What Dark Matter Actually Is | KeShawn Ivory (dark.mattering)

In this episode of Curiosity Theory, hosts Dr. Dakotah Tyler and Justin Shaifer sit down with KeShawn Ivory, a soon-to-be PhD astrophysicist who studies the large-scale structure of the universe, for a deep conversation about dark matter, cosmology, and the invisible stuff that holds the universe together.

The discussion moves from what dark matter actually is to how the universe became clumpy and lumpy instead of smooth, why the first atoms appeared minutes after the Big Bang, and how primordial black holes (a mountain's worth of mass packed into the size of a proton) became one of the more compelling candidates for what dark matter might be. Along the way, they get into how scientists detect something they can't see, what counts as evidence, and how scientific consensus actually moves.
The conversation also dives into the hunt for dark matter through detection experiments, the role of skepticism in good science, what it means to know something, and KeShawn's favorite idea of all: that dark matter works as a framework for any force that is deeply impactful but hard to see, from race and systemic disparities in sociology to genomic dark matter in biology and trauma in art.
Chapters
00:00:00 Intro and meeting KeShawn Ivory
00:02:30 The PhD as a credential and the path to science communication
00:08:55 What dark matter actually is
00:10:00 Why the universe is clumpy: large-scale structure
00:11:30 The early universe and the first atoms
00:20:30 The cosmic microwave background and the universe's baby picture
00:30:00 How we know dark matter is really there
00:33:30 Primordial black holes as a dark matter candidate
00:40:00 Dark stars and other exotic candidates
00:47:40 Healthy skepticism and how scientific consensus moves
00:53:00 Science, truth, and what it means to know something
00:59:00 The hunt for dark matter: WIMPs, axions, and detectors
01:08:00 How theory predicts the particles we look for
01:17:50 Astrosociology: dark matter as a lens on race and systemic forces
01:24:10 Dark matter as a storytelling tool in biology and art
01:26:18 Where to find Kishan and Black Space Week
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Guests
Kishan Ivory (Dark Mattering)
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Transcript

SPEAKER_02 0:00

What's going on, everybody, and welcome back to another episode of Curiosity's Theory. It's your boy Justin, Mr. Fascinate Schaefer, STEM Media Producer and Curious Guy, joined here with my main man, Dr.

SPEAKER_03 0:11

Dakota Tyler, also known as Dr. Star Kid, astrophysicist, and curious guy. I feel like you took Curious Guy from me. I felt like that's my I feel like that was that was my thing.

SPEAKER_02 0:20

That's mine, it's mine now.

SPEAKER_03 0:22

So we got a we got a super special guest and expert in cosmology and dark matter. We're gonna dig into a bunch of interesting things about like how the universe formed and what that structure looks like. Um talk a little bit about primordial black holes, which are the little known and I mean more interesting cousin to some of the more massive black holes that a lot of us are familiar with. With us, we got Keyshawn Ivory, a PhD candidate, astrophysicist. He's wrapping up his dissertation here soon. So soon to be doctor. Thanks for coming on, Keyshawn.

SPEAKER_00 1:00

Yeah, my pleasure. Uh soon to be like in a couple of months. It's it's coming up.

SPEAKER_02 1:05

Yeah, yeah, you can do it, man. Thank you. Thank you. All right, so everybody stay tuned and tap in with us right now.

SPEAKER_03 1:23

Keishon is doing his PhD in specifically, well, astrophysics, but specifically in dark matter and cosmology. Would you consider yourself a cos cosmologist?

SPEAKER_00 1:34

I love that question. I consider myself as somebody that works right at the border of astronomy and cosmology. I do, I that's why I always say large-scale structure because it feels like a good tip either way, and we'll get into that.

SPEAKER_03 1:51

Okay, so you're about to, you're like working on, you know, as we say, you're dissertating currently, so you're writing up all of your results, which are like a collection of individual research projects that you've done, or do you have like one big project that you've done?

SPEAKER_00 2:10

Yeah, so I would say my PhD has been very unconventional. And that's maybe one thing I would convey to people who don't know a ton about like the PhD process is that it really is your own journey. And it you it the shaping happens between you and your advisor or advisors. Um, so a really important part of the process is like making sure people who advise you that you trust them a lot. Because I knew coming in that I didn't want to be a researcher, like endgame. And that in itself is I mean, it's more, it's more common nowadays, but traditionally and classically, the PhD is it's a research degree, and it still very much is. Like that's what you get the degree for is by conducting a research project. But it used to be the case that essentially, like, you were going to grad school to learn how to be a professor. That was the idea. It's that professors replicate themselves by advising you. And that model doesn't super hold up with in the current like job market and landscape. There's just more people getting PhDs than there are room like for professor jobs. And so now people come in with all kinds of different goals. So for me, the PhD was really, it was like it was it was a credential. It was three letters behind my name that would get people to take me really seriously when I go into the worlds that I was actually interested in, which are like science education, science communication, science outreach. And I knew there were positions that were, you know, unfortunately, like they would be kind of behind a locked door if I didn't have like that credential. So that's what I came in wanting.

SPEAKER_03 3:52

Paywall is like your soul, which you have to give up to get your feet.

SPEAKER_00 3:56

Yes. So that's what I came in wanting. And I was really, really clear about that, um, which was risky, but it was good because I ended up in a department where they they didn't mind that. And I did my master's through this uh Fisk Vanderbilt Master's to PhD Bridge program, which is how I ended up in Nashville and familiar with like Vanderbilt faculty. Um, and so I knew that even then in the master's phase, like once I transitioned to the PhD phase, like I'm gonna be in good hands. And so to answer your question, I've always had the same projects. Um, there was a brief moment where I thought I was gonna switch projects because my master's advisor moved to DC to be a program director for the NSF in 2021. So, like after I finished my master's and started started my PhD, like right in that interim, he moved. And so I did my whole call, my qualifying exam, where I submit after my first two years. So after your first two years of PhD, this is how Vanderbilt does it. Your first two years, you've been like a teaching assistant, you've been grading, um, that kind of thing. You submit a like an abstract, like a research proposal for what you're going to do as your project, and you're not bound to it. You don't have to do your PhD on that. Really, it's just testing you on all of the astrophysics that you've been learning in class for the past two years, and then testing you on your ability to write about research, plan a project, talk about it, defend it, that kind of thing. So I wrote about something totally different because I had switched advisors since my master's advisor had left. But once I got past my qual and I passed it, I thought about it some more and I said, you know, that old project, I don't feel like I'm done. There, there was a lot to, we have a lot of meat left on the bone. I really liked it. I don't want to switch from large-scale structure to black holes. And Andreas, my old advisor, he might be in DC, but he's still on my committee and he he's still happy to meet with me. He even offered to advise me remotely if I wanted to, which was so kind. Um, so I said, you know what? I'm gonna jump back to that old project, and that's been my project. So now, really, truly, for the better part of seven years, I've just been working on this one thing.

SPEAKER_03 6:15

Gotcha. Um, you mentioned that you know, PhDs traditionally have been people with PhDs who are professors training upcoming people who are gonna be people with PhDs who are professors, and now there's like 10 job absorption for the number of PhDs in a given field. I think that probably holds on average. I know that's true for astronomy and and physics. So even if everybody wanted to go and become a professor, 90% of people would not be able to, and that's sort of us an interesting so that that I think that shows us a little bit something about um, like I don't know, PhD inflation, maybe, which is odd because in in academia, there's like too many people getting PhDs, but like in society, there's too many people that don't know anything.

SPEAKER_00 7:13

Yeah, it's weird funny dichotomy, yeah.

SPEAKER_03 7:17

Yeah. Um, but you're so yeah, the the first it was the same at UCLA. The first two years are for us are um like classwork, coursework, grad grad courses. So you're still just kind of learning everything that everybody already knows, and you're you're trying to like catch up and get to the you know, at least the base level of knowledge to be considered an expert, and then it's after that that you move on to PhD candidacy, yeah, where you start can doing your own research and your research. It sounds like at one point you had the option to switch to black holes, but you wanted to stay with what you keep saying, large scale structure, which is like you know, if you zoom back and look at the universe at the largest scale, what does what does everything look like?

