The Milky Way and Beyond

DR. MOIYA MCTIER The Story of Our Milky Way Galaxy

GERALD HARRIS: Moiya McTier is an astrophysicist, folklorist, and science communicator based in New York City. After graduating from Harvard as the first person in the school’s history to study both astronomy and mythology, Moiya earned her Ph.D. in astrophysics at Columbia University, where she was selected as a National Science Foundation research fellow.

When she’s not researching space or imagining new worlds, Moiya can be found watching trashy reality TV with her cat, Cosmo. She’s a real person.

Welcome, Moiya.

MOIYA MCTIER: Thanks so much, Gerald. I’m happy to be here. HARRIS: What I want to do to get you started is just to allow you to introduce yourself in the opening comments. So who are you? Tell us what you want us to know. MCTIER: My story starts in rural Pennsylvania. I grew up in a cabin in the middle of the woods. I didn’t have running water. I didn’t have TV. But I did have a really big imagination. And I had a mom who shared with me her love of reading. So I don’t think anyone in my family was surprised when I said, “Oh, I wrote a book.”

But I got out of my hometown. I went to Harvard, where I studied both astronomy and mythology. Before I graduated, I wrote a science fiction novel that was set on a real planet outside of our solar system that I researched. And then I went to get my Ph.D. in astronomy at Columbia, where I specialized in studying the motion of stars around the galaxy and how that affects the habitability of different planets.

One thing I really want people to get out of my story, if they’re interested in pursuing a career in STEM, is that there is no time that’s too late to start. So many of my astronomy colleagues

PHOTO BY NATE RAYFIELD ON UNSPLASH

got interested in space when were five years old and looked up at the night sky for the first time. I was 19 when I started. I know people who went to astronomy grad school when they were in their thirties and forties; so it is never too late to get into STEM. HARRIS: We had a an astronaut here who basically said the same thing with a bunch of teenagers we had in the room. He said he was a C student in high school, and he didn’t really get going until late in his college career, and then he ends up being an astronaut. So he was echoing what you’re saying in terms of really, really encouraging people.

Let me ask you this. I read through at least more than half of the book, and then I was learning so much that I was having a hard time sleeping at night, because I was thinking of all the great ideas in this book. There’s a lot of stuff in there and I’m sort of, you know, a science person; I’ve got my Scientific American here and that kind of thing.

But if you were to say to the curious person, here are two or three things I really want you to take from this whole topic—because a lot of people don’t know how to think about this topic, they don’t know what they want to grab a hold of—give us your top two or three. You say, “Hey, really think about these.”

MCTIER:

I think the first thing that I would want people to know about space is how big it is in space. Like it’s physical volume, but also in time.

I feel we as humans have a really hard time imagining these huge scales. But I hope that by reading the book you get a sense for how far apart stars are and how far apart different galaxies are and how long it takes things to happen in space. I mean, it can take 10 to 100 million years for a planet to form around a new star. So I hope people get a sense of scale.

I also hope that they start seeing space as a dynamic thing. So many people think of space as static, that it’s standing still and it’s not changing, but space is moving and changing all the time. Our Milky Way galaxy is moving toward the Andromeda Galaxy at 100 kilometers per second. That’s really fast. Our sun is moving around the galaxy. We do one full orbit every 250 million years. So we’re moving. But these scales are huge. And I would hope that by getting more comfortable with those scales, people feel less intimidated by space and that they maybe start to zoom out from their own individual perspective a little bit. HARRIS: That’s something I took from the book as well, which is that maybe there’s something about the human experience that we don’t understand that we’re moving. So just in the short period of time you and I have been sitting her, we are a very long way from where we were 5 minutes ago. All of this is moving, including not only is the Earth moving, but the solar system is moving. MCTIER: The solar system, the galaxy—it’s all moving on different scales. HARRIS: So can you say more about these distances? Because it seems to me that when someone says light speed is traveling at 186,000 miles per second, one way I kind of think about that is someone told me that when the sun strikes my face, those photons left [the sun] about eight and a half to 9 minutes ago. Can you give us more about how far this is? MCTIER: [Laughter.] Really, really far. One calculation that young astronomers often can do when they’re in their early classes is to calculate how many stars will collide when the Milky Way and Andromeda galaxies merge in about 5 billion years. I remember starting to do that calculation and assuming that it’s going to be thousands or hundreds of thousands of stars having collisions, because it seems like that’s what should happen. Each of these galaxies has hundreds of billions of stars in them.

