Show Notes

• Google+: Fraser, Pamela
• Images of Tunguska
• Leonid A. Kulik — Virtual Exploration Society
• Tunguska Blast Still a Mystery 100 Years On — CNN
• Tunguska Event Caused by Comet – Universe Today
• Book: 100 of the World’s Greatest Mysteries
• Tunguska Event -- World Mysteries.com
• Was the Tunguska Fireball a Comet Chemical Bomb? — Universe Today
• Tunguska Event overview — The Planetary Society
• Lake Cheko and the Tunguska Event – National Geographic
• Nikola Tesla and Tunguska – Cracked.com
• Torino Scale (Ep. 242)

Transcript: The Tunguska Event

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Fraser: Welcome to AstronomyCast, our weekly facts-based journey through the Cosmos, where we help you understand not only what we know, but how we know what we know. My name is Fraser Cain; I’m the publisher of Universe Today, and with me is Dr. Pamela Gay, a professor at Southern Illinois University – Edwardsville. Hi, Pamela. How are you doing?

Pamela: I’m doing well. How are you doing?

Fraser: Doing really well. We’re actually ahead of time now. We’re actually recording in early December shows for mid-December and even late December, and that is how dedicated we are to getting this show back on track. We’re serious, we’re serious; we’re sorry, and we’re way ahead of schedule now.

Pamela: Yay!

Fraser: And as always we are recording this episode as a Google plus hang-out, and so if you want to participate in a live recording of AstronomyCast, all you have to do is circle me or Pamela in Google plus, and then we’ll, sort of, make a mention of when it’s going to happen, and then you can jump in and join the hang-out and ask us questions and watch us record the show, and then stick around afterward and we’ll answer questions until we’re tired. So super-fun, but you gotta be in Google plus to do it. OK, cool. And so today’s episode was…came from a fan, and they said they wanted a show on Tunguska and – sorry, I don’t remember who it was, but um, I remember someone asked for it, and we said that sounds like a great idea

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Fraser: Ready to roll?

Pamela: I hope so.

Fraser: OK then, so on June 30, 1908 something exploded over the Tunguska region of Siberia flattening thousands of square kilometers of forest and unleashing a force that rivaled the most powerful nuclear weapon ever detonated. What could release that kind of destructive energy, and will it happen again? So Pamela, can you, like, set the stage and tell us about this unbelievable event that happened in Siberia?

Pamela: Well, it was an otherwise perfectly normal summer in an utterly isolated part of the world. This part of Siberia — it’s north of Lake Baikal which is one of the clearest, cleanest lakes in the world, an area where there were still people who lived by herding reindeer to eat — no real cities, no real anything, and out of nowhere at 7:14 in the morning, something streaked across the sky, reportedly as bright as the Sun, and then exploded knocking people off their feet, breaking windows. The shock apparently reverberated such that it was detected as far away as Britain, and the thing was, this was World War II (editors note: World War I) time period, this was right before the Russian Revolution, and no one really actually went to see what all the fuss was caused by.

Fraser: For, like, years…

Pamela: For years…it wasn’t until the 1920s, and this to me is totally crazy because looking at the various reports, people were talking about the sky glowed at night for a couple of nights, observatories all the way around the world reporting that the opacity – how much light is transmitted through the atmosphere, the atmospheric transparency — was for months after this was worse than it had been in the past due to all the dust in the atmosphere. The entire planet knew something had happened.

Fraser: And so you say that it took a little while, but an expedition was sent to find…and what did they find?

Pamela: Well, they actually found the weirdest pattern of tree destruction ever known to mankind. So in 1921, using what is perhaps the strangest logic I’ve ever seen to fund a scientific expedition, Russian mineralogist, Leonard…I wish this was written in Cyrillic because then I could pronounce it correctly, but written in English it looks like it’s Leonid Kulik went, and he said to the government — this is coming off the heels of many wars, “Hey, it’s possible that an iron meteorite crashed in Siberia; we can use the iron for industry. Can you fund me to go look?” Now, here’s the thing: most meteorites that are found aren’t that big. It wouldn’t have been enough to do significant industrial work with, but it was still enough of an argument that they got the money they wanted, so this poor man took the train all the way across the country, found guides to guide him through the woods, got to the point where superstition said, “We’re going no further,” found a different group of guides to take him through the woods, and he found this area where there was essentially a swamp with a bunch of perfectly upright trees surrounded by a bunch of trees that were pushed over, sort of in a bull’s eye pattern with the pushed over, they were pushed away from the bull’s eye, and the bull’s eye, you can imagine, are the trees still pointed straight up. All the trees are scorched, and the ones in the center of the bull’s eye have all of their leaves, limbs lopped off, and all around are all of these bog pits that, at the time, he thought might have been caused from debris from an exploding meteorite.

Fraser: And so, you know, if you haven’t seen the pictures, you really should take a look at them. You know, the only thing that I’ve seen that even kind of compares is the destruction after Mt. St. Helens, where you have these slides, where you have just these trees that are completely flattened in all directions, but you can just imagine…and so the…like, how much space was flattened?

Pamela: The entire area of damage was over 800 square miles, so this is a fairly significant area.

Fraser: Yeah. Yeah.

Pamela: So roughly a little under 30 x 30 square…30 x 30 miles is the way to think of it — under that, but that’s like the size of a good-sized town, city.

Fraser: Yeah, and so OK, so then he finds this evidence, and then what does he do? No sign of the rock?

Pamela: Well, he went home because he had to [laughing], but once he got home, he sought funding to go out and do things a little bit more rigorously. So, when he first got out there, there were all these what he called pothole bogs, all of these – it’s basically swampy areas, and there were all of these places where there were these deep areas of bog, for lack of a better term, pothole bogs is what he called them, and he didn’t have the tools to excavate down into any of these, and so he went back, he got the money to do that, returned and started draining swamps in hopes of finding the meteorite at the bottom of the swamp. So here he is — huge region of damage, in the center is this one bog that he decides this must be the impact bog. It’s in “ground zero,” basically, from the destruction. He drains it out completely, and the only thing at the bottom of it, unfortunately, was a just a tree stump. So, that was rather unexciting. So, now he has this really weird situation where there’s 830 square miles of damage (that’s over 2000 square kilometers for those who are thinking European units, or actually units of everywhere except for the United States), and with all of this destruction, there’s no crater that they can identify, and this was completely mystifying to scientists of the time.

Fraser: Right, because they were starting to understand that some of the craters that they were finding on Earth, and the ones that you can see up on the Moon are, you know, were impact. They thought they were volcanism, but now they’re starting to discover that they’re from these impacts. So that made sense, but yet where’s the crater?

Pamela: Right, and so here they had this mystery. So, trying to figure out what it was, they started off with ideas like, “Well, maybe it was a meteorite that exploded in the atmosphere,” and so that was one of the models that people were working with, and another model (this one was put forward by Fred Whipple in 1930), he suggested that maybe it wasn’t a meteor, maybe it was actually a comet coming in and maybe the comet just happened to melt, ionize, blow up, whatever term you want to give to the transformation of comet to ionized material, water, and dust in the atmosphere, maybe that’s what happened instead.

Fraser: So, why, I mean, why wasn’t there a crater? I mean, wouldn’t you expect that there would be a crater every time?

Pamela: Well, if an object particularly big comes through the atmosphere, the expectation is large things — and this was estimated to have enough material to generate an explosion roughly 5 times the size of the explosion in Hiroshima, so this was a lot of energy… It was figured this was a several-meter-across object. How many meters might add a couple factors of 10 depending on what the composition was.

Fraser: Right, if it’s made of metal it’s one thing. If it’s made of rock, it’s something else, and if it’s made of snow, it’s something else.

Pamela: Right, but the expectation was something with that much energy probably would bring something through the atmosphere. Now, what’s been interesting is to watch over the past more than 100 years now since this event took place, how our ideas have changed. This is one of my favorite things to look at because I remember, just as a little kid, I had a book on this, like, “World’s Greatest Mysteries.”

Fraser: Me too! I think I took it out from the library, and it was like “What Caused the Event?” and we’ll get to the crazy theories in a second. I wonder if it was the same book. That’s funny!

Pamela: It just might have been.

Fraser: You and I both gravitated to the library, grabbed the same book, you know, half a world away. Yeah.

Pamela: I remember sitting on the floor between my bed and my window, like kind of hiding, reading the book with all the scary monster stuff, ‘cause like Loch Ness monster was also in the book I had, and it was just these pictures of all these trees destroyed and everything, and back then they were like, “Well, it was probably this, but there’s no crater. It was probably a meteor, but there’s no crater, but some people think it might have been a comet.” And today we think we actually understand what happened. It’s neat looking through the history.

Fraser: My book was a lot less rigorous than yours because mine went into the crazy ideas. So maybe we’ll get to that later on and dismiss them all. Mine also included black…microscopic black holes, and UFOs and all kinds of…so anyway, we’ll talk about that later, wormholes and stuff…let’s go to the realm of reality here, so please. Sorry.

Pamela: So in 1978, astronomer Lubor Kresák, um, pardon pronunciations again, he actually made the really astute observation that the Tunguska event happened at the height of the Beta Taurid meteor shower. So, this particular meteor shower was caused by Comet Encke, and he proposed that maybe this was a fragment of the comet that we just didn’t realize there was a big ol’ chunk still hanging around, and this big ol’ chunk decided to come through the atmosphere and aim itself at, well, Tunguska. And when they looked at the most likely path through the sky, based on the reports, when they looked at the timing and everything else, this kind of seemed to make sense. And over the past several years, people have done a variety of different things trying to look at chemicals in the area and different…what’s the mineralogy in the sediments, and all of these different things trying to figure out, “Well, what’s the answer?” And it’s gone back and forth from meteor to comet, meteor to comet every few years. So, in the 1990s there were some Italian researchers that looked at tree rings, and they looked for the particles that were trapped in the tree rings that grew during 1908, and what they found was that there was a lot of material commonly found in rocky asteroids, but that is found, albeit rarely…but is found in comets, so that pointed the finger at asteroids — wasn’t conclusive — points the finger at asteroids.

Fraser: So, like, it sprinkled the region with asteroid dust, and then the asteroid dust got incorporated into the trees as they grew? Hey, that’s cool. That’s really clever. Clever scientists…

Pamela: [laughing] So, this is basically the same thing as the KT Boundary only much, much smaller.

Fraser: In trees, yeah.

Pamela: But the thing is they had all of these different data points they had to explain as well. So they had be able to explain what was up with the noctilucent clouds, the glowing skies, all of the material in the atmosphere, and all of that pointed towards a comet exploding and blowing all of it’s materials into the atmosphere, and what was interesting is the reports for what was seen in the atmosphere actually matched the phenomena that we associate with the exhaust plumes of space shuttles launching at night, so there’s this new finger that points instead at comet, probably. Then in 2010, Vladimir Alexeev, they went and used ground-penetrating radar to look at the region, and what they found was it looked like there’d been some sort of a violent impact. They found a layer of permafrost on top — it’s Siberia, it’s cold, it’s still cold…that may be changing; beneath it were damaged layers of materials. So this was the shock wave hits everything and it…what happens when a crater forms is the material goes up, the material from inside the crater gets pushed out of the way, you have the fragments of whatever made the impact comes in, and then the material that got thrown up settles back down on top of it. So you can actually flip the surface material upside down in the process of forming a crater, and so when they used their ground-penetrating radar, they found this evidence for what looked like, well, no large rock, but none-the-less, shredded asteroid. Now, one of the weird things I can throw in that goes into the I-don’t- know-if-it’s-true-or-not-but-there-was-this-guy category is I was actually a foreign exchange student in the Soviet Union back in 1991, and I was studying at the Six Meter Observatory in the Caucusus mountains, and I met one scientist who had a small jewelry box with like the cotton that you usually get a necklace on in it, and on top of it was this really weird shard of material that he said was slightly radioactive, and he claimed was a shard from the impact at Tunguska, and I remember thinking, “I don’t know if this is a crazy dude or not,” but it’s something that I still remember.

