A discounted dark matter discovery

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Speaker 1: Hey, Daniel, as a particle physicist, what's the one thing you would most like to discover? If I could pick just one thing to discover? Yeah, like go wild? What's your biggest scientific ambition. Well that's a great question, but it's not actually that hard to pick. I would want to discover dark matter because it's such a big mystery. Yeah, it's one of the biggest open questions in modern science, and I personally really want to know the answer. Right, But here's a catch. What have you discovered what it is? But nobody believes you? Are you still interested? Oh? Man, like a modern day physics Cassandra. That sounds a little bit like torture. But you know, as long as I know the answer to the questions about the universe, I would still want to find out. So it's all about you. Science is personal. Hi am or handmade cartoonists and the creator of PhD comment. Hi, I'm Daniel. I'm a particle physicist and I'm desperately seeking dark matter. How desperate are you, Daniel? Not desperate enough to make up my data, but desperate enough to consider almost anything. You're desperate enough to move to Italy maybe to do your research. I do like that black pasta to have over there, so called that dark matter. Than yeah, it's called squid in tasta. Well they've discovered something delicious at the very least. But welcome to our podcast Daniel and Jorge Explain the Universe, a production of our Heart Radio in which we take a bite out of the tastiest intellectual questions of the universe. We true, we swallow. We explain all of it to you. Sorry, we serve it up on a dish and hope that you slurp it all up so you can think about the universe and everything in it. Because everything about the universe is wondrous and hazing, and it makes us curious. But it doesn't just make scientists curious. We think it makes everybody curious. That curiosity is wonderful and we want to cherish it and satisfy it by explaining to you some of the mysteries of the universe. And there are still a lot of mysteries out there. There are big chunks of the universe we don't know anything about, and there are big questions about the very nature of our cosmos and where we came from, and also what is even in it. That's right, Recently, scientists have cracked open the universe and discovered that there's a lot of stuff out there that we don't know, that we don't understand. There are new kinds of stuff out there, and it makes us desperately curious. What is it? Why is it? Why is there so much more of it than our kind of stuff? So many questions, so few answers. And is it delicious? Also? It's a big question, and everybody's fine, how much of it should you have on top of your pasta? And can you put cheese on it? Are there rules for what you can put parmes on cheese on? Absolutely, you can put parmesan cheese on everything. That's the rule, even sea food pasta. I feel like that's an unstage it a rule that's a whole other podcast episode. We can't get into that today. Man, We have to stay on topic seafood matter, seafood matters. But anyways, a big bite of the universe that we don't know anything about is a big mystery called dark matter. Of all of the energy and matter in the universe is something called dark matter, but we don't know what it is, and we would love to understand it. We would love to break it apart and figure out isn't made out of some tiny little particle we've never seen before. Is it lots of different particles? Is it something else which isn't even a particle. So physicists all over the world are using lots of different techniques to try to isolate dark matter and figure out what kind of particle it is. Yeah, because it's sweating all around us, right like it's it's everywhere. In fact, probably when you eat pasta you are taking big bite fools of dark matter at the same time. That's right, but fortunately your body doesn't digest it, so you don't gain all of that mass. But yes, dark matter, we think is all around us. It's part of the universe, but it's not. And evenly through the universe it's clumped together, just like our matter. So we think that our galaxy is swimming in a massive halo of dark matter, and that the Earth is flying through a wind of dark matter. And so physicists are using lots of techniques to try to discover this, looking at it colliding with itself in the center of the galaxy. We're trying to make it in underground collisions at the Large Hadron collider and also we're trying to detect this dark matter wind. Yeah, everybody seems to be looking for it, but it's really hard because you can't touch it or see it, and so far nobody has really got in a chest to figure out what it is, or have they. It's been an open puzzle for decades now in physics what is dark matter? What is it made out of? And everybody knows that the people who figure that out will go down in history as having answered one of the biggest questions in physics. And so it's definitely a big fat prize out there waiting for somebody to win. Yeah, and in fact, there is somebody out there who believe eves they've seen it and maybe even know what it is, and in fact they've been certain about this for about twenty years. That's right. Of all the folks out there looking for dark matter, there's a group in Italy that are very confident in their signal they've seen something that they think can only be explained by dark matter. Well, Italians being confident about something Danna that feels