But I was proven wrong. I did the calculation where I took into account how fast these galaxies are moving and how far apart stars are on average in each of these galaxies. What I learned and what most astronomers get when they do that cal-

culation, is that only a handful of stars will actually collide. Because even though there are so many stars, they’re so far apart. I think that illustrates how spread apart things are.

The fun thing about those photons that take 8 minutes to get from the sun is that they take 8 minutes to get from the surface of the sun to you, but those same photons actually probably took millions of years to get from the center of the sun to the surface. HARRIS: Wow. I mean, it’s amazing that we don’t think about something that is hitting our face is over a million years old. MCTIER: That photon has gone through a lot before it reaches you. Imagine when astronomers are studying galaxies that are billions of light years away, collecting the photons that were emitted by those galaxies a billion years ago. That’s how long it takes the light to get to us, because that’s how far away they are. But even then, those photons, they make it billions of light years to come to us, and they get stopped from hitting the ground by our body being in the way or by our telescope being in a way.

I think that that’s just so beautiful that these photons go on such a journey and then get trapped on our puny little human instrument that we make. HARRIS: Can you say more about that? Because one of the things I kind of puzzle here is how small we are, because we’re really, really, really, really, really, really, really teeny and we don’t live that long, and our brain is kind of a blunt instrument for what it is we’re trying to figure out. So when you think about human beings, how should we think about ourselves in relation to the universe?

That’s a kind of a crazy question, but I really don’t have an answer to it once I realize how insignificant we are. MCTIER: It’s actually the type of question that I think humans should be asking and one of the things I tried to address in this book. There’s a section in it when the Milky Way—because this book i s told from the perspective of the galaxy— compares the human lifespan to that of a mayfly, which only lives for about a day here on Earth. The Milky Way says, “Do you ever wonder why the mayfly bothers to do anything? I mean, it lives its whole life in one room of your house. Why does it bother?” Then the Milky Way says that that’s how it feels about us humans. It’s amazed that we even bothered to do anything at all.

What I was trying to do with that was say, Yeah, we are tiny—physically in space and in time, we don’t live for that long. But that really does mean that all of the moments we have are precious and that we should make the most of the time we have and make the most of the possible connections with the humans that we can. HARRIS: I think that that’s wonderful.

The beautiful thing you did in the book is there’s almost a time sequence from the beginning and where’s it going to the end. As I’m reading the book, I feel like I’m kind of moving through really large scales of time. But along the way, you stop off at some very interesting points.

So when you start talking about gravity and black holes and dark energy and those kinds of things, tell us how you put those things in perspective, because it’s such a dense area, but you put it in sequentially. HARRIS: The book was in the form of an autobiography. I wanted to be inspired by autobiographies of humans, and those usually are written chronologically. It starts with the subject’s birth and then goes until whenever the others were ending their autobiography.

But the Milky Way has this extra, I don’t know, oomph to it. Like it knows what’s going to happen next. Unlike a human writing their own autobiography. So the Milky Way can actually project forward to say how it is going to die eventually when the universe ultimately ends or loses all of its energy. So it made sense for me to go chronologically through

DR. MOIYA MCTIER

shares the “personal story” of the Milky Way galaxy, the colossal place we call home, and helps us understand better the universe around us. Excerpted from the August 17, 2022, Technology & Society Memberled Forum program “Moiya McTier: Understanding the Milky Way.”

Dr. MOIYA MCTIER, Ph.D., Astrophysicist; Folklorist; Author, The Milky Way: An Autobiography of Our Galaxy

GERALD HARRIS, President, Quantum Planning Group; Chair, Technology & Society Memberled Forum, The Commonwealth Club of California—Moderator

that. HARRIS: When you start talking about the structure, the thing itself, and black holes, dark matter, dark energy, how it shapes things and how it doesn’t interact with anything—you get kind of descriptive. And I was thinking, it’s very interesting; sometimes you can describe something, what it does, but that still doesn’t mean you know what it is. MCTIER: There’s a lot of that in astronomy. We know how dark matter behaves. We can see it interacting gravitationally with stars and other galaxies, but we don’t know what dark matter is made of. We cannot see it. It doesn’t interact with light. Photons seem to just pass right through it as if they don’t care that the dark matter is there. But we can still see gravitational influence. So that’s how we learn about it. HARRIS: So there’s a lot of mathematics here. MCTIER: There is a lot of math behind what goes in the book, yes, but there is no math in the book. MCTIER: When I was reading through it, I was thinking, well, there’s a lot of math behind figuring out the fact that there’s dark energy in the universe. Someone had to do a calculation that something seemed to be missing here based on how the universe is operating. It must be something there. So you have some sense of what percentage it must be and all these kinds of things.