Fraser: Well, and I think that there’s been some recent discoveries of hybrid asteroid-comets, so you know, so it’s not necessarily that anything is just an asteroid or just a comet now. You‘ve got these, you know, much more mixed-up, you know, snow and ice and rock and dirt, you know, everything, and so that, I think, really starts to blur the line, but it could be anything. And I know there was a really interesting…well, we were actually at the AAS — I think it was in Austin. There was a really great… someone had done a really beautiful simulation of an event, and showed almost perfectly these really amazing almost funnel-shaped impact where it airbursted, but it was almost like a gun, and it just shot the force straight down through the atmosphere creating a kind of pattern that we saw, and it really did sort of explain it, you know, that a lot of it just comes down to the angle, the speed, the direction of the Earth, the direction of the object. You get the right combination of factors together and you get this really interesting pattern. It’s interesting. I mean, it makes you think that maybe there were a lot more impacts that we just weren’t even aware of.

Pamela: The things is that…

Fraser: Maybe these are more common than we think.

Pamela: Yeah. The more I read, the more I keep noticing this sentence that’s just sort of tossed in there, over and over I keep seeing the sentence that, “If these occurred over the ocean, prior to the 60s and 70s prior to when we had satellite monitoring, no one would have noticed.” And, you know, that’s true. Most of our planet is ocean and no one would have noticed. And there’s lots of other places no one would have noticed. Deserts…

Fraser: Like Siberia…

Pamela: Well, Siberia, but there the trees get knocked over. But if you think about some of the deserts, no one would notice; prairie — unless you set it on fire, no one’s going to notice, so we’ve got all of these places where you just don’t notice. Now, one of the more intriguing things that I found looking up this story was there’s a lake north of where Tunguska took place. It’s about 8 km away; that’s, I think, about 4 miles away, and it was realized, you know, this lake it’s the right shape to be a crater, but it’s a lake, so they then had to go and measure it, and when they measured it and they looked at the thickness of the silt, the thickness of the silt corresponded to a lake that was only a couple of hundred years old, about how old it would be if it were formed by the Tunguska event, and when they mapped it out, it was crater shaped, and they found evidence from magnetic detections for a rock in the bottom that is about a meter in size and could have made sense if you had some sort of an exploding object. I mean, who knows how it’s going to distribute itself everywhere?

Fraser: Yeah, and I mean, with the evidence the impact actually jumbled up the terrain, it could have created new lakes, and hiding the impact all over the place, so that’s pretty neat. So, OK, so let’s go back to some of the crazier theories.

Pamela: [laughing] You just like this!

Fraser: I can’t wait. So, I’m trying to think…so microscopic black hole?

Pamela: No.

Fraser: But, why not? You can’t just dismiss it outright.

Pamela: So microscopic black hole…in general, it’s just not going to produce enough energy. I mean, that’s the thing about microscopic black holes is if [missing audio] one – yay! Great! We give Hawking a black hole because we finally observed one, and it’s going to evaporate. So, I’m not worried about a microscopic black hole.

Fraser: Right, and if…and so a microscopic black hole would just probably just pass right through the Earth and maybe interact with the occasional atom, but probably not, just go straight through to the other side.

Pamela: And, I mean, the thing is if it was a microscopic black hole, and it wasn’t one that happily, spontaneously evaporating over Siberia, if it was passing through, there would have been an exit event. We would have seen something on the opposite side of the planet along some sort of a vector.

Fraser: A crashed alien spacecraft?

Pamela: Yeah, no. We would have found it.

Fraser: Well, what if it was a crashed alien spacecraft made of rock and ice and dirt…

Then it’s not exactly going to stand up real well to the vacuum of space.

Right, OK. Alright, I’m trying to think, what were some of the other…if anyone in the chat room remembers — some of the other wonky theories…what are some of the other crazy theories that you’ve heard of?

Well, my favorite wonky one and I think this is because I watch “The Sanctuary,” which…I’m a connoisseur of really bad sci-fi shows, and I’m a fan of “The Sanctuary” and it qualifies as really, really back science fiction, and it has Nikola Tesla as one of the, like, characters in the show, and so that’s long lead-up to one of the theories is that it was caused by, I’m going to mispronounce this, the Wardenclyffe Tower, that was basically a giant Tesla coil that Nikolai Tesla had commissioned to be built, but they ran out of money before it was ever built, so one of the theories is somewhere there was one of these things built and Nikola Tesla was doing an experiment, and this caused it.

Fraser: And the field got away and detonated over Siberia, or he was building it in Siberia.

Pamela: It was just the field got away [laughing].

Fraser: Or anti-matter, right?

Pamela: Anti-matter, that’s true, but how did it get there without interacting with something else?

Fraser: Right, like the atmosphere, or dust, or the solar wind, or anything…yeah, yeah.

Pamela: Yeah, unless it’s carrying its own containment field that spontaneously broke up, which is another way of saying alien spacecraft. It wasn’t anti-matter.

Fraser: Well, that was cool, so I guess the one last thing is we talked about the Torino Scale last week, and I guess, this would be…someone mentioned that this would be a “seven” on the Torino. This would be a regional event with absolute certaintly,

Pamela: Only if we detected it first.

Fraser: Yeah, like a half an hour before, “Seven!”

Pamela: And the thing is, things like this are predicted to be happening every…people debate whether it’s every fifty-ish years, or every 300-ish years, so somewhere between those two very different numbers, but these are still time scales of humanity; these are still time scales of civilizations, and so this is the type of thing that could be happening fairly frequently, and we just don’t know it because, well, we’re mostly made of water and our planet is mostly made of water.

Fraser: Right.

Pamela: Or covered in water, it’s not made of it.

Fraser: Right, but were this to have hit Paris, or Moscow, or New York…

Pamela: Bad!

Fraser: It would have been…yeah. I mean, the damage would have been catastrophic.

Pamela: Instead it killed a few reindeer, which is bad, but differently bad.

Fraser: Which is bad, and probably some people somewhere in that region, but [missing audio], but it would have been just probably the worst disaster in natural disaster in modern history. It would have been horrendous.

Pamela: It would have rivaled Haiti, and Chile, and some of the other big earthquakes.

Fraser: The tsunami…

Pamela: I don’t think it would have been as bad as the tsunami was. That was horrible over a much larger region than 800 square miles.

Fraser: So, you know, the good folks who are working on the various missions to search out and find various asteroids – thank you very much! Keep at it!

Pamela: LINEAR, LONEOS, Near-Earth Objects Survey (CINEOS) …we’re looking at all of you.

Fraser: Right. Alright, well thanks a lot, Pamela.

Pamela: My pleasure.

Show Notes

• Graz, Austria
• Galileo Galilei – bio from the Galileo Project
• Galileo Chronology
• Book: Galileo’s Daughter by Dava Sobel
• Saturn’s “Ears,” and info about the actual inventor of the telescope — UTK
• Dialogue Concerning the Two Chief World Systems
• Galileo’s Experiment at Pisa – PBS
• Galileo’s views on Motion — Thinkquest
• Galileo vs. the church — Wired
• Galileo’s thermometer
• Galileo actually went blind from cataracts and glaucoma — SDSU

Transcript: Galileo Galilei


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Fraser: Welcome to Astronomy Cast, our weekly facts-based journey through the Cosmos, where we help you understand not only what we know, but how we know what we know. My name is Fraser Cain; I’m the publisher of Universe Today, and with me is Dr. Pamela Gay, a professor at Southern Illinois University – Edwardsville. Hi, Pamela. How are you doing?

Pamela: I’m doing well. I’m jetlagged in Austria. How are you doing?

Fraser: Well, I was going to ask you, “Hi, Pamela — where are you doing?” but you are in Austria.

Pamela: I am. I am actually in the town of Graz, which is where Kepler had his very first position, and I found that out looking up things for this show, and so tomorrow I’m going to have to find out where he had his first position and walk there.

Fraser: Is there any chance to do some kind of “astro-vacationing?” Do a tour or something?

Pamela: I have no idea, and the thing is everyone I’ve been talking to who knows Gras, is like, “Oh my God! You’re in the most boring place on the planet Earth.” I find it quite awesome. It’s a medieval village that has a bunch of really cool architecture.

Fraser: Yeah, I liked Austria.

Pamela: Yeah, and there was a random castle that I saw from the window of the train on the way from Vienna. Like you just happen to look out the window and there’s like giant castle on a cliff with cliff faces, just like if you’ve been reading too much J. R. R. Martin like I have lately, or G. R. R. Martin. Yeah, I suddenly had a castle. It was awesome. Anyway, we should record it.

Fraser: You are recording!

Pamela: That’s true. That’s true.

Fraser: This is in the show — there’s no getting away from this. Alright, well yeah, that’s true. Well, let’s get on with it then. So it’s hard to imagine a more famous astronomer than Galileo Galilei. He’s widely recognized as the very first person to point a telescope at the skies and study what he saw. Galileo discovered the moons of Jupiter, the phases of Venus, and much more. It was his controversial stance on the nature of the Solar System that brought him into conflict with the Church. I cannot believe we haven’t done a Galileo show yet.

Pamela: I think we must have answered questions about Galileo, related…

Fraser: We did…yeah, and I was like looking back and thinking about who to do a show on, and I was like, “Have we done Galileo?” and we haven’t. Again we’re going to do a two-parter: Galileo today, and then for the next episode we’ll do the Galileo spacecraft, which is going to be really cool. So, let’s go right back to…who was Galileo, then?

Pamela: Galileo was…he started out pretty much as just a regular guy. He thought he was going to become a priest; he was urged by his dad to, instead of going into the priesthood, go to medical school. He enrolled at the University of Pisa, and may be one of the very few people ever to get distracted from something like medicine to go into instead mathematics. Here I’m showing a small bit of a bias, a large bit of a bias, but it was from that foundation of math that everything else he did derived from, and what’s interesting is, along the way, he also studied fine arts. He’s an amazing writer who told a lot of his science stories as parables by different characters that were acting things out, debating among one another. It was just a fascinating way to try and communicate, and he revolutionized everything he did throughout his very long lifetime.

Fraser: And I think we’ll get back to that, but that got him in a lot of trouble by the end. I mean, he essentially openly insulted the Church through one of these stories that got him into really hot water with… Right, so he went to University, was going to become a doctor, segued into mathematics…I guess astronomy wasn’t quite the formal science that it is today. So then what happened?

Pamela: So he went into mathematics, and got sidetracked by art along the way, and he was appointed the Chair of Mathematics at the University he attended in Pisa, and he, unfortunately, was someone whose life was never easy. He ended up…he was the oldest of six children…he ended up having to take care of one of his younger brothers. Money was always an issue for him. After just a couple of years as Chair in Pisa, he ended up moving to the University of Padua, where he spent many years of his life. He was teaching geometry, mechanics, and astronomy until 1610, and one of the things that kind of startled me is the contradictions in his life. He was someone who’s always trying to take care of his family; he is someone who thought a lot about joining the seminary, and then he had three kids out of wedlock all with the same woman, and all of his…he ended up sending his two daughters to both become nuns, and he actually maintained correspondence with one of them. He just had this very complicated life, and I think you can’t really give a chronological tale of his life that’s succinct. There’s a fabulous book that does it, Galileo’s Daughter, and it goes through and it uses the letters that he wrote with one of his daughters in the convent as a way of going through the story, but I think the best way to really look at his life is to just look one item at a time at all these major contributions he made one after another to the sciences and math.

