Planetary Radio • Feb 07, 2024

Exploring solar eclipses through time

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Ed Krupp

Director of Griffith Observatory

Asa stahl portrait

Asa Stahl

Science Editor for The Planetary Society

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Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

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Sarah Al-Ahmed

Planetary Radio Host and Producer for The Planetary Society

This week on Planetary Radio, we delve into the evolution of humanity's relationship with one of our planet's most awe-inspiring phenomena: total solar eclipses. Ed Krupp, the director of Griffith Observatory in Los Angeles, will share insights from the fascinating field of archaeoastronomy. We'll explore how cultures throughout history have interpreted and imbued solar eclipses with meaning. We'll also introduce The Planetary Society's latest addition, Asa Stahl, our new science editor. Then Bruce Betts, The Planetary Society's chief scientist, shares a new random space fact and his experience with historic astronomical sites.

2017 Total Solar Eclipse
2017 Total Solar Eclipse The total solar eclipse on 21 August 2017 captured the attention of millions as it passed across the United States. This image of the eclipse during totality, taken in Douglas, Wyoming, captures our star's streaming corona in stunning detail. Total solar eclipses provide a unique opportunity to study our Sun's atmosphere without the use of space-based coronagraphs.Image: Blake Estes
The Planetary Society communications team at Griffith Observatory
The Planetary Society communications team at Griffith Observatory On Feb. 15, 2023, The Planetary Society’s communications team and new director of government relations, Jack Kiraly, visited the historic Griffith Observatory in Los Angeles, California. From left to right: Danielle Gunn, Jack Kiraly, Mark Hilverda, Andrew Pauly, Sarah Al-Ahmed, Merc Boyan, Rae Paoletta, Kate Howells, and Ambre Trujillo.Image: The Planetary Society


Sarah Al-Ahmed: We are exploring humanity's evolving relationship with total solar eclipses this week on Planetary Radio. I'm Sarah Al-Ahmed of The Planetary Society with more of the human adventure across our Solar System and beyond. You and I might be excited for the upcoming total solar eclipse in Mexico, the United States and Canada in April, but our ancestors, they might've had a different take. Ed Krupp, the Director of Griffith Observatory in Los Angeles, joins us this week to talk about the field of archaeoastronomy and the various ways that cultures have interpreted solar eclipses over time. But first, you'll get to meet The Planetary Society's new science editor, Asa Stahl. He's putting his PhD in astrophysics to work sharing space with everyone. We'll close out our show this week with Bruce Betts, the chief scientist of The Planetary Society for What's Up. If you love Planetary Radio and want to stay informed about the latest space discoveries, make sure you hit that subscribe button on your favorite podcasting platform. By subscribing, you'll never miss an episode filled with new and awe-inspiring ways to know the cosmos and our place within it. We've been very fortunate to add two new people to The Planetary Society staff this last month. Dr. Asa Stahl, our new science editor who you'll meet in a moment, and our new development associate, Simone Rein. I've had the chance to meet both of them in person, and as is the case with all of our coworkers, you can feel their enthusiasm in everything they do. It's always wonderful to have new people in the crew to help us share and advocate for space together. As a member of our communications team, you'll be hearing more from Asa in future shows. He's an astronomer, an award-winning children's book author and a science communicator. Here's how he fell in love with space. Hi, Asa.

Asa Stahl: Hi. Thanks for having me.

Sarah Al-Ahmed: It's so wonderful to have you on the team. It's an interesting thing when you know that you're about to have a new coworker but you have no idea who it is and then magically they're an awesome person. So it's great to meet you.

Asa Stahl: Wow, thank you. I really appreciate it. Yeah, I was also imagining that, but from my end times like 30 of meeting everyone at the same time and then everyone also turns out to be super amazing.

Sarah Al-Ahmed: That's great. It's always very overwhelming when you meet the whole team and you're like, "This is instantly awesome. Cool space people everywhere." But still a little overwhelming. Can you tell us a little bit about your background?