Talk about your background and being sort of a mathematician as well. You know, how you grew up, and a lot of people say people don’t like math, girls are not good at math. But that’s obviously not true of you. MCTIER: Well, it’s not true in general. Girls are great at math—girls, young women, non-binary folks—they have interest in STEM and they are really good at it. The problem, the reason we don’t see a lot of women in STEM careers or people of color in STEM careers is because it’s not a very welcoming environment for us.

I love science. I enjoyed much of doing research, but I got sick and tired of the way that I was treated in some spaces and I know that I didn’t get the worst of it. I know that there are other young researchers who are coming up who are having to fight to stay in this field, in this community, as they’re dealing with all sorts of nonsense.

So I think that it’s not a lack of interest. It’s not a lack of skill. It is a matter of what we call the “leaky pipeline” in academia, letting people slip through the cracks. HARRIS: It’s sort of lack of, I guess I would call it a welcoming, encouraging environment for people who don’t look like what they think they should look like or something of that nature. MCTIER: Yeah, exactly. Let’s I’ll use my experience as an example. I was 17 when I went to college. I came from a really rural town, a public school that definitely did not prepare me as well as my other peers had been prepared by their fancy prep schools. I walked into those physics classrooms and didn’t see anyone who looked like me. When I went to meetings, when I was looking for potential advisors, I didn’t see anyone who looked like me. I had one professor my freshman year tell me that I would never make it as a physicist because I was struggling too hard with the coding. I had never used a computer as anything other than a word processor before that year, so I was teaching myself coding on the fly. I had another professor my senior year who told me that I would never make it through grad school.

And here I am, Dr. Moiya, with a Ph.D., so these people say these things to young, impressionable students and researchers coming up through the field, and that can crush their confidence. The fact that I’m still here today is because of the small but growing community of women and people of color in astronomy who supported me and surrounded me in that moment and helped me see

“I love science. I enjoyed much of doing research, but I got sick and tired of the way I was treated in some spaces, and I know that I didn’t get the worst of it.”

—MOIYA MCTIER

that those professors were wrong and that I did bring value to the field. HARRIS: Absolutely. I’m so glad you’re able to express that, because I think we need people to hear that encouragement from you, to see your success, to validate their interest, to validate their drive.

Let me ask you kind of a tough question here. It has to do with the fact that as I was reading the book, I felt that I’m learning a lot about the Milky Way, but I’m also learning a lot about you and your personality, because, as you know, the Milky Way actually doesn’t have a personality; I don’t know that personality is exactly like yours, but I found it entertaining.

You’re pretty matter-of-fact; facts are important to you, logic is important to you, common sense is important to you. And I kind of [understand] that you don’t suffer fools very easily. MCTIER: [Laughter.] I used that exact same expression the other day. I was talking to my mom. I was like, “Mom, I just don’t suffer fools.” HARRIS: That was the impression I got from them. What that brought up for me, though, is your comment about mythology and folklore. Tell us a little about your thinking there and how this fits into how you develop your worldview. MCTIER: Absolutely. I studied both astronomy and folklore in college. As a folklore major my specialty was fictional world building. But I see mythology and folklore, these stories that people have been telling and passing down through cultures, as an early attempt at science. They weren’t just making stories up—I mean, some of them were, they were for pure entertainment. But a lot of mythology that sticks with us today was useful. It was based on observations that people made of the world around them. These stories were meant to try and explain what was happening.

This is why we have myths about the changing of the seasons or thunderstorms or eclipses. This was their attempt at trying to make sense, but it was also a way of encoding important practical knowledge, like how to use space to keep time or navigate or connect with other members of your culture.

There is this one example that I really love of Aboriginal Australian mythology, that they had a constellation in their sky and it was actually a dark constellation. So it’s not made of stars that you connect the dots with. It’s actually like a void that is shaped like an emu. They call it the

Emu constellation. And that constellation appears in the sky around the same time that the Earth emus started laying eggs every year. The Aboriginal

Australians would be able to use those eggs as nourishment. The constellation reappearing—they didn’t have Google calendars, they didn’t have cell phones to put reminders on, so they needed this constellation to be like, Oh, okay, we have the food now.