SPEAKER_00 8:12

Yeah, exactly. Exactly. I my the the advisor I switched to when my old advisor moved to DC, um, she does a lot of black hole gravitational wave work. Um, and so for qualifying exam purposes, that that's why I proposed a project that was more along the lines of what she does. And I was learning, I was ready to do it, I was talking to the right people and figuring out the right kind of codes, but it just it's not my thing. I I feel that the large scale structure thing, the dark matter thing is is my thing. At this point, I've really leaned into making it my thing.

SPEAKER_03 8:51

Yeah. And I guess don't keep the people waiting. What is dark matter? What are you talking about here? What's the what's the relevance between that and large scale structure?

SPEAKER_00 9:01

Where's yes, yes? So I'll I'll start by saying, Um, my my dissertation work is it's not literally, I don't work on dark matter as in terms of like studying what it is or like how like looking for it, right? So dark matter is we'll start there. It's matter in the universe that we cannot see because it doesn't interact with light in ways that are familiar to us in ways that we recognize, but we we infer its existence by the way it interacts with things that we can see. So the way it makes things move that we can see, like gravitationally, it interacts with things in ways that we can measure. And so my actual research is on, as I keep saying, large-scale structure, and and I wanted to define structure here. For for me, I really like to define structure as the opposite of homogeneity. So things are not even, things are not randomly distributed, things are not um, things are clumpy, things are preferentially distributed. There's some stuff here, there's no stuff there, there's some stuff here, there's no stuff there. Clumpy, lumpy. That's how the universe is. And all those clumps and lumps, that's structure. So large-scale structure, I know in space everything is like large scale, so that sounds very vague. So I'll define a scale for you. Um, I'm really talking about we live in a galaxy, the Milky Way, but I'm talking about bigger than that. The Milky Way has uh like maybe on the order of like 50 or so little dwarves and things that circle it, little small galaxies that circle it. Bigger than that, okay. There's a local group of the Milky Way and the Andromeda Galaxy nearby, and all of the little satellites that circle both of those. Okay, bigger than that, you get groups of groups, you get clusters of clusters. That's the scale that I'm talking about, like clusters of galaxy clusters. I'm talking about like sheets and filaments of galaxies on galaxies. When you zoom out to that level, even there, you see that things are clumpy and lumpy, not smooth, not even, not randomly distributed, but preferentially. Stuff here, nothing there, stuff here, nothing there. And what dark matter has to do with that actually goes all the way back to the start, all the way back to the start. So if we take it back to the beginning in the universe, like immediately post Big Bang, we had already there was dark matter, we think it was there already, because it needed to be there to do to do this.

SPEAKER_03 11:47

When you say um already there, you mean like in that you know, tenth of a nanosecond, whatever before the Big Bang, or just like no no no.

SPEAKER_00 12:01

I mean when like post-Big Bang, when matter, like when when matter comes to be, dark matter is also coming to be.

SPEAKER_03 12:07

Gotcha. So within, and then that's just for folks that's like within the within under like a couple seconds, right? You start to get matters. Yeah, very timescale, is it within minutes? Uh it's it's it's short.

SPEAKER_00 12:22

I feel like well, what does that mean with with this early universe stuff?

SPEAKER_03 12:26

Um basically all the I well, I know this that basically all of the protons and electrons and neutron, the stuff that is here now is pretty much here after around uh 15 or 20 minutes. So, I mean, how long have we been talking? 12 minutes. So we've we're like on the order of how long it took for all the stuff right those atoms like first appear.

SPEAKER_00 12:50

We're talking seconds to minutes in. I'm gonna we're gonna get to something that happens a few hundred thousand years after, but right now we're talking very, very shortly after the big bug.

SPEAKER_03 13:01

Okay, and so that's actually interesting, right? Because if you go before that, then there was no matter in the way that we think of it, like the stuff that you could touch, but everything was kind of just it energy, it was like the soup of energy, right? And then as the universe is expanding, everything can kind of cool off, right? Because the density goes down, the universe gets bigger, uh, stuff can cool off, and as things cool off, then you start to form the first atom. So that's kind of a cool thing to think about. At one point within the first, you know, 15, 10, 5 minutes, whatever, you see you get like the first protons appearing.

SPEAKER_00 13:40

And dark matter does play a role with we'll get to a couple hundred thousand years after the Big Bang when those when those first atoms are forming and we get that we can see, like we can see for the first time, but we'll we'll get there. Um, so first let's talk about let's contextualize like where dark matter kind of comes into the equation as far as structure. Because it it gets set at this early, as we're saying, this very early time, like seconds to minutes after the Big Bang. So um I mentioned that dark matter is we infer its existence by how it interacts with things gravitationally, because it doesn't, it doesn't do light, it doesn't do radiation. That's what makes it dark. What's special about that, the special kind of gift that imbues dark matter, is that gravity, you know, it really only comes in one kind of flavor. Mass wants to be where mass is at, so it's it's attractive. It is always fomenting collapse, coalescence. It wants things to get to get close and fall in. So dark matter is only really being subject to this attractive force that wants it to coalesce and fall in and condense. And so dark matter is able to very efficiently seed structure because it's able to make what we what we now call dark matter halos. I don't super know why we call them that, but we do just kind of stable clumps of dark matter. And so dark matter is able to do that first. Normal matter, like you and I are made up of, the kind of fancy astronomy word for that is baryonic matter. There's a million-dollar word for the day. Um, that kind of matter is subject to like radiative processes, thermal processes, much more like messy, complicated processes because it does make light and get hot and all that stuff. And so that means you've got a fight, kind of a battle that we see all the time in astronomy between gravity wanting things to collapse, pointing inward, and then expansion, these thermal processes pointing outward and kind of washing out the structure that wants to form. So normal matter is a lot slower to collapse and coalesce. So dark matter ends up kind of telling it where to go. Because remember, gravity is like mass wants to be where mass is. So if dark matter is already kind of coalescing in these pockets, regular matter slowly makes its way there, and those become the formation points for stars and then planets, galaxies, and then groups of galaxies, clusters of galaxies, groups of clusters, clusters of clusters, and that's why you get non-smooth, non-homogeneous, you get preferential organization. So it's really seeded very early on by dark matter and just its gravitational influence.

SPEAKER_03 16:34

Right. So let me see if I if I got this right. So you have all of this, there's just matter, right? Some of it's dark matter, and some of it's normal matter. Um, if you take a bunch of normal matter, like what's in a star, it also can be gravitationally attracted to itself. It will be for sure. But I and a part of that process in a star can lead to like fusion because of the way this matter interacts with itself, and then that fusion is like in the core of a star pushing outwards. So, you know, the sun wants to collapse because of its gravity, but then it also wants to explode because of the radiation in the center.

SPEAKER_00 17:13

Yes, the bat the in and out, the fight, constant astronomy story, right?

SPEAKER_03 17:18

But something like dark matter uh in the early universe is not having this secondary process where um light is bouncing off of stuff and increasing pressure, or um, it's being like fused together to make um like a dark matter, uh like dark matter stars or something like that. So you can kind of the the dark matter can kind of settle in these big clumps, but because it has its uh has gravity because it's matter, that is like funneling the normal matter, which is a little bit slow in doing things, into the centers, and then so you could imagine, you know, if you were constructing the universe, the first thing you're laying down is all the dark matter, and then all the normal matter is kind of like filling in the center of those cavities and filaments and and all that stuff, like tracing it out a bit, yeah.

SPEAKER_02 18:13

Yeah, yeah, I guess what's confusing to me though is how the dark matter arrives before the matter. I got I don't understand how it predates the matter arrived.