Asa Stahl: Yeah, absolutely. So I got into space I think in a weird way, unlike most other people at the society and probably members of The Planetary Society as well. Instead of being with it from the beginning, or I didn't look through a telescope at Saturn's rings when I was five or anything like that and fall in love with space. The first time I saw Saturn through a telescope was when I was in graduate school, when I was already doing my PhD in astrophysics. So I was a late bloomer for sure. What did it was probably what did it for a lot of people who love space, which was reading Cosmos. I thought when I was a kid that I wanted to be an inventor because my favorite movie was Back to the Future and I just want it to be Doc Brown and have cool science experiments everywhere and crazy hair and goggles and stuff like that. But instead, I realized, probably a little bit too late, that that's not really a real job that you can have. So then I thought, "Okay, I always love stories and I always engaged with my understanding of the world around me through stories." When I first took a physics class, it really spoke to me as compelling as this is the true story of the universe and we can describe it so elegantly and objectively through math. I had a great physics class that started getting me into things and then I read Carl Sagan and that just kind of blew me away. But even then, I wasn't sure I wanted to go into astronomy in particular or particle physics. I thought I want to get down to the ultimate, I want to drill down to most fundamental, which means either understanding what's going on, the ultimate structure of reality on the tiniest level or huge cosmology. So I fell in love with exoplanets as a specialty. That's what I ended up doing my PhD on. My research at Rice University and my research was about discovering newborn planets around very young stars to try to better understand how planets form and evolve and basically where we came from, how earth was born and developed and how rare something like earth is. Those were the sorts of ultimate questions I was trying to work toward. I fell in love with all that, again, because of the story of it. The story the universe is super compelling, obviously, but also every planetary system, now we're getting into some really relevant stuff to The Planetary Society, every planetary system I feel like tells a story. Yeah, I just loved reading about every new thing being discovered by Kepler. That was going on at the same time that I was an undergraduate and realized that I really wanted to contribute to that in some way. So I went to Rice for my PhD. I started getting into science communication while I was at Rice. I wrote two children's books while I was there, pop astronomy children's books, and I started writing science news for the public. My engagement with astronomy, I guess my background in it has always come first and foremost through just the concepts and learning about it, and it's been really exciting to interact more and more with the communities around it. Actually, the coolest part of my PhD was always going out to the observatory and actually taking the data. I would go out to McDonald Observatory in West Texas and I was working with this 2.7 meter telescope, which looked like a giant death ray built in 1970, and it felt amazing to be in charge of this huge machine. I think I realized my first time when I went out to the observatory and I was standing by the telescope and it was completely dark and all you could see was starlight and you can barely even make out where the dome is opening at first, and I realized there's something so uniquely sort of receptive about astronomy, that in every other science it feels like you have to actually interact with what you're studying in a direct way to study it. But we're just accepting the photons that are already coming towards us, right? We're just sort of running around in a huge thunderstorm with tiny buckets catching different drops of what's coming toward us.

Sarah Al-Ahmed: I had a very similar experience the first time I started observing through telescopes. I did my planet hunting at Lick Observatory on a much smaller telescope, it was one meter. But just being up there at nighttime, you can feel kind of the legacy of all the people that have been in that place before you, but also you're just kind of bearing witness almost. You're just there watching these moments in the universe come to you through the light from across light years and then trying to piece it all together with all of your colleagues. It's a very compelling form of science for me and clearly for you as well. But now we just get to talk to people about it all day and I feel like that's one of the coolest parts for me. The discovery and all those things was always beautiful, but getting to share that with everyone else was my favorite, favorite part. Now, you're going to be working with us getting to share all this cool planetary science with people. What is your job here going to be like?

Asa Stahl: Communicating astronomy to the public. So you're going to see me hosting a lot of videos alongside Amber and Bill. I'm going to be designing some of the new courses for a digital community and I'll be writing some of our content online as well, like articles, stuff like that.

Sarah Al-Ahmed: That'll be so cool. We need more classes. I love the way that people react to our classes and we just came out with our new Eclipse course with Mat Kaplan, so it'll be really wonderful to have you on the team to help us do this so we can help share even more space with people.

Asa Stahl: Yeah, I'm very excited.

Sarah Al-Ahmed: You've only been with us for a few weeks, but what has it been like so far?

Asa Stahl: It's been incredible to just be surrounded by like-minded space nerds, people who are super passionate about space and who really, I think, are emblematic of what is supportive and constructive and passionate about this larger community that we're a part of. It felt really weird to me at first because I have always come from institutions that don't really have much science communication, especially not in astronomy. The Planetary Society feels like it's really going places, that this is an organization with motive means an opportunity to reach new people, more deeply engage its existing audience and then just it feels like we're really effectively organizing broad social support to make a difference in astronomy and policy. I'm really excited to see what happens in the next few years.

Sarah Al-Ahmed: Now you get to be on our team, and with the backing of all of our members around the world, we're going to try to accomplish things that have never been accomplished by humanity before. It's one of those things that truly shows the power of science communication and how many people's hearts and minds you can touch by just sharing what you love. I bet you would agree with me that it feels very nice to be a part of that legacy.

Asa Stahl: Yeah, absolutely. When I was in the office, I had a meeting in Bill Nye's office at the table, the Carl Sagan table. It was his office previously or it was-

Sarah Al-Ahmed: That was the table that he used. In fact, people can see that table in our incorporation images where everyone's signing the documents for the founding of The Planetary Society is on that desk.

Asa Stahl: Very cool. Now I'm working at an organization that was literally co-founded by him, and that is his legacy directly. That seed of an idea that he then trusted to grow really has taken off and blossomed.

Sarah Al-Ahmed: Well, I'm glad to have you with us to help continue on this journey. I'm so looking forward to seeing what you get up to in the next year. It's wonderful to have you on the team and wonderful to have you on Planetary Radio for the first time.

Asa Stahl: Thanks so much. It's great to be here.