Fraser: So, then, which one…I mean, should we talk about the astronomy contributions first? I mean there’s the big one, right, which is pointing the telescope up?

Pamela: Right, so, telescopes weren’t invented by Galileo. This is one of the strange misconceptions that kind of everybody has, but the reality was he was simply the first one to take a telescope that was being used to look across land, to look for boats coming over the horizon, and to look up at the stars instead. The telescopes that he had the first several years — they weren’t that great. He went from 3x to 30x to…he could just sort of barely make out Saturn’s rings, but that simple act…

Fraser: Saturn’s ears…

Pamela: Yeah, he saw them as ears, as handles, but that simple act in 1609, which we celebrated in 2009 with the International Year of Astronomy – that simple act changed the Earth’s place in the Solar System because he was able to prove for the first time that the Earth goes around the Sun and not vice versa. He was able to prove for the very first time that moons and planets aren’t perfect spheres, as had been predicted by Aristotle using thought. He just did so many things one after another, and his studies of Jupiter and finding its moons really laid the groundwork for showing that we live in a physically describable universe.

Fraser: Right — and this is really important, right? That he…when he saw the moons going around Jupiter, this shattered the preconceived notion to that point that the Earth was the center of the Universe, and that the Moon and the Sun and the planets and the stars all rotated around the Earth, and that when he saw the moons going around Jupiter, and then looked again a few days later, they had moved in their position and it was quite obvious that they were orbiting around Jupiter. So up until that point, the rule was everything orbits the Earth, and Galileo was able to say, “Uh, no, something’s orbiting around Jupiter,” right? And then, as you said, you know, everything in the Heavens were perfect spheres. He looked at the Moon and saw the pockmarked craters and could see that the Moon was not a perfect sphere.

Pamela: And I think, for me, my favorite — simply for the simplicity of it — piece of evidence he used to show that everything goes around the Sun was the phases of Venus because if Venus is going around the Earth, then the Sun would be able to illuminate it in radically different ways, and in fact, we’d never be able to see a mostly-illuminated Venus because Venus would always be between us and the Sun pretty much, and what he found was, “Oh, dear! You see Venus go through most of its phases as it goes from crescent to pretty much full, you lose it in the glare of the Sun as it passes behind the Sun relative to our position…” It’s just such a simple and elegant piece of proof.

Fraser: Yeah, yeah, and so, in the end, I mean, what did he get a chance to see? He saw the Moon, he saw Jupiter, he saw Saturn and saw what he thought were the “handles,” you know, the “ears,” but he couldn’t quite make out exactly what was going on there. It took Cassini…

Pamela: Right.

Fraser: …and Huygens later on to get a much better sense of the rings right? And he was able to see those phases of Venus, and again, these are all things which you take a regular telescope or a Galileo-scope, and you can see the exact same stuff that he saw.

Pamela: And the Galileo-scope is something that it’s really worth if you want a low-cost, lightweight telescope to give a kid that they can just beat the tar out of — Galileo-scopes are still available. You can find them at Galileo-scope…I think it’s .org. And these are telescopes that were designed to have absolutely amazing optics. They’re made out of plastic, you can drop them down the stairs, and they’re designed to pop apart, you scoop the pieces up, you put it back together and it just goes. But the really neat thing they did, is they included a lens that mimics that really horrible view that Galileo had.

Fraser: Right. Those are better…yeah.

Pamela: Yeah. And so you can look through and go, “Whoa! How did Galileo even point anything and find anything in the sky?” And it’s an eye-opener! So if you’re looking to get a really low-cost (under $50) that’s for a kid that may use it as a sword now and then, Galileo-scopes are the way to go.

Fraser: Sounds like my kids. So, I mean, he made these observations and I think what’s really important was he knew what he was looking at, he understood the implications of what he was looking at, that the observations he was making that anybody could make if they had a telescope, could repeat his observations, these observations were calling into question whole beliefs about astronomy and about our place in the Universe, so he didn’t keep that quiet, you know, he used that to sort of make the next logical leap.

Pamela: And this is where Galileo got himself in trouble…and his life spanned more than one pope, and when he was first getting started, he got along well with the Pope and the Pope supported his work, helped make sure that his life was good. He was smart — Galileo was smart about who he dedicated his books to most of the time, but Galileo was kind of cocky. He knew when he was right and he wasn’t going to let anyone tell him he was wrong, and when he got ticked off, he was an amazing writer and he wrote things that mocked people, so as he started to get basically annoyed that people weren’t believing some of the things he was saying, he wrote different documents that were scolding, were petulant, where they included far more emotion than you expect in a modern-day science journal.

Fraser: Right, and he was supporting the Copernican model, right? Once he heard the model from Copernicus, his observations matched that up and he supported Copernicus’ view, which was…Copernicus didn’t even publish his work until after his death; he was afraid to even tell anyone. Galileo took it up.

Pamela: And so not only did he take it up, but he printed things when he was told he wasn’t supposed to, he talked when he was told he wasn’t supposed to, and he just kept doing things in a politically stupid manner. And eventually it wasn’t so much that the Church was all upset that anyone was supporting the Copernicus model, they were upset that Galileo wasn’t playing nicely, and they beat him up for it, and that was what finally got him in trouble. He was even forgiven a couple of times, that’s the crazy part, is that they kept trying to forgive the guy, and then he kept like publishing books when no one was looking, or sneaking things out into Protestant Europe and…yeah.

Fraser: And what we sort of alluded to earlier in the show, right? He wrote his book…

Pamela: Discourses Concerning the Two Chief World Systems was the one where he basically argued the two ways of looking at it.

Fraser: Right, and he, you know, and as you said, he took this kind of clever way of approaching this, where he would have one person speak one philosophy and another person speak another philosophy and have them have a debate with one clearly besting the other in the debate, and this was done in a way to kind of humiliate the Church — and they didn’t take it well.

Pamela: No, no, and you can sort of see why they wouldn’t take it well [laughing], and…

Fraser: And they had all the power, right? So…

Pamela: Yeah, and at least they did allow him to live out his life in his own home and his daughters never suffered because one of the things about back when he was alive in the 1600s is you sent your daughter to the convent, and in his case, he sent both his daughters to the convent because he didn’t think that as bastards in the traditional sense of the word that they were marriage material, and so he did the only thing he knew how to do with a daughter back then, but when you sent your daughters to the convent, you kind of had to pay their rent for the entirety of their lives and he was able to keep supporting his daughters, so they never really suffered too badly while being in the convent.

Fraser: Yeah, you know, it’s weird to say, I mean, I kind of oscillate back and forth, right? On the one hand it’s like, it’s outrageous that the Church even got annoyed to the point of jailing him for questioning their beliefs, I mean, that’s ridiculous! But at the same time, they were the ones with the swords, and you behave that way toward the Church, telling the truth, then you were going to kind of get yourself in a lot of trouble. In a way, he should have just kept his mouth shut, but at the same time, it’s like how could it even be a crime to question the nature of the Universe? So, it’s a fascinating, fascinating story and I think it’s really complicated and very interesting to dig into it and see all of the letters that went back and forth, and the, you know, I’m holding air-quotes here, they gave him a bunch of chances, right? Chances…you know, that’s ridiculous that they were giving him chances, you know? He was just calling nature as he saw it, right?

Pamela: I think that the impression that I got, reading Galileo’s Daughter, was that had he just stopped mucking with the Pope…the science they were kind of OK with — just go over there with it.

Fraser: And even if he had taken a little bit longer to release it, or had thanked the Church more in helping come to the bottom of it… They were kind of on board, it’s true, it’s a really interesting, complicated political piece of history to look into and it’s, you know, it’s like every story that we’ve heard so far is really simplistic about what actually happened on both sides.

Pamela: And at a certain level, there were just points in his life where Galileo was a spoiled academic brat, and if he had just been more of the stereotyped quiet, shy, afraid-to-talk-to-people scientist, it might have gone better for him.

Fraser: Right, but then…and that’s where you oscillate. It’s not about it going better for him, it’s about him telling the truth to power. Like I said, I think it’s an absolutely fascinating story, but, I mean, that part of it we talked about, I mean, like when in his life did he start to make those observations? I mean, it was quite later in his life, wasn’t it?

Pamela: Well, he started making observations in 1609, and he was born in 1564 (it’s 1:20 in the morning and I’m doing math in my head), so it made him about…he was in his late 30s.

Fraser: Yeah, yeah.

Pamela: Going into his 40s…

Fraser: So, old.

Pamela: So, it was later in his life that he started making these observations, and he’d already been playing the system for a long time. He’d already been a prominent scientist for a long time, and that’s the thing that you have to keep in your head is he’d had time to make friends and he’d had time to make enemies before any of this ever started, and it wasn’t just with the Copernican theory where he was poking at people, he actually poked at Kepler, saying that he didn’t think that Kepler’s elliptical orbits were right because a circle was the perfect shape, so even Galileo, who was showing that planets orbited the Sun, not the Earth, fell prey to the conceit that orbits must be circles. Even the man who showed that there were mountains on the Moon and the Moon isn’t a perfect sphere couldn’t let go of that one conceit, and then he got himself into trouble with comets, where he was arguing left and right with someone about comets, and he was trying desperately to prove tides, and refused to understand that the tides had something to do with the Moon. He thought it was “slushing” back and forth evidence of the Earth’s motion because they didn’t have gravity — gravity hadn’t been invented yet. So he was just someone who argued with people about things.

Fraser: Right. I think we know people like that.

Pamela: Yeah, we do.

Fraser: But, so I think that, I mean, that and as you said, that was one whole story, right? That the getting his hands on a telescope, being the first person to think about pointing it up in the sky, making these incredible observations, publicizing them, and backing Copernicus’ model, getting in trouble with the Church, and then living out a sort of quiet life under house arrest…but that’s not the only story. I know there were some other stories about Galileo that you wanted to tell, right?

Pamela: Right, so my favorite one is when Galileo was doing his physics experiments it was sort of assumed that the natural state for everything was to come to rest, to come to a stop, but if you’re trying to imagine a universe where the Earth goes around and around and around and around the Sun, the idea that everything eventually comes to a stop just sort of breaks your logic. And so Galileo started doing experiments on friction and acceleration, and to do accurate experiments — they didn’t have clocks back then — so you had to develop a method of timekeeping, so he developed a water clock that the number drops that fell out of the water clock was proportional to the amount of time, and through his experiments with inclined planes that we still replicate in a lot of freshman physics labs, he was able to come up with the laws of inertia, and the idea that an object in motion tends to stay in motion unless acted upon by a force, and an object at rest stays at rest unless acted upon by a force, and he did all of this before we knew what forces were!

Fraser: We did that experiment in our physics class, you know, you do the one with ramps, and rolling balls and stuff down ramps, and timing how long they take to reach the bottom.

Pamela: Right, and what was awesome about what Galileo did is he actually figured out, “Oh, shoot! Balls roll — that might be slightly different,” so he was doing things by sliding things in grooves, and he just took everything into consideration, and when he wrote this up, he actually did a thought experiment of…so let’s imagine that the friction is actually little devils trying to slow down what’s rolling, and the number of little devils is proportional to the amount of friction, and it was just this fabulous little discourse trying to show that it’s a something that’s stopping the ball and not a nothing that’s stopping the ball.

Fraser: Right, and didn’t he do the famous experiment on the Leaning Tower of Pisa?

Pamela: You know, no one actually knows if that’s real or not. That actually comes…

Fraser: Oh, really?

