Dark matter and the end of answers

Five-sixths of all the matter in the universe is this invisible stuff called dark matter, and scientists barely understand what it is. So what happens if we can't answer arguably the biggest mystery in the universe? One physicist decided to quit because he started asking questions that went way beyond what he initially thought science was for. Guest: Joseph Howlett, reporter at Scientific American To watch this episode on video, find us on ⁠Netflix⁠! For show transcripts, go to ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/unxtranscripts⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ For more, go to ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/unexplainable⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ And please email us! ⁠⁠⁠⁠[email protected]⁠⁠⁠⁠ We read every email. Support Unexplainable (and get ad-free episodes) by becoming a Vox Member today: ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/members⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ Thank you! Learn more about your ad choices. Visit podcastchoices.com/adchoices

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Speaker 00

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• 0:39Speaker 01

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• 1:10Noam Hassenfeld?

  Take a look around you. Wherever you are, the table, the TV, your own body. At a basic level, it's the same stuff as everything else. And everything you see if you look out the window, or even further out, the ocean, the rest of the planet, the sun, stars. It's all matter. We can see it, we can feel it, but all of that stuff is just 15% of all the matter in the universe. The other 85%, 85% is something called dark matter, this kind of invisible, untouchable matter. But we don't know what it's actually made of.

• 1:54Noam Hassenfeld?

  Scientists have been trying all kinds of things for decades to try and figure out what it is, but so far, they've got nothing. So what does it mean for science if we can't find it? If we can't answer arguably the biggest mystery in the universe? Today on Unexplainable, I'm going to talk to a physicist who spent years looking for this stuff and then realized he couldn't do it anymore. So he quit because he started asking questions that went way beyond what he initially thought science was for.

• 2:31Noam Hassenfeld?

  And stick around to the end of the episode for an update on some dark matter news.

• 2:50Noam Hassenfeld?

  Joseph Hallet, thanks for coming on the show.

• 2:53Speaker 03

  Thanks for having me.

• 2:54Noam Hassenfeld?

  So you are, you are a science writer now. You used to be a physicist. What made you want to be a physicist? Like, what got you so excited about it in the first place?

• 3:05Speaker 03

  Yeah, I mean, I, I always liked these kind of big questions, like the questions humans have always asked, like, how'd we get here? What is stuff made of? I had that instinct always to go deeper, right? Like, if you're in chemistry class, you hear that everything's made of atoms. And then you hear that atoms are made of electrons swirling around a nucleus. Then you hear that the nucleus is made of protons and neutrons. And then you ask, well, what are those made of? They say you have to take physics.

• 3:29Noam Hassenfeld?

  Right.

• 3:29Speaker 03

  So if you do this enough times, you end up with a PhD in physics. And then you very quickly learn that there's a lot of things that we don't know. And you run up against that.

• 3:37Noam Hassenfeld?

  Favorite stuff.

• 3:38Speaker 03

  Exactly. The unexplainable. And when you actually become a working scientist, that's the stuff you work on, right? So the decision I had to make is which of those questions to work on. And for me, it was obvious that it was going to be dark matter. At least like when I heard that everything I had been learning about is only one-sixth of everything, at least for the picture I had of what science is supposed to do, that came as a real shock.

• 4:02Noam Hassenfeld?

  So it's been a while since we've talked about it on the show. We had our first episode of the show on dark matter, but what is dark matter? And, and why did you get so excited about it?

• 4:12Speaker 03

  Yeah, so dark matter is a thing that we know is there, but we don't know what it's made of. Really, it's thanks to Vera Rubin. In the seventies and eighties, she catalogued how fast stars are moving around their galaxies. So she looked at all the stars, they're orbiting the center. This is the way we're orbiting our sun, right? But the problem with every galaxy is that all the stars are moving way too fast, especially the stars on the outside. I compare it to like a race car on a racetrack, right? If a car is going around the track and it speeds up and speeds up and speeds up, eventually the tires won't be able to hold it on anymore and it'll fly off the track.

• 4:49Noam Hassenfeld?

  Yeah.

• 4:50Speaker 03

  And when Vera Rubin looked at all the stars in all the galaxies, she was like, they're all going way too fast.

