The quest for dark matter

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1:0310,000. That's the number of new businesses that join Odo per month. Join Odo today at Odo.com. That's oddo.com. Welcome to Inside Sans from the BBC World Service. I'm Roland P. standing in for Tom Whipple, who's off recording a future episode at one of my favourite places. Home of the large Hadron Collider, where they discovered the Higgs boson, and where they hope to uncover many more secrets of the stuff of the universe. Though we've got our own mysterious stuff to talk about, dark matter which has frustrated physicists for decades. We've also got hope for corals, increasingly endangered in this warming planet, but hope in the form of probiotic therapy. Also, veteran environmental journalist Fred Pierce has reasons to be cheerful. When I was a young journalist, we were talking about acid rain. Nobody much talks about that now because we've fixed it, lead in petrol. We fixed that. We have quite a good track record of being able to address problems.

2:05Well, you can find out more about that later in the programme. Also, I'm joined by Kit Yees, Professor of Maths at Bath University, ever watchful of what's going on in the world of science. Thanks for joining us, Kit. What have you got for us? Yeah, so I'm going to be telling you a little bit about a new method of dating artifacts, and they're going to be telling you about polygons on Saturn. Polygons, polygos, poly here we are. The quest for dark matter just got interesting. On Tuesday at three in the afternoon, researchers on an international project called LZ reported that it had seen a ping in their detector some years ago that after a lot of scrutiny looks different from all the other thousands of ping they'd recorded and might just be the signature of a piece of dark matter passing through an underground line in South Dakota. The embarrassment for physicists is there's six times as much dark matter as there is the normal atomic stuff that we're made of, and which is studied at places like Sun. Astronomers know about it, they can see its effect on the motions of galaxies, and yet

3:08here on Earth, despite decades of increasingly ambitious experiments, there's been no sign of what it might be. One of the early experiments hunting the stuff was a detector sitting in a mine at Bulby on the Yorkshire coast called Zeppelin, the Z in LZ, whose operators later teamed up with the Luxe collaboration in South Dakota had been waiting for something to happen since 2021. Rewarded now with a single, inexplicable ping from inside their 7-ton detector. Kimberly Paladino, Professor of Physics at Oxford and also a member of that LZ collaboration, explained to me that when you're looking for something as mysterious as dark matter, you have to start with some assumptions about what it might be. Dark matter could be a lot of things, and the type that I particularly look for is some sort of tiny thing that has mass, but no electric charge, and no other known forces, except gravity acting on it, that there could be novel forces, and it could interact with things

4:11like the Higgs boson, so we know about it from gravity, but in our heads it's this tiny, tiny billiard ball usually that bounces into things, but doesn't interact with magnetism or light or charge for the most part. It's the most passive sort of experiment, then, that you do with this, is you just fill a vat with atoms and hope that one day one of these billion balls will ping off one of those atoms. Yes, and so we build a very special vat in that we don't want there to be other regular things bouncing around in it, so we make sure we make it with low radioactivity materials, we put it deep underground, we put vetoing detectors around it, and we use a target material that has very little residual radioactivity in it, liquid zen on, and then indeed we do just wait, but there's a lot of effort in that waiting. Well, I mean, I suppose a rare event when it happens, you've got to try and make sure that

5:13you don't miss it and that you get some information, and that when it happens, as I understand it, in this case, was actually back in June 2023. Exactly, it was back in 2023, and we really started looking at this data set in 2024, and so we've been doing an analysis on it for quite a long time. What we see are flashes of light in our detector, and some of this light comes from zen on getting off, scintillation light, so immediately when zen on gets hit, we see a flash of light. And then in our detector, we put a big electric field, and we extract electrons from the detector out into some gas, where it makes more light, this is kind of exactly how neon lights work, and we have detectors that sense that light. So we get two flashes of light that we interpret it back to being one atom of zen on that got hit. I mean, looking at the paper, in the time period you got 1700 other flashes of light and so on, what was it about this one that you said, yeah, this is intriguing.