Sarah Al-Ahmed: Asa mentioned his children's books in passing. If you'd like to check them out, they're called The Big Bang book and Picnic Planet: A Lunchtime Guide to Your Galaxy's Exoplanets. Now for something completely different, the countdown to the April 8th total solar eclipse in Mexico, the United States and Canada continues. We are now 61 days from our Eclipse-O-Rama celebration in Texas. Total solar eclipses have fascinated humanity for millennia, but fascination and understanding are two very different things. We're fortunate to live in an era where science not only demystifies these events, but allows us to appreciate their beauty and significance on a different level. Total solar eclipses happen when the moon passes directly between the earth and the sun, casting a shadow that briefly turns day in tonight. They're breathtaking if you understand them, but for much of human history, the sudden darkening of the sky wasn't an event that was eagerly anticipated by millions of people, each of them equipped with their protective glasses and their cameras and their telescopes. Eclipses were mysterious but also scary. There are still many beautiful cultures on earth today that have practices that reflect this. Thanks to the field of archaeoastronomy, we can bridge the gap between how our ancestors viewed these celestial events and how humanity thinks of them today. Our guest today is Dr. Ed Krupp. He's the director of Griffith Observatory in Los Angeles, California, and his thirst for understanding humanity's evolving relationship with the cosmos has taken them to archaeological sites around the world. Hi, Ed. It's wonderful to talk to you again.

Ed Krupp: Nice to see you, of course, Sarah.

Sarah Al-Ahmed: You've been the director of Griffith Observatory for decades, and I believe that this year marks your 50th anniversary of the appointment of your time as acting director of the observatory. I think it's an anniversary that's worth marking because you've spent decades sharing astronomy with people from all around the world, and that's something that deserves at least a cake.

Ed Krupp: Very sweet. As long as you brought that up, I should just put it a little bit into perspective. It's actually quite a privilege to get to be able to do astronomy. There's no good reason why someone should be paid to do astronomy, but in fact, our civilization and our society has managed in one way or another to make that possible. I'm ever grateful that something I had a mind to do as a kid and always wanted to do was actually possible to do. So it seems marvel to me that it's been that way.

Sarah Al-Ahmed: I feel very similarly privileged. I just get to spend all day sharing what I love with people and studying the wonder of the universe and who doesn't want to have that job. That's so lucky and amazing. I want to say during the lead up to the 2017 total solar eclipse in the United States, you gave a wonderful talk about the different ways that cultures have classically interpreted solar eclipses, and that you have this beautiful unique knowledge of the subject matter because you're an archeoastronomer. For our audience who's unfamiliar with the term, would you mind explaining what archaeoastronomy is and what's so important for understanding ancient cultures?

Ed Krupp: Sure, and I hope you'll forgive me for making a minor correction. I don't regard myself as an archeoastronomer and I'm not sure they really exist. There is archaeoastronomy, although these days the people interested in that subject, a word that's got way too many vowels, usually call it cultural astronomy or astronomy and culture, and it embraces everything from prehistoric and ancient astronomy to anthropological studies, ethnography and so on, and even popular culture. It can be everywhere and anywhere. But that said, the whole business of relating the meaning of the sky to people is certainly something that has attracted my attention ever since I first got involved with it was also a little bit more than 50 years ago.

Sarah Al-Ahmed: How did you first become interested in the field?

Ed Krupp: Well, a couple of things. I think there's a general curiosity that most people have in things like dinosaurs, paleontology, astronomy, and the wonders of the cosmos and archaeology and all of those ancient ruins and whatever mysteries people might imagine they contain. So that kind of just comes along from childhood. When I was a lecturer at Griffith Observatory, we did a show that was about ancient astronomy, Egypt and Stonehenge, at least as it was understood at the time. None of that though really propelled me in any particular direction with this material. But the fact is when I first started working full-time at Griffith Observatory in 1972, and it was my first full-time job, I was suddenly realizing that a year from that time the city would pay me to go on vacation for two weeks. I thought that was really miraculous, quite a marvel, especially after six years in graduate school where there is no vacation. So I thought I better do an astronomical mission. I should make use of this vacation. There were a couple of false starts with an eclipse in Mauritania that never happened, but that was the sort of gist of it. Gee, I think I'd tried this and that. During those months of '72 headed toward the summer of '73, because I was a collector of books and I would get catalogs from various places including Blackwell's in Oxford, England. So I get these catalogs and I page through them and see if there's anything of interest to me. I was going down one page and I came across this title, Megalithic Lunar Observatories by Professor Alexander Thom. I thought, "I know what megalithic is. That's big stones. That's like Stonehenge. I know what lunar is, for God's sakes, that's the moon. Observatories, well, those are observatories, but I do not know how these three things go together." So I sent away for the book just as a lark to see. After reading the book, which is rather technical, I thought, "Gee, this is odd. There are all these places in England and Scotland and Wales, nobody knows anything about them." There are over 900 stone circles in Britain and those are just the only ones that are left. There was way more of that in antiquity. So I thought because interpretations had led to some astronomical elements of these places that I should go have a look, that I would go on an expedition to see and photograph these sites, evaluate them in the field and come back sort of as people might say, back in the last century, like Frank Buck who went out capturing wild animals and bringing them back to zoos and circuses, I'd bring back the prehistoric British monuments alive to Los Angeles and maybe we do a planetarium show or something. I didn't know. So I went off on that trip, and the trip itself had a number of unexpected marvels develop out of it, including running in, quite by chance, to Professor Thom who wrote the book as we were on the way to Orkney, which he had persuaded me to visit when I contacted him by mail prior to ever leaving. So had a look at a number of these places, came back with 100 and what 20 rolls of film. I know people don't know what film is anymore, but that's how we took pictures in those days. Then I had the curious discovery that it was possible to go away out of the country for two weeks and come back and people thought you were an expert for going and looking at these things. So the next thing I knew, UCLA was asking me to put together a course, and then to put together a course you have to find people. I realized there was this handful, and it was literally a handful of people in the U.S. and beyond who were interested in this kind of thing. So that began a kind of more serious and formalized pursuit of this, and the studies themselves evolved out of that. More people found more people. But I started this long winded anecdote by saying, "I'm not really an archaeoastronomer, although I think there's archaeoastronomy." That's because this examination of ancient and prehistoric and traditional astronomy is really a conversation that includes everybody that has an interest. I mean, it includes art historians and archaeologists and anthropologists and historians of astronomy and astronomers and engineers and people who are interested in history of religion. So its cross-disciplinary character is what actually made it work, that you wound up talking to people who knew things that you didn't know but you needed to know and that continues how it's proceeded. It's gotten more organized, more developed since then, but that's how it began.

