Astronomy Cast &#187; Astronomy

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?

Fraser: Doing really well. So once again we’re recording this episode of AstronomyCast as a live Google plus hang-out on air, which means that if you’re a big fan of AstronomyCast you can actually watch us live as we record the show and go through all kinds of audio hassles and headaches, and…yeah. But it’s pretty cool, and so we’re still figuring out all the bugs and if you want to check it out you can join us live. The easiest way to do that is to circle me or Pamela on Google plus, and then you’ll see announcements of when we’re about to record. And as we sort of settle out the technology, we’re going to do this more often and do it on a more regular schedule. In fact, the easiest way to find us or me anyway is…I’ve actually redirected FraserCain.com to my google plus page.

Pamela: Wow!

Fraser: Yeah, I know, that’s brave, right?

Pamela: Yeah!

Fraser: So…cool! Alright, any more announcements? No, we’re good — let’s just rock.

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Fraser: So the number of moons, the age of the Sun, and our placement in the Milky Way all had an impact on the formation of the Earth and the evolution of life on our planet, but what if things were different? What would be the implications? So the goal of this show, and this was suggested by a listener, was what would life be like, or the Earth be like if some aspect, some physical aspect of the Universe, was different? If we had a different number of moons around the Earth, if we had a different structure of the galaxy, if we were located in a different place, if we didn’t have some of the giant planets, different metalicity of the star, and just what would the implications? What do astronomers think would be the outcome? So, Pamela, let’s start with sort of the big picture and then we’ll sort of zoom in as we go.

Pamela: OK.

Fraser: So, you know, we know that our Milky Way is located in a galaxy cluster. We’re in the Virgo Supercluster in the Local Group…

Pamela: We’re in the Local Group on the verges of the supercluster, we’re not really in the supercluster, but we will be — but we’re not there yet.

Fraser: But when you look out into the Universe with the Hubble space telescope and things like that we see regions with tons of galaxies clustered tightly together, and other regions where the galaxies are more far-flung apart than what we have here. Some have…so I guess just galaxy density, let’s say that we ended up in one of those situations? How would things be different?

Pamela: Well, we probably wouldn’t have ongoing star formation. One of the things that I actually studied as part of my doctoral dissertation is how the lives of galaxies change as they go from low-density environments to high-density environments over the course of the history of the Universe. And what we find is in the biggest clusters out there, the Bell clusters that look so beautiful with all their gravitational lensing in Hubble pictures – these clusters don’t have any star formation. What’s happened is over time, as the galaxies have swept one past the other, the gravity of them tearing at each other has sucked all the dust out into the spaces between the galaxies, and without dust there’s no star formation. So in a large cluster, much larger than the one we live in, with all these interactions over the billions of years of our Universe, you crush star formation, so we’d be living in a dead system — no Orion nebula to look at, no Pleiades to look at, the Hydes might not even have had a chance to form. It’s much more depressing.

Fraser: Right, and so it would less the chance…the stars would have been sort of young and hot, and then all have burned out, or be burning out right now and you just wouldn’t have the same…but on the flipside, what if you had the galaxies too far flung apart?

Pamela: Well, in that case, it would simply be a boring sky. There’s all these isolated galaxies and the places that we look trying to find nothings. There’s a researcher, Martha P. Haynes, who’s looked in these giant voids trying to find someplace empty, and what she finds is isolated spiral galaxies. If you let a galaxy form, leave the sucker alone, most of the time it’s going to end up being this nice, beautiful spiral galaxy, lots of star formation – not too different from the place we live.

Fraser: But is there a situation…it’s the galaxy collisions that help some aspect, causing more star formation and helping with the amount of metals in the stars, things like that. I mean, do you need a certain amount of galaxy collision, or is none OK?

Pamela: No. Well, once you build the galaxy, I mean, we think that large galaxies like our own form out of little tiny puffs of galaxy that build up over time to form the giant galaxies, but once you get to the giant galaxy stage, any galaxy interactions that you have are either going to be minor things — like we keep eating dwarf galaxies, it’s what the Milky Way does — or they’re going to be giant star formation, crushing events that initially trigger massive star formation. I mean, that’s the irony in this: you get two galaxies that interact just right, you get this massive burst of star formation, but then after that, nothing — no more stars, and without new star formation, there’s no pretty nebula to look at, but worse than that, there’s no new planetary systems forming. If you have this happen too early in a galaxy’s life — that means that high-metalicity stars haven’t had a chance to form; you might not end up with nice, interesting planetary systems. This massive burst of star formation’s going to create everything, but there’ll be nothing coming after that.