Pamela: Yeah, that actually comes from one of Galileo’s students, Vincenzo Viviani (forgive me if you’re Italian). He wrote a biography of Galileo that’s one of the primary sources of information other than Galileo’s notes. The thing is that while the student wrote this fabulous story…Galileo was an amazing record keeper; he was your quintessential scientist who took notebook after notebook after notebook of records. He wrote everything up in his various publications — and Galileo never mentioned doing this, and it just seems like one of those things he would do. So it’s now generally considered that even Galileo who fought so hard to get people to look at physical reality and do experiments, it’s considered this was probably actually a thought experiment, and the thought experiment runs along the lines of, in modern terms, imagine you have a bowling ball and you drop a bowling ball, it all falls at the same speed, now you cut the bowling ball in half and connect the two halves with a thread, well, how is that different than the bowling ball as one piece? And so as you extend this out, it becomes the two halves of the bowling ball falling side by side at the same rate as the original fully-connected, put-in-one-piece bowling ball — again, different object for Galileo.

Fraser: Right, but you can see that thought experiment. I mean, that’s the kind of thing that Einstein was really good at was looking at that in a sort of conceptual way, and coming up with the experiment in his mind that would prove it, so it’s too bad it’s apocryphal, but it’s the same as the Newton apple dropping, right?

Pamela: Exactly, exactly. Everyone needs a few apocryphal stories in their lives.

Fraser: So did he discover, or discovered, sort of, friction, and…

Pamela: He developed the theory, I guess is…

Fraser: Developed the theory of friction and developed the theories that went into inertia. A lot of that was heavily used by Newton later on.

Pamela: Right. He worked on pendulums, didn’t get his work exactly right, but he opened the door for other people to start doing research on pendulums. He did work on math throughout his entire life, and he just wrote and wrote and wrote and wrote, and…

Fraser: And in this really accessible style…I mean, you can…anybody can pick up some of his books, and they’re entertaining.

Pamela: And he lived at such an amazing time. He, in his lifetime, saw both the birth and death of Kepler, he overlapped with Rene Descartes, he was watching the Protestant rise in the north of Europe, while living in Catholic Italy, and all of these things were going on around him and they were trying to get letters back and forth and build a scientific community, despite the schisms between the Protestant and Catholic parts of the continent, and throughout all of this he just kept trying to spread information while constantly trying to learn more about the Universe. One of the things that keeps cropping up over and over about the various scientists that we’ve talked about is no matter how friendly or not they are, they were always communicators, and this sort of goes back to…I think it’s something that you’ve said on the show before, that you can be a fabulous scientist, but if you never say what you’re doing, no one will ever know.

Fraser: Yeah, and it’s interesting to hear Galileo had to invent the tools that he needed as well, right? I mean, you know, he had to develop a better telescope for himself, he had to develop a way of keeping time…

Pamela: Right.

Fraser: It’s the same conversation about Huygens, you know, just like, “right now, I need to invent a clock, now I need to figure out a way to…” you know, just necessity of invention, necessity if the mother of all invention…yeah.

Pamela: He was also one of the early developers of the microscope. He was looking at bugs with it and presented one to one of the Cardinals. He was friends with the Cardinals until he poked fun at them too many times. He just…

Fraser: Didn’t he also develop a thermometer?

Pamela: He developed a thermometer; he was a man who never got bored. And one of the saddest things about the way he ended his life is he studied the Sun with a telescope (not realizing that that was a bad idea), and so he was the first one to document sunspots, and he went blind in his old age.

Fraser: First one to document going blind looking at the Sun…

Pamela: Yeah, so when they say, “Do not look at the Sun with your telescope,” we have an experimental reason why.

Fraser: And so I think we’ll wrap this up now, but next week we’re going to talk about the Galileo spacecraft – a wonderful spaceship that orbited around Jupiter and helped uncover, you know, a tremendous amount about the “giant planet,” so that’ll be cool. Alright, well, thanks a lot, Pamela!

Pamela: That sounds great! I will talk to you later. Bye-bye.

This transcript is not an exact match to the audio file. It has been edited for clarity.

Show Notes

• Google+: Fraser, Pamela
• Christiaan Huygens –bio
• Physics timeline – Weburbia
• Fresnel Lens — HowStuffWorks
• Centripetal Force by XKCD
• Translation of Huygens’ paper on Saturn’s rings
• Huygens’ Clocks Revisited — American Scientist
• Christiaan Huygens, the Discoverer of Titan — ESA
• Huygens Refractors -- STSCI
• Huygens and the Measurement of Time and Longitude at Sea – Princeton
• Transits of Mercury
• Huygens and his belief of other life in the solar system — his book Cosmotheoros (1698)

Transcript: Christiaan Huygens

Download the transcript

Fraser: Welcome to Astronomy Cast, our weekly facts-based journey through the Cosmos, where we help you understand not only what we know, but how we know what we know. My name is Fraser Cain; I’m the publisher of Universe Today, and with me is Dr. Pamela Gay, a professor at Southern Illinois University-Edwardsville. Hi, Pamela. How are you doing?

Pamela: I’m doing well. How are you doing, Fraser?

Fraser: Doing really well…so this is the third live show that we’ve done, and by live I mean we’re doing it as a “Google hang-out.” So about once a week, we all connect as a hang-out and eight of our closest friends can watch as we record this show. We typically answer some questions beforehand and stick around and answer questions afterwards, so it’s quite a lot of fun, and so if you’re listening to this episode and you want to get involved, probably the best way is to get a Google plus account and then add me and/or Pamela as “friends.” If you don’t have a G-plus account, then I would suggest you email me (probably me not Pamela), frasercain@gmail.com, and say, “give me a Google plus invite please.” I will send you the invite, and then also add you to the circle so you can get notified when we do these live recordings, and hopefully, down the road, they’ll add more people to the hang-out so we’ll have more people to listen.

Pamela: And we are working on figuring out how to do things like share it through Ustream via CamTwist or something like that. We’re just not quite there yet, and nor is our bandwidth.

Fraser: Yeah, well this is just so easy, so convenient. We can kind of stick around and chat with people, so you know, if people want us to do more of this, we’ll figure out some long-term solution. I like the ones that don’t require a lot of effort and expense, which is what this does. OK, alright, so now we finish our trilogy of Saturnian astronomers and missions with a look at the Dutch astronomer and mathematician, Christiaan Huygens. It was Huygens who discovered Titan and figured out what Saturn’s rings really are, so it makes sense that a probe landing on the surface of Titan was named after him. Ok, Pamela, so this is great, I mean, so the first episode we did on Cassini, the guy who did some of the best observations of Saturn, next we did the Cassini mission with the Cassini-Huygens mission, and so I guess part 3 we’re actually going to talk about Huygens the astronomer. So where do you want to start?

Pamela: Well, I think the best place to start is by saying that astronomer really doesn’t characterize him. Christiaan Huygens was a truly frightening intellect that basically got curious and just did stuff. So, he did advanced mathematics, where the only thing that seemed to limit him — he’s doing a lot of his mathematics work just a few years before Calculus was invented, so he tried to do things like calculate what is the shape of the hanging rope, and he couldn’t quite get there because you need Calculus. He did astronomy where he actually built all of his own lenses, and he devised new and better ways to grind and polish lenses. He was a physicist working to try and solve all sorts of interesting mechanics problems. He was also one of the people who worked on designing early clocks, where he didn’t build the clocks himself, he hired other people to do that, but he was the person who came up with the idea for the pendulum clock, and thought maybe that would be one of the ways to solve the latitude problem.

Fraser: Now, could we kind of place him sort of in the annals of astronomers? Like who were his contemporaries? Was he sort of after Galileo? Before Hubble?

Pamela: He was after Galileo, sort of contemporary with Newton in terms of both of them were alive at the same time, but they were different ages. Um, he was…protégé may be too strong a word, but Descartes used to take him under his shoulder and watch his mathematical upbringing. So he had these amazing mentors. He worked with Fresnel, so if you’ve ever driven a motor home or a giant bus with one of those strange, textured things on the back that magnifies — that’s a Fresnel lens, and he worked with Fresnel on a variety of different projects. So he was right there in the heart of the scientific revolution, and was working as hard as he could to keep up, and he built on Newton’s formula of f=ma, to figure out…he is the inventor of centripetal force which has led all of us to enjoy XKCD all the more.

Fraser: Right, so he…after Galileo…what about some of the other astronomers of that time, right? Like Copernicus? After Copernicus?

Pamela: He’s after Copernicus. He’s in those early ages of telescopes, so he and Cassini were contemporary of one another. He was contemporary with Hooke who was one of those observers of transits, another person into clocks. He was just in those early days where telescopes were new, and people were mostly getting their names known for what they did in physics.

Fraser: Right. And so then where did he get his start? He’s Dutch, right? But what was his, sort of, early life?

Pamela: He had the benefit of being the son of a mathematician who was friends with Rene Descartes, so growing up he had all of these amazing people constantly in and out of his life. He was also from a wealthy enough family that he had private tutors until he was sixteen. And he transitioned from private tutoring, which included Descartes looking over his shoulder, to then attending the University of Leiden, and then going on to the College of Orange in Breda. He studied mathematics, he studied Law — he was your quintessential “Renaissance man” in time and education.

Fraser: And so then when did the big astronomy discoveries really kind of kick in?

Pamela: So he was born in 1629, went to university young, got involved on politics side of things before he actually turned to doing science actively. It was in 1657 that he did his first publication, which was in astronomy; it was in probability theory. He was someone who could name-drop anyone. He was encouraged by Blaise Pascal to look at probability and to write the first book ever on probability theory. He then went on in ’59 to discover centripetal force – not discover, but to derive the mathematical formulation for “what are the forces on an object that’s getting twirled around your head on a string?” He then got distracted by light, and in the late ‘70s began worked on writing his treaty on light. So he’s just bouncing all over the place, but it was his engagement in light and optics that all tied in with what he was doing with astronomy. I think where his name most closely gets tied to the mission is because he was the one who discovered that Titan exists; he’s the one that found that happy little moon that kind of got us all started, and the reason he was able to discover it is he was he was using some of the best optics in the world because he figured out more effective ways to grind glass. And he was also the first one to figure out what the rings are, even though everyone argued with him because they couldn’t see it because their lenses weren’t as good as his.

Fraser: Now, what was the set up? I mean, many of these famous astronomers were all set up at the university or they had some rich patron, and they had some you know, set-up. Did he…where was he working out of?

Pamela: Well, he worked both out of The Hague and then later on he went to France and then was able to return to The Hague later on…

Fraser: But was he backed by some sort of institution, I guess, is what I’m…or was he doing it solo, you know?

Pamela: No, no one did anything solo. In his life, he was mostly tied to different royal societies, so he kind of had royal backing. These were the days when scientists were the pets of kings. Science wasn’t a necessity, but it was an amusement, and it’s kind of odd to think that you’d have the court jester and the court astronomer side by side, but in some ways you did, so it’s because of him. He was first involved in the Royal Society in England, and after seeing their set-up when he was invited to the Royal Society of France, he helped them set up that Royal Society and get that organization going.

Fraser: So then, let’s talk about those big discoveries that he made that really relate to the trilogy that we’ve done so far, which is the discovery of Titan and really his comprehension of what the rings really are. So what were sort of the observations he made leading up to that?

Pamela: So back in the 1650s, he was grinding his own lenses; he was making his own telescopes, and as he’s making his observations, documenting day by day the changing alignment of the rings of Saturn…this is one of the most amazing things, is when Galileo looked at Saturn, he saw at one point it looked at one points like Saturn had a pair of handles.

Fraser: Or ears…

Pamela: Yeah, and at another point it looked like the rings had gone away. Well, what happens is over time, the inclination, the angle at which we’re able to observe the rings changes, and with his superior optics, Huygens was able to see the angle of the rings change to see that they were rings not attached to the planet and to see this little blob of light that turned out to be the moon Titan orbiting around and around near the rings.

Fraser: And I guess, orbiting sort of on the same plane as the rings, right?