Sarah Al-Ahmed: There have to be some really unique challenges to trying to interpret ancient cultures' different sites that were based on astronomy. How do you even go about trying to figure out what they were trying to do with the site if no one has figured it out before?

Ed Krupp: Yeah, you're absolutely right about the fact that, one, it's difficult, and two, maybe it's even impossible. What those conditions do is invite speculation, and speculation is really dangerous because it just romanticizes the past and doesn't necessarily get you closer to the truth. So you really do have to wrestle with what evidence you have and how well then you can know something given the evidence. That means there is no clear cut methodology that says, "Okay, if you do this, this and this, you've got it right." I think the primary principle that's required when you look at any ancient site is the insistence of finding independent lines of evidence that converge, and they're not going to prove your point, but they might at least make it seem more plausible, more sensible. Some problems are harder than others. For example, I had the pleasure really of working my way through the field notes of John Peabody Harrington, an extraordinary American anthropologist. He went all over the country collecting information on tribal peoples and languages, and he put them on notes and filled trunks with them and then leave the trunks one place or another, a lot of them now are at the UC, University of California, some are in the Smithsonian, but he never published much of this stuff. But I was going through some of Harrington's notes on a very deliberate project for the Luiseño tribe of Southern California. They're still all out there. There are a number of Luiseño bands. Harrington describes this rock that actually his consultant that was riding along in the car with him between Pala and Temecula in Southern California, and the consultant Jose Albano says, "Oh, that's the Milky Way rock." Although he uses the Luiseño word. I'm thinking, "What the Milky Way rock? What's that about?" As it turns out, I put out a kind of feelers to people I knew in the area and one of them, an archeologist, Dr. Bruce Love, after I let him know where I think this rock is and would he go out and see if he could find it. Within four days he got back to me, "I found the rock." So we went out there with a couple of the Luiseño singers to have a look at it and it's extraordinary. So this is something that's mentioned in the ethnography. The ethnography also tells you part of its meaning, and so you can, in fact, relate that to other aspects. That's a very different kind of a problem than when you're just looking at a structure that has an alignment say on the moon at its northern extreme, and you say, "Well, was that intended or was that by chance?" Very often it's not possible to say.

Sarah Al-Ahmed: Such a complex and fascinating subject. I could listen to you tell these stories about your adventures for days because I'm sure you've been to all kinds of really interesting sites around the world to learn more. I would love to ask you more about how cultures have classically interpreted total solar eclipses. Because I feel like they're probably an awe-inducing event for anyone who witnesses them no matter their level of understanding. But for cultures who didn't really understand what was going on there, that must have been a really puzzling and perhaps terrifying thing to witness.