like pretty on brand. Yeah, So the big question is why doesn't anybody believe this experiment and the results they found. So today on the podcast will be tackling the question why doesn't anybody believe the DAMA experiment. Now, Daniel, this is DAMA, d A m A not Dharma experiment. Like in the TV series Lost, I feel like maybe there's a conspiracy here, Maybe the to are connected. Maybe Lost was actually about dark matter the whole time. Maybe yeah, yes, the monster watch me to ad have like this dark cloud, it could have been dark matter, It could have been in dark matter. They were physicists the whole time, and we finally put it together right here on the podcast and unlocked the mister Jack never had a chance. That's right now. It's the DAMA experiment, and it's had several iterations. It's called Dama, it's called Dama slash libra, but they're all fundamentally the same experiment in the same location, seeing the same amazing signal that looks like dark matter. But nobody seems to believe that. The consensus in the particle physics community is that DAMA has not discovered dark matter, and other experiments continue to hunt for dark matter in lots of different ways. So it's a fascinating question when one group sees something but nobody else believes it. What do you do? Wow? What does DAMA stand for? The d A comes from dark and the m a comes from matter, so da mash is just short for dark matter. You know, people can't be bothered to say the whole name dark matter, so they just squished it together into DAMA. Okay, they've just appropriated the first two letters for the acronym. That's right, and the follow up experiment will appropriate the other letters. It will be alright. So these folks in Italy twenty years ago claim they have found a signal for dark matter, and they've been pretty confident about it, but nobody in the field believed them. And I was wondering whether people outside the field have followed this, if it's trickled through into mainstream media, if people are aware of this incredible, unexplained signal and a dark matter experiment, because usual Daniel went out there into the wilds of the Internet to ask people, why does nobody believe the DAMA experiment discovered dark matter? So thank you to those of you who are willing to speculate on a physics question without googling. If you'd like to participate, and here your uninformed speculation on the podcast, Please write to us two questions at Daniel and Jorge dot com. Here's what people had to say. I'm not sure I've never heard of this experiment before. Then there are so many experiments right now and I'm not sure I heard about this one. I don't know. Um is it? Has there been no further evidence of dark matter that's been found? Have they not been able to replicate it? I imagine it's something like that, or maybe they like look back at the results and we're like, no, this could just be interference. Um, I don't I don't know. I would assume that the discovery of dark matter would be on par with the photo the first photo of the black hole ever taken, and that was from Page News. And because I haven't heard anything about dark matter being discovered, that maybe they didn't discover it, there was noise in the data, or they're still taking their time to calculate the results. If the Deema experiment did discover a dark matter, you think that we have more information about what it is, all right? Not a lot of brand recognition for Doma. No, I don't know. That means they should have chosen a better name, or they just need a better pr team. But because nobody in physics has really accepted their result, it doesn't seem to have trickled out to the wider community. I like this answer that somebody said, there are so many experiments right now, I'm not sure I've heard about this one, Like, do you feel like maybe you saturated the market with acronym experiments. Oh, there are a lot of dark matter experiments, you know, and they have crazy names. There's Zenon, there's lux those LZ, this co signed, this cogent, there's Zeppelin, this coupe, there's dark Side. These are just like, you know, half of the dark matter experiments out there. It's an enormous race. It's like a land grab. You know. Everybody's rushing to figure out what dark matter is, knowing that one of these groups might figure it out and not only win a Noel Prize, but you know, answer a deep question about the universe. So it's very tempting. It's a very hot area of research. Yeah, and it's a big part of the universe. It's twenty seven that's right. If you add up all the energy in like a random cube of space, then twenty seven percent of that energy is devoted to making dark matter, whereas only five percent of that energy is a the stuff you and I are made out of, and stars and dust and gas and most of the stuff that we think about in the universe. It's just a tiny little fraction. So discovering dark matter doesn't just like answer some abstract physics question. It tells us what the universe is, because it's much more than just what we're made at. Yeah, all right, So these folks have discovered dark matter, or claim to have discovered it, but nobody believes them. Daniel, Is that like a night mer scenario for you as a scientist, Like to discover something amazing and then have everybody think that you're crazy. It's one of several nightmares, you know. Other varieties of those nightmares are like you see something amazing, you published something, it makes a big splash, and then you realize that it was wrong. That's