• 4:55Noam Hassenfeld?

  Like, they should all fly off into space.

• 4:57Speaker 03

  They should, everything, including our sun, should be flying off into space because there's not enough stuff inside to be holding it at the speed that it's going at, right? So either we don't understand gravity and all the, the laws of how much stuff it takes to hold a thing in going that fast, we're wrong about. Or there's stuff we're not seeing that's gravitating, that's extra glue, like, holding that thing in. So you, if you imagine a race car, it can go way faster if you like stick a stake in the middle of the track and tie a rope to it, right? And it's like, there's some additional thing we're not seeing that's holding everything in, that's holding all the stars in.

• 5:34Noam Hassenfeld?

  And that's dark matter.

• 5:35Speaker 03

  That's what we call dark matter, just because we can't see it and we have no idea what it is. It's just a blanket term for this missing stuff.

• 5:44Noam Hassenfeld?

  So, so it's matter that interacts with stuff via gravity, right? It, it can pull in these fast-moving stars at the edges of galaxies via gravity, but we can't see it. Why can't we see it?

• 5:59Speaker 03

  We don't know that. I mean, we just know that whatever this stuff is, it doesn't interact with light. It's somehow invisible.

• 6:04Noam Hassenfeld?

  And, and when astronomers, physicists do calculations, the only way to have enough of this stuff to make sense of the way galaxies move, that's how they get to 85% of all matter is dark matter, or five-sixths of all the matter is dark matter.

• 6:21Speaker 03

  Yeah, that's where this number comes from, this, why I say five-sixths of the universe is missing. It's because that's how much stuff you would need to add, how big that cloud would have to be, to explain how fast the stars are moving. And since Vera Rubin, we've established it in all kinds of other ways. Like, you can make maps of the mass distribution of faraway things by looking at how they bend light around them. Our earliest picture of the universe, which is called the cosmic microwave background, it's like the light that was released very shortly after the Big Bang, when the universe began to cool, that light tells us what matter there was then. And it's very clear that there was five times more of some stuff we don't understand.

• 6:57Noam Hassenfeld?

  Right.

• 6:57Speaker 03

  Like, there's all of this additional evidence and all of it aligns with this five-sixths number.

• 7:02Noam Hassenfeld?

  So why is it still such a mystery to us?

• 7:05Speaker 03

  Yeah, it's because we don't know what it is. I mean, like, it's a big, it's a big thing not to know. Especially if you're like me, right? If you're asking these questions like, okay, what's in that? What's in that? What's in that? If you keep doing that, like, you want to know what stuff is at a fundamental level. Dark matter, if you picture some galaxy, it's like this shadow realm that's on top of the galaxy. You can't see it and it's only like interacting with it through the way it tugs on things, right? All together.

• 7:31Noam Hassenfeld?

  Through gravity.

• 7:31Speaker 03

  But what is that a cloud of, right? I'm not satisfied that we know what dark matter is if we don't know what that cloud is.

• 7:39Noam Hassenfeld?

  But scientists are trying to figure out what it is, right? They've been researching this for decades.

• 7:46Speaker 03

  Yeah, so one thing to say is that like shortly after Vera Rubin, there were these two explanations. There's either we're wrong about gravity, or there's this missing stuff. Over the decades, that first hypothesis has kind of fallen apart. It's very hard to adjust gravity in a way that makes everything make sense, all of this evidence we have.

• 8:03Noam Hassenfeld?

  We're pretty sure we understand gravity pretty well.

• 8:06Speaker 03

  It's a good theory.

• 8:07Noam Hassenfeld?

  Yeah.

• 8:08Speaker 03

  So there's this missing stuff. And there was this kind of arms race. There was people trying to build detectors on Earth to detect this stuff that we know is going through us all the time, but we don't know what it is, right? So the next question is like, okay, let's figure out what it's made of by trapping it in a lab, right? That's how science works, right? Like you, you, there's this missing part of the universe, so you develop a theory that can explain it and that gives you a testable hypothesis that you go build in a lab. And what's great for us is that theoretical physicists in the eighties already had an idea for a type of particle that might exist in the universe that exactly explained all the dark matter.