Ed Krupp: There's no question that eclipses were troubling to just about everybody. It's quite ironic, in fact, in the genuinely correct use of the term that something that just about everybody on the planet worked hard to avoid in antiquity now draws millions of people spending lots of money in order to be able to see them. As is the case for a total solar eclipse where you have to be right on the path. Of course, in antiquity, most of the time people didn't ever come close to experience a total eclipse. Those would be relatively rare for any particular location, although from time to time you might get a major settlement that really was completely immersed in the darkness of a total solar eclipse. But even partial eclipses would be unsettling, and they were known to people and they were known from deep antiquity. We have, for example, Chinese records from the Bronze Age references to eclipses on oracle bones. You're talking about the middle of the second millennium BC here. So that's explicit. It's easy to imagine that that kind of experience and understanding goes very far back in time. Then if you survey what various people have had to say about eclipses, there's a remarkable consistency. The details vary, but there's a remarkable consistency, and the primary principle that comes up is, of course, obvious, these eclipses are trouble and they're trouble for a very obvious reason that's hard for us to absorb because it no longer relates to our experience of the world. For antiquity, an eclipse, partial or total, of the sun or the moon was not just an inconvenience, something that was changing temporarily the character or the appearance of the sun or the moon. It was in fact a challenge to the natural order of the universe. They saw the foundation of the cosmos under threat because the things that made the cosmos work the way they knew it did were suddenly being subverted. The sun comes up, it shines, it sheds light, it goes down, it happens every day. People are used to this. Then in the middle of the day, the sun doesn't do this thing that it's doing every day, that is out of joint. Same thing with the moon. When you get an eclipse of the moon, you're dealing of course with a full moon, and that's, again, a bright round moon, everybody knows what it looks like, and then it looks like a bite is being taken out of it. Well, that shouldn't be happening. So that is a challenge to the established order of the cosmos, and that's why people get anxious. It's not just the sun or the moon that is in trouble, it's we who are in trouble because the very order of our world appears to be challenged.

Sarah Al-Ahmed: We'll be right back with the rest of my interview with Ed Krupp after the short break.

Mat Kaplan: Hi, it's your old friend Mat Kaplan of The Planetary Society. A total solar eclipse is coming to North America on April 8th. More than 600 million of you will be able to see at least a partial eclipse, and over 40 million people live in the path of totality. If you want to be ready to experience this rare cosmic event to the fullest, take The Planetary Society's online course all about solar and lunar eclipses. It's only available to Planetary Society members in our wonderful member community. So join us today at That's

Sarah Al-Ahmed: How did humanity go from this space where we fundamentally didn't understand and found these things very terrifying to a place where we could scientifically interpret and predict these eclipses?

Ed Krupp: It's not a quick process at all, or even one that you can point to something and say, "Ah, that's it. There's the change." It's a gradual change. If you even look broadly across any given culture, the comfort that parts of that society might have with the event compared to other parts of society could vary. We find even today as worldwide eclipses are very familiar events and broadcasted and described, there are still pockets of communities where even if they know what's going on, they're still not comfortable about it and people will keep their kids inside while it's taking place and so on. So there's not a kind of a uniform moment where you throw a light switch and everything changes. But what does make a difference is the incremental accumulation of knowledge and experience, and that is particularly coupled with mathematical astronomy that allows people eventually to get to the point where they are predicting eclipses. So you can do that without necessarily even understanding exactly what's causing them because there's periodicity in the way these things appear. That's one of the things that we see in the very few Maya records of astronomical phenomena. There are eclipse tables in the Dresden Codex, one of the few books to survive the conquest in the burning of the books in Yucatan. But there's enough there for us to realize that they had an arithmetic system of being able to anticipate when eclipses might occur, and that's good enough. Because if you're ready, then you can do the next thing, which is to undertake whatever ritual action is judged to be efficacious in order to deal with this emergency. So that kind of thing obviously went on in various cultures, and in a few of them we have the remnants of it. But at the same time, that periodicity provides a kind of reinforcement of understanding and I think inspires an effort to figure out more. So gradually you get to the point certainly in the historical tale of the development of what passes these days as a so-called Western astronomy, it's really world astronomy, where you go from just a kind of a sense that there are seasons when these eclipses can occur. You have gravitational theory that allows you actually to predict and to know exactly when and why and how they're taking place. So that's the full pageant. I mean, you've got to go from Ptolemy, through Copernicus, through Kepler, you got to get through Newton as well, and all of those people have contributed, and many more, to this ability that we have now today to just send everybody out there and buy T-shirts.

Sarah Al-Ahmed: It's so funny because I have never seen the grounds of the observatory so packed is when we had eclipses. One of my favorite memories was always us during lunar eclipses going around and banging on pots and pans to try to banish the dragon or whatever monster or demon was eating the moon. That was always one of my favorite experiences with you personally.

Ed Krupp: Well, as you know, we were always successful.

Sarah Al-Ahmed: Well, we are awesome. But also it brings up this question for me, we knew that that was something that they did for lunar eclipses, but what did cultures around the world do in the context of solar eclipses to try to reestablish that power or bring the sun back if it was being eaten?

Ed Krupp: Yeah, it varies of course from culture to culture, but it's not a whole lot different from the kind of thing that you just described for the moon. Making noise of some kind was considered important by a variety of people, and it was essentially intended to make that creature, whatever it might be, that appeared to be taking a bite out of the sun to just back off, to go away. So you would find a similar kind of thing of banging on pots and pans taking place or other ritual activity that sort of like equivalent to marching around the breakfast table where people mobilize, they burn incense, they undertake activities that seemed culturally sensible to them, but the primary issue really is to try to interrupt the process in order to restore order.

Sarah Al-Ahmed: Well, this upcoming total solar eclipse on April 8th is occurring in Mexico, the United States and Canada. Do you have any tales of how people in North America used to traditionally interpret these events?