6:13Well, that 1700 is, we've seen even more than that, that's even after some cuts against kind of really boring things. In our detector, we can tell if we initially hit the nucleus of the zen on atom or the electrons around it. And luckily, most of the types of things that are natural backgrounds for us, being electrons and high energy photons called gamma rays, they're always going to interact with the electrons first. And so those 1700 events were that type. This one looks really special because it looks like we hit a nucleus, and it only did we hit a nucleus, but we hit it with a lot more energy. Right, so it's kind of head on smack and sound, so you think of bash. Yeah, so it looks like the equivalent of 250 K EV of the energy in nuclear recoils. And this is, number, that doesn't make my sense, but for our types of low energy searches, this is a lot of energy. It's very little for the big, high energy particle physics colliders, but for the types of searches we do, our previous on dark matter searches really went up to about

7:1450 K EV in nuclear recoil energies. This is five times more than where we even planned our searches under the most boring types of dark matter that we were going to do before. So, well, this goes to something. I mean, this experiment has been running since, I don't know, this has been running for a few years, I guess. This has been running since 2021. And there have been experiments, smaller experiments like this going back decades? Yes, multiple decades. I mean, my point is, it feels like we've been waiting an awful long time for anything to happen. We have, and that maybe lends itself to thinking that this is a thing, that it is a more rare, more unexpected one. We have no idea. In my head, I have that old pop song, one is the loneliest number. We just can't tell with one event. And it's the strangeness of statistic. At the moment, can you tell anything about what this dark matter particle might be, if that is what you've recorded? Is it something that's light like an electron or something that's

8:17sort of about the same mass, let's say, as a proton? This is going to be much heavier. So, at least, kind of over kind of 200 times the mass of a proton might be even more like a thousand times the mass of a proton. So, it's a much heavier type of dark matter. And I think this is also why the particle physics community is really excited for this, because it links a lot more, the types of dark matter models that the lighter experiments it's stirring could look for. And indeed, I've seen already theorists coming out with great descriptions that this might be something like a Higgsino. Look at up on Wikipedia if you want to find out more. That was Kimberly Paladino of Oxford University and also of the LZ collaboration and of a proposed success approach called X-LZD, which might take up residence at Bulbymine in Yorkshire. Anyway, it's a next week for us to have, on hand, a mathematician, Kit Yates from Bath University to talk about the statistics of these experiments, because Kit, you know, a single ping is for me more like an

9:22anecdote than data, but Kimberly seems to think you can make out more of from it than just that. Yeah, so, and the scientists who are doing these experiments suggest that they might see an event like this, just purely due to known background processes, so non-dark matter processes. On average, once every 200 times they run this experiment, so a 0.5% chance of this result happening even if no dark matter were detected. So, you know, to put that into context, it's like tossing a coin eight times in a row and you get eight heads. That's the sort of unlikeliness that we're talking about if the coin is genuinely fair. It's unlikely, but it's not impossible. And like you say, one event just isn't really quite enough. So the way that dark matter is likely to be confirmed is if they see similar results in the same facility or even better at other facilities around the world, which were given more confidence that this wasn't just a fluke. Well, I could tell that Kimberly is certainly pretty excited by the fact that they're detected and things. So, well, fingers crossed for them. So, what we're thinking of such cosmic things, Kit, one of the stories you've brought along

10:26involves mathematical figures in space. Yeah, exactly. So, for a long time, decades, in fact, scientists have known about a seemingly mysterious hexagon that encircles the North Pole of Saturn. It's this remarkably stable six-sided phenomenon, should we say, which has persisted since at least when it was first spotted by the Voyager machine in 1981. So, over 40 years now. And there are lots of competing hypotheses about how the hexagon on the North Pole developed. But interestingly, if you read the Wikipedia page for the Saturn hexagon, which has its own Wikipedia page, if you read it a couple of days ago, you would have read that there is no corresponding hexagon on Saturn's South Pole. But a paper just came out this week in the journal Science Advances, which reports the discovery of a ten-sided or decagonal atmospheric wave in circling Saturn's South Pole region. So, the author's first spot of this in 2023 using the Hubble Space Telescope and by 2025, it was well enough established to be visible from ground-based observatories. As a mathematician, you must be absolutely fascinated by the sort of regular shapes. I could imagine some kind of circular wind