Pamela: Exactly, so this little moon as it’s orbiting around the rings, it appeared to be in the same plane, it just appeared to bounce back and forth parallel to the rings and the sky and this led them to understand that this was something orbiting, just as the Galilean moons orbiting Jupiter, this was something orbiting Saturn.

Fraser: So he made those observations, saw Titan on the same plane of the rings, and I guess what really made some observations overtime and just saw that…

Pamela: He saw that the angle of the rings was changing and he was able to figure out that there’s a planet with inclined rings, that, as it goes around and around the Sun, just like our poles maintain where they point relative to the stars, we have the North Pole in a constant place, well, Saturn’s rings maintain their tilt relative to the stars allowing us to see a constantly changing angle on the rings.

Fraser: I mean, we see the pictures now, we see the pictures from Hubble, we see the pictures from Cassini, and it’s obvious — you look at it and you go, you know, those are clearly a big ring, you know, you might not know what it is but at least the shape of what that is, is very obvious to us. But you can just imagine the leap that they would have to make, especially, you know, with how terrible the objects were back then you could just barely make out that, I mean like in my telescope, when I look at Saturn, if the ring plane is really at its big angle, I can just barely see the gap on either side and you know I’m looking you know with a fairly…I’m sure a telescope that’s many times better than anything they ever had. So I just can’t imagine you know if you look back…you remember when we played around with the Galileo scope, at the AAS? You could just make out theses little moons poking out of the side of Jupiter and some bands, and that was kind of it, so it just amazes me that they would make this cognitive leap. It really had to be someone sitting there, you know, Huygens sitting there looking at what he was seeing in the telescope and going, “What am I looking at?” and running through the ideas in his mind. It’s astonishing that they came to that realization so early on. You know, later on it would have been obvious, but in the beginning – yeah, just amazing!

Pamela: And one of the things that the poor guy ran into was he reported his discovery of Titan and he reported his ring theory and everyone’s like, “No, sorry dude, we just don’t believe you.” And he had to wait for other people to build comparable telescopes before people started to believe him, and this was one of his frustrations, and it was actually he was able to figure out that other people did not have telescopes as good as his by who denied his ring theory.

Fraser: That’s awesome!

Pamela: It was just one of those things where it took a while for people to believe him and to confirm his results because he was just too good at what he did.

Fraser: Wow! OK, so he made this announcement, you know, as you said, involved in various royal societies, I guess that was the way that news sort of percolated out. What did he work on after that?

Pamela: Well, so he was writing books, he was working on actually clocks next, and if you think about it, you’re trying to understand orbital periods, you’re trying to understand all these different kinematic problems. He was referred to as a mechanicist in some instances, and to understand all of these things you really need good timekeeping, and these were in the days where we didn’t have good clocks, and being someone that thought in terms of force, thought in terms of energy, he figured out, “Oh! Pendulum clock!” and this was back in the days when people still, even in the field of science, had the idea that if you pull a pendulum back even further, it will take it longer to get from the high point on one side and let it swing to the high point on the other than if you only pull it back a little, and it turns out that that’s just not how it works. And so he was able to figure out how to relate all these things with the periods of different pendulums. And that was kind of cool!

Fraser: So, pendulum research?

Pamela: Pendulum research.

Fraser: What else?

Pamela: I’m probably far more excited about that than other people.

Fraser: Than Titan? Discovery of Titan and Saturn’s rings?

Pamela: Well, no Titan was way, way cooler.

Fraser: I didn’t know you were such a big pendulum clock fan.

Pamela: No, I’m not. No, I’m not

Fraser: No, it’s an interesting physics challenge. No, I know. I take the kids, we go to the park, I take the kids, and I ask them not to pump the swings, but I will hold them up to my face with their feet straight out, right? And then I let them go and I’ll show them how I will won’t move my face as they swing back because it’s impossible for them to kick me in the face.

Pamela: You totally trust your children.

Fraser: As soon as they pump, I move my face out of the way because I see that this is about to backfire.

Pamela: [laughing] You know they’re out to get you.

Fraser: But just in general, but no, no, no…but there’s this amazing clock in Vancouver, in the HSBC building — it’s beautiful! Huge pendulum clock, like the pendulum itself is, I don’t know, you know, 10 meters tall, 15 meters tall, and probably 2 meters on the side. It’s quite amazing, this huge pendulum that swings back and forth, and you can kind of see it working in the same way, so anyway, pendulums, uh, what do you know? I love pendulums too. Alright, let’s move on. Right.

Pamela: [laughing] So yes, he did pendulums, which was kind of totally awesome. He went on…so if you think about it all of this kind of built he’s like, “OK, I’m doing astronomy, I’m going to figure out how to make better lenses…OK, need better timekeeping to do better astronomy, so let’s figure out how to build a pendulum clock, along the way try and solve the longitude problem,” and then he…

Fraser: [laughing] Sorry to interrupt you again…that is crazy, you know?! “I need better timekeeping; I have to invent a whole new kind of clock.”

Pamela: Right, right!

Fraser: “I need to figure out where I am on the Earth; I need to invent a whole new way of discovering where I am on the Earth.” You can see he really had the forces of, you know, arrayed against him because they just like oh you know its just like us. “Great, I need to invent a microphone, OK, great, now I need to invent the internet, to get some information I need.” I can just see, you know, [laughing], its crazy!

Pamela: So, you went from there to, well, light — he’s thinking a lot about light because that’s what you do when you’re working with telescopes and getting annoyed with the telescopes, and these were in the days when we still hadn’t come to terms with the fact that light is both a particle and a wave. That just…that was something that took quantum mechanics first to get past, so people were still having this argument, and he came up with a wave theory of light that was able to very successfully explain how it was that light got focused through lenses, how it was that light got passed through different media, and then when he got together with Fresnel and they figured out how diffraction played into all of this…was so they were able to explain how light passed around the edges of objects. They basically defined the first several weeks of what we learned in optics courses in modern physics. And so that was how he spent a lot of the 1670s was working on solving problems with light and polarization and diffraction and all of these other amazing things.

Fraser: Right again, back to being able to build a better telescope.

Pamela: Exactly.

Fraser: Right.

Pamela: And, in the middle he was one of the people who observed the 1661 transit of Mercury across the Sun. He did that from London. Mercury does this fairly often so it wasn’t nearly as exciting as Venus, but nonetheless, it was…

Fraser: Yeah, the transits of Venus…

Pamela: Yeah, he was also someone that was involved in building community, and he had the misfortune of being alive during the Eighty-Year War, and seeing the Napoleonic Wars, and this periodically prevented him from being able to go home. If you’re in France, and France is in the process of trying to conquer Holland, you’re not necessarily welcome home, but wherever he went he worked to pull together the scientists to help build collaborations. He was constantly publishing and publishing in collaboration, and publishing things like probability that weren’t his own work, so while he’s responsible for making these great discoveries, he’s also responsible for being one of the communicators during the scientific revolution that brought together different ideas to different people, and that’s a completely different way to be a major influence. Or this is something we talked about with Planck, who a couple centuries later was dealing with similar things as well.

Fraser: But again, it funny, that’s the same to me as needing to discover how optics works, and then you get a sense of “Oh, I see, collaboration is our problem now, so I need to fix that, I need to help everyone kind of connect together.” So it seems like it’s a real vein running through his personality, where he clearly identified the gap and didn’t care what it was, he was going to figure it out and solve it and fix it, so then everyone could benefit from it. What an amazing guy! Now, there’s one thing that I kind of know, is that he had some theories about extraterrestrials.

Pamela: Yeah, he was actually a very strong believer that there is life out there in the Solar System, and in a book published after his death, he discussed his belief system. He figured that the other planets must be pretty close to what we experience here on Earth. He thought about things like, “Well, what is essential for life?” and back then, water — that was one of those primary things. He figured there is sunlight. He thought about things like well, what temperatures are alright. He thought about things like the thermodynamics: “Well, Jupiter’s probably too cold, maybe Venus…maybe Venus is too hot.” He’s one of the ones who looked to Mars and saw as you can see in most amateur telescopes that the surface of Mars isn’t all one color, and that led him to think, “Well, maybe the dark, maybe that’s vegetation.” And that’s a notion that actually many people help up until we started sending things to Mars, and going “Oh, shoot! Not alive.”

Fraser: Yeah, we’re only sixty years away from that theory being widely held by many people.

Pamela: It was a good theory, it was just wrong. Wrong happens.

Fraser: Well, had he lived a little longer, I can just imagine him inventing rockets and, you know, all kinds of stuff.

Pamela: So he’s someone that lived a fairly long life, and he just spent his entire life thinking and collaborating and doing and bringing the community together, and the thing about someone like him, is there were specialists — there were people who only did physics, who only did astronomy, who only did mathematics, who only did timekeeping, but he was someone who did everything, and who knew everyone, who lived a long life and was thus able to bring together all sorts of different people to discuss ideas and build a real scientific community.

Fraser: So, where did he die?

Pamela: He ended up dying at home in The Hague, and was buried there in Grote Kerk, so nominally, you can go on a pilgrimage to see the place of his death.

Fraser: Alright, well thanks a lot, Pamela — that was great! I really appreciate that, and I think from what I remember last time, we were going to go on to Galileo and the Galilean missions, so we will sort of pick that up next week. Thanks again, and thanks to everyone who listened in live as we did this as a Google chat. Sorry for the technical hiccups. I’m sure Google’s working on it. Talk to you later, Pamela.

Pamela: Talk to you later. Bye-bye.

This transcript is not an exact match to the audio file. It has been edited for clarity.

Transcript:Giovanni Cassini

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Fraser: Welcome to Astronomy Cast, our weekly facts-based journey through the Cosmos, where we help you understand not only what we know, but how we know what we know. My name is Fraser Cain; I’m the publisher of Universe Today, and with me is Dr. Pamela Gay, a professor at Southern Illinois University – Edwardsville. Hi, Pamela. How are you doing?

Pamela: I’m doing well. How are you doing, Fraser?

Fraser: I’m doing really well. This is kind of cool – we are doing our first-ever, live, hang out version of recording Astronomy Cast, so while we’re doing our Astronomy Cast recording, we’ve actually got eight of our good astronomy friends listening in and watching us on video as we do the recording, so no pressure.

Pamela: Please, please be kind to us — that’s all we ask.

Fraser: [laughing] Now, we’ve got a bunch of announcements. We’ll get through them as quickly as we can; we know you don’t like them. So first, I was a guest on the Caustic Soda podcast, so my good friend Toren Atkinson and [missing audio] because of weird time dilation, the episode that I recorded is going to be showing up in July, but we’re saying this is April 11, but in fact, time is all wiggledy-timey-wimey.

Pamela: Time is just relative, that’s all.

Fraser: Time is just relative, so we’re moving at a faster velocity, or is it a slower? Anyway, could you do the math, please?

Pamela: No.

Fraser: The next thing that is important to note is that Pamela and I are going to be doing a live episode of Astronomy Cast at Dragon*Con, which is the Labor Day weekend, 2011, and that’s going to be really fun. The…oh! Go to astrogear.org; buy our stuff.

Pamela: It’s summer…you can look sexy in an astronomy t-shirt. Go show off your non-geocentricity.

Fraser: Perfect! I’m not wearing one today; I’m usually wearing them. That’s all I wear actually. And then finally, you’ve got an announcement about a lunar phases calendar.

Pamela: Right, so Astronomy Cast is a joint production of SIUE/Universe Today, and a little non-profit that Fraser and I formed along with our friend, Phil Plait along with a couple of other people, and we’re trying to raise money for our non-profit so we can keep on doing cool things like this show and 365 Days, and so one thing that we’re going to do is a lunar phases data visualization contest. All of the rules are up at astrosphere.org, and the winning poster design could get turned into a poster we sell in our store.