Ed Krupp: Well, it's again not so very different depending on the eclipse and the group of people. There is a retreat in many traditional societies of the general population inside to keep away from whatever is going on. Sometimes, for example, in the Great Plains, Rocky Mountain slopes, the idea was to burn a big fire, which would again disturb through that process the creature that was up there and causing this kind of mayhem. Even in historic times, there is a fine tale of one of the tribal men going outside near Fort Sill, and in the midst of an eclipse firing his rifle at the eclipsed sun, and of course the whole community around him applauded because, again, it all backed off and no one doubted that he was effective in taking care of that problem.

Sarah Al-Ahmed: I've definitely heard some stories of native cultures in the United States firing arrows at the sun and that kind of thing to try to get it back. It's really beautiful to learn how all of these different cultures interpreted this, but it seems that across cultures, across continents, humans had a similar perception and dealt with it very similarly.

Ed Krupp: Yeah, I think the underlying theme is, for all practical purposes, universal. There are a couple of exceptions, but they are rare. It just goes back to that same point mentioned earlier where people realize that the world is not how it should be and they need to do something to help bring it back because they're under threat. The visualization of the threat, for the most part, as a creature taking a bite, whether it's a dragon or a dog, a snake, any of those things would be always imagined as being visible by the fractional disappearance of the circular disc of either the moon or the sun because it does look like something is taking a bite. So that way of talking about it cuts across almost all cultures with very, very few exceptions, and it's because that's what they're seeing, and as a result, they're just trying to make sense out of the phenomena that they are encountering. In the case of ancient Mexico, particularly the Maya, but it bleeds into Central Mexico as well from more southern Maya territory, the planet Venus in particular was known and it was regarded as the agent, or at least a primary agent of eclipses, and it was portrayed most often, not exclusively, but most often as a snake, as a serpent with jaws taking a bite. But the reason that that occurred that way is that Venus pops out almost in every eclipse. So when the sun goes into total eclipse, you will almost invariably see Venus in the sky with it. Normally in the daytime, most people wouldn't see Venus up there with the sun, and so it's an intruder and it becomes the agent somehow of causing this trouble, even though it's just a spot of light, it has the power to cause this difficulty.

Sarah Al-Ahmed: It was absolutely startling in 2017, that was my first total solar eclipse, but watching the planets come out in the middle of the day, or even just looking up at that total solar eclipse as the moon passed in front of the sun, even with all of my understanding and all of my prep, it still filled me with this unbelievable sense of awe and trepidation. I could almost feel my ancestors shock and awe at the experience just being there.

Ed Krupp: I don't blame you because everything is a little untimely as well. I mean, the way the lighting changes, I mean you're used to daylight coming in the morning and disappearing in the evening, and you have just a kind of habitual sense of how those changes ought to occur, and just the lighting levels as well, and the character of the lighting as you approach totality and reach it is different. That's not lighting that we encounter. The shadows aren't shadows that we encounter. You'll get a sharp edge and a fuzzy edge. Everything looks a little grayish steely, a little off, and that's just part of what's essentially a three ring circus of so many things going on at once. It's actually hard to keep track of all of them.

Sarah Al-Ahmed: What are some of the coolest total solar eclipses you've personally witnessed?

Ed Krupp: The one coming up will be my 17th.

Sarah Al-Ahmed: Wow.

Ed Krupp: The fact is you can't do coolest because the bottom line with a total solar eclipse is everyone is different. So their charm is in, "Oh, I never saw that happen before." So we also have a perspective that there's a certain total solar eclipse we're supposed to see. We imagine all of the effects that we read about, and so we go to them prepared to see all these things, or at least a number of them. Well, every once in a while, just to speak of among some of the complications that occur, there's weather, and weather can completely obliterate your expectation of totality. So I've lost a couple of totalities to weather like that, but in doing so, I've seen things I would've never seen before. So your understanding of what's going on with the earth, what's going on with the sun and the moon, it becomes expanded by this experience that you didn't go to all that trouble to see. I was in Mongolia in 1997, waking up in the middle of the night in my room in the lovingly known Russian Hotel and looked out the windows and I could see stars, and I was thinking, "This is great. We got a chance." I went down early the next morning to the front porch only to discover, it was of course still quite black and it was snowing. So we were supposed to get mobilized outside when it's snowing and dark, and I had no idea what to do. I hadn't a clue. So we just headed north and we found ourselves where there was a great camp of eclipse watchers all under a cloud, and you continue to get teased by the sun because it shines through the clouds, and a lot of it, even when it's partial and you think, "Well, we've got a chance." Then we hit totality and I laughed out loud because everything just disappeared, it just went away. But then in a moment, I saw the shadow of the moon crossing over the clouds over my head, just rolling over them, which I would've never seen before heading out to somewhere like Lake Baikal where I could see there was this tiny window of clear sky that was getting a visible total solar eclipse. I was saying, "Those lucky folks out there." But I soon realized, "Wow, I would never have seen this shadow like this before."

