Vera Gluscevic is a professor of Physics and Astronomy at the University of Southern California. As a cosmologist, she studies the entire universe as a physical system. In doing so, she explores the nature of dark matter, dark energy, and the birth of the universe. Vera is the project leader of a new $4M grant from the John Templeton Foundation that will bring together astrophysicists, computer scientists, artists, and philosophers in a new research hub to explore the nature of dark matter and the early universe. She joins the podcast to discuss dark matter, collaboration among scientists, observatories, and more. 

What are the strangest objects in the universe? It’s almost certainly black holes, objects that are so powerful that even light cannot escape them.  To learn more, check out our podcast episode with Shep Doeleman, whose team produced the first-ever images of a black hole.

Transcripts of our episodes are made available as soon as possible. They are not fully edited for grammar or spelling.

Tom: Welcome to the podcast, Vera.

Vera: Thanks for having me.

Tom: I wanna start off by asking you, can you tell me where you grew up and maybe a few of your favorite memories as a child?

Vera: I was born and raised in Belgrade, the capital Serbia former Yugoslavia at the time. And, if you wanna know what my neighborhood looked like, you can imagine these monolithic concrete residential high rises kinda stacked in these really long rows. And then, these big green courtyards in between, kind of sandwiched in between the rows of buildings, and that going on like for miles. So it’s very like dystopian kind of looking neighborhood. But then us, the kids from the blocks, we loved it. It was our concrete jungle to explore and own, and you know, like it could, in a matter of minutes, gather up a crowd to play a game of dodgeball, like every afternoon. So it was a happy childhood.

Tom: Yeah. What do you cherish most in, in your family growing up?

Vera: Every family’s special, but I think it’s maybe a bit unusual, given that I am a professional scientist, is that I don’t come from a family of intellectuals. Neither of my parents completed college. They were middle of the working class in, you know, Serbia in the nineties. But they did have deep appreciation and respect for knowledge and learning. So growing up, I felt very supported to do whatever I wanted to do, to explore whatever I wanted to explore. But I also knew that, coming where I’m coming from, I had to work really hard to stick out, to prove myself, to show myself out there. And I took school very seriously. I took education very seriously. That was my job, that was my responsibility. And I, I gave it my all.

Tom: Yeah. Tell me about how you cultivated a love of science. Where did science specifically kind fit into your education and your strivings?

Vera: There was really no science in my family. But there was this curiosity. So, if you think about my mom, the first thing that actually comes to mind is. Her stunning poetry and her capacity for language and using language in like flavorful, mischievous ways. And so, I think she instilled that in me. And even in my profession, I used this, this is who I still am. But my dad had this almost wacky curiosity for everything scientific. One of the core memories I have growing up is, I remember us sitting in this little tiny kitchen, again looking through a microscope, which he acquired at some point. I have no idea how and when, and why. But we were looking through it. And what we were looking at was a drop of water from the potting soil. And we were taking turns. And I remember, while I was looking, there was this little tiny bacterium with a flagellum, this little fiber, right? Moving around it, like kind of whooshed through the field of you. And I just remember being beside myself with joy. I, I mean there’s this life that I cannot see with my eyes.

It’s like in the books, and there it was. And I vividly remember not just that, but also when I turned to my dad, who had missed the whole scene ’cause he wasn’t looking through, him standing there with his mouth open, like absorbing my joy and wanting to know more about what I saw. So, I think that’s when this idea that I can reach out and understand the world came into my life.

Tom: In high school in the United States, a lot of people, when they enter a physics class, feel very overwhelmed by the technical nature of it, the heavy amounts of mathematics, and how abstract it feels. What did you find as you began to study this? The discipline of physics, most engrossing.

Vera: Definitely not math.

Tom: Interesting. Please tell me more.

Vera: This is blasphemous. No, I hated math. I, I am not good with numbers. I do analyze data. I love data analysis. It’s my life. It’s my bread and butter. I am not good with numbers.

And that’s all that math was in the all of schooling until I got to college. So math was not what got me into physics. Oh, I think what got me into physics might have been my Serbian language teacher, kind of paradoxically. And I like to tell this story because it’s so unexpected the things that make our core memories that make us figure out who we are and what makes us happy, like never come from where you think they should come from.