11:30or cloud pattern doing that. But having corners in it seems bizarre. Yeah, that's exactly the question that fascinated me. Why does Saturn have these polygonal waves? And the answer is because the planet is rotating. And it causes a jet stream to form very much like the familiar jet streams that we have on Earth. We have one which encircles the North Pole and another half the world where encircling the South Pole. And people probably know the jet stream isn't just one continuous jet of wind that blows from east to west. The wind path actually meanders in large north South oscillations called Rossby waves. This is what gives us our variable weather patterns in the UK and much of the rest of the Northern Hemisphere. And actually the same thing is happening on Saturn. Only on Saturn, the jet stream is really narrow and strong because Saturn rotates very quickly. So instead of looking like a looping wave, the peaks and troughs get flattened out and they look like a polygon when they're viewed from above. And those corners aren't actually sharp corners. They're just the peaks of the wave. And they're actually in reality quite smooth. They just look sharp because of the huge scale of the wave. You're listening to Inside Science from the BBC World Service. Tell us what

12:32science you think we should be investigating. Our email address is inside science at bbc.co.uk. I'm Glenn Washington. This is Snap Judgment from KQED. When everything is falling apart, what do you do? Hurricane Helene shut everything down. No roads, no cars, no way through, but his daughter was getting married. And somehow some way, he was going to walk her down that aisle. All systems down. A new Snap Judgment mini-series from KQED, wherever you get your podcasts.

13:33Prepare to deck upgrades. So leave it to the pros who will get your jobs done well. Angie, the one you trust to find the ones you trust, find a pro for your project at Angie.com. Now, probiotics are all the rage in help yourself. Health, bacteria in the yoghurt's typically that boosts the vitality of the micro-biome in your gut that sits there doing good things for us. The surprising news this week is the pro-biotics may also be good for corals, which are increasingly being denuded and threatened with extinction by bleaching events triggered by recurrent marine heat waves. What I call microbiologist, turned ecologist Erica Santoro, who's been testing the probiotic treatment on reefs in the Red Sea. That's a confess I've never even thought about the possibility of a coral microbiome. Every single organ is an on planet host back to year and all the micro-organisms. This is not different in the ocean as well. The corals also host a big amount of bacteria and micro-algae. It is a big

14:38mix and super-forder micro-organisms that live together with these coral hosts. We call these a hollow biome because they actually work together and they're both together as well. You mentioned the micro-algae. These actually live inside the coral animals and give them the color but also help power them through photosynthesis. But when there's a heat wave, they get lost don't they from the corals and that's a trouble. The coral itself, they are translucent. So the tissue are not the color that we see but that is given by this micro-algae that lives inside the coral tissue. So they host the micro-algae inside and the micro-algae produce a lot of compounds that are going to be used by the corals and nutrient and exchange the corals protecting this micro-algae. The thing that happens when there is any stress like the temperature is raising in the ocean, there is a trigger which like cause a lot of stress in the micro-algae. They produce a lot of compounds that are stressful for everybody including

15:43the coral host and a couple of process can happen there that these algae can be expelled by the host they can escape, the cell can just like break apart and like a these mutualistic relationship, they just break up. But somewhere along the way you thought that there was some way that using probiotics, in other words adding extra bacteria to unhealthy coral would help them. Yes, so the idea here is we look at the coral and try to understand the beneficial relationships that exist between the coral and the microorganisms and we isolate and manipulate those beneficial ones. Not giving anything that is extra or different to the coral but something that's already native to them. I'm wondering how you do this because it's a bit different from taking a teaspoon of yogurt. So what's the process? Currently we are doing these in the ocean so

16:43we are upscaling through on the lab setups and bringing to the field. We cultured those beneficial cells, we increase them in number and put them in syringes and apply on top of the coral. So this is going to create kind of a cloud of beneficial bacteria on top of those colonies and we apply these often so we guarantee that those corals are going to actually take those offering to them. What difference did you see between the treated and the not treated coral? So we observe first of all some proxies that are related to coral health, one of them in observing like how good they are doing these photosynthesis and what is up these were decreasing along the time when we don't treat them. But when we applied the probiotics with time they were actually recovering. They were actually having like a better photosynthesis in those colonies that were treated with probiotics. So we saw good results. I mean if you are seeing these coral being