There’s so many other examples of that around the world and throughout time up until a few hundred years ago. And that is why I think that mythology is a type of science. I’m glad that we have science today in the way that we do with telescopes and beakers and hard numbers. Because I’m a nerd. I love numbers. But I also see and appreciate the value in indigenous knowledge and in traditional knowledge; I like to say that if you squint your eyes and turn your head to the side, you can look at those myths and see some scientific facts. HARRIS: It’s interesting the way that we think about mythology sometimes. In industrialized societies, we don’t see stars. We don’t see the Milky Way. We don’t see these things. So we’re out at the bar or whatever we’re doing at night, but we’re not [seeing the night sky]. In other societies where they don’t have all this stuff, they can look up every night and see that. How do you think that affects consciousness? MCTIER: I like the Dark Sky Association estimates that about 80 percent of the night sky for people around the world is affected by both light and air pollution. This makes it harder to see the stars, which makes it harder for us to connect with them.

I love that you ask how that affects our consciousness. I think it has had a real effect. Psychologists have studied how the loss of different types of connections for modern day humans has had a negative impact on psyches. One of those lost connections is connection with nature. You can [see] this in terms of getting out to the forest or like seeing greenery. But the night sky is also a really important part of nature. So many of our ancestors connected to the night sky daily, and it was a huge part of their lives. And that’s a part of the human experience that so many of us are missing now.

But I think that experience of looking up at the night sky, coupled with our modern scientific understanding of the universe, would be so powerful in helping

“I see mythology and folklore, these stories that people have been telling and passing down through cultures, as an early attempt at science. They weren’t just making stories up.”

—MOIYA MCTIER

people shift their perspective to thinking about things bigger than us. When astronauts come back from space, they talk about something called the overview effect, where they can look at every single person on earth through a tiny little window on the International Space Station. And when you’re up there, these identities that we have, like race or sexuality or religion, those start to seem less important when you can see the whole picture, and instead you see us as humans. You stop seeing borders, you stop seeing these conflicts that are real for us, but in the universe’s mind, they’re really petty.

I think if we could have more people look up at the night sky regularly and feel connected to it while knowing that it is an ever-expanding universe, billions of light years across—ah, that’s such a powerful message. HARRIS: I completely agree. I was humbled by it. Several years ago, we were off in northern California and at night the stars came out at a particular time. When I first saw it, they were so bright and it was just like they were right on my eyeball. I’ll be honest with you, I was initially frightened by it. But it also humbled me in a sense of [not only how] small I am, but just how wonderful existence is.

The fact is, some people are humbled occasionally by the magnificence of the universe. Maybe it leads to some thought process that’s not healthy. MCTIER: Yeah. I think Kendrick Lamar should write a song with me about how space makes you humble. HARRIS: Let me throw out a topic that is very popular, that people are talking about, which is the Webb telescope—what we’re learning, what we’re seeing. Give us your take on that and what it means for us and what we should do with it. MCTIER: Love to. The James Webb Space Telescope or JWST is this amazing instrument that we launched out into space on Christmas Eve last year, and it has in the last month or so given us some of its first images. And they’re gorgeous. What I love about them is that they aren’t showing us spaces of the sky that we haven’t seen before. What JWST is doing is showing us those same parts of the sky in more detail than even some astronomers ever imagined we would have. There’s this beautiful image of the deep field; in this tiny patch of sky that is as big as a grain of sand held out at arm’s length, you can see thousands of galaxies. Some of those galaxies were the first galaxies ever formed less than a billion years after the Big Bang; we can measure how far away they are. This is helping us understand more about what the universe was like early on. It’s helping us understand more about how galaxies form and how they can change.

But JWST is not just a one trick pony. It is also looking at star formation. There’s another gorgeous image of the Carina Nebula. Some people call it cliffs or whatever. But we are seeing through the clouds of gas and dust that we couldn’t see through before to see new stars forming.

There’s another really great instrument on JWST that doesn’t take images at all. It’s a spectrograph, so it’s actually looking a lot at the atmospheres of planets to try and figure out what elements you can find in those atmospheres. We got this gorgeous spectrum of a planet that showed us that it had water vapor in its atmosphere and we could see it so clearly, which is something we’d never be able to do before JWST.