Fraser: Very cool! And so people can get the lunar phases organized.

Pamela: Yes.

Fraser: Awesome! Alright, let’s get on with the show then. So another two-parter coming at you. This week we talk about the Italian astronomer Giovanni Domenico Cassini, best known for discovering Saturn’s moons, and the biggest division in Saturn’s rings. Cassini made many other important discoveries in the solar system, and in the fields of physics and astronomy. And next week, we’ll talk about Cassini: the mission, but now let’s talk about Cassini: the man.

Pamela: He was an amazing, well, he was an amazing person — I won’t say amazing man. This is someone who was working in the days when we were still trying to figure out where the heck we were in space. He grew up thinking that the Earth was the center of the universe, and had to re-find his place in the universe as an adult. He grew up believing in astrology, and as an adult became a hard-core, science-focused astrophysicist in the earliest days of that field.

Fraser: Where would we place him on the timeline of all the famous astronomers, you know, the Galileo and the Copernicus?

Pamela: So, he was after Galileo, he was after Kepler and Brahe, but they all kind of overlapped at various points of their life. So he was born in 1625, and so he was growing up learning about all these things going on, but he got to follow far enough behind them that he had much better optics to play with.

Fraser: Right, I mean, Galileo was one of the first people or the first person to point a telescope up, so he discovered everything that was worth looking at with a telescope…but he saw the moons of Jupiter and Saturn’s ears, but then Cassini and all these other people got their hands on much better instruments and got to take the science a lot further.

Pamela: Right, and he got to be around for interesting things like the discovery of gravity, which he actually didn’t believe in initially — and I just love the concept of not believing in gravity.

Fraser: [laughing] What! Not believing in gravity? That’s easy to prove, you know?

Pamela: But it was something where the whole idea of gravity being a force that kept the planets in orbit around the Sun — that was revolutionary! It forced you to change how you view the entire Solar System, how you view the entire Universe. To go from being a kid with a geocentric view of the Universe, and a belief in astrology to an adult who had to believe in a heliocentric with gravity — that’s an amazing change to go through in your lifetime.

Fraser: He was an early adopter.

Pamela: He was truly an early adopter, but he wasn’t the first. He was the one who waited for his buddy — he found all the bugs, and then bought it after his buddy did.

Fraser: Right…of course…yeah. OK, so then why don’t we start with his early history, then? I guess the astrology side…

Pamela: It was just one of those things. When we’re kids, we’re all into strange stuff; some people pick up all the frogs in their backyard, he picked up all the learning he could on astrology, and that’s really all anyone ever says about it. It’s only after he went and he got a what was then an excellent Jesuit education that people really start looking at his life, and the thing that I just sort of look at and go “wow, things were different back then. He was a professor at the age of 25, and I didn’t have my PhD yet.

Fraser: Well, not long after, Pamela.

Pamela: Well, still – I’m not full professor yet, and here he was…

Fraser: But you got your PhD pretty quick, though.

Pamela: So he got his PhD at age 25, and he had this interesting joint career where he was working in Bologna, and he was both a fortress builder, and an astronomer, and I love the juxtaposition of walls and sky. He was both grounded and had his head in the clouds.

Fraser: But the math is the key.

Pamela: Right, it’s all physics — it’s all stress, strain, motions, kinematics…

Fraser: Yeah, yeah, and you could see it was a natural fit for him. And you know he loved astrology as a kid. How did he move into the astronomy side of it?

Pamela: Well, I think it was a matter that he just kept discovering amazing things with the observations he made. He worked with some of the craziest telescope configurations, where he actually built a tower at Paris Observatory and would put lenses up at the top of the tower, and then have the eyepiece, in some cases, hand-held, in other cases, mounted separately. So can you imagine building an open-air telescope that is two non-connected pieces of glass?

Fraser: So you would hold a piece of glass and just sort of move it around and look at it?

Pamela: And line it up with the one up at the top of the tower.

Fraser: Right, but you can imagine that might have been the best, fastest way to get images, right? I mean, it was an open frontier back then, so there’s all kinds of different ideas that people are trying out. That’s neat just to hear about that kind of experimentation. You can imagine the connection with this fortress-building experience, right? Where he’s kind of like, “Oh, we could easily buttress up that telescope over there, and support it with that, and hold the eyepiece over here and get some images.” Yeah.

Pamela: He was definitely the nuts and bolts kind of physics guy. I have to admit this is the type of physics I like [missing audio] not so much my thing, I can do it but the whole “if you do this, you get this reaction, nuts and bolts, gravity, kinematics, stress strain, this is how you build a building that doesn’t fall down, this is how you build a solar system that doesn’t fall in on itself” – he was that kind of a scientist, and he made discoveries so along those lines too, so just straightforward, linear thinking, so in 1665 he was using his amazing telescopes to look at the planets because they’re kind of the coolest thing to look at, and he was making out markings about the sides of the planets for the first time, write down and determine the rotation rates, and so he was able to look out and go “Wow! Jupiter – it’s orbiting faster than we are! Oh, Wow! Look at Mars” (not orbiting, it’s rotating faster than we are). He was able to look at Mars and accurately figure out “Wow, its day is just a little bit more than 24 hours.” That’s really impressive.

Fraser: But I mean most people who are listening to this podcast recognize the name from the mission, which we’ll get to next week, so he clearly makes an impact in the research on Saturn.

Pamela: So he was someone who was out there determining moons. He was the person who discovered Iapetus, the little white and black, completely funky-colored moon that kind of looks like it ran head-first into something. He was the one who while observing the [missing audio] Saturn’s rings, realized “wait, there’s a gap in those rings,” and that gap now bears his name. It’s the Cassini Division.

Fraser: Right. And what is that gap?

Pamela: It’s where there’s a moon located, and then the moon shepherds the rings and clears out the gap.

Fraser: But he had no idea that’s what he was looking at.

Pamela: No. It’s taken us a long time and, well, it’s taken the Mission Cassini to really help us understand these rings.

Fraser: Right. OK, so he discovered…what he ended up discovering, what four of them, right? Four of Saturn’s moons, the Cassini Division…

Pamela: Right, and he determined the rotation rate of Jupiter, which has features unlike Saturn — which is kind of beige — and I think one of the neatest things he did was he was a very careful observer, and he was tied up in trying to understand how to measure time, he was tied up into trying to accurately measure longitude. And he followed the recommendations of Galileo in terms of realizing you can use Jupiter’s moons to keep time, except while recognizing that, he realized “wait, there’s this weird lag that keeps cropping up,” so you’re watching Jupiter, you’re watching Jupiter, you know how long it takes its moons to orbit. You go away for a couple of weeks, you come back, and there’s this either acceleration in when you see the moon complete an orbit, or a lag. It can be many, many, many minutes – tens of minutes, and this was confusing, and it was actually one of his colleagues that figured out “wait, this is just the speed of light.” So it was his observations that got us to the speed of light.

Fraser: Really? So is it because the moon is further away, or further away on its orbit, so it’s taking longer to get to us?

Pamela: It’s the whole system is moving further away, so if you look at Jupiter when it’s at closest approach, and you measure when Io passes directly in front of it, and then you wait a few weeks and you come back expecting to see that transitive of Io in front of Jupiter again, well, if Jupiter’s now further away, that transit is going to lag behind when you expect to see it. And that lag is because Jupiter is now in a different place.

Fraser: Right. Right. Right. OK, yeah. That’s crazy. It’s crazy, but they had no idea. I mean did they interpret it correctly? Or did they interpret it…

Pamela: They interpreted it correctly, and the reason they were able to make this light/travel time discovery is because of earlier work that Cassini had done with a Frenchman named Ritchey and …

Fraser: Sorry to interject — is that where the telescope name comes from? There’s a Ritchey–Chrétien …

Pamela: Yeah, I’m pretty sure that’s…it’s…they were all working on optics back then; they were all working to figure out the best telescopes, but in this case, poor Ritchey got stuck on a boat and got sent far south, and the reason he did this, the reason they did this was Cassini and Ritchey both looked at Mars at the exact same time because they were working on determining accurate ways of measuring time with new clocks and watches. They looked at Mars at the exact same time, measured its location relative to the stars very accurately…

Fraser: But from different places on Earth.

Pamela: But from different places on Earth. They knew their separation on the planets, they knew the distance between them, they could measure the angle that Mars moved on the sky, and this allowed them for the first time to accurately measure the distance to another planet, and using geometry and using Kepler’s Laws, once we knew where one planet was located, we could figure out where all the planets were located.

Fraser: I mean, that was one of the times when they finally understood the scale of the Solar System.

Pamela: And so they were able to then go from “OK, I know exactly where Mars is” to “OK, I now know where Jupiter is…OK, I now know how much the distance to Jupiter has changed between now and three weeks ago…OK, I now know how much the predicted time of Io transiting in front of Jupiter has changed…I now know the speed of light,” and that’s just an amazing train of logic, and you can see in this how Cassini went from astrologer to astrophysicist in one lifetime.

Fraser: But that’s a completely independent method of measuring the speed of light. Then I know they did another experiment. Didn’t they do an experiment where they were on mountaintops and rotating mirrors…?

Pamela: Yeah, that’s the much more difficult way to do it, where, basically, you’re trying to get the rotation rates just right, and the flashing just right so that it passes through things as they rotate, and it’s very complicated and we’ll link to it because that requires photos.

Fraser: But that was a completely different method of independently determining the speed of light. I wonder how accurate they were. How accurate Cassini was. So we’ve got these really cool, you know, discoveries…helping measure the speed of light, understanding the scale of the Solar System, discovering the moons of Saturn…

He also did a Zodiacal light. So in 1683, he was…basically he did what we’ve all done at some point. He stayed up all night; he looked at the sky and went “Huh! Why is it suddenly getting brighter in the direction opposite the sunrise?” And he correctly figured it out that’s there’s just particulates out there, and that was sunlight shining off of stuff that wasn’t in the shadow of the Earth, but was behind the Earth, so you can actually as it’s getting ready to be sunrise, you can see the sunlight in the opposite direction of the sunrise illuminating particles that are not quite on a straight line, but almost on a straight line from the Sun to the Earth and out to the space behind us, and that space behind us is just filled with stuff left over from comets, stuff left over from asteroid collisions, stuff that makes the Zodiacal light that was interesting to Cassini and Brian May used to write his PhD.

Fraser: I’ve actually never seen it. Have you?

Pamela: I’ve only seen it once. I saw it from Southerland Observatory in South Africa, and it was surreal because the Zodiacal light got to be as bright as the Milky Way, and that’s just kind of creepy.

Fraser: Wow! So you need a really dark place to observe, and then when would you be able to see it?

Pamela: It’s brightest before the sun comes up, so wait before astronomical twilight starts and that’s an excellent time to take a look at it, and it’s the opposite direction of sunrise.

Fraser: Now, he didn’t stay in Italy the whole time, did he? He moved to France.

Pamela: Yeah, he ended up being the director of the Paris Observatory. He was the astronomer for the Academie Royale of Sciences. He actually escaped being one of the Pope’s minions because the Pope tried very hard to lure down into the Vatican territory, but he just wanted to be a scientist, and what was amazing is the Paris Observatory actually sort of became a family legacy. He was the first director ever of the observatory, but then his son, his grandson and his great-grandson went on to run the observatory after him, and his poor great-grandson was director of the observatory when the French Revolution hit and got thrown in jail for many months for his ties to the royal house. Basically, if you’re the “astronomer royale,” and it’s the French Revolution, you’re as bad as anyone else, but well, that was the end of the astronomical dynasty. It’s just neat to look back over Cassini, after Cassini, after Cassini having this scientific legacy.

Fraser: Hmm. Yeah, there’s a lot of those stories where you’ve got the father, and then you’ve got the sister…you’ve got the…right? And then the son…

Pamela: Uh…you wouldn’t be talking about the Herschels, now would you?

