Short Wave - The Ancient Night Sky And The Earliest Astronomers

Episode Date: February 1, 2023

Moiya McTier says the night sky has been fueling humans' stories about the universe for a very long time, and informing how they explain the natural world. In fact, Moiya sees astronomy and folklore as two sides of the same coin. "To me, science is any rigorous attempt at understanding and explaining the world around you," she explained to Short Wave's Aaron Scott. "You can see that they knew enough about the world around them to predict eclipses, to predict annual floods in Egypt, for example. I think that you can use folklore and mythology to understand the early scientific attempts of humanity." Moiya McTier is the author of The Milky Way: An Autobiography of our Galaxy. She joins us to draw out the connections between astronomy and folklore, why the night sky is more dynamic than it might look, and what it feels like to live on an astronomical timescale. See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. We don't know when ancient humans started to contemplate the night sky, but some of the oldest stories have been passed down by indigenous Australians for thousands, maybe even tens of thousands of years. They have in Australia both light and dark constellations. This is Moia McTierra, an astrophysicist and folklorist, and she explains that while some cultures create constellations by drawing lines between stars, like a giant game of connectadots.

Other cultures also focus on distinct patches of darkness and the otherwise crowded starry sky. They look like dark blobs because they're actually fields and clouds of gas that block light in the Milky Way. But they would assign shape and meaning to those. And one of the big dark constellations to the indigenous Australians

was the emu constellation. It looks like an emu with wings that's flying through space, so the wings and the feet are all streaming behind her. But the cool thing about the emu constellation is that she appeared in the sky right around the same time that emus on Earth were laying their eggs. And that was an important source of nutrition for a lot of indigenous Australians. And so we can see instances of this practical connection between astronomy and everyday human life all over the world, not just in Australia, although

there are many indigenous Australians who claim that they are some of the world's first astronomers. Moia sees astronomy and folklore as two sides of the same coin. It's a relationship she explores in her recent book, The Milky Way, an autobiography of our galaxy. We know that Polynesian wayfarers traveled thousands of square miles of oceans without compasses because they were using the night sky. And we know that, for example, ancient Egyptians could use the appearance of a specific star on their horizon, the serious star, as an indication that the Nile River was about to flood. And since Sirius is known as the dog star, this is where they're saying the dog days of summer

comes from. We did an episode about it, and we've got a link to it in the show notes. So they used it for very practical reasons, like timekeeping and navigation. But that's also where a lot of their gods lived. So people incorporated astronomy into their religion, which people hold very closely to their hearts. And so astronomy gets wrapped up into people's beliefs about how the world is and how it should be. And that's one of my favorite things about astronomy, that ancient humans were able to do it without advanced tools. As long as you have a memory of where things were before,

you can do really cool astronomical research. You don't have to know advanced math. You don't have to have fancy equipment. You just have to live in a place that's dark enough. So I think astronomy is like the people's science in that way. Today on the show, Moia McTeer takes us on a tour of humanity's long relationship with the night sky. And how the sky our ancestors saw looks different from the one we see today. I'm Aaron Scott and you're listening to Shortwave, the Daily Science podcast from NPR.

Moia, when we're looking up at the night sky, what are the stars that we're seeing? Would you please locate us in the universe? Yes. Oh, I love playing this game. Where in the universe are we? Okay, so we are in the Milky Way galaxy, which is itself in a little cluster of galaxies that we call the local group. Astronomers have identified about 50 galaxies that are all gravitationally bound to each other. But let's zoom in to just the Milky Way.

If you picture the Milky Way as a spiral galaxy, it has the black hole and the bulge in the center. That's where about 30% of the stars are. and then surrounding that that central part of the galaxy is the disk, which is what most people think of. It has the gorgeous spiral arms. It has most of the stars in the Milky Way. And our solar system is about halfway between the center of the galaxy and the edge. So we're about 25,000 light years from the center of the galaxy. And we're just outside one of the spiral arms of our galaxy. So, Moia, then on a clear night, that dense hazy band of stars that we see is then the disc,

of the Milky Way. And I love some of the stories that you tell in your book about how different cultures have explained it. I mean, the name Milky Way itself comes from a Greek myth involving Zeus tricking his wife, Hera, into nursing a baby Hercules that then ends in her scattering breast milk across the sky. Would you tell us another one of your favorite myths behind the creation of this path of stars? Yes, I would love to. People have been looking up at that path of the Milky Way and trying to explain it for thousands of years. One of my favorite explanations comes from the Khoisan people of Southern Africa. They have this story about a young girl who was out at night dancing around a bonfire. And according to this legend, before this moment, before this story,

the night sky was completely dark. There weren't any stars or anything to light your way at night. But after a night of dancing, this young girl was tired and hungry and she wanted to get home. I'm sure many of us have been there after a long night of dancing. And so she had to walk home but needed some way to illuminate her path. So she took some embers from the fire, threw them up into the sky, and that became the beautiful swath of the Milky Way. So they would see that as fire, but other cultures around the world saw the Milky Way as a flowing river of water or milk.