the kind of thing that happened to the Opera experiment that claimed that neutrinos were going faster than light, and then it turns out they had miscalibrated because one of their cables wasn't jiggled in the right way. They were Italian too, weren't they They were also Italian, although you know that could just be coincidence on not casting expersions on the Italian physics community. Lots of wonderful Italian collaborators on the outlets experiment with me. But yeah, that's one nightmare, and the other one is that nobody reproduces your result, and so nobody believes your result and you're left there with data that you believe that you just can't convince your colleagues, because remember, science is a human endeavor. It's by people and four people, and in the end you have to convince the community that what you've done holds up, that you've uncracked something real about the universe and not just an artifact of how you've done your experience. Yeah, I feel like that's that's a similar nightmare for cartoonist. It's like you write the perfect joke and nobody gets it. Would I still be satisfied? Like, I think maybe I would still be satisfied. I'd be like, yes, I wrote the best joke, but everyone else is a fool. Well, that's a good question for you as a cartoonist. Is there any correlation between how popular our cartoon is and how much you like. Alright, So Dama claims they saw dark matter and measured it. So Daniel step us through it. What exactly did they see? So what are doing is they're looking for a tiny little particles of dark matter. Now we don't know that dark matter is a particle, but it's just sort of the best idea we have is that matter is made of particles, and so we figure maybe dark matter is also made out of dark matter particles, some new kind of particle we haven't seen before. Now we think that dark matter is made out of matter because we see that it affects the rotation of galaxies. Galaxies are spinning really really fast, and without dark matter they would tear themselves apart and throw stars into interstellar space. So we think dark matter is real. It's made of matter. We're pretty sure that it's not made of any kind of matter we're familiar with. It's not made out of quarks or leptons, because if so, we would have seen it already and it would have affected the way the universe formed in very early moments. So we think that dark matter has stuff to it. We think it's probably made of particles. We think it's a new kind of particle. But the thing that makes it hard to find is that it doesn't really interact in the ways that we're familiar with. Yeah, because everything that has matter that we know about is a particle, right, Like, can you think of a way in which something could have matter but not like a particle or a particle field. Actually, there are a set of really fascinating ideas about unparticle matter, matter that's made us something that's smooth and continuous. We're going to dig into that in a podcast in a few weeks, which is really fascinating. But it's hard to think about. It's harder to think about than particle matter. And when you don't know what you're doing in physics, what you do is you start with the familiar, and until you've ruled that out as a possibility, you don't really take steps into the weirder, crazier options. And so we start with the simplest idea that, since everything we know is made of particles, maybe dark matter is also made of particles, but we don't actually know that. It's like you have to check off the obvious first. Yeah, you start with the simplest explanation. It's easiest, you know how to do it. It makes the most sense, and so you start there, you know. But we have a variety of folks working in a variety of different ideas, but this is sort of the main us. That's the first time I hear that phrase on particle matter. What did you just call it? Like smooth matter or creamy matter? Creamy matter sounds like something I would like to put on top of my pasta about dark creamy matter even better? Oh yeah, that sounds like something my wife would study. But the thing that we don't know about dark matter is how to see it. Because dark matter doesn't give off light, it doesn't reflect light. It's basically totally transparent to matter. You might think of dark matter and think of something black or dark that you couldn't see through, but it's the opposite. It's something invisible. Life passes right through it without interacting, except of course, that dark matter has gravity, and so it can bend space and slightly distort the path of light. Right, So dark matter doesn't interact with us. Our devices are stuff in the usual ways through electromagnetic forces. But people think that it may interact with us through other forces like the weak force. Yeah, we hope that dark matter has some way of interacting with our kind of matter, not just because we want to feel connected to dark matter, but because all of our experiments are made of our kind of matter, and so if we're gonna try to catch some dark matter, that we have to build our experiments out of something that matter will interact with. You Imagine like dark matter is flying through the room and you're trying to catch one, but you're using a catcher's mit that dark matter flies right through. Now you have no chance to catch a particle of dark matter. So we hope that dark matter does have some kind of interaction with our kind of matter. We don't know exactly what kind of interaction that would be. We're pretty sure it's