SPEAKER_00 18:23

No, I don't think of it as like it exists before matter. I think matter is it's coming out of this energy pool, is like condensing out of this energy pool. And when matter does that, that includes the normal stuff and the dark stuff. But it's that the dark stuff is able to collapse first because it's only being acted on by gravity. So it doesn't have this radiative processes that make it do this kind of pulsation. And and we have a there's a name for this too, the um baryon acoustic oscillations. Okay, so like BAO is is the an imprint, like it's a literal imprint that we can see from this in and out kind of pulsation that normal matter has to go through because gravity wants it to collapse like this, but then it gets hot and it you know radiates and it wants to expand like this. And so in the early universe, it's kind of there's waves going through. And I guess so now we can jump ahead to about 380,000 years after the Big Bang. As Dakota mentioned, in the interim, things had been expanding, things had been cooling, still very hot relative to our day-to-day lives, but things have been expanding, things have been cooling. Eventually, what you get is things cool off enough that your like protons, so like what goes on to be like the cores of nuclei of atoms, they can they can hold on to electrons. Because before things were so hot and chaotic that electrons would just go whizzing about and they would get caught and then get free again. And there were so many that the universe was opaque. So like light just light could not get through. So, us today, we can't see that era because the light doesn't reach us from there. So the moment where light could finally you know break free, like Ariana Grande, like that song from back in the day, the moment that light could finally get through was when things had cooled down enough for protons to hold on to electrons and start forming like stable hydrogen atoms. And so at this moment, we get our first snapshot of the universe, which at the time was very hot radiation, but in the billions of years since is now quite cold, about three Kelvin, and it's microwaves now. So, this is if you ever hear cosmic microwave background, that's what that is. So, back to this, these oscillations. We actually do see the imprint of those oscillations in the cosmic microwave background, because when we when we get that snapshot, that's a moment in time where normal matter is somewhere along in this pulsation process. And wherever it is in the process, the size of that wave, we can not only can we see it in the cosmic microwave background, but we can actually see it in the distribution of like where galaxies are in the universe because they are preferentially a particular distance apart because of that initial oscillation, and so dark matter not having to do this, it just does this, yeah. And so it's able to get structure first.

SPEAKER_03 21:40

Yeah. So one of the um one of the things that uh maybe we can hopefully we can remember to put like a um an image of the CMB, the cosmic microwave background up here, is that you'll notice they're colored um in like typically greens and yellows and reds, maybe. And that's you know, that's not. What it quote looks like, right? Um, but that's how we differentiate what we are looking at, and what we are looking at are these tiny, tiny, tiny differences in like temperature, for example, and um, that's gonna tell you something about the density of that region. So there are like some regions that have slightly more stuff, and some regions that have slightly less stuff, which is really important, actually. Um, this uh this uneven clumpy distribution that Keyshan was talking about. Because if we didn't have that, which you know, if you were guessing, you may think, oh, hey, if a universe starts, maybe everything is just completely evenly distributed. Like, why wouldn't it? We know that symmetry is a huge thing in our universe. However, if that was the case, then you would have never had the uh potential for like galaxies. Uh whoops, you would have um you would have never had the potentially potential for galaxies to form because there would never have been an overdensity that things could like clump around. So you need clumps to get ice, you need that, and so like in that way, dark matter is actually essential to having life in a universe. You know, we could imagine that there's another universe maybe that doesn't have dark matter, and so normal matter doesn't have as easy of a time um just following these like trade routes that have been carved out for it so that it can clump together and and form things.

SPEAKER_02 23:36

Trade route. I like that. Yeah, so that's really interesting. Um, I my question still kind of remains around scale, scale the scale with which we can observe this, right? So I know you know you're describing Keyshawn, these large-scale structures. Uh it sounds like we have observed these dark matter halos, uh kind of in galaxies and perhaps also like clusters of star formations as well. Um, but like, you know, could we observe the presence of dark matter within our solar system, for example? Do we have the instruments to measure that? Or is that even something that is that even a practical question?

SPEAKER_00 24:10

No, it is a practical question. And it's a question that people were asking for a long time before we kind of arrived at our modern perception of like what dark matter is and where dark matter is. Because um, okay, so like historically, we kind of go back to like before, let's say before the 20th century when people started working towards this conception of dark matter that we've been talking about. There was still there was always the idea that there's matter out there that we can't see. Because in a simple sense, you would look out at the night sky and you would see stars and stuff, but then the rest would just be dark. There's just dark sky. And so naturally there's the question of, well, well, what is that? Is that is that something or is that nothing? And actually, lots of people, even some big names in in physics and math and astronomy, Henri Poincaré, Lord Kelvin, um, all the way back to like ancient Greeks, like lots of people were kind of wondering like, is that something? Is that nothing? Are there things beyond what we can see? Um, I think even Henri Poincaré was the one to maybe even like coin dark matter, but he did he was French, so he did so in French Mathieu Noir, which literally means black matter, which it's funny given what we're gonna get into about what I well what I like to do now with dark matter stuff. Um but people have been thinking about this a lot. And so before we kind of got this large-scale dark matter halo idea, people, one of the reasons people kind of doubted that dark matter was even a thing was because they tried to calculate it locally. They went looking for it in the solar system in our neighborhood. And they were saying, essentially they were saying, well, if I'm running the numbers and I'm looking at how everything is moving and how gravity's working, and I don't see a need for any extra mass. Like I don't see any need for any extra stuff around here, so it must not be out there. The right start, wrong conclusion, right? When we actually got to looking, and I would say um in the 1930s with an astronomer Fritz Zwicky, um, he starts to look at uh the coma cluster, which is a big galaxy cluster. So we're going up in scale to a cluster of galaxies. And he's looking at a quantity that's called velocity dispersion, which is one of those weird astronomer numbers that we that we do. But it's essentially it's it's kind of a measure of how fast the galaxies in the cluster are moving, like relative to like the average motion of the entire cluster, something like that. And he's using that to figure out if there must be extra mass. So when he goes to that scale, at that scale, it's pretty undeniable that these galaxies are moving way too fast for there to not be something extra to hold them together. And in the 1970s, more astronomers, Vera Rubin and Kent Ford, find the same thing, but at a smaller level, at the individual galaxy level. So they look at Andromeda, our kind of nearby neighbor, and they're measuring the rates of rotation of stars in the arms. It's a it's a beautiful spiral, kind of like our own Milky Way. It's like our sister over there. So they are measuring rates of rotation in the arms of the stars in the arms, and they're seeing the same. Like these stars are moving way too fast for there to not be some extra mass to keep them moving like this. And so at these scales, that's where it's evident there's got to be something else. But the when you go locally, when you're talking about in our solar system near Earth, yeah, sure, there's definitely some dark matter. There definitely is. But the further you zoom out, the more of it you're gonna see. And so this is why only when we started looking at whole galaxy scales and then galaxy cluster scales and then kind of whole universe scales, do we really, really see the influence and the, as Dakota was saying, the necessity of dark matter to shaping this world. Yeah.

SPEAKER_03 28:24

And so the I we may have talked about velocity dispersion uh in terms relating to stars before, but it's just like if you look at a clump of stuff, um, even if everything in a galaxy, for example, is orbiting around, you still expect some random velocity dispersion, like the sun may be pointed kind of this way, and you know, the next closest star maybe pointed that way a little bit. And although everything is um orbiting around the galaxy, there's just this spread of velocities. And so when you look at a cluster of galaxies, um, you realize that if the if the dispersion of the velocities of those galaxies in that cluster is too high compared to the amount of gravity there, then they should kind of just like fly off and go somewhere else, right?

SPEAKER_00 29:15

Because motion is fast and it's disorganized, exactly.

SPEAKER_03 29:19

So the only way that you can have galaxies with a really high velocity relative to another and still remain bound in that cluster is if there's way more mass than we're seeing with our eyes. Um, so there must be this extra matter, and it's kind of one of the undeniable observations that lets us know that even though we don't maybe know exactly what dark matter is, there has to be something there. Otherwise, you know, just like basic physics one, these galaxies would be flying all over the place, or the stars in the Milky Way would literally just be like fly off the handles. Yeah, they would just be like spraying out into intergalactic space.

SPEAKER_00 30:01

I don't know if you notice what's happening here is that the as we're talking about more forms of evidence, so we've gone over galaxy clusters, we've gone over uh rotation curves, we've gone over the uh microwave background, large-scale structure, we even got to very unacoustic oscillations, um, which is a high-level one that I don't always get to talk about. So that's fun. But maybe you notice like emerging are these kind of like, I think of it as like two big categories of dark matter evidence. There's the more kind of like dynamical, like it's about how things move and how fast and and where. And that addresses the question of like, is dark matter there to begin with? Does it exist? Must it be there? Then once you kind of wrap your head around, okay, it's there because all these things wouldn't be moving as fast if it wasn't there, then you get to these cosmological forms of evidence like the cosmic microwave background and these things that are more about, okay, well, how much is there? What is the ratio of the dark matter to the normal? How lumpy, how clumpy? If we had more normal stuff, would the universe be less clumpy? Would we still get planets? Would we still get galaxies? Would we still get people? Like when you're talking about those ratios, that is more of a the cosmological thing. So it's like two kinds how much or like is it there at all?