Fraser: So then let’s roll back the age of the Universe a bit. So what if events conspired, and the Sun formed much earlier or our galaxy’s evolution, was much earlier in…after the Big Bang, like say almost right away? Like, I’m not sure how old the star could be, or how young a star could be after the formation of the Universe. What if we were as close as possible to, you know, the formation of the Universe early on?

Pamela: Well, if our Sun had been one of that 0th generation of stars which formed pretty much 400,000 years after the Big Bang, it would have been giant. It would have been a runaway star because it wouldn’t have had any metals to help it cool off. That’s one of those strange things in star formation.

Fraser: Right, so that’s one of those “we wouldn’t be here” situations.

Pamela: Right, and well, and there wouldn’t have been any of the stuff to make planets. Initially, it was hydrogen, helium, trace amounts of lithium, and beryllium — none of the silicon we need to make rock, none of the iron we need in our blood, none of the metals at all existed initially, so that first generation of stars, if we’d been one of the first generation of stars, no planets would have formed, and the Sun would have been this giant short-lived thing. So that’s just different.

Fraser: Then, you know, on the flipside, if we were trillions of years into the future, you know, where the expansion of the Universe is quite large…I mean, I know it would have implications for astronomy in that we wouldn’t see other galaxies. We might not even know that there was an expansion of the Universe at all, but would it have any impact? You know, will stars still be forming a trillion years down the road?

Pamela: No.

Fraser: No?

Pamela: No.

Fraser: Really? Wow.

Pamela: Yeah, that’s the thing to think about is our Universe is slowly using up all of the material or spreading it out to the point that it’s spread out so much that it can’t condense down into new stars. There’s a few exceptions; there’s repositories of gas that’s fairly high-density in the centers of galaxy clusters. That’s not going to change, but really hot gas doesn’t collapse into stars either, so we’re going to reach this point where all of the gas that’s cold enough to form stars is spread out so much it can’t collapse. All the gas that is dense enough to form stars is too hot to collapse down to form stars, so there’s this future of no more star formation.

Fraser: So we really are at the right place. So I guess we could have a more loosely organized galaxy cluster, but we really are at the right time for this one.

Pamela: Exactly.

Fraser: OK. So let’s focus in on the Milky Way then. Right now we’re located more closely to the outer edge of the Milky Way, nice and far away from the turbulent and crazy galactic core, but what if we were located much closer to the core?

Pamela: Well, we would have still formed, we could have still formed with planets, but the probability that we wouldn’t have had the outer parts of our solar system constantly harassed by stars passing nearby… yeah, that probability says that we would have been harassed by other stars, and one of the things that astronomers think is that some of the past epochs of heavy bombardment where, all of a sudden, all the random rocks, ice, stuff from the outer Solar System came plunging in, creating craters in the inner Solar System, there’s thoughts that some of that might have been triggered by a nearby star passing. Now, if we’re living in an extremely dense environment, the probability that there’s going to be these chance encounters with a star disrupting the Oort Cloud, disrupting perhaps even the Kuiper Belt starts to go up. There’s even the possibility that we’ll pass so close that…we don’t worry about collisions. The probability of a collision’s very low, but passing close enough that Jupiter gets stolen, that’s…[laughing] that could happen, and three-body encounters start flinging things in all directions.

Fraser: Right, so we’ve got this situation where a lot of the stars passing beside each other are just wrecking the structure of the Solar System, and so, you know, do astronomers think that if we…you know, once we can better map the star systems that are closer in to the core, they’re going to have sort of stolen planets? The planets being flung around, and…?

Pamela: Well, you can’t actually tell in a lot of cases if a star has stolen its planets, but what we do think is that there’s probably a habitable zone not just around stars, but around galaxies as well, and it’s that region within the galaxy where the probability of two star systems encountering one another is sufficiently low that you don’t have to worry about life getting disrupted by an overly close hot neighbor coming through.

Fraser: Right, so you’ve got enough time of not getting your solar system wrecked that life can form and things can be stable. So then what about on the flipside, right? What if you’re further out in the galaxy? What if we ended up forming, you know, right at the very rim of the galaxy?

Pamela: [missing audio]

Fraser: But it wouldn’t really have any implication, but what about amounts of metals, or radiation?