not electromagnetic. We know it doesn't use the strong force. We're almost certain it doesn't use the weak nuclear force. So we're hoping there might be a new force, an undiscovered force, that connects dark matter with our kind of matter. It's like trying to catch a ghost exactly. It's trying to catch a tiny, tiny little ghost with a super tiny little catcher's mit. Alright, so then how did this DAMA experiment work? What are they using to claim to have caught dark matter. So there's a whole category of experiments looking for dark matter that are called direct detection. And what they do is they set up a big lump of material, usually very quiet material that doesn't interact very much with things normally, and they let it sit there underground under a bunch of shielding, and they hope that a piece of dark matter will fly through the Earth and bounce into a molecule in their lump of stuff. And when that happens, they'll get a little flash of light or in some cases a wiggle of an electron. And so they've built, you know, essentially a big catcher's mitt and they hope that a piece of dark matter will bump into it and give them a little signal. So that's the whole category of these kinds of experiments. And people use different kinds of material. Some use liquid zen on, some people use super cool semiconductors. This experiment is using crystals, crystals of sodium iodide, and so you put them on in like a box and your hope is that the dark matter goes through the box. But then somehow, you know, it causes your crystalline sodium to spark somehow, Yeah, you're hoping that dark matter can interact with the protons or the neutrons inside the atoms of these crystals, and then occasionally, one out of a trillion times, or ten trillion times, or a hundred trillion times, it will bump into one of those protons and give it a little boost. And the reason they choose this sodium idied crystal is that it has a special property. When it does get bumped, it tends to resettle back into its old situation, and it does so by giving off a little photon. So as you say it sparks, and physics we call that scintillation, So sends off a little photon and then you can catch that with these photo multiplier tubes. So you're basically looking at a dark crystal underground hoping to see a flash of mine, sorry, scintillating. Daniel and so Doma claimed that they've seen dark matter, that they have a signal for dark matter, but nobody seems to believe them. So let's dig into what they actually saw and why it's so hard to accept. But first let's take a quick break a right, Daniel, we're talking about the Dama experiment in Italy who have been claiming for twenty years that they found dark matter, but nobody believes them. And so they they have a big vat of crystalline sodium underground, shielded and they've seen it maybe interact with dark matter. So what exactly have they seen? Yeah, so what they see is really striking because what they're looking for are these little flashes of light. But of course dark matter is not the only thing that might give you those flashes of light. You could have like radioactive decay in the rock. This thing is underground in the Grand Sasso mind in Italy, and you know, the rocks nearby can have a little bit of radioactive decay or muans can penetrate the rock is sometimes and get all the way down to your experiment. So you have some sources of background that are not dark mattered. Isn't it shielded? Don't they put it behind big thick walls or something? And first of all, they have buried it in this mind under like you know, miles of marble and granite, which is awesome shielding. But then yes, absolutely they have the things surrounded by concrete and they have fiberglass. They do their best to shield it, but you can't always shield things completely perfectly, there will always be some level of background. So what they do is they look for something that only the dark matter could do, a signal that would look different if it was dark matter or if it was one of these normal everyday backgrounds. And the idea they had is to look for seasonal variations, like in in the fall, it tastes a little bit like pumpking spice, and then in the winter it tastes. In the spring it smells a little bit like flowers. No, they have this idea of taking advantage of the fact that the Earth is moving through the dark matter at different speeds, and when we moved through the dark matter at higher speed, they should see more dark matter interacting with their detector, and when we moved through it at lower speed, they should see less dark matter interacting with their detector. And that's just because we're going around the Sun, and so sometimes we're moving more with the dark matter and sometimes we're moving more against the dark matter. It's kind of like this old idea of the ether, kind of, isn't it. You know? If we are in a big cloud of dark matter and the Sun and the Earth is moving through it as we go around the Sun. Then you know, sometimes we'll see it going one way and then other times we'll be seeing the dark matter fly by another way. Yeah, it's very similar to the idea of the ether and that there's sort of a rest frame. All right. We don't know exactly where the dark matter is, but we imagine it's pretty smoothly distributed through the galaxy. Again, we don't know that it might have clumped, but dark matter is very slow moving, and so we think it's pretty diffuse. We think it's pretty much spread out. We also don't know how fast it's rotating. We