Right. So what my Serbian teacher taught me was logic clear, like critical thinking, putting up arguments and doing so creatively, and I think when I started learning physics. Which happens in a survey, actually, really early in sixth grade, we had physics as a subject.

I had no idea that I needed to be super good at math. So, I just took it for what it was. It’s the story of the world, right? And it’s a way for us to own that story in our minds. And I think that was like, from the beginning, incredibly empowering to me.

Tom: Yeah. You did your undergraduate studies there in Serbia, and then you came to the United States for graduate school. I wonder if you could tell me a little bit about coming as an international student, tell me in what ways physics itself might be different.

Vera: Let me start by saying there are standards in science that all science community adheres to, right? We understand science in a very general way to be a rational inquiry. Towards understanding the world. That’s evidence-based, right? That’s what physics is at the bottom of it. But how we do it is a completely human endeavor. So, everything about it is defined by who we are as a community and as individuals. And I think there are still large cultural differences in the way people talk, in the way people present, and how aggressive or reserved they are.

And also how these things are linked subconsciously in our minds to somebody’s quality as a scientist. One of the things that I think is very American, and it was a shock to me when I came from doing physics in Serbia, was that in Belgrade, I used to read a textbook and spend hours really deeply understanding every concept before I touch any problem set. That was the orientation right here. I came into a classroom full of folks who most of them were, from the us, and what they did is the moment they got a problem set, they went straight into problem solving. And I remember still going like, is nobody gonna read the chapter first? And then I realized there’s no time.

We were under such huge pressure. And you just had to learn by doing, but I think this culture of rush is a very real thing, here. And I, I have to say, I bought into it. And on some level, I like it. But then sometimes there are moments when I go back to Belgrade and I see people sitting in cafes sipping their coffee with no laptops. It’s good sometimes.

Tom: Yes. When you came to graduate school, were there certain questions at the forefront of your mind to which you thought the study of physics would give you the answers?

Vera: Yeah, I wanted to understand the universe. I still do all of it. So my question, even as an undergraduate in Belgrade, was okay, so what is the discipline of physics where I get to do it all? Turns out cosmology is the all of it. And so that’s what I do today. It’s the study of the universe as a whole, from the beginning, to thinking about how everything in it evolved that we see on largest of scales. And it’s also a way, as it turns out, and this was a huge surprise that I didn’t really appreciate this as an undergrad.

There’s this intimate connection between the things we see on cosmic scales and the things that are happening on the fundamental level of quantum scale down to particle level. And so that connection, I think, is one of the most fascinating things about our universe and about this endeavor of cosmology, that keeps me going every day.

Tom: Yeah. Can you tell me a little more about that? I’m curious how the biggest scale and the small scale might interact, ’cause it seems to me they’re the least directly connected.

Vera: Yeah. Well, if you think about it, our universe started small. It’s been expanding for almost 14 billion years, right? So if you take the entire visible universe today from the farthest galaxy over there to the fire’s galaxy in the other direction, something like a hundred billion light years across, and you rewind the movie of cosmic expansion back to moments after the Big Bang, this entire volume of the visible universe should pack into scale smaller than the size of the smallest particles we know of today.

So what particles were doing on those small scales on the quantum level decided what cosmic scales that emerge from those quantum scales one day, will actually look like. And so cosmology, macho cosmology, is about understanding this whole movie from end to end.

Tom: Yeah. That’s very helpful to me, ’cause as I think about the super big and super small, time is like the key ingredient to the two,

Vera: Yeah. And lemme give you a concrete example. So if you go back to the time when the universe was the size of a maybe baseball, with particles inside of that little region of space are doing how they’re bouncing off each other, can change many things about this young universe.

One of the things that interactions between particles can change is how matter is distributed in this very early universe. And we now understand that galaxies are these huge concentrations of matter, but they were born out of little tiny densities. Little tiny inhomogeneity in this young baby universe. But if particles, for example, dark meta particles, which we don’t understand yet, if they happen to be bumping into normal matter at those early times, they could erase these little perturbations, these little homogeneity flatten them out such that many billions of years later, you don’t end up with a universe full of galaxies as ours is.