17:43more resilient. So presumably somehow these bacteria are being taken up by the corals but do you actually have any idea of what they're doing that makes the symbiosis with the micro healthy inside? How does it all work? Yeah that's also like one of our questions but while we know so far they are probably working on kind of this is stressing a little bit the coral. So when there is like this bleaching or some thermal stress there's a lot of reactive oxygen speeches that are produced by this micro algae that makes these relationships and the whole whole of bio into like very stressed. They don't have time to recover and to kind of buffer those reactive oxygen speeches and those bacteria can actually buffer that. They produce some enzymes and some products that can actually buffer these. So this is one mechanism. Another mechanism is these those strains that we select they really they can fight against pathogens. So when we have like some stress moments like the microbiome of those corals they can change and get unbalanced. That means that some

18:48opportunistic bacteria that live nationally in the microbiome can increase in numbers but those probiotic strains can fight against those pathogenic and opportunistic ones and can kind of reduce theming numbers. Corals in the world cover a greater area than just the United Kingdom. This would be if it became practical a huge effort. What are the steps before you even get that far? We have been observing like these positive effects and beneficial effecting different ischoro specias for different reasons to protect against bleaching mortality even like against diseases. So we are really getting excited about like the results and we see that it really works. Now I think our question is not if it has an effect or not but how to apply this in a in a big scale. Erika Santoro is based at King Abel University of Science and Technology and the results of her experiments were just shared in the journal cell reports. And we're continuing with a tone of

19:51optimism here on Inside Science with the book, despite it all, a handbook for climate hopefuls. With the UN Environment Programme declaring that the idea of limiting global warming to 1.5 degrees is now a busted flush and CO2 being pumped into the atmosphere as far as ever, maybe we need to think about what progress the human race has made in protecting the planet. And that's what veteran environmental journalist Fred Pierce has attempted in this short tone, one of six works on the short list for the Royal Society's coveted Travedi Science book price. Challenge one for Fred was to sum up his book in just half a minute. I spent 40 years reporting on the bad news of the environment and there's a lot of very bad news but these things are still on our own hands and we sometimes forget that. I think many environmentalists become overtaken by the scale of the problems and they give up really. Either that or other people just think there's no problem but actually is all to play for. There are many doors that we can push that will open whether they're technical

20:53fixes or simply the ability of nature to come back. It's one of the things that I find myself reporting more and more given half a chance given a bit of spare ground. It will come back. It will restore itself and there's something joyous about that. I have to say Fred, you know, having read your reporting over the years. As you say in the past it used to be this river is running dry, this forest is dying, this species is no longer there. Are you actually the same Fred? Pierce, have you been taken over? Is this the wisdom of age? Well, maybe it is the wisdom of age but it is the wisdom perhaps of thinking well we have an alternative but to fix these things and we have to look for the things that will work. None of this says that the problems that we face aren't really serious whether it's climate change or biodiversity loss or that many other things that we talk about so much. What we have to look for solutions we don't really have any other option. I mean, one of the chapters tackles the population time bomb and the idea that there were going to be too many people and that was a massive issue back in the 80s and 90s of the last century and in a

21:59sense your message seems to be that actually birth rates are coming down without all the aggressive interventions that were being discussed back then. Yes, I remember going to conferences in the 1980s where environmentalists were saying we have to force people not to have babies, you know, have to be a draconian population policies but what we've subsequently learned is that people are voluntarily without any of those horrible population policing activities are brought down their own birth rates, their own fertility rates really because most people have discovered that in the old days you had to have four or five children to be sure that two would get to grow up and produce the next generation. Now with much better health services or over the world and much better hygiene, most people only need to. So there's a positive story here without being pan-grossed in about this. We can make things better. The other side of this equation is the ecosystems. Again, in your book you often talk about the resilience of ecosystems if they are left alone to do their own thing rather

23:03than intervening. Yeah, I've looked quite a lot at the people talk about reforesting the world. Clearly we've lost a lot of forests. Clearly that's a huge amount of damage to the climate and to biodiversity and many other things. It's a major issue but we can have more trees. We are having more trees and very often I think that's going to happen not by having a mass spree of planting but simply giving nature room to regrow. I've seen it in North America, the Appalachians in fact are a great example because that was more or less deforested to destruction a hundred years ago. Now there's a huge regrowth that's been going on and the great majority of that has been natural regrowth. We begin to see that in parts of the tropics as well. Even in the Amazon you'll see that trees come back given half a chance. There are technical fixed stories as well. There's a big chapter in the book about how, well again when I was when I was a young journalist we weren't just talking about population bomb. We were talking about acid rain. Nobody much talks about that. Because we fixed it, lead in petrol, we fixed that. The ozone hole. We haven't fixed that but we're