think it's rotating around the center of the galaxy, just like our kind of matter is. But regardless of how fast it's rotating, you can imagine some rest frame for the dark matter. And then the Earth is moving in that rest frame because it orbits the Sun, and so some part of the year it's moving through it faster than other parts of the year. So their idea is, well, let's look for that. If this is dark matter or not muans are crazy, radioactive decay or something else, then we should see a seasonal variation in our signal. We should see more interactions in June than in December, because we're assuming that dark matter kind of has a velocity, and sometimes we're going against the current of dark matter and sometimes we're going with the current. Yeah, well, you don't have to assume that dark matter has a velocity with respect to the galaxy. It's our velocity relative to the dark matter that's important. So you can always just pick your rest frame. And if you pick your rest frame as the dark matter, then our velocity through that dark matter has to be changing year to year because we're orbiting the Sun and dark matter is not orbiting our Sun, right. But I think you have to also account for the fact that we're going around the galaxy, right, because if we were just going around the Sun then and dark matter was static, we would seed go the same speed by us. It would just be in different directions. It's it's more about the interactions with with our rotation around the galaxy to right. Yeah, you can think about it that way, you know, think about it like the Earth and the Sun are moving in the same direction relative to the dark matter or relative to the rest of the galaxy during part of the year, and in the other part of the year that you're moving the opposite direction. So the Sun is moving around the galaxy in one direction and the Earth is going the other way, because it's a different part of its cycle around the Sun. And so these velocities add up differently. Sometimes they add up to make a larger velocity relative to the dark matter, and sometimes they point in the opposite direction of each other, and so they make a smaller velocity relative to the dark matter. So like if you're just standing on Earth, you would sort of see dark matter sometimes flow past year really quickly and sometimes more slowly, like a dark matter wind. Yes, just like a dark matter wind. And so that's the idea is like let's look to see if there are more dark matter interactions in June then in December, because that seasonal variation would be what you expect to see from dark matter, which has this seasonally varying velocity relative to the Earth. And it has nothing to do with pumpking spice or maybe we're shorts in the summer. Tip. Well, you know, nobody understands the results of this experiment, and so maybe it is just the cumulative effect of pumpkin spice, lot pumping spice espressos because you know there in Italy, all right, So they've seen a signal. Basically, what is what you're saying is that they've seen a seasonal variation in their detection of dark matter according to sort of the motion of the Earth. So which might be like, hey, maybe dark matter is there and it is seasonal. Yes, exactly, they are seeing this seasonal variation. If you look at a plot of their results, the sort of number of sparks they see is a function of the day. Then you see it goes up and it peaks in June, and it falls down and it minimizes in December, and then it goes back up again. And you know, they've been running this experiment for years, which allows them to see lots of these cycles. And so it's not just like one little wiggle which could have been anything. It's definitely a cycle, and it's definitely annual, and it definitely peaks and dips in the right places. Wow. Yeah, they've been seeing signals for fourteen years. Like it's not a one time fluke that they see the pattern. It's like they've they've been measuring this and it goes up and down yearly for fourteen years. Yeah, for at least fourteen years. They've had a few iterations of this experiment. They've upgraded this, they've tweaked that, and so different plots have different numbers of years on them. But you know, almost twenty years ago they started seeing this signal. In the first few years people were like, nah, keep taking data, we don't believe it. But now they have these plots of just like wiggle and wiggle and wiggle and wiggle, and it's very unlikely that it's a fluke. You know, if you do the calculation, what are the chances of seeing this kind of wiggle from something which is actually flat, it's very very small. The threshold for discovering particle physics is five sigma, which means like, you know, one in millions of chances of being a background in fluctuation. But they have nine sigma, which is like almost unimaginable. So this is definitely a signal something is happening here. The remaining question is is it really dark matter? All right? So they have fourteen years of data, it's a pretty clear wiggle that there's dark matter, but nobody believes them. So what's going on, Daniel? Do people just don't believe their data? Are they suspicious? And is it that nobody has been able to see it in the same way. What's going on, Well, there's a lot of things going on here. Some of them are technical and scientific, and some of them are sort of sociological and maybe personal. Some people don't like pasta. Everybody likes pasta. Some people just don't put parmesan on their shrimp pasta, which is