Tom: Yeah. There are very few people in the world who have the opportunity to study and conduct research on a professional level to use huge instruments, you know, make observations to explore galaxies far beyond ours. And yet this fascination with outer space, I think, permeates our culture. What do you think it is about outer space and the night sky that fascinates humans, even without the instruments to look beyond?

Vera: I can tell you what it is for me. I still, when I look at the night sky, am able to make eye contact with stars. Which I will never touch, never smell, never come anywhere near. And to understand that there’s a connection here between me and the stars, very concrete. One not poetic, very physical. Every atom in my body that is in hydrogen is made in the core of a dying star. I mean, that’s totally poetry, but it’s right. It’s this beautiful connection between the universe and us.

But even more to be able to sit in that moment where you hold that thought and you see this enormous universe where we are just negligible small right, and yet fully capable of holding that universe in our minds and making sense out of it and understanding what came before and what’s gonna come after.

That’s incredibly empowering. And I feel all and wonder and comfort, and joy in those moments, and I still can hold those moments. Every time I walk out, I look at the night sky. Sometimes my kids make fun of me for it, but it’s true. This gives me comfort, it gives me joy.

Tom: And it somehow also, in a way, belongs to us in a very real way. What are just some of the most surprising things that you’ve encountered during your professional career in physics?

Vera: Yeah, I think understanding the impact of the human aspect on science. As you pointed out, being here today. You know, as a kid coming from, the blocks of New Belgrade, it’s an incredible, privileged position to be in, to be able to have this be my profession.

Something I’m supposed to do every day, when I would do it. But the thing is, we sometimes like to tell ourselves, and sometimes tell the world, that this is an exclusive endeavor, that science is for those who are really smart and really talk math and are like really special in some way or other. You have to be special for every profession, for science included. You have to really badly wanna do it and put in a lot of hard work and have some talent, but beyond that, there’s far more people who are super smart and super ready to do science.

There are just not that many positions in this profession to accommodate everybody who would like to do it. So, realizing that is kind of humbling. And it’s also a reality check, and it’s also a check on, oh, this is how the society works, right? And I think that was a surprise to me. And, part of my own journey was buying into this narrative and being like, well, let me see if I’m good enough.

But actually, most of the time it was a lot of sweat. A lot of the nights, you know, when I didn’t sleep, but actually worked. Yeah, I had some good ideas, but I had a lot of luck too.

Tom: Yeah, you’ve had the opportunity to use, I imagine, many different observatories to probe the night skies and distant galaxies. I wonder if you could pick one observatory and tell me something that’s really special about it that I’ll remember.

Vera: The big deal in our field is definitely the Rubin Observatory, and that thing is certainly going to revolutionize what we understand about the universe. This thing is basically created over the period of, I think, something like 30 years of work since conception to the first light, which happened a couple of months ago. It involves something like a few thousand people on the collaboration. I’m one of them. A lot of people in the us participate in this collaboration. But there is something like a few hundred key contributors. These people who built the software, made it happen, built the instruments, came up with technological innovations that enable this thing to go on the sky. It’s going to map the entire southern sky. So, it’s located in Chile. It’ll man the entire southern sky to incredible depth, seeing things that are so faint that we couldn’t imagine seeing them until this instrument, and it’ll do so every few nights for 10 years, there’ll be this massive survey of kind of everything that there is that’s visible in our universe. And given this timeline of 10 years, it’ll also tell us about the things that are changing in the sky.

And so there’ll be things that are popping up because they’re moving and they’re close by, like asteroids. But there are also gonna be a lot of data for cosmologists, like myself, looking at these first galaxies and so forth. And I think the numbers are, something like over the course of 10 years, it’ll provide a catalog of 20 billion galaxies. There’s a few hundred billion in the universe. We’re talking about a significant percent of galaxies that there are. Period.

Tom: I know very little about astronomy, but from those that I’ve talked to, in the electromagnetic spectrum, one can look at different bands of it. So there’s visible lights. And then there’s infrared and radio telescope. So the Vera Rubin Observatory, what is it looking at, so to speak?

Vera: Yeah. So all of the visible spectrum and then some both sides. So a little bit of UV and a little bit of infrared.