Sarah Al-Ahmed: That's such an amazing experience, and I hope someday I'll be able to say that I've seen 17 total solar eclipses. This is going to be my second one.

Ed Krupp: That's good.

Sarah Al-Ahmed: Do you have any plans for the upcoming April 8th eclipse?

Ed Krupp: Yeah. Griffith Observatory Foundation has mobilized two tours, one to Texas and one to Mexico, and I'm leading the group to Mexico. We'll stop first in Mexico City and visit a number of the major sites, Tenochtitlan, which is the heart of the Aztec capital and has astronomical imagery and alignments built into its monuments. We'll go out to Cerro de la Estrella, that's the hill of the star where the Aztecs watched at a particular time in a 52-year cycle of their calendar for the Pleiades to continue going overhead at midnight, and if they kept going, that meant that the world was not going to end, and it was all actually related to what was going on below. But we'll go to Cerro de la Estrella, and out to Teotihuacan, the site that really was the first and major city in the Americas long before the Aztecs and such, which also has some astronomical components. Then we had to Mazatlán on the West Coast. That's the place where the eclipse on April 8th first hits continental territory. It does a little waterski bump over some islands, and then it hits the continent there at Mazatlán and we shall attempt to see it there.

Sarah Al-Ahmed: That's going to be so fun. We're all throwing a giant Eclipse-O-Rama event in Texas, so we'll be with you in spirit as we watch this wild event pass over the United States and Mexico and Canada. I think millions of people are about to have their minds completely blown. What do you think people should do to understand more about the cultural traditions in the areas where they're going to go see the eclipse?

Ed Krupp: It's not such an easy thing to do, particularly with this eclipse. Mexico is easy. If anybody going to Mexico, there's a lot of material written about eclipses in ancient Mexico, and you can find them in my books and books of plenty of other people as well. When you start moving into the U.S. territory that you're talking about, the evidence gets a little sparser in terms of detail. I don't think that there's really a sort of a one-stop shop where you can possibly figure out some of the things that are going on, and in many cases we don't even know.

Sarah Al-Ahmed: Just sounds like there's a need for even more people to follow in your footsteps and all the other people that are interested in this field to try to put together the human puzzle and the scientific mystery that is these eclipses.

Ed Krupp: Well, you got that right.

Sarah Al-Ahmed: Well, thanks for joining me today, Ed. I wish you all the most beautiful weather in April. I hope we're all going to see this. Archaeoastronomy is such a fascinating topic that we've barely scratched the surface. Dr. Ed Krupp has written many books on the subject, which you can find under the name E.C. Krupp. Some that you might be interested in would be Echoes of the Ancient Skies: The Astronomy of Lost Civilizations, Archaeoastronomy and the Roots of Science, and Skywatchers, Shamans & Kings: Astronomy and the Archaeology of Power. On a personal note, Ed played a huge role in my development as a science communicator. He edited my articles for years and I learned a lot. Here's to all of the mentors that helped us along our way, and speaking of which, here's The Planetary Society's chief scientist and generally awesome person, Bruce Betts for What's Up. Hey, Bruce.

Bruce Betts: Hey, Sarah.

Sarah Al-Ahmed: I had a really good time talking to Ed Krupp about the ways that people throughout history have thought about solar eclipses, and I think what really stuck with me most was this idea that eclipses were like a violation of the natural order. I don't know if you've ever felt like that starring up at an eclipse, but I kind of get it.

Bruce Betts: I can see that, especially when you don't understand the natural order as was true hundreds of years ago. But I guess I think it's truly amazing and cool, but I see it more as a real example of the three-dimensional nature of the objects and the orbits and something we don't get to see, particularly with our own eyes, our carefully protected eyes. So I guess in that respect, I think it just demonstrates the natural order.

Sarah Al-Ahmed: What's more ordered than a perfect syzygy. But honestly, I mean, even-

Bruce Betts: The word syzygy?

Sarah Al-Ahmed: Syzygy. I didn't even know what that word was until I graduated from college and someone gave me a bottle of wine called Syzygy, and I had to look it up.

Bruce Betts: That's funny.

Sarah Al-Ahmed: I really felt as I was staring up at that total solar eclipse, even with all of my knowledge, it was like I could feel the trembling of my ancestors looking up at that thing. It was just so profoundly outside of my everyday experience.

Bruce Betts: It's super weird.

Sarah Al-Ahmed: Super weird, so we get it.

Bruce Betts: Yeah, no, it's super, super weird, and if you didn't expect and know that was coming or what the heck was going on, yeah, that'd be bad hoodoo you'd think.

Sarah Al-Ahmed: Part of what's really cool about the things that Ed Krupp said is that in order to gain this knowledge, he's basically gotten to travel around the world looking at these ancient archaeological sites that were designed for astronomical purposes. Have you ever been to such a location? I am sure that that's happened at some point in your life.