Fraser: The Herschels…yeah, yeah, so there’s the Herschels right? Where it’s like him and his sister, and then his son did some work with them as well.

Pamela: The Struve family had a couple of observatory directors across a couple of different continents. We just see this, and then there’s husband and wife teams galore through astronomy.

Fraser: So then how long was he working in Paris, then?

Pamela: He ended up spending the entire latter half of his life there. He actually stayed at the Paris Observatory even after his son took over. I think the sad part was, in 1711, he went blind and it was another year before he actually passed away at a fairly old age, but still to be an optical astronomer in a day when you could only observe with your eyeballs, and to go blind. That was pretty bad, but he left a really good legacy behind him.

Fraser: So it was still, like,100 years before any photographic observing was done, right?

Pamela: Yeah, so he was essentially there from 1669 onwards, and he became a French citizen, and what’s neat is that poor, imprisoned great- grandson actually had the French version of his name, and so his great grandson was Jean Dominique, instead of Giovanni Domenico.

Fraser: Right, right, but still Cassini…

Pamela: Exactly.

Fraser: So I should…there’s one thing I think that you didn’t touch on yet, which was that he did a lot of work with Jupiter’s Red Spot, right?

Pamela: Right, so he along with Hook were the co-discoverers of the Red Spot, and they were able to determine this is a lasting structure; this is something that is tied to the rotation rate of Jupiter, and it was part of how they started to realize the different rotation of the bands on Jupiter. So it was through his careful observation, his high quality optics for the time that they were able to start realizing that it wasn’t just the planets weren’t on perfect circles, the planets themselves have ever-changing surfaces, so this was more of that revolution in how we view the Solar System.

Fraser: But again, did they have any inkling about what they were looking at? I mean it was a blotch on the surface of the planet that helped determine the rotation rate, but…did they know what they were dealing with?

Pamela: We really didn’t know what Jupiter’s Red Spot was until we sent the Pioneer and Voyager missions out; it was just this weird artifact on the surface. I think the place where he was able to start making wild guesses was he was also one of the first ones to look at Mars and see its polar caps. So there you see the ice forming and going away and forming and going away, and you could sort of start to guess what that is, but Jupiter’s Spot — how you get from being a European to understanding it’s a giant hurricane back in the days without satellites, I mean, could they even imaging what a hurricane looked like from above?

Fraser: Yeah, I don’t know…you’re right, but it’s also a testimony to how long that storm has been raging on the surface of Jupiter, I mean, the fact that they made those observations in what the late 1600s, and here we are four centuries later and, you know, it’s still going.

Pamela: Still going…so he just watched everything change in terms of our conceptual understanding, and he also is responsible for making France smaller than any war ever made it larger, and it was simply through science that he shrunk France.

Fraser: Uh, you’re going to have to explain that one.

Pamela: So he was a mapper. He was one of the first ones to understand how to accurately measure longitude and so in mapping France, in determining accurately where its borders were, he inadvertently shrunk the country. Prior maps had France much bigger than his map that was determined using triangulation.

Fraser: That’s the kind of geography mistake that gets your head chopped off.

Pamela: He actually apparently was able to make the king laugh, and the king joked that he had shrunk the country more than any prior war.

Fraser: And then killed him?

Pamela: No, no, he was able to live to a ripe old age, but none-the-less what was interesting is that it was his sons who carried on the mapping as well, and went on to map other countries, and his grandsons and great-grandsons… So he created not just an astronomical dynasty (and I mean that in the literal and not the figurative sense), but he also created a map-making, geographer dynasty as well.

Fraser: That’s really cool. Alright, well that’s great, Pamela. Thanks a lot! I really appreciate it and we’re going to continue on with next week’s episode where we actually talk about the cool mission.

Pamela: That sounds great and we might sneak in a little bit of Huygens as well.

Fraser: Oh, that’d be cool!

Pamela: Make this is three-parter?

Fraser: A three-parter, yeah, that’s a good idea…or a four-parter.

Pamela: Four?

Fraser: Cause there’s so much that Huygens did with Titan, right?

Pamela: So, Cassini/Cassini/Huygens/Huygens…we may have a plan.

Fraser: That sounds good. Alright, we’ll talk to you next week, Pamela.

Pamela: OK, sounds great, Fraser!

Download the transcript

Fraser: Welcome to Astronomy Cast, our weekly facts-based journey into
the Cosmos, where we help you understand not only what we know, but
how we know what we know. My name is Fraser Cain, I’m the publisher
of Universe Today, and with me is Dr. Pamela Gay, a professor at Southern
Illinois University at Edwardsville. Hi, Pamela how are you doing?

Pamela: I’m doing well, Fraser, how are you doing?

Fraser: I’m doing great. It is still really cold and snowy, so we can’t go
outside yet, but that’s going to be changing soon. OK, so this week — we
don’t have a lot of time so we gotta roll! The sun moon stars and planets
are visible with the unaided eye, so there were astronomers before recorded
history, but some of the earliest records we do have tell us what the ancient
astronomers thought about the heavens and how they used the changing
night sky in their daily lives. Let’s look at archaeoastronomy.
Archaeoastronomy? It’s like archeology and astronomy. Is it archeologists
who like astronomy? Or is it astronomers who like archeology?

Pamela: It’s like one of those bad interdisciplinary fields where everyone
lays claims to it, and so you really have to be good at all of it to be good at
the field. So you have…even anthropologists get thrown into the mix, but
that then becomes a word no one can say.

Fraser: Sort of an Indiana Jones with a telescope?

Pamela: Exactly!

Fraser:Or a [missing audio] with a bullwhip?

Pamela: Not so much…

Fraser: OK, so can you give us some examples, then, of what would…are
we talking about buildings, documents…what is Archaeoastronomy?

Pamela: Generally, it’s a matter of talking about something that is
physically built that allows you to use the structure itself to make
predictions to make measurements about sky phenomena, so the classic
examples are the “spiral and dagger” that is seen near Chaco Canyon in the
American southwest. This is a place where sunlight passing between two
rocks makes a dagger of light that, on different special days of the year,
either appears just beside a spiral on one side or the other, or pierces it
directly through the center. And these alignments only occur on the
solstices and equinoxes.

Fraser: Oh, but this isn’t a natural structure. Some hard-working rock
chisellers went out and actually figured out the math, lined things up and
then cut the holes.

Pamela: This is actually probably something that required even more
patience than that — where someone noticed, “Hey, these two rocks make
this dagger of light. Let’s mark in (whatever the Stone Age equivalent of
pencil is) the location of that dagger on this equinox, on that equinox (well,
the equinoxes will be in the exact same place), on the winter solstice and on
the summer solstice…” and then very carefully, once they had figured out
where the dagger was on these three extremes of most northern, most
southern and central position, let’s carve a spiral into the rock to denote
when those locations occur.

Fraser: I’ve never seen this, so maybe you could kind of give people a
picture of what this…maybe people in the U. S. are more familiar with it,
but I’ve never even seen a picture of this. What does it look like?

Pamela: So, you’re looking at a rock, well it’s the inside of a cave, and the
way the sunlight comes through, there’s a spiral pattern carved into the
rock, and just like any spiral, there’s a central point and then it curves
outwards and forms basically – it’s round — and on the winter and summer
solstices, the dagger of light appears just touching one edge or the other of
the spiral, and then on the equinox (in both equinoxes the sun is in the exact
same place), that dagger of light pierces exactly through the center.

Fraser: Wow! So, can you give us some other examples? I mean, there
are some pretty famous ones, right? Stonehenge, the Pyramids…

Pamela: Those are the two big ones that everyone points to, and what’s
interesting about Stonehenge, in particular, is it’s an example of where we
do archeo-astronomy without having any social context for trying to
understand what we’re looking at. Archaeoastronomy…there’s two general
ways to do it: you either start from, “I have a giant something I don’t
understand,” and you try to find astronomy references within it using
statistics, or you start from the, “I know Venus was culturally very
important to this society,” and you look for references to that particular
thing that you know was important. So you’re either looking for
astronomy within the context of the society, or you’re trying to find
astronomy to give you context to the society. So these are two different
ways of doing it, and Stonehenge is the, “Wow! This is kind of awesome!
I wonder if it lines up with anything?” and it was very quickly realized that,
yes, there are summer solstice alignments with the heel stone in Stonehenge.
And people since then have been looking for all the possible alignments you
can find between “Stand here, look there — ah look, there’s the sun, a
planet, a star…”

Fraser: And so what is the event? If you wanted to go to Stonehenge on
the right day and really appreciate its use as an astronomical tool, what day
and what would you be seeing?

Pamela: Well, the big day to go to it that everyone goes to it — and I’ve
been there the day after, but not the day of is the summer solstice — and this
is because of the sun’s rising position directly over the heel stone…the
place, Stonehenge, is a lot smaller than you think of it. The rocks are huge,
the circle is huge, but the place that it’s located is wedged between the
north-south or east-west, I forget the directions of the highway…it’s kind
of odd…so you’d be crammed into this area between the two directions of
the highway, along with a lot of people who smoke interesting things.

Fraser: Great…

Pamela: …and potentially are dressed as druids or wiccans, and then, of
course, you have all the photographers who are there and all the scientists
that are there, so it’s highly chaotic; but nonetheless it’s the kind of thing
that, looking at all the photos and being there the day after or the day
before, can give you a real appreciation for: “That is a giant well-aligned
rock.” And make you wonder just how is it that the ancient people were
able to do the things that they did.

Fraser: Making sure that rock was lined up with the sun on the summer
solstice was clearly very important to them.

Pamela: Right. It’s one of these things where we can’t even figure out
exactly how they moved these rocks. And then the idea of using a system
of pulleys, and logs, and rope…basically, you dig a hole dig a hole dig a
hole, stand the stone upright in the hole, and once it’s standing up, you’re
looking at leaving the entire village to adjust how it’s standing in that hole
– and it’s a perfect alignment.

Fraser: So Stonehenge is one great example, and I talked about the
Pyramids as well, which is, again, on an even grander scale…

Pamela: And with the Pyramids, it’s potentially even a double-alignment.
You have, on one hand, the directions of the Pyramids are exactly lined up
with the Cardinal points, and this is to within all observable limits of the
human eye…

Fraser: Sorry, Cardinal points, what does that mean?

Pamela: North, South, East and West…

Fraser: OK so, what is it – the corners are North, South, East and West?

Pamela: The sides.

Fraser: So if you draw a line from two corners, you’ll go North-South, and
if you draw a line from the other corners, you’ll go East-West?

Pamela: Exactly. So one of the really neat things you can do with the
Pyramids is just go to Google maps and type in “Pyramids of Giza,” and
when you look at them you can see, “Wow! The edges are exactly North-
South – exactly East-West!” And then when you look at the 3 pyramids
(the 3 big ones), they form this slope. And when you look at them, yeah,
you can go “OK, they’re exactly lined up neatly on diagonals,” but the
other thing that people say is that they were designed to look like the belt
stars of the constellation Orion, so what the ancient Egyptians were actually
building was the belt of Orion when they put these three pyramids where
they put them. Now, it’s not known for certain if this is exactly what was
intended, but it’s just one of those neat things to look at on Google maps
and go, “Huh, yeah, I can see that!”

Fraser: If they had more time to build more Pyramids, then they could
have had the shoulders and the feet and the sword, and the shield…so yeah,
I guess they just didn’t really commit.

Pamela: Well, considering how big those suckers are, I’m not sure that you
really need to worry about commitment issues.

Fraser: Have you ever seen them?