• 8:46Noam Hassenfeld?

  Yeah, they, they were trying to map all potential particles, right? This is the, the standard model of physics?

• 8:52Speaker 03

  Yeah, the standard model of physics is the 17 building blocks, the Lego pieces that everything we know about is made of, right? So it's the quarks that make up protons and neutrons. Electrons are one of these particles. And together of these 17 particles build everything that we can see, right? But It only explains one-sixth of everything, right?

• 9:11Noam Hassenfeld?

  Right.

• 9:11Speaker 03

  Like, we know that it doesn't account for this extra stuff, so we know that it's incomplete.

• 9:15Noam Hassenfeld?

  And we had some kind of predictions, like, there may be empty spots on the standard model, and what you're saying is that one of those empty spots would be the dark matter particle.

• 9:26Speaker 03

  Yeah, it was really convenient, and physicists like convenience, right? It's Occam's razor, like, the simplest explanation is the one you go for first, right? And this is what's great about this theory they had in their desk drawer, is that it interacts gravitationally, it goes through us like a ghost, right? Like, we knew about dark matter, but very, very rarely, on rare occasion, the ghost becomes corporeal for just a second and smashes into one of our atoms.

• 9:52Noam Hassenfeld?

  Wait, that's the theory?

• 9:53Speaker 03

  That's the theory.

• 9:54Noam Hassenfeld?

  Okay, okay.

• 9:55Speaker 03

  This particle that they had in their desk drawer, it was, it explains all the dark matter, but in addition to its gravitational pull, there's a very, very, very weak coupling to the normal stuff in the universe. So, dark matter's going through us all the time, very, very rarely, imperceptibly rarely, one of those particles smashes into one of our atoms. We don't feel it.

• 10:13Noam Hassenfeld?

  Got it.

• 10:14Speaker 03

  But that means that you can build a detector of regular matter to detect that. And that was key, right? Because that meant that, okay, we can, on Earth, look for this particle.

• 10:23Noam Hassenfeld?

  And this is where your research enters into the picture, right? This is when you became a physicist. What kind of experiments were you working on? What kind of experiments are out there to find the dark matter particle?

• 10:34Speaker 03

  I mean, the way things went down is Vera Rubin and others convinced us that there's this missing stuff. And then theoretical physicists said, oh, we have an idea for what this missing stuff might be made of, and you can build a big detector. A detector is just a tank of atoms that they light, the tank lights up when one of the atoms gets hit, right? I said-

• 10:57Noam Hassenfeld?

  Gets hit by a dark matter-

• 10:59Speaker 03

  By anything.

• 10:59Noam Hassenfeld?

  Okay.

• 11:00Speaker 03

  So, when we get hit by a dark matter particle, you don't notice. You have a tank of liquid xenon, for instance, which is a cryogenic liquid, it's kind of like liquid nitrogen that you play with in a lab.

• 11:09Noam Hassenfeld?

  Okay.

• 11:09Speaker 03

  When a xenon atom gets hit by a particle, it lights up. So, that's all a detector is. So, they said, okay, if I put a detector on this table, it would see stuff all the time, because there's particles coming from space.

• 11:19Noam Hassenfeld?

  Got it.

• 11:20Speaker 03

  So, you would never see the dark matter particle that interacts once in a year or something. So, it wouldn't work here, but it would work underground. So, I was working to build this big dark matter detector underneath a mountain, one of Italy's biggest mountains.

• 11:34Noam Hassenfeld?

  Okay.

• 11:35Speaker 03

  Yeah.

• 11:35Noam Hassenfeld?

  So, dark matter would go through the surface, it would go all the way into this underground lab or wherever.

• 11:44Speaker 03

  Yep.

• 11:44Noam Hassenfeld?

  And the idea would be that maybe there we could see dark matter-

• 11:47Speaker 03

  It would go through-

• 11:48Noam Hassenfeld?

  -hit some other atom.