Tom: Are there projects in which scientists are getting that kind of data, interacting with people who are studying the higher frequency, light, and then trying to map a combined picture? Where you get a sort of density of reality that we don’t access with our senses.

Vera: Absolutely. Absolutely. So Rubin is only one of a kind of an ecosystem of this new generation of surveys. And there are other ones in other parts on the electromagnetic spectrum. I think a notable one is the Simons Observatory, which is, looking in radio frequencies, micro frequencies, trying to make the most precise and highly resolved map of the heat leftover from the Big Bang.

Which is a completely different realm of the electromagnetic spectrum, as it’s not looking at a galaxy, it’s looking at these ripples of heat that map onto the ripples of space time, from the very, very early universe before any galaxies formed. So this ancient light, but as that light traveled to the universe, to us, it also had to pass by all these structures we see with something like Ruben. And often, one of the things that can happen is that when the light passes by massive structures, it gets bent and deflected. And so the way that those deflections distort the map of the cosmic micro background radiation tells us also something about galaxies. And so there’s cross-collaborational efforts between these various surveys trying to exactly do what you’re saying, to put the picture together and learn things about. The universe as a whole from various perspectives. combining all of these ways of viewing it.

Tom: One of the things I know that you study is the topic of dark matter. So it’s some matter that we suspect must be out there, but we can’t directly observe it. So tell me what method you use or you’re going to use to observe something that’s unobservable or unobserved at least.

Vera: Yeah, all of these surveys, all of the surveys that we talked about are near and dear to my heart, because we do learn very complimentary pieces of information from every observation that we can get our hands on. And the beauty of the way science is done these days is if you’re a cosmologist like myself, you get to participate in these large collaborations.

You get to enable and shape the science of these instruments that are gonna bring about the science. But then you also get to dig through this data in ways that nobody else has done before. So these data become publicly available, and that’s wonderful, and enables so much broader variety of science than what just the collaboration of a few hundred people can do. So, the way that we study dark matter is by looking at what it does to the things we can see.

Tom: Aha.

Vera: And that requires quite a bit of understanding of this interplay between dark matter particles and the rest of the universe that we do understand. So just to give you an example, so we know now, that every galaxy we look at in the universe, you know, think and drama, for example, this little beautiful spiral, is kind of like a tip of the iceberg of a much more massive, typically six times more massive structure that lies underneath and that massive structure we call halo of dark matter. It’s like a blob of dark matter, and that blob, like normal matter, has gravity to it.

It falls towards where the denser regions are, and so this gravitational force is something we can track by seeing how it affects the things that we do observe. So, for example, when we look at galaxies, we can measure how fast they spin. And every single galaxy Ruben measured back in the sixties was spinning way too fast. To stay together. And that was an indication that either we really do not understand gravity, like badly do not understand gravity or somewhat more simply.

There is some material there that actually adds up more gravitational force, and we just can’t see it directly with light. That sounds really weird if you’ve lived your life on earth like all of us have. But if you’re a particle physicist, it’s like totally cool. There’s no problem with that. Not every particle is keen on interacting with light.

Tom: Let’s not be biased towards the visible.

Vera: Yeah. So the reason that we are so used to light is because, you know, it’s useful to us as creatures on this planet. Our eyes are very used to detecting light and so forth. But there are plenty of particles that are not, so interested in photons. So it’s not only that. In particle physics, there’s a pretty serious indication that the zoo of particles we know and love and have been able to explore so far. So all the things that make the stars in galaxies and earth and planets and all of the stuff we know how to detect and observe, and all of that, that all those particles, and not really enough to explain all the phenomena we see in physics. Even as recently as a decade ago, we discovered a new particle. And the history of physics is full of discoveries of new particles. So to imagine that there are more particles, that there’s more content and maybe even more forces to our universe than the ones that are easy to see, that we have seen so far, is really not unnatural, right? This very simple thing to think about.

Tom: As you were talking, I had this crazy visual metaphor in terms of looking at galaxies and really understanding that there must be so much more to it than these stars I’m seeing. So now I’m thinking of stars as like sprinkles on a donut. If I only see the sprinkles, I’m not really grasping the whole thing. I want to see that you’re Vera, you are studying the donut, right? You’re looking for the donut?

