and diabetes. So I do wonder if this kind of a barren regulation of glucose or freely available glucose might have a role. And maybe we'll see more about that in the future. Yeah. So but back to this exercise study, and I know it's small, it's in mice, but it is really is really promising.

7:14I mean, you hear anecdotally about people who do loads of exercise after they've been diagnosed with cancer. And sometimes you do hear these really positive stories and outcomes that they have. And I've always been in awe of that, of those stories when, you know, to have a diagnosis and then go out and really do all this exercise. and you just think, well, they must be so tired and worn down by it, but maybe that's the treatment that's doing it. But if we can find more strength in this link, this apparent link between exercise and the out-competing cancer, that is really exciting and promising.

7:54Yeah, it's kind of empowering, isn't it? But then at the same time, it's not going to solve every case of cancer. and you hear about people feeling like they've been blamed for not beating their own cancer. So there's that kind of narrative to be sensitive about too, isn't there? As you know, The World, the Universe and Us is a podcast that's all about science and technology, which is why we're big fans of Nick Gray and G-Tech. Nick is the founder of G-Tech, the British design company that took on some giant global brands. And he first built a cordless sweeper in his garage back in 2001, which is still going strong today.

8:27G-Tech is all about making life easier with things people love to use, which is why they're the UK's most trusted home and garden brand. So whether it's an air ram vacuum, a nifty garden tool, or just something that gets rid of all those pet hairs on your sofa, G-Tech have got you covered. Plus, if you're like us and care about the planet, you'll love all their interchangeable components and batteries. G-Tech stands for Innovation, Simplicity and Engineered Perfection. Find out more at gtech.co.uk. Now we return to a story that we first spoke about on this podcast a few months ago, and that's the Interstellar Object Comet Alleged Spacecraft 3i Atlas.

9:05And this is only the third object to visit us from another star system that we know of anyway. And since we first spoke about it, astronomers have been gathering a lot of data on the comet, and it looks pretty weird. Alex Wilkins is here, and Alex, you've been covering this for us for months. What have we learned? Yeah, so to cast minds back, we first saw this thing in July. Since then we've been pointing the world's most powerful telescopes at it So we've got the James Webb Space Telescope We've got Hubble which has been there for decades We've also got all these powerful telescopes in Chile And we've basically been finding out really interesting and quite strange stuff about it The first thing to point out is it's not an alien spaceship Probably Breaking news Yeah, it's functioning very much like a comet Or at least what we know comets function Or how comets function in our own solar system So I guess it's more likely to be a weird comet than an alien starship.

9:55That seems most likely, right? Yeah, exactly. And all the things we've seen about it suggest that it is a comet. So it appears to have something called a coma around it, which is this ball of gas and ice that we know comets in our own solar system have. And the coma looks similar in some ways to comets in our own solar system. It has lots of water vapour in it, but it also has really high amounts of carbon dioxide, which is very unusual. It has around 16 times more than average comets we see in our own solar system, which is strange. The same team that found that high level of carbon dioxide also found that it was giving off these complex or relatively complex carbon-bearing species.

10:33So things like hydrogen cyanide and methanol. And for methanol in particular, which is this very simple alcohol, not the kind of alcohol that you can drink. You'd get very sick drinking it. You'd get blind, I think, drinking methadone. Yeah, I think that's the one. And these levels of methanol were the highest we've seen pretty much in any comet ever. Again, making it very strange. Another early study found that there were traces of nickel vapour in the coma as well, which suggests that maybe there's metal coming from the core of the comet also. So these molecules aren't from inside the comet itself, they're around it?

11:06Exactly, yeah. So as the comet kind of comes in towards the sun, it will heat up. and then a lot of these molecules that will be locked in ice will do something called sublimate they'll turn into a gas and we can kind of say if we're seeing these things in the coma then they're likely coming from the nucleus it's not exactly a kind of one-to-one relationship but it does give us a really good idea about what is inside three-eyed atlas i spoke with one researcher who modeled what would happen if some of the water inside the meteorite became liquid and he said that if it reacted with metal species in there like iron it would produce loads of methanol which is exactly what we're seeing so he says maybe the fact we're seeing methanol in the coma means that we can then infer the presence of metals inside the comet itself it's also giving us hints about what other star systems might be like as well which we can't measure directly we can see the light coming from them and infer what species might be in there but we can't go there ourselves so it's possible that other star systems like the ones that this comet might have come from might be really high in methanol unlike our own solar system or might have more hydrogen cyanide or more carbon dioxide and that has really fascinating implications for life as well because if there are things like methanol, which is this kind of byproduct of lots of the chemical reactions that are needed for prebiotic molecules, then maybe that suggests that other star systems have more of these prebiotic molecules than even our own solar system and maybe increase the chances for life.