I could talk about this forever, but it’s a really exciting telescope that’s helping us get a closer look at space that astronomers have wanted for a long time. HARRIS: Yeah, and you just said something that I don’t think people understand, which is those images are from a very tiny look at just a very small little area. There’s a lot more, so that if that’s what’s in this small little area, oh, my God. Wow. MCTIER: Exactly; wow. The thousands of galaxies in that one tiny patch—we have in astronomy something called the cosmological principle. It tells us some basic tenets of the universe. One of them is that the universe is isotropic. That means that the universe is the same everywhere. So if we are seeing thousands of galaxies in this one little patch of sky, then that means all of the other patches of sky also have thousands of galaxies in them. HARRIS: That’s why when people say if there’s not another planet out there with some life on it, this is a big waste of space, right? We just can’t be that unique, can we? MCTIER: There are a couple hundred billion stars in the Milky Way galaxy alone, and there are hundreds of billions of galaxies in the universe. And we think that on average, every star has a couple of planets. So there are trillions of planets out there. If we are the only planet that hosts life—like what? How?

Yeah, you’re right. There’s no way we’re that special or unique. But I do have to make my advisor proud and say, as a scientist, we have not found evidence of alien life. HARRIS: Let me go back to that Webb photograph, because this is something that I’m confused about. I think it was either the BBC or someone had a writeup about this and they said you see the ones that are red in color versus these others. So something about this is an image, this is not a photograph. So that tells us in a sense some data and some information around certain spectrums that allowed us to create these images. So a galaxy that may be really way out there close to the beginning of the Big Bang, and it’s probably not still there in that exact form, because that’s a long time ago.

“We’re not seeing those images how they are today— some of those red galaxies, we are seeing them how they were like 5 to 10 billion years ago.”

—MOIYA MCTIER

So w e just have this picture of it, but that’s not what it is today. Is that correct? MCTIER: Yes, you are correct. We are not seeing those images how they are today—from that deep field image, some of those red galaxies, we are seeing them how they were like 5 to 10 billion years ago. It’s almost like imagine you have the fastest camera in the world that can take the fastest picture. But you’re trying to take a picture of a moving train. By the time you snap the picture and it shows up on your screen and you take a look at it, the train is far gone. But you still took a picture of that train. HARRIS: That’s what I was trying to get to, because I was thinking, do people really understand that this is an image, it’s not the same as a photograph? MCTIER: I was a little confused, actually, when you asked the question about the distinction between an image and a photograph. And then you said that this image has data in it. Photographs also have data in them, because the way that modern photographs are taken is that the camera collects photons and essentially puts those photons into different blocks on a grid to show you like what the image looks like.

We’re essentially just taking pictures of space and looking at the photons in each grid to see what kind of photons are there. HARRIS: The limitations of these things we have as eyes, what we can see, this brain we have, is limited; so I kind of got the impression that even though we’re kind of in a learning mode—you talk about this at the end of the book that you really want us to kind of stay in this learning mode. But are we handicapped in some kind of way by the human desire to think that what we see is all there is? MCTIER: For a long time, we only knew about space in terms of photons. We were only collecting information about the light out there in space. Then we started thinking about other ways to collect information, and [we] started looking at gravitational waves to see how mass and matter gets distributed around space. We now have instruments that can measure temperature, that can measure electric currents and the strength of electric fields. These are senses that we don’t have as humans, but other animals do. There are sharks that have this sense of electric impulses around them. We can sense magnetic fields and electrical fields.

But just because we don’t have the senses doesn’t mean we don’t have scientific instruments to measure those quantities. So now we are putting those types of instruments on telescopes, and we’re not just getting light data anymore. We are not just limited by what we could see, even though we have been exploring in different regions of the electromagnetic spectrum for a hundred years. HARRIS: Here’s a question from one of our online listeners: Do you have a favorite constellation? Someone says “one that might be worthy of a tattoo.” MCTIER: [Displays a tattoo near her shoulder].Yes. I have a tattoo of the constellation Orion, which is more than just Orion’s belt. That is my favorite constellation.

I am terrible to go stargazing with. I got this tattooed on my body because it’s the only constellation I can reliably ID in the night sky. I’ve always had a very personal connection to Orion because it comes up in the sky in January around my birthday. I’ve always loved Greek mythology, especially the story of Orion, the Hunter.