you know, unimaginable. That's a no no, that's a yes yes for me anyway. One problem is that they have not really shared the details of their data. Like they show up at conferences, they write papers, they show these results that look great, but they haven't opened up their box to show us, like the nuts and bolts how they analyze the data and shared a lot of details. And as you can expect, physicists want to see details. You can't just show up with your one discovery plot and say, look, we discovered it, let's all move on. People want to dig into it and understand it and think about how to double check it. And they've been pretty closed with their data, right. Well, it used to be that people who are super closed, but I think the more recent trend is for everyone to just open up their you know, files and let everyone sift through your numbers. Yeah, and you know, extraordinary claims require extraordinary evidence, and so you have to like respond to questions and give details when people ask you send a paper in for a review, for example, the reviewers can to ask for more experiments or additional plots, because what they want to do is make sure this is real, that it makes sense to them. Can't just be one pretty plot has to reflect something true about the universe, and so people want to consistent story, something that tells them this is really dark matter and not something else. So what's their case for not releasing the data? Are they under audit or something? I don't know. It's a bit of a cultural thing, you know. They show up at conferences, and as one dark matter theorists described to me, they seem aggressively uninterested in what other people think about their data. I think you're saying they're too cool. They believe their results, they're very confident in it, but they haven't shared enough details for other people to really gain confidence in their results. And so instead people have had to turn to other experiments, which should be sensitive to the same signal, to see if they can confirm right. Because maybe another experiment that with a similar setup, like with a vat of stuff waiting to interact with dark matter, would also see like these seasonal spikes. Yeah, you would expect so. And in fact, one of the other big dark matter experiments in the world, the zeno On experiment, is sitting in the same labs. Like they have this big holid out space under this mountain to do these kinds of experiments, and they gave part of it to the Doma experiment and part of it to the Xenon experiment. So the Xenon experiment is literally in the same place as the Doma experiment. So if there's any issues with like seasonal variations on temperature or something else, right, that's the concerns that there might be some seasonal source of background that they haven't accounted for. Zenon is in the same place, it's in the same lab. They do not see this seasonal variation they see, So nobody's seen this seasonal variation. There's several of these dark matter experiments, but nobody has seen this kind of variation with the year. That's right, there's a huge variety of dark matter experiments. They have different like active materials like liquid zenn versus sodium idide crystals. They're in different places around the world, they have different sensor technologies. Nobody has seen the results that's consistent with what DAMA has seen, and so you might ask, like, well, would they have seen these results? Is it possible for dark matter to only interact with this one kind of material and not the others? And so people have built like boutique theories of dark matters to try to explain this Dama experiment. Why DAMA would see it but Xenon wouldn't. Maybe it only interacts with neutrons and set of protons or prefers protons in one arrangement to another kind of arrangement, But nobody has been able to explain it. And in the meantime, people have built copies of the Dama experiment that are essentially the same technology, the same active material, the same kind of sensors, but just in different locations to try to double check DAMA really interesting. They've used like this crystalline sodium also, and they've put it inside of a mine and and do they see anything. They don't see anything yet. So there's an experiment in South Korea called Cosigne, and I have no idea what that stands for But they basically have duplicated the DOMAS experiments set up, but they don't see the results. Now, this is a difficult thing to do. It takes years of data to say are we seeing a flat line or are we seeing wiggles. So so far they only have a couple of years of data and they say their results are in quote severe tension with the DAMA results, but they also admit that it could be consistent with DAMA. They just don't have enough data yet. So time will tell if Cosign sees a wiggle or not. But so far the indications are that they haven't interesting. They want to see it happen before they co sign the certification. There, that's right, they want to see their own cosign in the data. Let's see their own wiggles. H alright. But still DOMA is pretty confident about their result. DOMA is pretty confident in their results. You know, they believe that it's dark matter. People have thought about all sorts of other sources of background, like maybe the rock heats up in the summer and it gives off more radiation and that leaks into the experiment, And they have all sorts of ways to monitor this and they don't see that kind of thing. So physicists in the community has been a lot of