Bruce Betts: It has, although I don't know that there's a sure way to know that, but yes, but when I was a wee bit of a tyke. I mean, old enough to remember things, but when I was 10, 10-ish, 10 to 12, we went to Chichen Itza where there is an observatory building the Mayans had, which of course they had their grasp of the calendar, which caused us to all die in 2012. No, that was a confusion of modern people. So anyway, yeah, it's pretty wild to think about it and it would be interesting. I look forward to hearing your interview about the archaeoastronomy sites.

Sarah Al-Ahmed: That is a challenging thing, right? Trying to interpret what people were thinking hundreds or thousands of years ago when they were building something. But we actually had a building in my hometown where the sun would shine through a little hole up in the wall on winter solstices. The whole town would try to be out there to go see this specific moment when the sun, it's crossing high overhead across the meridian would go right through that hole. It was awesome.

Bruce Betts: Cool, I got to do that. Where's my drill?

Sarah Al-Ahmed: Right? How cool would that be? We should drill a hole at the HQ just up in the wall.

Bruce Betts: Yes, we should do that, but not let anyone hear this because they might know who it is.

Sarah Al-Ahmed: We'll just ask Bill Nye. I don't know if people know this, but every once in a while, Bill Nye just adds something cool to our office. I went in there a few months ago and caught him screwing a piece of Martian meteorite into the wall. Didn't see that coming.

Bruce Betts: Oh, yeah, that was good. I liked that he did that. That piece of Martian meteorite was living in my file cabinet for quite a while, so I'm glad it's free and displayed now.

Sarah Al-Ahmed: We also had Asa Stahl, our new science editor on the show this week and-

Bruce Betts: Oh, good.

Sarah Al-Ahmed: I think that's really cool. We've got one more scientist on the team. It's wonderful to have another astrophysicist to talk to about all the nitty-gritty weird stuff that we are very passionate about.

Bruce Betts: Except for the astrophysicist part. But yeah.

Sarah Al-Ahmed: We'll be on that side and you can argue with us about planetary science, and then Bill can teach us all something cool because he's magic.

Bruce Betts: Wow, I did not know that. That explains several things, but anywho.

Bruce Betts: Radnom space fact.

Bruce Betts: So eclipses. Over hundreds of years, it turns out when you have enough statistics, there's a latitudinal dependence of total versus annular eclipses. So total when the sun gets completely blocked out, and annular when you're left with a ring of fire around the outer edge, the moon does not completely block the sun. This seemed odd, but it doesn't work on shorter timeframes because you need a lot of statistics. But over hundreds of years, you do see annular eclipses more towards the poles and less towards the equator, because on average, the poles are just a little bit farther from the moon making for more annular and fewer total eclipses. But then this one's more complicated. Total eclipses are more prevalent in the Northern Hemisphere, and annular are more in the Southern Hemisphere. There's also the total have the inverse correlation to the annular in terms of the first point. So why? Why, you may ask yourself, would this be true? Well, let's start with summer. Days are longer in the summer, more chance, so these are visible eclipses, more chance to see a visible solar eclipse if it happens to be summer. Well, you'd think that would not matter, except that northern summer, the earth is roughly at aphelion, and so the sun is smaller, farther away, and so the moon can block it more easily, so you get more in the Northern Hemisphere because our summer happens to be around aphelion, and the reverse is true for the Southern Hemisphere, of course, so you get more in the North and fewer in the South as well as the polar effect. So all very exciting. Not something that affects us a lot at any given moment, but it's a random space fact.

Sarah Al-Ahmed: That's a helpful one for me because I was actually kind of thinking about that the other day and wondering if anyone had actually done those statistics, particularly about annular solar eclipses and where you'd be most likely to see them. That's actually really cool to know.

Bruce Betts: I will send you a paper.

Sarah Al-Ahmed: Oh, I would love to read that, and then we can post it on the community so people can read it, but that was actually a really interesting random space fact. Thank you.

Bruce Betts: Thanks. I try every once in a while. We done? We out of this thing?

Sarah Al-Ahmed: Yeah, let's take this one out.

Bruce Betts: All right, everybody. Go out there, look up the night sky and think about the color green for no apparent reason. Thank you and good night.

Sarah Al-Ahmed: We've reached the end of this week's episode of Planetary Radio, but we'll be back next week with the team behind National Geographic's new documentary, The Space Race. It celebrates the triumphs and struggles of the first African American astronauts. Love the show? You can get Planetary radio T-shirts at, along with all kinds of other cool spacey merchandise. Help others discover the passion, beauty and joy of space science and exploration by leaving your review or a rating on platforms like Apple Podcasts and Spotify. Your feedback not only brightens our day, but helps other curious minds find their place in space through Planetary Radio. You can also send us your space thoughts, questions, and poetry at our email at [email protected], or if you're a Planetary Society member, leave a comment in the Planetary Radio space in our member community app. Planetary Radio is produced by The Planetary Society in Pasadena, California and is made possible by our members around the world who stare into the face of the unknown and pull out a telescope. You can join us as we share the joy of space science at Mark Hilverda and Rae Paoletta are our associate producers. Andrew Lucas is our audio editor. Josh Doyle composed our theme, which is arranged and performed by Pieter Schlosser. Until next week, ad astra.