Vera: Yeah. The metaphor that I give to my students was that of a cupcake, right? Our universe is like a cupcake. And I tell ’em this, at the end of my 100 class, if you take anything from this is the universe is a cupcake, okay? It’s delicious. And so, the dough is dark energy. This is the stuff that makes it expand faster and faster. The icing that would be dark matter. It’s what binds galaxies together and enables structure to form in our universe.

And, you know, ultimately, probably us as well, in the sense that we wouldn’t be here if there weren’t for galaxies. And then the sprinkles, that’s the normal matter we get to see directly, the normal matter. But hey, I mean, we study things in ways that don’t necessarily involve the things we can see anymore. You’ve mentioned radio waves. There are also gravitational waves, which have been a beautiful thing, in more recent years, as a way to view the cosmos. So there are ways to explore reality beyond with our eyes.

Tom: With the time we got left, I want to turn back to some personal questions, and I think the first one I wanna start with is, what is harder for you, answering some of your students’ hard questions or answering some of your daughter’s hard questions?

Vera: The hardest questions always come from people who know the least about the subject. My kids and I talk a lot about science, but when you ask me that question, where my mind goes is to my students who are not physics majors. I teach this course frequently. It’s called Astronomy 100. It’s for you know, musicians and business majors, people who think that they’re not scientists. And it’s always the most unassuming students raising their hand and going like, What is inside the black hole? Okay, so this is a question that’s really easy to answer for a graduate student studying physics.

Well, singularity, right? And I’m done. I’m just done.

Tom: Yeah.

Vera: Then comes the follow-up for my master’s 100 students. And what, what is the singularity? Okay? This is where you start to sweat a little bit. That’s the point at which, you know, the laws of general relativity and physics as we understand them really don’t apply anymore. What does that mean? Right? And this is typically where I have to be like, you know what? I have to think about this. I have to think really hard and bring in everything I know, my entire physics experience, to really answer this question, and I ought to be able to do that. Right? And this is also where you realize that what we consider knowledge isn’t just the equations that are going to make a prediction.

We really feel like we’ve understood the universe when we can come up with these natural human language narratives on what’s actually really happening, and math is not the only language of science. It’s one of them. It’s unnecessary. One, it’s incredibly powerful, but it’s not enough. And I think as a community, my hope is that we lean more into valuing. our ability to communicate and share, truly share, these stories of our universe when we understand them and make an effort to share them with people who do not speak our language.

Tom: Yeah. Yeah. Have you found that degree to which you teach undergraduates and graduate students, you find yourself being a learner as well, beyond what you’re studying with your research?

Vera: Absolutely. Yeah. I think it’s hard to imagine this profession for me personally, as something I would do in isolation without other people. We’ve leaned for a really long time into this narrative of lone geniuses, right? People who will make breakthroughs and then impart them to the world. But I don’t think this is really how science works. I don’t think this is what drives science now, even. I mean, look at Rubin, right? This is this huge collaboration of so many people. Not all of them are lone geniuses; maybe none of them are geniuses.

They’re smart people, they’re driven. But what they’re accomplishing is by working together, by bringing their different perspectives and their different expertise together with this common goal. And to do that, you have to be able to talk, you have to be able to exchange ideas, you have to be able to operate in this space of community. It’s an inherently human endeavor. It’s an inherently shared endeavor, too. If I figure something out and die with the knowledge, I haven’t changed the world. I don’t feel good. But the mission isn’t accomplished really at that point in time. And moreover, I do think that, when they take the most joy out of my science, there’s that moment when I sit down with my kids, and tell them the story of neutrino particles that don’t really like to talk to other particles very much, so they travel billions of light-years through space before ever bumping into anything. And as they travel, they get to ruffle up the galaxies in ways we can see through our telescopes, and they can understand this story.

And this story is naive and goofy and childlike, and I should be ashamed to tell it this way as a serious scientist, or that’s at least the sense of the way our communities work. And yet it’s also in a sense very true.

Tom: So, Vera, thanks for taking the time to talk with me today. I learned a lot, and I really appreciate the enthusiasm and joy you have for science.

Vera: Thanks, Tom. It’s been fun.