SPEAKER_03 31:20

Yeah, yeah. And then the interesting thing is that we, you know, you keep we you say it when we refer to it, and you know, people may be thinking, Well, okay, well, so what is it? And uh I mean, that's a good question. You figure that out and you will get a Nobel Prize.

SPEAKER_00 31:37

You will. Oh, you will, yeah.

SPEAKER_02 31:39

I think the the thing that kind of just feels like right on the edge of, I don't know, like like something that I would specifically be curious about with dark matter, because I, you know, I've kind of read about it leisurely from time to time and kind of gained a base level understanding, and this is like super helpful for building on that. I mean, we think about matter that we can observe, right? It like has different states of existence, and it has like you know, like different numbers of atoms that comprise different elements, and those different elements react in different ways. And so it kind of makes you wonder if you know what, like you said, like what it what dark matter is made of, and does it have dark matter atoms or dark atoms, you know, and is that or are there some other building blocks that this is comprised of, and what are their properties?

SPEAKER_00 32:22

Like, I think that that's a fascinating um yeah, your instincts are so good there to immediately draw a parallel between all the different ways that normal matter shows up, because it's the same here. Like, I it brings me no great joy to tell you this, but there's no reason that dark matter has to be only one thing. So, like, if we find a type of dark matter, there is no physical reason that that has to be all of it, that that has to represent all of it that's out there, which makes our search difficult and long and hard. But I mean, that means somebody's gonna be employed. So that's a good thing, I guess. But yeah, you're you're spot on that like there's no good reason to think that you know you find you find one particle and that's it. It's gonna be something that we can that we can find, that we can measure, that we recognize, and then and we we crack the code. Like it's very unlikely that it's gonna be that simple, you know. Um, yeah, your instincts on that are fantastic, spot on.

SPEAKER_03 33:24

One of the, in my mind, most interesting uh hypotheses. I don't know if this is really favorite anymore, is dark matter being this enormous amount of like primordial, tiny primordial black holes that um that are just like scattered around the universe. And so they're tiny and they're black, so you can't see them. So that could that could explain. And I mean, you may think, well, there should be there should be like evidence, or like maybe we could find one, but I don't know. I don't I don't know if we could. There, you think about how large spaces are like how much larger the dark matter halo is than um the normal matter in a galaxy, and you could you could like spread the black holes so far apart that they're almost never interacting, or at least never like officially colliding with each other. But I don't know if that's one of I don't think that's like one of the leading leading, no, but it's very much still on the table.

SPEAKER_00 34:26

There's still papers out pretty frequently about them. I know someone um here at Vanderbilt who worked on them for their masters. Um so yeah, the questions around primordial black holes that are or the work that people are doing around them right now is about so okay, so primordial, I will clarify like that these are different than normal black holes that form like when a star dies. I don't know if you guys have talked about those before, but like when it's a massive star.

SPEAKER_03 34:56

What happens?

SPEAKER_00 34:56

Yeah, so when a star that's massive enough, maybe like 20 times as massive as our own sun or or more, when it reaches the end of its life, meaning it runs out of material in its core to power itself, to fuse, um, it has this very dramatic death where it kind of like implodes and you get this big explosion, um, supernova. And if it's massive enough, um, that's that about 20, 20 times uh more massive than our sun number, it will leave behind um a black hole because it'll it'll collapse it on itself, um, and it'll basically it'll collapse so hard that it leaves a uh a region of space where the speed you would need to reach to escape it would be the speed of light or faster than the speed of light. Um, that's how a normal stellar mass black hole forms. So these primordial black holes are not that, so they're not forming from collapsed stars because they would have been forming before stars even were a thing. That's the primordial part. They're like very old, kind of exotic. Not we're not, this is part of it too. We're not totally clear on how they would have formed. There's a number of pathways and channels people are thinking. But the work people are doing around primordial black holes as dark matter is about restricting the mass range. So, across what range of masses they could exist if they were gonna be dark matter. So trying to get that down to some particular part of the mass scale. And some work around that has been done because larger mass primordial black holes have kind of been ruled out as a dark matter candidate because well they've kind of been ruled out. We can we can get to why. Um and they found they found a range that would work. So restricting the mass range, and then just do you have any idea what that what that is? I made a short form about this. Oh yeah. Um something along the lines of maybe a million. I I think in my short form I said maybe a million times the mass of the Eiffel Tower. Something along those lines.

SPEAKER_03 37:07

Uh, which would be a black, a primordial black hole than maybe what had a in an event horizon that was like an inch across or something like that?

SPEAKER_00 37:16

Yes, they rule out small, or they rule out a certain size because they're thinking about like things that I don't understand super well, like Hawking radiation and what it would take for a black hole to like evaporate itself out of existence. Very like black hole theory heavy stuff that I'd probably know more about if I'd gone down that other project route instead of staying in my little large-scale bubble. Um, but that is what one thing that they've been doing a lot of work on is trying to narrow down, okay, if primordial black holes are dark matter, what mass range could they exist in? And then the other question is getting at what I had said a few minutes ago, if primordial black holes are dark matter, how much, what percentage of dark matter would be could be primordial black holes? Because there it seems like not all of it, but maybe some of it.

SPEAKER_03 38:04

Okay, I just wow, this is nuts. The uh so I just looked up like the mass of a a primordial black hole. So 10 to the 12 kilograms would give you a black hole within like an event horizon diameter that was on the scale of like a proton.

SPEAKER_00 38:23

So yeah, okay, that sounds about right.

SPEAKER_03 38:25

That gives you like an idea of how much mass is packed into this tiny thing.

SPEAKER_02 38:32

Yeah, well, that's like about as massive as a mountain, right? As I I kind of did a similar search, so that the mass of a mountain fitting into the size of a proton, a proton, right?

SPEAKER_03 38:41

Which is like so small that the most powerful telescope or uh microscope that's ever existed doesn't even get you close to seeing a proton.

SPEAKER_00 38:49

But now you see why maybe it's such an attractive, like it's such a nice idea for a candidate because like you you need to you have a lot that you need to explain. You have five times as much um dark matter as you do normal stuff, so you got a lot of missing mass you need to explain, and you can't see it. Mountains of mass in the size of a proton is a really attractive way to try and explain where all that mass is.

SPEAKER_02 39:15

Now that makes a lot of sense. And the other thing I was thinking about, and I know this is more with stellar mass black holes, which have already been ruled out, but to my understanding, you can't really directly observe a black hole in space, you just observe the effect that it has on everything else, right? Like the event horizon or when it's a supermassive black hole at the center of a galaxy and what's orbiting around it. So it's it's kind of the same property as dark matter, where it's kind of like we can't really see it directly.

SPEAKER_00 39:41

Yes, yes. You you see the way that it for black holes typically, or for like the supermassive ones, I'll say at least, you you see the way that they uh heat up thing, the the things that fall into the disk that's around them. Uh yeah, that that's true. Um, it is it's a similar thing, except for for the primordial case, they're the ones you we're talking about would be so spatially small that they're not gonna make a disk. They're not going to be making light that you can see, which normally as astronomers, we don't like it when we can't see things. But in this case, if we're looking for a candidate, we're like, okay, it's good that this would be this would not be making light because we're specifically looking for a candidate that would not be making light, because then it's eligible to be to be dark matter. Um, and a fun one while we're talking about like people's theories and like candidates and things, a fun one that uh Dakota, you mentioned this kind of like off offhand a while back. You mentioned like we were talking about dark matter coalescing, and you mentioned the idea of like dark matter stars. That is an idea that people have thrown out there. Um, and the idea is that rather than red like how normal stars are powered by fusion, because they they collapse, and then you you get protons smashing into each other and you get energy out. Um obviously, you know, dark matter wouldn't do that. Uh the idea is instead um you would this would need to be dark matter that self-annihilates. So it would be dark matter that when when two dark matter particles run up on each other, they they they panic and they release a bunch of energy. Um, we don't know for sure that it does that. We don't know for sure that that happens, but we there are particles, many particles in the universe that do do that. Um, and so dark matter could do that. Um, and if if so, dark stars powered by self-annihilation could be out there. Crazy concept.