energy brainstorming possible explanations for what might explain is other than dark matter, more prosaic explanations, and so far they haven't figured out anything that they can point to that says, here's why DOMA is seeing this signal. It's not dark matter, it's you know, growth of plants on the top of the mountain is releasing something in June or something like that. But nobody's found that explanation yet. All right, let's get into what maybe DAMA is seeing in their signals of dark matter and why nobody believes any of these. But first let's take a quick break. All right, Daniel d DAMA experiment has been seeing a dark matter signal for fourteen years, but nobody believes them and nobody can replicate the results. So what are some of the possibilities heres of what they could be seeing. Do they have like a wire that's not connected right but only once a year, or is it could be the air conditioning in the room that you know, in the summer it kicks up more, or what could it be? So the sort of two categories of possible explanations. One are non dark matter explanations right, and ideas there are like they use nitrogen in their experiment, but it also has a little bit of argon in it. They surround the experiment with argon, and it could be that some of that are gone has seasonal variations in it, that is more activated during June than in December, based on based on what how how would the argon know what the season was? Well, it's not that an individual argon adom knows the season or like celebrates Christmas. It's that the amount of radio active aregon around the experiment depends on the season. The contaminant we're interested in here is are gone thirty seven, which is made when neutrons hit calcium in the soil or are gone thirty six in the atmosphere, and the neutron flux, the number of neutrons coming in to make are gone thirty seven has a seasonal variation due to the variation and atmosphere density, which it determines like how many it make it all the way down. But you know, people are really scratching their heads trying to think of crazy explanations, because of course, the folks and Dama are solid physicists, and they've taken care of all the obvious effects that have as much you know, climate controlling as they can manage in this environment to try to isolate themselves from any sort of seasonal variations. But you know, at the colliders were also sensitive to really really tiny effects. The phases of the moon affect the shape of the rock near Lake Geneva, and that affects the bending of the accelerator because it's under the rock, and people notice these things. What you see title effects in your data. Absolutely, the train schedules in Geneva affected the results of colliders in those tunnels, and so we can be very sensitive to very small effects. What how did how did the trains affect your the particle closure? Is it like the vibrations of the trains or just more people on campus at certain times. It's really amazing. Actually it was the electricity from the trains. Some of the extra current leaks down and made little gentle magnetic fields which actually influenced the operation of the collider. And so when you're hunting down tiny little explanations and you're trying to separate the ideas from like dark matter to other basic prosaic explanations. You've got to go all the way down the list for really small effects. All right, So what else could this signal they're seeing? What else could it be? Could it be, you know, some other kind of theory about how dark matter interact. It could certainly be, like there could be other ways that dark matter interacts. It could be that dark matter is something weird that we hadn't imagined before, and that's why we're seeing it only in these crystals but not in others. Now, the cosine experiments and the other ones that are replicating this make it pretty hard to follow that kind of explanation because they're basically a copy of DAMA and they don't see it. But put those aside, and let's say maybe cosine and the other experiments that are trying to replicate it just don't have enough data yet. People have cooked up theories that try to explain why dark matter interacts with sodium iodide more than it interacts with zenon, for example, like dark maybe dark matter pre first Italians or you know, less of vacation in Italy more than it does in South Korea. Yeah, and it also has to do with the mass because xenon is heavier, for example, than other elements, and so dark matter is very very low mass. If it doesn't have a lot of oomph to it, then it might be that it's just harder for it to push zen on than to interact with sodium iodide. And so people have come up with these theories of like very light dark matter, but those theories are also hard to explain because DAMA builds a new system in their experiment, one that should be sensitive to sort of lower energy results, and they don't see any difference in the low energy results and the original ones. And if there was very very light dark matter, they would expect to see a larger signal in these low energy recoils, but they don't. So people have been a lot of time trying to construct these fancy dark matter theories that could explain DAMA as dark matter, but none of them really hold water. So the consensus in the dark matter community is that DAMA is not seeing dark matter. They're seeing something else. We just don't know what it is yet. I guess the problem too, is that, you know, as we go around the sun, it's not just about more sunlight