• 11:49Speaker 03

  It would go through this whole mountain in Italy, it would go deep into the center of the mountain, it would go into the lab, it would go into the detector, and 99.999% of the time, it would go through the detector without doing anything. But the idea is, once in a blue moon, if you wait long enough, you make the detector quiet enough, one of those dark matter particles will become corporeal, just at the right moment, smash into a xenon atom, light the detector up, and then we say, okay, we've found dark matter, we know it's made of these particles. And then the problem's solved, right?

• 12:18Noam Hassenfeld?

  Yeah, tell me about the mountain, the lab, like, what does this look like in Italy?

• 12:24Speaker 03

  It's an interesting commute, like, you pile into, like, a little Fiat, and you drive down these mountain roads, you go on the highway, and the highway has a tunnel that goes through this mountain, but we don't go all the way through the tunnel, we go halfway through the tunnel, and then there's this turnout for the scientists.

• 12:39Noam Hassenfeld?

  It's like a little secret?

• 12:40Speaker 03

  There's a little secret entrance with these Italian guards who mispronounce your name, and, "Olet," they called me, yeah.

• 12:47Noam Hassenfeld?

  Okay.

• 12:48Speaker 03

  And, you know, you show them your badge, you go through, and then you're in this cavern, it's like a big underground cavern, it's kind of chilly, it's expansive.

• 12:58Noam Hassenfeld?

  Is that ceiling like cave?

• 13:00Speaker 03

  It's cave, yeah. Yeah, yeah, yeah, yeah, it's cave. I mean, it's finished in different places, but you know that you're underground. It's a little claustrophobic if you're someone like me, but we'd never see the sun, basically, because you'd stay there most of the day, when you're really working at it, yeah.

• 13:14Noam Hassenfeld?

  Wow. I think I have a photo of you, is this you in Italy?

• 13:19Speaker 03

  Yeah, this was, I think, 2019, something like that, underneath the mountain, closing the giant detector. So, you can see it's kind of the size of a very small sedan.

• 13:28Noam Hassenfeld?

  This is the actual, so like, this is full of xenon?

• 13:30Speaker 03

  It will be full of xenon, so where I'm standing will be water, basically, and this thing will be contained in vacuum, because it has to be very cold, right? But first, you have to build it and close it up, and that's what we're doing in this picture.

• 13:45Noam Hassenfeld?

  What do you think 2019 Joe is feeling at that point, looking at that detector?

• 13:50Speaker 03

  I mean, it was really invigorating to be, like, building the thing. Our experiments were working really well, they were getting very sensitive, and we were about to make that jump to cover the region of predictions that was exactly what the theorists predicted. It felt not probable, like, I don't know that I would have put money on it, but there was optimism around, yeah, definitely.

• 14:17Noam Hassenfeld?

  Then tell me when you started to feel differently.

• 14:22Speaker 03

  Yeah, so we ran this big detector, and I was working on the analysis, so you have all this data, you have, like, whatever, many months of this thing sitting quietly and looking for the light. And there was this one big Zoom call with my entire collaboration, people all over the world, hundreds of people on one video screen, in all their different universities. And it was this moment where we were going to find out if the experiment worked or not. It had already run for a long time, we had already built out this big method for analyzing whether or not the data contained dark matter, and all at once, we were going to push a button, and the experiment was going to tell us whether, yes, you discovered dark matter, or no, you didn't.

• 15:05Speaker 03

  And I remember that moment, when we pushed the button, we watched it churn through all this data and say, no, you didn't find it. And I remember watching what seemed like despair wash over everybody's face, I watched, like, the stages of grief in fast motion.

• 15:21Noam Hassenfeld?

  What did you see on people's faces?

• 15:24Speaker 03

  At first, like, a kind of denial, like, I think, I think everybody was like, it's okay, it's okay, like, instantly, they went from, from, I think, a sincere belief that we had a good chance of seeing it, to like, okay, well, it's not the end, we can build more, like, dark matter could just be a little more ghostly than we thought before, build a bigger detector. And we immediately started doing that, that was most of my PhD, was building bigger and bigger detectors, and waiting longer and longer. The bigger you, the detector you build, the longer you wait, the more sensitive you become to this rare dark matter interaction. But that day had an impact, like, especially when I talked to young people who I was working with. So, you know, I was in Italy, I was going underground, and you would have these conversations

• 16:06Speaker 03

  over lunch, over dinner, and you would get the sense that, like, nobody actually thought the thing was going to work anymore. Like, the disillusionment, at least among young people, was pretty universal. The professors who had spent their whole career working on dark matter, they showed more optimism, they showed more like, okay, well, maybe the next one. But especially all those young people who had seen that first failure, I think they were shaken, their faith was shaken.