24:06on the way to fixing that. So we have quite a good track record of being able to address problems when we deal with it and maybe we're on the way to doing the same thing with climate change. Along with all your travels, huge number of anecdotes in the book. Is everyone that's sort of at the time you thought was hopeless beyond, beyond repair and actually you've seen that encapsulates your optimism. I encapsulate my optimism. Actually I think in the climate change story because it is the biggest story. It's the one that involves everybody and everywhere. And I remember going to the earth summit in 1992 where all the world's leaders were there and they passed the climate change convention which said we were going to prevent dangerous climate change. Well we haven't done that but right then they didn't know how they were going to do it. Winterbines were just a few kind of windmills on a hill in California. So the power was something for powering satellites where you had no other option and nobody talked about electric vehicles at all. And now all those are mainstream and cheap and becoming the dominant technologies.

25:12If you'd asked me in 1992 whether in three decades or so we would have got as far as we have, not sure that I would have thought we would. We're not there but it is a surprise to me how far we've got. Fred Pierce on his hopeful despite it all which is published by Granta. Despite my inner ear I really couldn't help being swept up by Fred's optimism. There is a place I guess for accentuating the positive as opposed to dwelling on despair. Yeah I think we all need a little bit of that. What I thought was really interesting is the idea that we need these optimists as well as the pessimists. You need the pessimists to highlight the problem and the optimists to provide the hope. So I think if you go too far down the doom spiral of pessimism then you get to the point where you believe there's no hope which causes an action as a sort of positive feedback like a vicious circle. But I think it's also important to note that optimism isn't the same as denial. So suggesting we don't need to do anything because everything's fine because that also leads to an action. So I think the being optimistic about the potential to fix

26:13climate change isn't the same as denying its impact or its potential to the left unchecked. Keep on trying. Yeah absolutely. Before we finish kit you've got one more story for us. Yeah this is about dating artefact so our listens will probably be aware of a number of different ways of detecting art forgeries by determining the age of the artefact who like radio carbon dating works for things like canvases or frames on paintings which contain organic matter. But what if the artwork isn't a painting but it's a sculpture or if it's made of clay? Well there's a technique published this week in the proceedings to the National Academy of Sciences based on a technique which uses the magnetism of the particles in the clay. So the idea is that the magnetic field of the large particles in the clay artefact if it were fired today they would point to where the earth's magnetic north pole is today. But if something was fired you know 800,000 years ago if we were doing things like that back then then the earth's magnetic field was reversed then and its magnetism would point towards the south pole where the magnetic north was then. But on its own that

27:16isn't enough because if you change the orientation of the artefact then that would change the direction of the magnetism. I was going to say just after turn it around and that bombs your uncle. Exactly right so that's not enough but fortunately the magnetism of the smaller particles of clay never actually really settles but instead it accumulates keeping a sort of record of the magnetic field they've experienced over time. But this accumulated magnetism can be erased by gently heating the object that the key is that the longer it's been around the higher the temperature you need to erase that accumulated magnetism. So by heating the object and determining whether this is what's called viscous and remnant magnetism has been erased or not you can determine how old the object is the higher the temperature required to erase it the older the object. I mean if they tried this actually on actual artefacts from the past? Yeah they have they've got a couple of nice pictures actually with the paper where they've tested older artefacts and more recent artefact and the research is hopeful that they can start using this method for museums to you know apply to

28:19articles which are of debated authenticity and even as evidence in trials about alleged forgery of these sorts of artefacts. Well they probably won't find anything that old to date in my house I'm sure it'll be very useful though in museums. Thank you very much kit for joining us. Kit Yates is professor of mathematics at the University of Bath and that's it for this program you've been listening to inside science on the BBC World Service with me Rowland P's. Tom Whipple will be back as usual next week. Plus 24 packs of Canada Dry or 7-Up 12-ounce cans are 499 limit one with digital coupon. Enjoy fresh and delicious savings for every meal. Hurry in these deals won't last. Visit vans or Albertsons.com for more deals and ways to save.

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