SPEAKER_03 41:47

And it's and you can see even in these conversations how hard it is to search for these things because as astronomers, you know, obviously we're stuck on Earth and we're trying to look at these enormous sweeping areas that are at literally as big as the observable universe, and the only thing that we can easily observe is light, so you know, stuff on the electromagnetic spectrum, and it doesn't always have to be visible light, right? It could be it could be infrared light, it could be radio waves, which are a long wavelength form of light, it could be X-rays or gamma rays. And when you're trying to observe, you know, when you're very, very well equipped to observe light, but you're trying to find something that doesn't produce or interact with the light, then you've kind of have, you know, your best tools are inert against uh, you know, the answers that you're looking for, like the questions that you're trying to answer. You you don't have your main tool.

SPEAKER_00 42:46

Yeah, yeah. And gravitational waves are um powerful but new. Uh they're they're a recent thing that we've been able to harness, and they're powerful because you know, dark matter, as we've been saying this whole time, is not immune to gravity. So this is good news that gravitational waves do maybe this could be an avenue for learning more about all kinds of matter, including dark, but it's new. We really just got our first uh gravitational wave like sort of confirmation signal in like what was that, 2017? So it's recent. Like we we are still figuring it out, and most of what we're figuring out right now is like big massive events like like mergers of like black holes and things like this, neutron scar mergers. We are not to a place where we could really be measuring like super. I mean, we we have a lot of work to do if we want to be using gravitational waves to their full potential. Um, because we we we just we just started. We really just started.

SPEAKER_03 43:54

Yeah. And what we can see uh in terms of gravitational waves. Are like the the final nanoseconds of the most dense objects that it exist in the universe essentially colliding with each other. And so, you know, you think about that, you have these two massive things that are, you know, everything's creating gravitational waves. Um, like you and I, as we we are moving through space-time, so we're like affecting it in some way, but uh we can really only detect the things that make the most like the most high magnitude waves, I guess maybe is a way to put it.

SPEAKER_00 44:33

And that's a terrible irony, too, because we were just saying that for dark matter, you really need to zoom out. And there's the unfortunate circumstance that gravitational waves are really good at getting us information about huge masses very close together, doing very dramatic things, spiraling in, orbiting in, merging. And we just said dark matter is not about that, like close in, like you have to zoom way out.

SPEAKER_01 45:00

Yeah.

SPEAKER_00 45:01

And so if you're going about looking for something very, very quiet that's barely making any moves, gravitational waves aren't the best for that. So dark matter, it's elusive, it's it's elusive.

SPEAKER_03 45:16

I um I think that there's this, I feel like I've heard this kind of esoteric out there idea before that um, and I don't know if this actually was applying to dark matter or to dark energy, but that maybe it's some like ancillary or adjacent effect to uh for like some multiverse where maybe maybe dark matter is like an effect that has something to do with something that's like outside of our universe or like operating on in like this higher dimensional plane than our three dimensions. What do you think about those ideas?

SPEAKER_00 45:58

You know, I'll say this. I I always want I want people to notice like in astronomy, how much is how much of it is about like dreaming and theorizing, and how much of everything remains on the table? Because like I'm the kind of person where like it's on the table until it's off the table. And for me, it it truly takes a lot to fully remove it from the table. Um, and so I people all the time when you do when you do this kind of work specifically, even and on social media, when you make like content around this, people will absolutely come into your comment section with all of their ideas and all of their theories. And a lot of it is this like other universes, like they've they've clearly done a lot of reading on things that I've never read, which is fascinating. Um, but I'm always my thing is always look, I am I I don't take things off the table until they're off the table. Like it's a wild universe out there. I don't know. Like you could absolutely be right. The rule is always this, though. I'm just gonna need to see some evidence. That's always it. I'm just always gonna need to see some evidence. And I'm not taking anything off the table. We can dream, we can theorize, we can throw anything out there. And a lot of great science does begin that way with just asking, like, what if? But when it all comes down to it and rubber meets the road, like we're gonna need to test something, like we're gonna need to design something that we can test to help us rule some things out, and and and with dark matter specifically, I think people's there there's a very healthy skepticism people have because it really does sound, and I I'm I'm self-aware enough to know it. Sounds so pie in the sky, the whole thing.

SPEAKER_03 47:50

Like, oh, so you're telling me that your equations don't work out for what so you're gonna say that there's five times the amount of stuff that we can prove is there, we just can't see it and doesn't interact with anything in any way.

SPEAKER_00 48:03

Maybe it's black holes, like it it's it sounds it sounds PhD and something that you can't see. It sounds goofy, it sounds goofy. I'm self-aware enough to know that it sounds goofy, but if it sounds goofy to us, you have to know that it sounded so goofy to everybody that came before. Yeah, and yet they would design an experiment. Fritz wiki looked at the coma cluster, he said, Hey, I see what I see. Somebody else was like, I don't know about that. They tested it too. Okay, I kind of see what you see. Vera Rubin and Kent Ford, look at Andromeda, look at the rotation curves at the stars in the arms. They I see what I see. Somebody else looks at other galaxies to confirm, okay, I kind of see what you see. And so it was not this like overnight flip. Everybody believes in dark matter now. It took a long time for consensus to move in this direction because people were just like, Are you sure? Like, we really need to make sure that it's not something else before we just because this is crazy. Um, but it it really kind of became quite undeniable.

SPEAKER_03 49:18

Yeah. Um, yeah, and what you're describing there is, and I think this is something that a lot of people in just regular discourse miss the the power of an explanatory theory. Um, oftentimes people will say, Oh, well, you know, it's that's just a theory, but when you when you map out all these observations that have been made, like those are the facts. Um, a theory isn't necessarily a fact, but the facts are the facts. We know for a fact that these galaxies are moving way faster than than they could otherwise. We know for a fact that the stars are moving way faster, like we know that we know the shape and distribution of stuff in the universe. Those are those are the facts, and then the theories come along and they weave together all of the facts. And when you get a nice observation that just tanks a theory, then people adapt the theory and they they go with something else. Yep, and as more and more observations are made, you know, a theory that can still explain them gets stronger and stronger, and any alternative theory has to do a better job of explaining everything that we see than any you know pre-existing theory. So when a new observation is made, it can be fun to like come up with this weird, mystical, magical explanation that explains just that observation, right? But you can't forget about all the other facts that still exist, like you can't wipe that that stuff away. And I remember this uh resonating deeply with me when JWST uh first went online and they said that oh, like the universe was broken, or it saw things that meant that the universe we were wrong about everything. Yeah, and it's like, well, there's definitely space for us being wrong about some things, but you can't throw away all the other observations that we made, right? Yeah, like we still know that the cosmic microwave background exists. Um, we still know that the universe is expanding, and if you roll back the clock of time, it puts us at about 13.8 billion years when everything was was together. And you can't you can't reject or forget, you know, you can't get amnesia about all the existing facts just because you got some new ones. That just means that you know you have to get finer in your in your theory. And for anybody that um may not be aware of this, for that reason, no theory is ever complete, right? There's never a time where a theory can't be altered or updated with new observations, and you can never make all the observations, so therefore you can like never complete a theory.

SPEAKER_00 51:59

And this is why the first part of a PhD is like you taking a bunch of courses, as you were saying earlier, to get up to speed on what is already known. And this is why the first part of any like project research project is a literature review, because you also need to know what is known about this question already, so that whatever you find, you you know what you are potentially coming into conflict with, or what you're potentially calling into question, or what you might need to square with, or like you you know exactly what you're walking into and the set like the precedent that there is, because you do you do need to understand that you're you're coming into this kind of like on the shoulders of those who came before, other people have examined similar questions, done similar work, and your your stuff is in the context of all that stuff, it's not standalone. So you're absolutely right. And to anybody who's kind of uh maybe like an aspiring scientist, like looking to get into science, on this, my advice is always kind of like as you proceed, like remember why it is that you got into the game, because your allegiance is not to the idea of being correct, it's to the idea of getting us as humans, humanity, like closer to the truth, like closer to knowing what's really going on. And sometimes that means not being right. And even being wrong is learning, like even being wrong is learning something. So I always tell people they they kind of wonder if you finished your PhD and then years down the road we found out that everything you worked on was a lie and it and it wasn't true, you know, what how would you feel? And honestly, maybe I'd feel like an initial sting of like, oh, kind of kind of wish it were legit. But at the end of the day, I'd feel fine about it because it would it would mean that we we got closer to knowing like what's really going on. And even my being wrong would have been a little tiny part in that, which is fine with me because that's that's what I wanted to do here, which is help us like figure some stuff out.