There are so many ways to look at the Milky Way. And people have throughout history. And I mean, this is really where you focused on this convergence of science and folklore. Can you tell us a little bit about how you think of that interplay, especially when it comes to the night sky? I would love to. So I actually have a very broad definition of science. To me, science is any rigorous attempt at understanding and explaining the world around you. And to me, that definitely incorporates mythology and folklore because

our ancestors weren't just making up these stories from nowhere. But if you look at the explanations that are encoded within myths, you can see that they knew enough about the world around them to predict eclipses, to predict annual floods in Egypt, for example. And they would use, often astronomy to do that. I think that you can use folklore and mythology to understand like the early scientific attempts of humanity. So a lot of these cultures have watched the stars, and they've figured out that they're all moving together in this giant kind of cosmic dance around us. But then I've also read that the actual alignment of the stars and the shapes of the constellations changes some over time. So if we were to say time warp an ancient astronomer to today, would they recognize our stars as their stars? And as, And what would have changed in what they look like? Yeah. By and large, I don't think any ancient human would be super surprised by our night sky today.

But there are a lot of things that could change the night sky because space is very dynamic. Everything in the universe is constantly moving. So I'd say the most immediate and shortest time scale change that we can talk about here is the Earth's procession around. its axis. So Earth is tilted. We have an axis that we rotate around and it's tilted at an angle of like 23 and a half degrees. But that axis changes. It moves around and every 26,000 years, our axis makes one full rotation. So it's kind of like a top that you spin and as it starts to kind of wobble before it eventually falls down. Exactly. But this does take place over 26,000 years. So it's pretty slow, especially compared to human timescales, but we can still notice it. So right now,

our North Star is called Polaris. But in about 13,000 years, the Earth's axis will have moved enough that our new North Star will be Vega. And something like 3,000 years ago, in the time of the ancient Greeks and late ancient Babylonians, the star that our axis pointed to, would have been different. Can you talk a little bit about maybe the concept of proper motion and like how, like even the constellations and these other stars are going to shift a bit over time, especially if we were to step back in time to, you know, like 200 million years ago? Absolutely. I love that you brought up proper motion.

As an astronomer who did many research projects based on the motion and position of stars, That has been the bane of my existence in the past. So proper motion tells us how a star appears to move in the sky as Earth moves through space. So Earth is moving around the sun, which means when we're on one side of the sun, stars can appear to be in a different position than when we're on the other side of the sun. But our sun is also moving through the galaxy. We're moving, it takes us about 250 million years to make one full round. Wow. Also, we have to remember that not all of the stars we see are technically disc stars.

Some of them are in the halo of the Milky Way, so they're passing in and out of the disc, and they don't have to follow this circular motion. So we've really been talking about what is relatively a small time frame. There is a giant impending change confronting our galaxy some four billion years down the road. Will you introduce us to Andromeda and kind of our impending, union? What a nice way to put it. Yes. So in about five billion years, we will be long gone by then. Our sun will be gone by then. But in about five billion years, the Milky Way and Andromeda galaxies are going to collide. Our two galaxies will come together. Their gas will start to mix. So there will be this cascade of new stars forming. But they're not just going to come together and clump in one pass. They're actually going to do this really beautiful dance. So they'll come together, they'll pass by each other.

Some of their stuff will mix. And they're going to pass by each other several times until the momentum between them gets absorbed. Like all of that energy fizzles out and they stick together. And what will be left is going to be a new elliptical galaxy that's made out of the chaos of these two spirals coming together and joining their lives. So in the book, I do talk about it as like a romance. I say that the Milky Way galaxy has been in love with Andromeda for billions of years, and it's just anxiously awaiting their eventual collision. This long-distance love is finally coming home.

Yes, they've been writing love notes in the forms of hyper-velocity stars for billions of years. So they are ready to meet. I think a lot of us think of the night sky is this very static thing. What is it like to take a step back in how we see it over like a much bigger time scale and think of it is actually a really dynamic dance taking place around us? Oh, yeah. I have been pretending to be a galaxy for the last two years as I was writing this book. And at first it was kind of a silly exercise and it made me feel very disconnected from humans around me. But then, when I started to take seriously the fact that I was now thinking on time scales of billions of years instead of just decades.

And I was thinking on size scales of billions of light years instead of just, you know, like the five-minute walk I take to get to the grocery store. When I started expanding my perspective in that way, I actually felt much more connected to everyone around me. And especially in terms of time, it helped alleviate you. a lot of anxiety that I have around feeling like I should be somewhere by some set time. In my own personal life, you know, I have goals that I feel like I should have achieved by now. I have milestones that I feel like I should have reached. But when I think about the long time scales of the universe and how slow everything is, I just relax and I go back into galaxy mode and I remind myself that things are moving,

even if I can't see it. I love all of this so much. Moia, it has been a pleasure talking with you. Thanks for gazing up at the stars with us. Oh, thank you so much, Erin. It's been a pleasure to be here. If you want to hear Moia McTeer talk about space on the regular, you can check out her two podcasts, ExoLore and Pale Blue Pott.

This episode was produced by Thomas Liu, edited by Gabriel Spitzer, and fact-checked by Anil Oza. Our audio engineers were Valentino Rodriguez Sanchez and Josh Newell. Rebecca Ramirez is our supervising producer. Brendan Crump is our podcast coordinator. Beth Donovan is our senior director of programming. And Anya Grundeman is our senior vice president of programming. I'm Aaron Scott.

Thanks as always for listening to Shortwave from NPR.