Pamela: So the thing you do have to worry about is if you’re still in the disk of the galaxy, most of the disk of the galaxy still has metals in it, but as you start to get out into the halo of the galaxy – this is the spheroid of globular clusters and random stars that just sort of… it’s still part of our galaxy, but isn’t part of the pretty disk we think of. Those stars are generally so metal-poor that they can’t form planets, so once you get to these older areas…and that’s the thing too is these are stars that formed much further back in the history. In fact, for a long time, globular clusters were thought to have been some of the very first objects that formed in the Universe. These systems – they don’t have the metals you need to have planetary systems, and so far we haven’t found any planets in globular clusters.

Fraser: Now, you mentioned globular clusters. That would be crazy, I mean, we formed in a nebula kind of like the Orion nebula or the Pleiades or the Hides…but what if we formed in a globular cluster? Cause then the stars would be still around us, right?

Pamela: Right and there’s some fabulous art, I believe, by the artist Loretta Cook, who sat down and then figured out all of the science behind what it would look like, and literally… if you have a thin atmosphere, so you don’t have to worry about scattering of light that creates an opaque, blue atmosphere like what we have, if you’re sitting on an atmosphere-free moon, for instance, as you look about, it’s stars everywhere, and it’s not just stars little points, it’s you can resolve the disks, you can go, “Oh wow! There’s a massive solar flare on that thing that’s half a light year away. There’s…” You can start to see details.

Fraser: Like Venus brightness? Like moon brightness?

Pamela: Somewhere between the two…

Fraser: Yeah, OK, alright, so brighter than Venus…wow! And depending on the age of the cluster, you’d have variation on the brightness of stars. If the cluster was older, you’d have just a smaller…

Pamela: Well it would be red in general, so imaging Betelgeuse everywhere you look.

Fraser: Right, but you know, we typically don’t see those. We see the red giants, but we typically don’t see the red dwarves as easily just because they’re dimmer, and so we don’t see them very far away, but if they were packed in a globular cluster, they’d be all over the place. OK, so then let’s talk about the Solar System itself. So what if, for example, I mean, we have this sort of nice, series of planets, and then we have some gas giants, and then we have this, you know, the icy area around that, so what if, you know, some of those things were different? For example, what if we didn’t have some of the gas giants?

Pamela: Well, the gas giants are actually kind of useful because they’re vacuum cleaners gravitationally. We used to think that things hitting Jupiter was probably a once-in-500-year kind of event, but we’re [laughing] now learning, yeah, we’re now learning if you look at Jupiter long enough any given year, you’re going to see it get hit by something.

Fraser: Like, we’ve had two major impacts in the last 20 years.

Pamela: I think…aren’t we up to three now?

Fraser: Yeah, but anyway two big ones for sure: Shoemaker-Levy 9, and there was another one just a few years ago that smashed into Jupiter. So yeah, this is happening a lot.

Pamela: So you have Jupiter eating things, you look at all the outer planets have what were probably once upon a time Kuiper Belt objects or comet cores now as their moons… Gas giants are vacuum cleaners; they protect us from some of the large rocks that might otherwise come into the inner Solar System, and by protecting us by eating things, that means there’s a lower probability that we’re going to get hit by things, so it’s thought that perhaps you need these giants out there vacuuming up as many rocks as they can to lower the probabilities low enough that life has a chance to evolve.

Fraser: But in our solar system, Jupiter is sort of the size that it is… and you know, Saturn and Uranus and Neptune, but at this point now with the thousands of planetary systems that have been discovered, thanks to Kepler, you know, we’re seeing every variation. So there would be worlds with far more gravity, a lot more mass — I know they don’t get a lot bigger than Jupiter, but they would have a lot more mass than Jupiter. So you know, if we had some of those, would that have an implication?

Pamela: Well, so here you have to worry where’s the trade off? When our planet first formed, it got completely blasted dry by an early hot Sun, and so that dry Earth got the oceans we now enjoy from comets hitting the early planet, and re-giving us back our volatiles. Now, if you had too heavy an object, or too many heavy objects protecting us, then maybe we wouldn’t have gotten enough water, but that’s really one for the planetary modelers to play with, but there is this trade off where you don’t want to get hit too much, but you do need to get hit some to get your volatiles back.

Fraser: For the right period of time for…to give life a chance to form, and then what about the rocky planets, then? We have the four rocky planets that we have. Would it have an impact if we had more or less?

Pamela: Boring skies? I mean, that’s the impact of things that wouldn’t cause “negativeness” is they just make the Universe more boring.

Fraser: Right, but if we end up with say a Mars-sized object in the same orbit as the Earth, as we’ve seen, you know, that has it’s implications.