or less sunlight. It's also kind of there's other stuff going out there in space, right, absolutely, there are very variations and like how many Muans strike the Earth because Muans come to the Earth from cosmic rays and not just from the Sun, but also from galactic sources, like there are mus being created by other stars from from the galactic center that hit the Earth, and so that varies also with the seasons for similar reasons. And so it could be that they're seeing some weird dawk Off effect from these cosmic Muan seasons. It could be that nobody's really nailed that down yet, all right, So the consensus is that they're not seeing dark matter, but how they told DAMA that they that everyone thinks so, or is it's just sort of a like a background whispering, Like I don't think they've seen it. DAMA is definitely aware that their explanation is not accepted, but they are very confident, you know, they are sure that their experiment indicates the presence of dark matter particles in the halo. There's a quote from the long time leader the experiment saying, there is no alternative explanation for our signal. So they're very confident. They are aware that nobody believes them, but they're powering forward. You know, what do you think, Daniel, Are you aggressively interested or aggressively uninterested in this result? When I've heard about it, I was super excited. I was like, what a beautiful signal, what a nice experiment. I would love to believe it. But you know, before you believe something like this, you really have to see it replicated. Because we're not interested in one cute story of an experiment that sees a cool wiggle. We're interested in the actual story of dark matter. And if it's a real story of science, you should appear in more than one place. You should be able to see it using more than one technique, or you should at least be able to tell coherent story about why it's here and not there. Because the universe we think is a coherent story is that we should be able to pull it apart by looking at it from different angles. And this is so difficult to see that you really have to see it in more than one place before you believe it. Right. You don't want it to be weak pasta right, that's right. And so there's an other experiment being built in the southern hemisphere, in the Saber experiment, and it's very similar to the Dama experiment, except again it's in the southern hemisphere, and so it should have the opposite seasonal related systematic uncertainties because it's cold when Dama is warm, and it'll be warm when Dama is cold. If it's not related to the dark matter, but if it is, it should see the same seasonal changes, right, because it's moving along. It's it's about the movement of the Earth exactly, and so it's just another cross check, like let's move all temperature related things off by six months. The dark matter shouldn't change at all. So if they see a signal and it's shifted, that suggests that it's temperature seasonal variation thing. If they see a signal and it's not shifted, then that removes a lot of the possible explanations for temperature variations. It doesn't change things like you know, cosmic muon seasons, but it helps us sort of isolate what this might be, right, and did they find anything. They're still building it and so we don't know the results of the Saber experiment. It's being built in a gold mine in Australia, and everybody is very eager to see what that experiment has to say, all right, So I guess the answer is stay tuned. I guess nobody believes the DAMA experiment because it hasn't been replicated, and it could still be other things that cause it the signal. That's right, there's no coherent explanation in which DAMA is seeing dark matter and somehow nobody else is able to see it, and so the most likely explanation is that it's some weird source of signal that they haven't isolated yet. But it could still be. It could be that there are pockets of dark matter where the dark matter is interacting with some weird kind of matter that only exists around the DAMA experiment in Italy for some weird reason. But you have to have sort of crazier and crazier thoughts to explain this and to explain the lack of signal and all the other experience. I guess it's it's sort of the charge for both sides of people trying to prove this data, right, Like, it's it's getting harder to come up with excuses, but it's also getting harder to applicated. Yeah. Absolutely, but it's also a fun puzzle if you're an experimentalist, and you'd like to dig around in the data and understand where is this coming from? Why is it look this way and not the other way. It's not a deep mystery of the universe, but it is a fun question to ask, like what could be the source of this. It's a nice little detective mystery, and the person who actually figures it out eventually might not win the Nobel Prize, but they will scratch longstanding itch in particle physics, a dark a dark itch that really matters. All Right, We'll stay tuned and maybe in the next couple of years we'll hear news about whether it's a real or not, whether they deserve the Nobel Prize, or just a nice dinner with a nice glass of Italian one and plenty of parmesan sprinkled on top. All right, thanks for joining us, see you next time. Thanks for listening, and remember that Daniel and Jorge explained The universe is a shin of I Heart Radio or more podcast from my Heart Radio. Visit the I Heart Radio, Apple Apple Podcasts, or wherever you listen to your favorite shows.