12:25I want to get into that. It is really interesting. And we saw on the asteroid Bennu that was sampled in 2020, that was the OSIRIS-REx mission. That's an asteroid that goes around the sun. so it's not passing through it just goes around the Sun between Mars and Jupiter and they found all sorts in there amino acids formaldehyde and all five of the nuclear bases that make RNA and DNA have been found on that asteroid and then now they've also found ribose and that's a sugar that's part of the rung that makes up the the helix of RNA and DNA so there has been this sort of this is really telling us a lot about the origin of life from NASA and from some other scientists.

13:08And you've just said that as well. It's interesting about origin of life. But is it? Well, because what I think what's cool about it is that it tells us that these organic molecules are everywhere. That is really interesting. But it doesn't tell us about the origin of life, which needs an energy source and a gradient like you get on a hydrothermal vent or something like that agreed there are many more ingredients that are needed for life as far as we understand it but we still don't know where those basic building blocks come from or how they're formed we know there are certain chemical pathways but it's possible and lots of scientists kind of think that maybe these ingredients were delivered by asteroids and comets early in earth's history that these pre-biotic molecules were made and forged in the the comet of asteroids like Bennu or maybe like 3i atlas and it just kind of tells us we can trace the story of how life began from the very kind of building blocks made maybe elsewhere from earth and then it was delivered to earth where all of those other conditions that you mentioned exist yeah i i think it's more likely that those complex molecules can just self-assemble pretty much anywhere and i don't think i think the delivery thing is a bit of a red herring and also if you think about those classic experiment experiments like Uri Miller or your zapping mixtures and seeing if amino acids crop up increasingly like you say these things were just being made everywhere possibly and so that's not the key question about where life comes from or how it came together.

14:36No I think the question isn't where where do these organic molecules come from it's rather how do the organic molecules that are everywhere we look how do they become organized into life? Yeah oh we've got a cover feature this week which is actually related to this because so often in origins of life the question is well you've got to have genetics you've got to have information that's one one core bit of life you've also got to have metabolism like you say energy gradients and actually doing stuff and trying to work out how those came together is really difficult and the our cover feature suggests that it was prions that did that wow well i'm looking forward to reading that but back to this very odd comet 3i atlas alex how much can we really trust that what we're seeing really is a comet it's not had the same journey as other comets in our solar system right it's not what we normally expect no not at all it had this really sudden activity when it came close to the sun so it went from pretty much not giving off much at all to suddenly spurting out all of this carbon dioxide and now methanol hydrogen cyanide and that happened really quickly and that's just that has been knocking around intergalactic space for quite a long time and probably not encountered any other stars that have heated it in that way there was one early study that said that it might even be eight billion years old which is possibly twice as old as the sun and and in that time it would have been blasted by cosmic rays for a long time it might have kind of developed this hard outer crust which means that what we're seeing now is the result of its travel through space and not actually how it was made or what's inside it it's amazing how is it propelled like was it flung out of its its origin system by some event and it's still just going on that there are a few different ideas that the current theory is that it was in the outer reaches of its own solar system which suggests maybe a smaller gravitational disturbance rather than kind of passing close by its own star but it's likely there was some sort of gravitational slingshot that flung out but we don't really know no and i love the idea of it just knocking around interstellar space and accidentally now it's coming through our solar system pretty unlikely isn't it yeah it just seems like a yeah exactly a freak event um and it's still passing through our solar system right now so we can find out more can we yeah exactly so it it reached its closest point to the sun in late october this thing called perihelion and it's currently exiting our solar system.

17:02It's just peeked out behind the sun so before we could only see it with things like the James Webb Space Telescope which are in orbit around Earth and ground based telescopes couldn't see it but now we can see them with all of Earth's telescopes so astronomers are scrambling to basically find everything they can before this leaves and never visits us again presumably. I recently re-watched Oppenheimer, the Christopher Nolan film I think it was last year about the development of the atomic bomb and I was really intrigued by the relationship between Oppenheimer and Einstein and also between Oppenheimer and Niels Bohr but what the film doesn't really get into is the relationship and the intellectual friendship between Einstein and Bohr themselves and that's just so intriguing because they are absolute physics titans of the 20th century.

17:51You know, Einstein in 1905, his work showing that light was a particle But then Bohr came along and suggested that light, well, actually, no, it's a particle and a wave. And they argued about this for years. And in 1927, they dreamed up an experiment that could settle their argument, their dispute. But back then, it was almost impossible. It was amazing they even conceived this experiment. It certainly was impossible to carry it out. But now, 100 years later, it has been carried out. And Jacob Aaron's here to talk about this. Jacob, first give us a recap about Niels Bohr, will you? Yes, as you say, he was one of the titans of 20th century physics, one of the founders of quantum mechanics.