SPEAKER_03 54:03

Yeah, yeah. Non-detections are meaningful. Oh, my bad, Justin.

SPEAKER_02 54:07

Uh I was gonna say, um, I think what I can always appreciate in both of you all is and in a lot of the researchers that you know I've worked with over the years, is this sense of duty on the part of scientists to expand our understanding of the natural world, universe, um, almost beyond their own egos. Like, as much as it would be satisfying to be the one person that was right out of everybody, like the idea that you advanced our understanding by being wrong, it's still satisfying. Um, I think there's like a humility in that. Um, and you know, I think I think it's a humility in that that the general public doesn't appreciate uh that you know, it's like, oh, these scientists don't want you to know, right? We were talking about that. Like, wait, we really want you to know. But here's the thing you do. Yeah, yeah. So it's always just funny how I think public perception of science kind of juxtaposes with like my perception of scientists, which is like stewards of the acquisition of knowledge.

SPEAKER_00 55:11

Yeah, and knowers about like a very narrow little branch of the of the un of the universe, because I am the first one to tell you when I don't know about something. Like even earlier when we were doing like the specific time, like beginning of the universe timelines, that's something that I learned and that I think about from time to time, but I don't have everything committed to memory, and I'm so quick to be like, hold on, let me let me search this up, let me look this up. Because like I'll tell you, when I have something at scale committed to memory, like the cosmic microwave background, like I know that one, that one got that one good. But when I don't have something, I'm so quick to let you know, hey, I don't got that. Give me two seconds, which I think is what expertise really is. If if you ask me to define what expertise really is, it's not that you just like know a bunch of stuff offhand, it's that you know where to go to get the stuff that you don't have offhand and how to vet it for trustworthiness in a very effective and quick manner.

SPEAKER_03 56:12

Yeah, yeah. Really getting good at applying those the critical thinking skills, which on some level require like a base knowledge of well, what what is there here to be critical of? Like what what doesn't what doesn't quite sound right? Um, and what and I think that that ties in very nicely to this theory about dark matter, which is well, I mean, your intuitive response to you know the person, average person listening to this may be what we said before. It's like you can't see it, can't interact with it, we can't scoop it up and look at it in a lab. There's like what you you should be critical about that because all the matter that you've ever interacted with, that's not the case. No, I used to I I like this um analogy of how we know about dark matter just looking out the window. You know, you imagine that you were like bubble boy and you were stuck inside your place because you were a germophobe and you could never go outside, and you see trees, and you see the leaves of the trees are like are they're moving, and you know that trees don't really move that fast, not on that short time scale. So you know that something is causing the trees to move, but you know, we can't see what it is. Of course, the answer is that it's gas, it's just it's matter that's slamming into it, but we can't see the atmosphere, so you know that there's like something out there that's hitting the tree. You're seeing the impacts of the air on the tree, and that tells you that there's at least an atmosphere outside, and you know, we're not like in a vacuum. And in a similar way, that's how you can think of of dark matter, except I know that the answer is that there's gas outside running into the tree, and I don't know you know what what dark matter is, like we don't know except for the fact that we can see gravity, that there you know is anything at all, and that's why I think it's cool. What so what are the what if you if you had the you know life on the line right now, you had to submit an answer for what you think dark matter ultimately is, what would your answer be? Or maybe like what are some of the top uh hypotheses or suggestions that you are attracted to?

SPEAKER_00 58:29

So the maybe so okay, what it is is gonna be like at least what constitutes part of it, because we talked about how it doesn't have to only be one thing, um, but there may be like kind of very popular candidates at the moment. Um WIMPS, so weakly interacting massive particles. Um, astronomers like to be goofy with the way that we name things, the acronyms. So the there were in addition to WIMPs, there used to be well, there are machos, so massive compact halo objects. When I said earlier that a certain higher mass range of primordial black hole had been ruled out, that's what that's what that was. So machos got ruled out. So massive compact halo objects. It was the idea that maybe, and this, and this is this is a very uh to its credit, it's a very intuitive idea that maybe the dark matter we can't see is just like it's like it's black holes, it's just like very massive, very faint things or things that don't make light, these primordial black holes, etc., that we just can't see. Um, the way that those got ruled out is kind of inherent in the massive part. So there is this phenomenon called gravitational lensing, where um masses they warp. I mean, this is kind of the way that Einstein explains like how gravity actually works, it warps space-time, masses warp space-time. And if the mass is large enough, then we could actually witness that warping because light, you know, it follows straight lines, but a straight line in a curved space-time looks like curvature. And so we could we can see the warping of light due to this large mass. And so that idea is called gravitational lensing. And so when they did like lensing studies, they saw, okay, it doesn't, it wouldn't make sense for dark matter to be machos because if there were this many like massive, like compact objects, we would see like a certain amount of lensing that we don't see. Okay. Um, but in that small regime, primordial black holes are still on the table. So that's just an aside. Opposite of macho is WIMP, weakly interacting massive particle. That one is still very much on the table. That one's pretty popular. Um, it's pretty popular because it uh, well, weakly interacting means that it would interact via the the weak force, so it wouldn't be doing any uh like radiation, it wouldn't be doing, you know, what we need dark matter to do basically be dark. It would be doing that. Um, it's it has a mass. So like the and the massive just means like it has a uh mass. Um, but it's not we're not thinking, it's not like a black hole type situation, not like that. Um, so this is, I mean, it's it's vague, right? It's literally just like weakly interacting massive particles. So the one way that people are looking for these, um, this is another thing where I'm self-aware that this sounds very goofy, um, but things sound goofy until they work. Um large tanks of liquid xenon are like underneath, there's like a like a facility, I think, in like Italy, where it's like beneath some like mountain. There's like a large tank of liquid xenon where it's just kind of sitting and waiting for a wimp to come along and interact via the weak force and it will measure the interaction. Um, well, the great thing about that is like you build it, you put it there, and then you just kind of wait for it to do its thing. And that's it's kind of the same thing that we did with gravitational waves, but um once we turned that once we turn it on that switch, we actually we got something pretty pretty quick. This these xenon tanks are not they're not giving us these quick results.

SPEAKER_03 1:02:36

How long have they been there?

SPEAKER_00 1:02:38

Um uh that's a good question. Xenon Xenon, Xenon, I I know the one in Italy. Hold on. 2014? It's over over a decade.

SPEAKER_02 1:02:57

And and Keishon, these are exclusively for this purpose.

SPEAKER_00 1:03:01

They are for WIMP searches. Yeah, at least the at least the the one that I'm thinking of at Grand Sasso, the Italian one, is for for it's a dark matter search.

SPEAKER_03 1:03:13

Yeah, it looks like in general, there's been they've been looking for 25 years with this method.

SPEAKER_00 1:03:18

So yeah, yeah. So that's ongoing. Um, another one, axions. So this one, I actually, if you if it was like a like a gun to my head situation, had to pick one, I would probably go with this one, and I'll tell you why. It's because axions did not begin in astrophysics. What's an axion? We'll we'll get there.

SPEAKER_03 1:03:45

Oh, okay.