• 16:30Noam Hassenfeld?

  Do you remember any of those conversations?

• 16:33Speaker 03

  Yeah, I mean, I started taking, like, an informal poll, right? I would ask people, so like, what do you think are the chances that this detector we're building, the next one, the bigger one, will find dark matter? And they would say zero.

• 16:46Speaker 03

  They would say, no, it's not going to happen.

• 16:50Noam Hassenfeld?

  So what does it mean for science if we never crack what might be the biggest mystery out there? We'll get into all that after a quick break.

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• 19:33Speaker 06

  This looks strangely familiar. Because we've been here before. We're going in circles.

• 19:41Noam Hassenfeld?

  So it seems like there's two possibilities here. Either we are failing as a scientific community, or struggling, I don't want to say failing, to detect the particle. We're not building big enough or quiet enough detectors. Or there's something about the nature of dark matter that makes it impossible to detect.

• 20:02Speaker 03

  Yeah, I mean, it could be that it's just this shadow realm that only interacts with our world through its gravitational pull. If that's the case, we'll always be in this place where we know it's there and we don't know what it's made of.

• 20:16Noam Hassenfeld?

  Yeah. I mean, you sent me a conversation you had with Siska de Barde Maker. She's a philosopher. And she said something that really stuck out to me.

• 20:26Speaker 07

  It is entirely possible that dark matter only interacts gravitationally.

• 20:30Noam Hassenfeld?

  Yeah.

• 20:31Speaker 07

  And that would be a worst-case scenario for physics.

• 20:34Noam Hassenfeld?

  Mm-hmm.

• 20:35Speaker 07

  But like, nature doesn't have to play nice.

• 20:37Noam Hassenfeld?

  What do you think about that line, "nature doesn't have to play nice"?

• 20:40Speaker 03

  Unfortunately, what Siska's saying is that nature doesn't have to have made a dark matter particle that you can ever know what it's made of, right? Like, we can only know what something's made of if we can trap it in a detector on Earth.

• 20:53Noam Hassenfeld?

  Right.

• 20:54Speaker 03

  That's how we answered all the questions I asked in high school and college, right? We can never answer those questions for dark matter if it only interacts gravitationally, right? Because you can never trap it in a detector. Gravity is too weak of a force.

• 21:05Noam Hassenfeld?

  It just seems like such a tantalizing situation, that we can see it doing all of this stuff. We see it holding galaxies together and spinning them faster than they should be, and we can't capture it, we can't detect it.

• 21:20Speaker 03

  It's horrible. Billions of them are going through us all the time. But we'll never know what they are. That's what I'm saying.

• 21:27Noam Hassenfeld?

  Mm-hmm.

• 21:28Speaker 03

  For me, that's, that runs up against my entire picture of what science is supposed to do.

• 21:34Noam Hassenfeld?

  Yeah. So you've talked to a bunch of scientists and philosophers of science. Did anyone disagree with your perspective that science can't tell us the secrets of the universe? That maybe it's unreasonable to expect science to reveal itself in the ways we want it to reveal it?

• 21:50Speaker 03

  You know, when you put it that way, when you ask a scientist, "Does the universe owe us explicability, comprehensibility?", they'll say, "Of course not." But if you ask them in any one situation, "What do you think is going to happen with dark matter?", including my former peers, the people who said 0% that our experiments have worked, all of them, 201, felt that at some point we'll figure it out. "I don't know what's going to happen, but some genius will come along, some Einstein, and change the paradigm, and we'll learn that we were wrong about everything and everything will suddenly make sense." All the physicists I talked to had this faith that I used to have. And there's good reason for that. There's a reason for optimism. It has done a lot of things.

• 22:33Speaker 03

  We've overcome a lot of mysteries.

