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