SPEAKER_00 1:03:46

They did not begin with astrophysics, they actually began in like pure particle physics land, which is a land that I do not know very much about, that I only learned about when I was writing a syllabus to teach some high schoolers about dark matter, and I had to teach about axions. So there is, we'll get I'm in explaining what an axion is, we first need to give some background. So there is this idea of um, I did a short on on this one too, so I'm pretty brushed up on this one. There's this idea of um charge conjugation symmetry in particle physics. So what so basically, like I'm gonna use my hands as exemplars. So charge conjugation symmetry is the idea that if you like you take a particle, so my hand is like a particle, and you swap it out with its anti-particle, there's um if you observe like the two decaying to the same thing, like the end reaction is the same, they release the same kind of particle at the end of a decay process, that's a symmetry. So that's a that's a charge conjugation symmetry. Then there is uh such a thing as a parity symmetry. So if you take your particle and you uh flip its uh what's the word, you flip its like alignment and it still decays the same way, that's a parity symmetry. So then if you do both of those things, take the particle, swap it to its antiparticle, and you like flip its alignment and it decays to the same thing, that is CP charge parity symmetry. Okay. So that's that's idea number one. So the reason that the axion came about is because we we noticed that when it came to uh the strong force, which that's the force that like binds atomic nuclei together, because maybe in chemistry class you were seeing that they were saying like charges repel, but then you were but then you were seeing that a nucleus is a cluster of protons, and you're like helium is literally two protons right next to each other. So, what is the truth? Right. Well, the truth is. The strong force is what is what keeps them like stuck and bound together. And so what we we find is that with the strong force, we for whatever reason, we just we don't see violations in CP symmetry. So if you do the switch with um the particle with the antiparticle and then change its orientation, uh we always see like the decay looks the same. Like we it's it's symmetric. And physically, like that doesn't need to be the case. And so particle physicists started coming up with another model that would suppress and and explain why we don't see uh like the like the symmetry violation. And that's where the axion came from, because as they're working out this model, out falls this other particle that they would need to explain. And that particle, they they call it the axion, and the prop the properties of it would be that it's like very, very light, um, very, very abundant, like in the early universe. And then astronomers are like, wait a minute, that sounds like something that we need. And so now it's kind of like you got two different areas of physics that both have a gaping hole in their in their theory that's kind of axion-shaped, you know? And so because it didn't arise in astrophysics, but it really it fits if it fits the bill in a way. If I had to pick a favorite, that would probably be the favorite. And um, as always, I'm gonna recommend Dr. Uh John Deprescott Weinstein's writing because Axioms is literally what she does, like that's what she studies. Um, she's written about them beautifully. That's how I learned what I know about them. Um, yeah, so I always recommend her her writing.

SPEAKER_03 1:07:52

We actually either just had her on recently before this or recently after.

SPEAKER_00 1:07:57

Perfect. So though oh my gosh, everybody's primed for axions. This is the timing is magical, wonderful.

SPEAKER_03 1:08:03

So uh uh for a little bit of reference, uh, you know, because that what everything you just described um sounds pretty abstract, but yeah, there is this thing called the standard model of of particle physics, where you know we have like this long list of equations and this formalism that describes a lot of the normal matter that that we know about and those interactions and how they produce certain particles, and what happens when you fuse things together or when things decay. And oftentimes it's it's like it's such a good model of at least most of what's happening in particle physics that in some cases it's accurate to like many like seven, eight, nine decimals. So it's like extremely, extremely accurate. It's almost like suspiciously accurate, accurate, yeah. Almost like too accurate, and when you see that, you're like, okay, wait a second. I'm exactly like if you're trying to model something and it's exactly right, then that oh that maybe like tips you off that it's a little scary, yeah. Like that that that doesn't seem real, that doesn't seem like um something a pattern that we see often, but it's been so accurate that this exercise that you're describing of saying, like, well, the math says that maybe there's like some particle that should be this mass or have this charge, um, is how people actually predict new particles, and oftentimes they build instruments to try and find them, and oftentimes they find them. Like, that's how um effective this method that you're describing of you know playing with what we know and kind of like seeing what what the math predicts. It's not, you know, it's not something that's uh you know, a completely like theoretical exercise that this is, you know, the the standard model of physics does help you predict some of these things. So, you know, the idea of um predicting uh part of this new thing in that way actually has like sort of a long history of being how we grow to understand this realm of physics.

SPEAKER_00 1:10:11

For sure, for sure. Part of it is definitely accuracy, and I think part of it also is definitely just like scale, because the universe has it is so vast and unfathomable that it's constantly pushing you to like either large spatial scales or just large numbers of things, where you can pretty safely say, like, if I believe that I should see something even sometimes, and I don't see it ever, that's worthy of investigation. Because with this in the universe, something that would happen one time in a million becomes commonplace because there's billions and trillions, and you know, it's so it with scale, it's we can we can do some cool maybe leaps of faith, maybe, that due to the technology we have quickly become not faith, but actual like backed data.

SPEAKER_02 1:11:04

Yeah, no, that's that's so interesting. I was looking into what you were saying, Dakota, and I didn't I didn't realize this, but the Higgs boson, which I know was like a theoretical particle for a long time. Like I remember reading about that in my science book when I was a kid, and then the large hadron collider actually discovered the particle right in 2012.

SPEAKER_03 1:11:22

And and this is yeah, I mean, that's probably like I don't know how much that whole uh collider costs multi-billion, I'm I'm assuming. And it's you know, it's still being used and stuff. So there's all this, like all these resources being poured into this thing that is just a product of the math. Like you're doing the math, and you're like, oh, well, there must be this thing must exist, right? If this math is right, then this thing exists, and you you know, you accelerate these protons to these damn near speed of light, super relativistic speeds, slam them into each other, and you find exactly what you're looking for. The the Higgs particle, which is predicted by the math.

SPEAKER_00 1:12:01

Yeah, so things sound goofy until they work.

SPEAKER_02 1:12:04

Yeah, I think that that's that's kind of frustrating to think about in today's era where there's so much public mistrust of science, and I think even the math that scientists do, when it's like someone was willing to spend billions or an organ, a group of people willing to spend billions of dollars based on a theoretical particle that was only derived in an equation that we had no proof that existed previously. And you know, and even like you know, we we talk about this on the show before, Dakota, like solar eclipses or you know, like seeing a lunar eclipse or all these other like stellar phenomena, you know, when you check Google search and you go and do it, it's like these are scientists making these predictions that we just intrinsically trust, but then we don't trust when they say other stuff, you know?

SPEAKER_00 1:12:46

I think there's a I love that you said that because it makes me think that the conditions that make for bad art and the conditions that make for bad science, I think are in many ways the same conditions, the same kind of like reactionary conditions. Because when you only ever want a safe bet, and you are not allowing people to take risks, you're not allowing people to try new things. This is why, in my opinion, a lot of the art that we see, a lot of the films, a lot of the music, it's it's real stale, it's real reboot because people want a safe bet. They want something they can recoup, they want something that's gonna get them their money, and that's not where art thrives. Similarly, I don't think that's where science thrives either. I think that science does require a bit of this like investing in something that doesn't sound like a super sure safe thing. Like it doesn't sound safe to and 100% sure to put liquid xenon beneath some Italian mountain or to just like run particles into each other until something happens. But when we do it, we learn, we always learn. Um, and I I think, yeah, I think similar conditions make for art and science go together in a lot of ways, but I I think similar conditions for bad art are conditions for bad science, and we're in those conditions.

SPEAKER_03 1:14:07

Yeah, that's a great saying. I'm gonna start saying that. Um, I'll I'll I'll I'll cite you as well. I appreciate it. That's so that's so true, and I like that um connection that you draw as well, where there for whatever reason, um, you know, there is this trope of scientists that they're not artistic and then they're not creative. And if you think about people who come up with um these understandings of the universe, that's exact, that's like not true at all, right? Like, even a mathematician, we can get down to like maybe one of the more logical professions you can think of. A mathematician um needs to be creative in how they handle and solve these equations and like output these potential particles that exist. Um, scientists that are trying to build experiments need to be creative to make these things that I mean, a lot of these instruments are completely unique, like they've never, it's not like uh um, you know, a Ford factory line assembly where you're kind of make you're making the Ford F-150 over and over. It's not like that at all. Almost all of these instruments that are finding new things are one of a kind. Yep, and you have to be creative, um, like in a PhD to try and answer a new question, to come up with a new question. First of all, it's interesting. Then you have to be creative in trying to answer it. And everybody who does a PhD comes to this point where it feels like you're slamming your head on the wall and you've looked through all the literature, and nobody has there is no answer to the thing that you're trying to answer, which is part of what you know a PhD is. Yep, but it absolutely requ uh requires creativity, and um, you know, we people revere the Einsteins or whatever as these these like lone geniuses or something like that, but he was he was just very creative based on his knowledge, you know. He's taking you know what I guess seem like logical steps to us now, but they're very creative when they don't exist yet. Absolutely creativity and and science go hand in hand, in my opinion, even though the I think view or sentiments about these two things are disconnected.

SPEAKER_00 1:16:25

They totally go together, they a thousand percent go together.

SPEAKER_03 1:16:29

Yeah, dope. So, is there anything else about dark matter or your research that you think we should know or cover?