• 22:36Noam Hassenfeld?

  Mm-hmm.

• 22:37Speaker 03

  But even if I'm wrong, and I might eat my words tomorrow, I'd love us to find dark matter. There is a wall somewhere, is what I've learned.

• 22:44Noam Hassenfeld?

  Yeah.

• 22:45Speaker 03

  Maybe this isn't it, but it could be this.

• 22:47Noam Hassenfeld?

  You used the word "faith".

• 22:49Speaker 03

  Sorry.

• 22:50Noam Hassenfeld?

  No, it's fine. It makes sense to me. Is that what this feels like to you? Does it feel like some of the scientists you talked to have faith that you no longer have in what science is and how it's supposed to work?

• 23:06Speaker 03

  Yeah. I mean, I threw that word at some of them. My advisor, Eleanor Preeley, she threw it back at me. She said, "How are you so certain, Joe, that we will never find this thing?". And it's true. I think I've been so disillusioned that I've maybe lurched into pessimism. Another philosopher I talked to told me to lighten up. That was his professional advice. But I've become convinced that even if dark matter gets discovered tomorrow, which could happen, I could eat my words, right? I would love to. But even if dark matter gets discovered tomorrow, I now feel that there will be another wall down the road.

• 23:47Speaker 03

  If the wall we can't penetrate in our understanding isn't dark matter, it will be something else. We'll never understand everything. It's something that sounds obvious once you say it, but like, the fact that there is means that I was asking the wrong thing of science.

• 24:01Noam Hassenfeld?

  Ah.

• 24:02Speaker 03

  Means that I was wrong about what science is. And maybe that means that there's other people who are misunderstanding the purpose of science. Maybe science is the thing that tells us that we can't know everything.

• 24:12Noam Hassenfeld?

  Mm-hmm.

• 24:13Speaker 03

  And like, maybe that's the point of science.

• 24:15Noam Hassenfeld?

  Maybe we're verging a bit into religion here, but it kind of feels okay. You know, I think about Maimonides, the medieval Jewish philosopher. He, his conception of God is that God is unknowable, and the reason God is anthropomorphized in the Bible is because God is fully unexplainable. And I feel like for him, that was meaning, right? And you're telling us that science maybe has gotten us to a point where it's shown us that the universe is at some deep level unexplainable, or mysterious, or out of reach. And maybe that is, that's it.

• 24:57Noam Hassenfeld?

  Maybe that's like, a reminder to us that we need to be humble, and we are not the kind of like, conquerors marching over the universe explaining everything. Like, maybe that actually is the meaning. I don't know.

• 25:15Speaker 03

  I'll go there because you invited me.

• 25:17Noam Hassenfeld?

  Okay.

• 25:18Speaker 03

  To go there. I think in medieval times, right, in the Christian Dark Ages, for example, there was all these weird mystics saying that God is unknowable, and, and the universe is unknowable, and that is God, and all this stuff, right? They were really comfortable, not only comfortable with unknowing, they worshipped unknowing, right? In that era. And then, the Enlightenment happened, and we were kind of like, "Well, never mind. Actually, we can kind of know everything."

• 25:43Noam Hassenfeld?

  It was working pretty well.

• 25:45Speaker 03

  It was working for a while, and I think we might have over-adjusted to now we're in this time where we could raise an idiot like I used to be, who thinks that eventually we'll figure out everything. And like, I think we could learn some lessons from those weird medieval mystics, who, of course, like, it's great, everything we've gotten from science, but we shouldn't mistake that for meaning. And I think there's a lot of meaning in this wall, in the unknowable. Yeah.

• 26:16Noam Hassenfeld?

  One thing I want to be clear about, though. I think there's a, there's a way that someone might hear this conversation and say, "Joe is saying that scientific research, specifically physics research, is pointless, or not going to go anywhere." When you're looking at these experiments to find dark matter particles, or building a bigger particle collider than CERN, are you saying that those experiments shouldn't keep going on? Or are you saying that like, your personal motivation doesn't necessarily line up with those experiments?

• 26:55Speaker 03

  Yeah. I'm, I'm really glad you brought this up, actually, you know? Because like, I think, you know, science funding is in crisis right now.