Pamela: Yeah, I was actually there. We actually left Alexandria two hours
before the New Year’s Eve bombing; so I was there, and if can find the
picture, we can post the picture of me, a camel, and a pyramid on the
website. They’re really quite impressive to see, but if you do visit the
Pyramids, take a tour guide who speaks Arabic and will stick to your side
because the Pyramids are surrounded by people who are going to try and
sell you things, and it’s very overwhelming.

Fraser: Yeah, you gotta learn “Leh, shokrun,” — “No, thank you.” OK
great! So the Pyramids are another one, but there are ancient buildings
around the whole world designed for astronomy. These are just a few
examples. Let’s have some more.

Pamela: The other really neat example that I particularly like to use is…
I’m going to mispronounce it…it’s the “Chichen Itza.” I can’t say it — I’m
just going to let you say the word for me. It’s this ancient observatory, and
when you look at it, you’re like “Wow! That’s an observatory built out of
stone, except the dome doesn’t rotate!” And the building was set out with
slits in the dome that allow you see when different things line up. So the
way the dome is designed, it’s not good for letting in light, but it is good
for saying “Aha! That is lined up there now; therefore, I know when I
am!”

Fraser: So, it’s in Mexico, right?

Pamela: It’s in Mexico, and it has a lot of sites on it that are related to the
planet Venus. This is an old Mayan relic. Venus is one of the particularly
important stars, whether it was (not stars, planets)…whether it was up as an
evening object or a morning object. And one of the neat things about
Venus is you can trace its pattern on the sky by taking observations at the
same time everyday, and depending on exactly where Venus and Earth are
in their orbits, you get different snake-like patterns, and so the path of
Venus on the sky from night to night to night during each of its appearances
is traced out in a whole variety of different Mayan relics.

Fraser: OK, I see, and so they would take that path that you would trace,
and then they would make it look like a snake and have it be embedded in
some other object.

Pamela: So, it was often feathered serpents, and this was how they viewed
it. And it’s one of those things where you’ve got to imagine how they tried
to piece together what Venus was because it’s this object that only appears –
it was two different objects to them – it only appears either right after
sunset or right before sunrise, and it’s so amazingly bright, but it never
hangs around the entire night, and both objects are never up at the exact
same time, and so it was seen as two different sides of, basically, a god
depending on which culture you were in.

Fraser: But some of them did figure it out, I mean, they realized that it
spends some time in the night, then it spends some time in the morning and
then it sort of lines up, so if you were going to use Chichen Itza, then you
would be able to — what? — see through a hole at a certain time and see
Venus, and then be able to know “OK, it is this day in the Mayan
calendar?”

Pamela: Well, we’re still trying to figure out how you use it. That’s one
of the problems that we run into. This is an example of where we’re
understanding astronomy within the culture of the people. So we look at
the building; we see the orientations of the building relative to north, south,
east and west. We look at the carvings on the building; we see references to
Venus. We look at the slots; you can tell the slots are designed for lining
things up, and we’re not entirely sure what. It’s a challenge! We’re still
trying to figure out all these different details. We do know that there are
places where, if you’re standing on the right platform, and you’re looking
past the right pillar, it lines up with Venus when it’s a morning or an
evening star, but it’s not particular to a time on the Mayan calendar. It’s not
necessarily particular to a certain orbit, but the alignments are there.

Fraser: Hmm…so then, astronomers would look at this from one point of
view, I guess, and they would say, “What did they know then? What parts
of modern astronomy did they ancient people have figured out?”…[missing
audio] and so on, but I can’t imagine astronomers going the other way and
saying, “What do these things tell us about the people?”

Pamela: And this is where it ends up being two different areas of
archaeoastronomy. With things like the Nazca Lines, which are these giant
lines in the Atacama Desert that trace out spiders and geometric figures…

Fraser: Yeah, Google map them. I mean, you can see them; they’re pretty
neat! They are like these enormous, almost like roadways, ground into the
desert — in the Atacama Desert –visible from huge altitudes, and these
really elaborate shapes. They’re quite amazing!

Pamela: And the thing about the Nazca Lines is you have to be in an
airplane to see them. There’s a monkey, there’s a spider, there’s a chicken,
there’s all kinds of crazy geometric shapes, there’s birds and no one’s quite
sure why, and the way they’re made. Different scientists have tried to
replicate them, and it’s actually not that hard once you figure out how you
want to shape the lines. It’s just a matter of going through and moving the
stones to make the shape you want, so if you can imagine making crop
circles, or something…all you need is rope and something to bash down the
corn, and you can make any shape you want, but you can’t see what shape
you’re making while you’re in the cornfield. Nazca Lines are the same
thing. All you need is a rope and a plan and you can make any shape you
want, just by moving rocks around. And so, in trying to figure out why,
one of the theories that was come up with is, “Well, maybe the head of the
spider lines up with something? Maybe the tail of the monkey lines up with
something…” And so people have looked for astronomical alignments,
and what’s been realized is that if you take any one place to stand, and any
one thing to line up with on the horizon, and you run simulations, you can
always find at least one day of the year that a really bright star or planet
aligns with that particular position and place on the horizon, and that makes
understanding a lot of this stuff hard because you have to ask yourself,
?What’s chance and what’s on purpose?”

Fraser: Yeah, I mean is that likely? I mean, could you take any object?
Could I take a kids’ jungle gym and stand at the various corners of it
outside and line up with stars and planets? I mean, is it unlikely that you’re
going to get that kind of a situation?

Pamela: If you start to narrow it down and say “an alignment only on the
solstices and equinoxes,” if you start to say “only with planets,” if you start
to say “only with certain stars of known ethnic importance” – so, like the
star Sirius has importance in several societies, then it starts to become a
matter of, “No, chance alignment isn’t likely,” but if you open it up to any
day of the year, and any star that is third magnitude or brighter, you can
pretty much find alignment with anything if you open up the calendar wide
enough.

Fraser: But I think you touched upon something that is really important
there, which is that if you find some kind of structure and it lines up with
Sirius, for example, perfectly on the winter solstice, maybe, then that really
tells you that Sirius is important to that culture. Then you can start digging
to find some references to it. So you can see how the archeology will help
you, and then knowing the astronomy will then help you find something out
about the culture.

Pamela: And this is where it’s been so neat looking at Mayan ruins and
seeing the “snakes” that mark out the path of Venus in the sky, and this is
where it’s been so frustrating with Stonehenge trying to figure out, “Well,
there’s been 165 different alignments found, and there’s a 50/50 probability
that that‘s chance,” and so trying to figure out what’s chance and what’s
real, and things like: there’s a set of holes at Stonehenge — the Aubrey
holes — and you can come up with all sorts of crazy ways to move rocks
from one Aubrey hole to the other Aubrey hole that could predict solar
eclipses, lunar eclipses, star cycles, and it’s just a matter of: “Well, what do
we know? Very little. What is possible? A whole lot.”…and trying to
infer, “Well, what was it actually used for? Here are our best guesses…”
We can only go as far as our best guesses.

Fraser: I can imagine it’s almost like a typewriter where all the keys are on
it, and there’s any combination of keys that you could be mashing, but
obviously if you’re a writer you can make words. But it’s hard to know –
if you don’t know what the outcome was — it’s hard to know how they
were using it because it’s so flexible with all of the holes that you could,
indeed, predict almost anything you wanted if you were using it right, but
at the same time, it could be that they just banged holes in them and thought
that it looked good.

Pamela: And this is one of those things where an understanding of statistics
becomes very important. It’s very easy to say, “Well, because this city is
laid out like a grid with roads going north-south and east-west, clearly, the
equinoxes are very important to this city.” No, we’re just boring, it’s the
Midwest; we lay things out as grids. It’s easy to infer a lot of stuff and then
if you take it one step further, and say, “and this Queen Anne Victorian
house that has four chimneys…because these chimneys happen to line up
with the rising of Gemini with…” and you can come up with all of this
different stuff and suddenly you’ve created a culture that is a cult of
Gemini.

Fraser: Right — incorrectly.

Pamela: And so you have to step back and say, “OK, what is the
probability, in general, of this happening by chance? What are all the other
possible things that could have happened?” And it’s just like the work that
Simon Singh has done, pointing out that with the Bible code, you can also
take Moby Dick and find all sorts of things predicted in it just be looking
for chance alignments of words.

Fraser: Right, and I think this is where this whole endeavor just leads into
pseudo-science and madness because, as you said, you can use almost
anything to predict anything, and so you can then retro-fit it back in and
say, “See? Stonehenge predicted the Great Fire of London…” you know?
If you’re using it right — but it’s hard to know whether a person is using it
right — you can predict almost anything. I know that a lot of the 2012
predictions, Mayan calendar, Nostradamus — all that kind of stuff — totally
relies on that. There’s so many ways that you could examine: it could be
nothing, it could be an astronomical tool…who knows? You’ve skirted the
issue, but with the Nazca Lines, if you could make a picture big enough for
only an airplane to see, then they must have had airplanes, you know?
[laughing], hot air balloons, or aliens…but no, they might have just said,
?Let’s make some great, big pictures because it’s cool, and fun, and it
shows that I’m rich.”

Pamela: Right, and this is where we can come up with some good
conclusions. We know that there are things that definitely align with the
solstices. There is the marking of the summer solstice at Stonehenge. At
New Grange in Ireland there’s a clear marking of winter solstice. With the
sun dagger, we have the solstices and the equinoxes all clearly marked in
the American Southwest. We can tell that human beings like to line things
up with north, south, east and west. It’s just something we do.

Fraser: As someone who lives in Canada, I can tell you that when the days
start to get longer, it is a good thing! You want to know that, finally, we’re
done having shorter nights, now it’s time to have longer ones. I can see
how a winter solstice is an important thing, and not that complicated, right?
You can figure it out pretty easily by looking at the shadows every day, and
eventually you’ll hone in on the shortest and the longest days of the year.

Pamela: And to get much beyond these solar alignments, and these
Cardinal direction alignments, it starts to require us to know something
about these cultures. So when we look for alignments…with the Pyramids
there’s actually windows that only the light of certain stars on certain days
do pass through and they were culturally important. With the Mayans, we
see Venus replicated. So this is where when we start looking for the
alignments that are statistically harder to prove; you have to understand the
culture you’re working within. So archaeoastronomy is a very rich and
complicated field, where sometimes you’re just left going, “Huh! That’s
interesting, but I can’t prove it,” and other times you’re left going, “Wow!
I see the same thing over and over and over and, wow! They could observe
Venus!’

Fraser: And I bet with modern computers, that’s really helped crunch a lot
of these numbers. As you said, with statistics you can take this thing,
model it in a computer, and then compare it against the night sky and start
running simulations. You start to tease out statistical anomalies and say,
“Hey, look at that! It does work for the solstice, or the Cartesian
coordinates…”

Pamela: And where this has become particularly useful, is the sky isn’t
where it was when the pyramids were built. The sky isn’t where it was
when Stonehenge was built.

Fraser: That’s right, and so the position of the stars, the procession of the
Earth’s tilt has changed all that, and so they line up with where they were,
right?

Pamela: Exactly, and so this is one of the things that makes the Pyramids
particularly amazing at how well pointed they are. There wasn’t a North
Star when they built the Pyramids. They had to actually stand there, watch,
figure out — based on the rotations of the stars — where the North Pole was,
and that’s a hard set of observations to make; but nonetheless, they made
them and precisely aligned these giant structures.

Fraser: Wow! Alright, well that was great, Pamela. Thanks a lot!

Pamela: It was my pleasure.

Fraser: Take care. Bye.

Pamela: You too. Bye.

Show Notes

Astrogear website for Astronomy Cast gear

Lyman Spitzer Jr. — Spitzer website

Interstellar medium — UNH

Project Matterhorn

American Astronomical Society

Hubble Space Telescope

ESA Hubble

This transcript is not an exact match to the audio file. It has been edited for clarity.