SPEAKER_00 1:16:41

Yeah, let's see. Well, okay, I guess I'll tell I'll talk about the thing that's been on my mind the most as of late, like besides my dissertation. So um, like I said, I work, I work on large-scale structures. So my actual like PhD project is uh something called group finding, galaxy group finding. So identifying which galaxies live together in a in a dark matter halo, in a clump of dark matter. So all like coding, you know, basically writing up an algorithm to figure out which galaxies live together and run some analysis, some statistical analysis on them. Um which is it's it's been fun. And I've been doing it for, like I said, like seven years now. Um, but as of late, the the other thing that's really been occupying my mind is um I've had the pleasure and privilege of working as a digital science communication fellow with the Museum of Science Boston. And so that's been me making a lot of content, um, typically short form content. But I I just finished a long form video. It's like processing right now. So by the time people see this, it'll be up. Um, called Astrosociology. I'm pretty proud of it. Um, but basically, what I what I pitched for the fellowship was the content of a course that I taught uh two summers in a row here at Vanderbilt for the program for talented youth. So it's like a week-long course for high school juniors and seniors that's about everything we talked about today, but like in hyperdrive. So it's it's five days. So um day one is like history of dark matter, so from kind of like ancient Greeks all the way through to like the Point Carré, the Lord Kelvin, all the way through to uh Vera Rubin, Kent Ford, kind of like taking us from ancient Greece to like 1970 basically. Then day two is the astrophysics, so all of the different um lines of evidence we talked about, microwave background, rotation curves, um, galaxy clusters, a few more, a few others. Day three, um, I do simulating dark matter. So we talk about cosmological simulations, the way astronomers use computers. I take them on a tour of the supercomputer here at Vanderbilt. Day four is candidates and searches. So we talk about axions, wimps, machos, like various candidates, things that are ruled out, things that are on the table, how people are looking for them. And then day five, my favorite day, is Dark Matter Beyond Astronomy, where we go interdisciplinary because throughout the whole week, we've been having discussions about the ethics along the way. So we don't just talk about uh instruments, we talk about telescopes, where we build them, we talk about sort of colonial agendas that nations have, right? And they let me do this for a bunch of high schoolers, which I will I will give in to both our tens for letting me do that. Um and so basically I pitched this to the Museum of Science. They awarded me the fellowship, and so I've been slowly converting my syllabus to uh to content. And so the other thing that I would want people to know about dark matter is that it's it's a useful framework to talk about things outside of astronomy as well. So um I'll give my favorite example, the one that I just did for long form. Um, a sociologist, um, Howard Weinant wrote a piece in 2015 called, I think, The Dark Matter, Race and Racism in the 21st Century. And uh basically the analogy he's making is that race in like so in our in our world sociologically is like dark matter in astrophysics because it is this invisible, and by that I don't mean like, okay, like we're we're we're black. You can see that, obviously. That's not what I mean. I mean like invisibilized, like rendered invisible. When you're thinking about like top-down initiatives, about like DEI or affirmative action, when you think about the Calais versus Louisiana decision, like um, you know, rejecting Louisiana's districting map as an as a racial gerrymander, race is made invisible, it's rendered this thing that you should not, cannot see, talk about, right? And so it's this thing that like the state is is very aggressively attempting to censor, this invisible thing that regardless of the fact that it's invisible, that it's hard to define, it's constantly in flux, it's it's hard to pin down, it's complicated, it's a construct, it still makes structure that is uh tangible, that we can really see. Bless you. That's tangible, that we can actually see in terms of like income distribution, in terms of um policing, in terms of military intervention, in terms of like colonialism, neocolonialism, in terms of health disparities, like you name it, right? Incarceration, like there's all of these things that you can study that are concrete and tangible that will point you back to the much harder to pin down elephant in the room. And um, that's a very powerful framework. And in in my video, I kind of explore that a bit. And I I talk to a historian here at Vanderbilt. I use Nashville's local Civil War history as like a real example. We look at some maps of the city. Um, yeah, I'm pretty proud of it. But yeah, dark matter is is not just for astronomers.

SPEAKER_03 1:22:04

Yeah, I love that there's this, it's it's literally the same thing, right? Like you look at you look at these uh these quantities that we can measure, right? Like where people live, how much people uh make in certain areas, life expectancy, um, you know, health outcomes. These are all measurables, right? These are like these are the facts, these are all the facts. And there's something, there's some like invisible force that is present in in all of those. And I like the analogy or or maybe the metaphor, I don't know exactly what's right here, of dark matter and like race and these racial outcomes. And there's this, you know, it's it's different though, because it's like these are sociological effects, and I think it's it's so interesting that something as fundamental as the distribution of stuff in the universe as it's you know from its birth to now, almost 14 billion years later, has a connection in the sociological dynamics that uh of humans that evolved on one planet, you know, all these billions of years later. And it's it's very interesting that there is a connection. It's very interesting that you that you should be able to draw that parallel at all, but it fits it fits like almost perfectly. And I love these science parables, um, because I mean that's literally tied to the way that we know our universe works, right? This is not this is not like a story that we're making up to prove a point. Um, it's like a story that we know happened about how the universe works. And maybe it's like maybe it's not so surprising that you see um that sort of those sort of effects show up at smaller scales. Yeah, I think I just think it's so informative and um so impactful as a as a as a storytelling um uh like a storytelling tool.

SPEAKER_00 1:24:10

Yeah, I that's been that's been my real joy of first developing the course and then now developing all the content for for the fellowship is like just seeing the way that anywhere that you have something that is deeply impactful but difficult to observe or difficult to visualize, you've got the makings for dark matter. So I've I've now seen it in sociology, like we talked about, where you've got this difficult to define, difficult to see thing using like a mediating force, gravity versus like, let's say policy, culture, stigma, stereotype to generate structure. I've seen it in biology where people talk about like genomic or microbial dark matter, right? Like genes or organisms that they can't cultivate in the lab or they can't study directly, but they know that they have some function. They have some functionality. That's dark matter too. Um, I've seen it in art. There was an artist, a visual artist who came into the show in Nashville, Benji Russell, and his collection was called Dark Big Bang. And for him, dark matter was all of the traumatic experiences from his youth that would end up shaping who he would become as an adult, but he can't necessarily draw like a perfect through line between like this happened and therefore I do this. It's just this kind of sum total of experience that somehow would structure who he became. So I've I've just I've seen it used all kinds of ways, and it's it's powerful, it's really powerful.

SPEAKER_02 1:25:37

That's that's fire, Keyshawn. Um, so I wanted to ask a couple questions. One, where can they find that video that I know is gonna be rendered out other things? Talk about it, and where can they find more information about you?

SPEAKER_00 1:25:50

Perfect. Um, so that video is on my YouTube, which is all one word dark mattering. So very easy to remember. Um, dark mattering is for where I'm gonna put when I do more long form stuff. That's where this one is. Uh my shorts on YouTube are dark matter minis. Um, so that's there. Uh on IG, I also put my shorts there too. That's dark.mattering. And then on TikTok, it's dark mattering, all one word. So a lot of shorts branching into long form. Um, and then for more about me, um, any any of those work as well. My personal website is kiki ivory.github.io. That's just got uh more about my what my research is, what my interests are. Um, you can also find a link to all the course materials for my dark matter course if you are if you teach astronomy and you want to incorporate any of the interdisciplinary units that I have, um, that's all there as well.

SPEAKER_03 1:26:47

Yeah. Dope. Also, do you want to plug uh Black and Astro and Space Week?

SPEAKER_00 1:26:52

Of course I do.

SPEAKER_03 1:26:53

Of course I do. Posted before uh Space Week.

SPEAKER_00 1:26:57

Got you. Yeah. So Black and Astro, uh, it's an organization that founded by our dear friend Ashley Walker. Um Black Space Week is our flagship shout out, Ashley. Um uh Black Space Week is our flagship event. We do it every summer of the week of Juneteenth. We have incredible panels, incredible invited speakers, research showcases, grad and undergrad, all for um, all presented by black folks in space field, space industries. Everybody is invited. Um, registration links are out on our social media, black and astro.com. Um, please come through, register for all the things, show up. We would love to see you. It's gonna be fun. It's always fun. Um, and it's gonna be uh it's gonna be awesome. We got some great panels this year. STEM outreach, STEM advocacy. Um, it's pretty interdisciplinary. We're talking about arts as well. The whole thing is music themed and arts themed. So it's gonna be a blast. Come through, register, and kick it with us.

SPEAKER_02 1:27:53

Awesome. Well, Keyshawn, appreciate you joining us. Everybody, if you're still sticking around with us, thanks for tuning in. And as we always like to say, stay curious. Peace.