• 27:04Noam Hassenfeld?

  Yeah.

• 27:05Speaker 03

  Including fundamental science funding.

• 27:07Noam Hassenfeld?

  Right.

• 27:08Speaker 03

  And like, it's important to say that the reason we had this discussion is because of science, right? Like, because of Vera Rubin's work, and everybody that followed her, and the 40 years we just had of failure of trying to find dark matter.

• 27:21Noam Hassenfeld?

  Right.

• 27:22Speaker 03

  It's how we're able to have this conversation. And the next 40 years of basic science will enable better, more informed conversations about the limits of knowledge, and like, what we can learn from them. Like, I love science research, and it, not enough of it is happening. That's the problem. I mean, I'm not saying we shouldn't build the next thing. I don't know what the next thing will find. It might find something crazy. We should build more next things, so that we can get more questions, and, and prove me wrong, right? Like, I would love for us to find dark matter. I would love to be wrong. I just think we should spend some fraction of our time stepping back and saying, "Well, we might not ever know everything." You know?

• 28:03Noam Hassenfeld?

  I guess I want to bring this back to you. But you're no longer a physicist. I mean, once a physicist, always a physicist, right? But at a certain point, you decided to stop doing research and become a science writer. Do you remember the moment you decided to stop being a researcher?

• 28:20Speaker 03

  I mean, there was a bit of an identity crisis, right? Like, I had decided that this is how you make meaning, and I was learning that it just isn't. I'm not an Einstein. I can't go step back and reframe all of physics. But maybe I could talk about people who are. I, like, I knew I would never be able to leave science behind.

• 28:39Noam Hassenfeld?

  I mean, you love it.

• 28:41Speaker 03

  I love it, and I especially love this, these, this edge of what we can know, right? But yeah, I had to give up on the idea that I was going to penetrate the wall, right? That I was part of this grand program that was chipping away slowly, marching along human knowledge until we figure out everything. And that made the world way scarier to me.

• 29:04Noam Hassenfeld?

  Mm-hmm.

• 29:05Speaker 03

  But I think it also ultimately made it more beautiful.

• 29:07Noam Hassenfeld?

  This feels like a, a very personal journey you've been on, of what you wanted from science to find out about the universe. What do you think you've found out about yourself?

• 29:20Speaker 03

  That I'm deeply uncomfortable with not knowing things. And maybe that all of us are. And I think I've learned that that's the thing I should be engaging with, right? That discomfort, what it means about me. And now that's what I spend like, all my time thinking about.

• 29:40Noam Hassenfeld?

  Mm-hmm.

• 29:41Speaker 03

  What we don't know, what we can and what we can't. And it still makes me uncomfortable. But I think it also makes me better because of humility. It also makes me appreciate people more. Like, I'm not looking out there, or down there, or at the fundamental reality anymore for meaning. I'm looking around me.

• 30:06Noam Hassenfeld?

  Are you still searching for meaning?

• 30:10Noam Hassenfeld?

  I feel like you you've searched for meaning in this one way. Now you're saying like, oh, I can't chip away at the wall, maybe admire the wall. But do you still feel like you're searching?

• 30:20Speaker 03

  Yeah, I think this is a weird place we've been thrown down, right? And left to figure it out. And like, yeah, I'm still looking for it. I don't know that I've found it, but like, I feel like I scratched the surface every now and then. Like, when you hear an amazing story, when you think about dark matter, like, it's the closest I feel to, yeah, like a deep, real meaning.

• 30:45Noam Hassenfeld?

  Maybe someday we'll figure it out.

• 30:48Speaker 03

  Yeah.

• 30:48Noam Hassenfeld?

  We'll have you back on the show.

• 30:49Speaker 03

  I would love to come, eat my words.

• 30:51Noam Hassenfeld?

  We can just say, hey, we know the meaning of life, everybody. Until then, though, Joe, thanks so much for coming on the show.

• 30:58Speaker 03

  Thanks so much. It was so fun.

• 31:03Noam Hassenfeld?