18:35In fact, he created the first quantum model of the atom in which electrons can only occupy specific energy levels, so it can be quantised. This actually only worked for hydrogen atom, the simplest case, but it was still good enough to win him a Nobel Prize. And he had this kind of ongoing friendly rivalry with Einstein, who, despite being another founder of quantum mechanics, kind of hated the whole thing altogether. So when Bohr said that light could be a wave and a particle, Einstein was completely insistent, no, only the particle model was correct. I just went down a little Bohr rabbit hole ahead of this.

19:09There's so many to choose from. So I didn't realise that, so just watched Oppenheimer, didn't realise that the UK had its own nuclear weapons programme, it's called Tube Alloys. That was going on before the Manhattan Project. and basically what happened was Bohr had fled Denmark, occupied by the Nazis, to Sweden and then he was spirited out of there to Britain and he started working on this tube alloys project but the Brits couldn't afford a nuclear weapons programme while they were fighting a war. So the whole project was subsumed into the Manhattan Project and there is this little bit in the movie Oppenheimer where Bohr does arrive at Los Alamos, he greets Oppenheimer but I didn't know the British had this nuclear weapons program ahead of the Manhattan Project.

19:55Well, it's not quite the same level, but I also have my own random Bohr fact, which is that he was also a footballer, played for the club Academic Bolt Club alongside his brother, Harold Bohr. Harold was also a mathematician, and in fact, he was a better footballer than Niels. He played for the Danish team, national team, in the 1908 Olympics, and they won silver. Wow. Proud parents in that family. Oh my God, yeah. Yeah, imagine. So, okay, let's go back to this Bohr-Einstein argument. So it's all based around the double slit experiment, Jacob. So give us another recap of that, if you will. Yes.

20:30So in the double slit experiment, you're shining light onto a narrow pair of slits positioned in front of a screen. And if light were a particle, as Einstein said, the screen ought to show a blob of light sitting behind each slit. But what we actually see is an interference pattern of dark and light stripes and this shows that light is more like a wave that's spilling through the slits interfering with itself so it's not like a particle but the weird thing is we see this interference pattern even when you dial the intensity of the light all the way down so that you know only a single particle of light a photon is actually passing through the slits and you know what's what's going on here is kind of the whole uh question of quantum mechanics Bohr's explanation for this was the notion of complementarity and he said it was impossible to see the photon's particle-ness when it was exhibiting wave behavior and vice versa but it still had this both particle and wave nature.

21:30And so Einstein came up with an experiment that he thought could counter Bohr's argument because he hated it so much right? Yeah so Einstein suggested so okay let's have our usual double slit experiment and we'll place another slit just before the experiment, and this slit is on springs so that it bounces ever so slightly when a photon passes through it. And then based on the motion of the springs, that could determine which slit of the double slit the photon had passed through. And Einstein said this would mean, okay, you'd be able to see the photon behaving as a particle, so traveling through a specific split like a tiny ball would but you would also see the the wave behavior from the interference pattern and that would contradict Bohr's idea of complementarity but Bohr hit back he said actually no according to Heisenberg's uncertainty principle you would only be able to measure the change in the slit's momentum from the the recall by essentially losing information on the position of the slit so this is this is Heisenberg's uncertainty principle that you're always trading off momentum and position and that means that it would become more fuzzy and that would destroy the interference pattern so einstein's idea wouldn't work so i can't wait to find out who was right um but but first they couldn't actually perform this experiment to figure it out at the time no so they had this great big argument about it back and forth but had no way of actually you know doing the experiment and seeing who was correct but now with the technology we have 100 years later, we can.

23:08So Chao Yonglu at the University of Science and Technology in China and his team created a version of this experiment in which a single atom cooled by lasers acts as that movable slit on springs. And by tuning their lasers, they could control the momentum as precisely as they wanted. And this revealed that Bohr was in fact exactly right. Knowing too much about its momentum destroyed the interference pattern from the photon. But what's really weird is they were able to go beyond what Bohr had even predicted and find this sort of more in-between regime where they sort of have a bit of the information about the recoil but also kind of a blurry version of the interference pattern.

23:50So really we're very much seeing the photon as exhibiting both wave and particle properties at the same time. I cannot get my head around the precision of this experiment with a single photon and a single atom. It's incredible, isn't it? What a piece of work. Yeah, so Lou told our reporter Carmela Padavik-Callaghan that the team really wanted to perform this experiment at the ultimate quantum limit. And I think, you know, they've really achieved that. You know, one thing to say is this isn't actually telling us that much that we didn't already know about quantum mechanics, or at least what we think we know about quantum mechanics 100 years on.

24:27You know, we're fairly sure this is the way we would expect photons to behave. But, you know, the fact that we're actually able to do it now, I think that really would blow Einstein and Bohr's minds. Yeah, it might actually persuade Einstein as well, right? I don't know. He was pretty stubborn. Well, we'll give him that, shall we? Generously. that's all for this week thanks to our guests and thanks to you for listening we'll be back next week goodbye for now bye

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