  All right, Joe, thank you for coming back to talk with me. We taped the episode a couple of weeks ago and then researchers at this huge underground dark matter experiment in South Dakota just made this big announcement about something that they discovered a few years ago. They noticed that this particle hit another particle in a way that they can't really explain. So did we just discover dark matter?

• 31:35Speaker 03

  I think when we talked, I told you I might eat my words tomorrow. I didn't like literally mean tomorrow.

• 31:45Speaker 03

  No, we definitely, I mean, we definitely don't know that we found dark matter. And unfortunately, I'm pretty sure, and I think most experts are, would tell you, they're being honest, that they're pretty sure we didn't. Like, I would bet $1,000 against this being dark matter. It's a bet I would love to lose, like, I would love to be wrong about that. But I just think it's very unlikely. But it is still the most interesting thing to happen in one of these experiments for a long time.

• 32:14Noam Hassenfeld?

  So are people so excited just because this is the first time in a long time anything interesting has been found?

• 32:21Speaker 03

  These experiments have been looking for literal decades for this thing that we know is everywhere, but we can't find, and they've come up with nothing. So it's very easy to get excited about any little thing that you see. It doesn't mean that it's dark matter. And that's not how science works, right? Like, you learn in elementary school, the scientific method, you make a hypothesis, then you go build an experiment to confirm or disconfirm that hypothesis. That's not what happened here, right? Like, the dark matter this experiment was looking for, it didn't find. It found something else unusual. But that's not confirming or disconfirming its original hypothesis, right? If you build an experiment that's sensitive enough, deep enough,

• 33:04Speaker 03

  run it for long enough, eventually you are guaranteed to see something you don't understand. It doesn't mean you found dark matter.

• 33:11Noam Hassenfeld?

  Does this make you rethink your feelings at all with the search in general? Like, maybe this is that ray of hope we needed in order to build bigger and deeper and more sensitive detectors so that we will find dark matter?

• 33:26Speaker 03

  I mean, I am excited about this event, right? It's the most exciting thing to happen in a dark matter detector in a long time. But also, I know what's going to happen to this field, right? It's going to take us five years to figure out what actually happened. And it's not the first time we've seen something unexplained. It's been a long time, but it's not the first time. And it always turns out to be nothing. Whether or not this is the wall, I think there is one. And I think we still need to be grappling with the questions about science that that raises, whether or not we found dark matter, and I hope we have.

• 34:01Noam Hassenfeld?

  Well, Joe, thanks for getting back on the line for the update. I do hope at some time in the near future, you do eat your words and we get you back on the show and we do actually discover dark matter.

• 34:15Speaker 03

  I'm absolutely down to come do my mea culpa on your podcast. I'd love to.

• 34:21Noam Hassenfeld?

  All right, till next time.

• 34:22Speaker 03

  Thanks, Tom.

• 34:28Noam Hassenfeld?

  If you want to see this episode on video, head over to Netflix. This was our second episode of our series with Scientific American. If you want to read more about this and other impossible questions, go check out their special issue. You can find it in print or on their site at scientificamerican.com. And check out their excellent podcast, Science Quickly. This episode was produced by Valerie Schenkman and me, Noam Hassenfeld. It was edited by Joanna Solotaroff with help from Meredith Hadenot, who runs the show. Our video editor is Jacob Reynolds, our animator is Karim Kereya, our fact checker is Melissa Hirsch, our studio engineers are Ibrahim Ochik and Joe Nebrous, mixing and sound design by Christian Ayala, music from me. And Bird Pinkerton leaned against a wall in the passageway.

• 35:13Noam Hassenfeld?

  She wasn't sure which path she should take. She lay down and then she heard it faintly in the darkness.

• 35:26Noam Hassenfeld?

  Special thanks, as always, to Brian Resnick for co-creating the show with me and Bird. If you have thoughts about the show, we would love to hear from you. You can email us at [email protected]. Or if you want to support the show, join Vox, become a member. Just go to vox.com/members. And if you signed up because of us, let us know. It would make us very happy.

• 35:49Noam Hassenfeld?

  Unexplainable is part of the Vox Media Podcast Network, and we'll see you right back here next time.

• 36:02Speaker 08

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