Pamela: Yeah, right.

Fraser: That’s the Moon, right?

Pamela: Yeah. [laughing] Once the Universe, once the Solar System is stable, what the rocky planets look like don’t matter. Having extras that hit you – that matters.

Fraser: Right, right. So it’s really all about…again, it’s sort of back to that clearing out the Solar System.

Pamela: Yeah.

Fraser: OK, well, now let’s take a look at our Sun. So we talked a bit about sort of if our sun formed at different periods of the Universe, if it formed early on in the Universe or later, but what about the age of the Sun? The Sun right now is 4.6 billion years. What if for some, you know, I mean…but we’ve had life on Earth for almost the entire period, so what if the Sun was younger right now?

Pamela: Well, the younger Sun was hotter and our planet actually had a point when its temperatures were hotter due to that hotter Sun, but at the same time, the composition of our atmosphere was different early on, so it’s hard to figure out how to put all of these different variables together. We had hotter sun, we had different atmosphere, and we had a planet that was quite honestly not acceptable to us because it was so methane-rich. It wasn’t until the Sun got a little bit older and a little bit cooler that we had an oxygen-based atmosphere to enjoy.

Fraser: So, I mean, that took billions of years to get going, right?

Pamela: A couple of them…not a lot. It’s really amazing how quickly our planet settled down to start getting amoebae, or amoebas.

Fraser: Right, but again, let’s run the clock forward. What if we were 5, 6, 7 billion years – the Sun was older?

Pamela: So when the Sun gets older, we’re kind of in trouble here on the planet Earth. Our Sun is going to switch how it produces energy in its core, and when it does this it’s going to bloat itself out and undergo extreme amounts of mass loss, and the combination of getting larger, getting brighter – it’s going to get cooler as well, but you still move that surface right against the surface of the planet and it doesn’t matter if it’s a little bit cooler. We’re going to get blasted, and essentially imagine broiling the surface of the planet and blasting it with a wind that is high-energy enough to remove the Earth’s atmosphere, and you’re looking at our future.

Fraser: Right, and we’ve talked about this in earlier podcasts that the Sun is actually heating up right now. You know, not “global warming” heating up, but heating up over the next 500 million to a billion years. It’s going to make temperatures on Earth a lot hotter than they are today, and this is just the process of the Sun converting hydrogen to helium and sort of changing its energy up, so actually that number is pretty tight. I mean, we’re within a few million years from [missing audio] life forms to be able to live?

Pamela: Yeah, the big thing that we have to worry about is as the Earth’s temperature goes up, it’s going to cause the oceans to evaporate, which is going to put more water vapor in the atmosphere, which is going to cause the planet to heat up, which is eventually going to cause a runaway greenhouse effect, which will evaporate our oceans completely. No surface water — it’s a lot harder to live.

Fraser: Right, and then I think one of the ones that’s most interesting to people is the Moon, right? I mean we have one moon, and we’ve mentioned this a lot that the Moon is kind of important. Why is the Moon important?

Pamela: [laughing] Well, gravitationally it stabilizes our planet. If you’ve ever watched a top when you set it spinning, this little top happily precesses around and around and around, and the amount that a planet does the same thing varies from world to world, and here on Earth, our precession is at least somewhat stabilized by having the Moon there, so for us, the Moon is a way of keeping that spinning top somewhat upright. Now, the other thing that the Moon does is, just like Jupiter, it helps sweep things up. Things hit it; we look at it and we see the poor thing has been completely obliterated with craters. Every part of its surface has been hit by something at some point in the past. This is what creates the regolith that we see. Now, the Moon also has the effects of churning up the tides, so when you see the ocean moving, that’s because we have a moon. And it’s thought without those tides, life might not have been able to evolve the way it did. Now, there’s still argument over whether life started in water, it started in volcanic springs, it started in dirt…we’re not sure where life started. It could have started in all of the above – that’s fine too, but no matter how it happened, we know that biological functions are at least in some part tied to the lunar cycle, so there’s a good chance that life would not be the way it is without our moon there.

Fraser: So then what if we had more moons?

Pamela: That would depend on their spacing, their sizes…more moons, if you have the Moon we have now, and then you’ve got a little one close in…

Fraser: Oh, OK. Sure.

Pamela: So imagine a little one close in, we call that one the International Space Station…

Fraser: Right, but if we didn’t keep boosting it up, it would crash.

Pamela: That’s true.

Fraser: So a little further than that…

Pamela: So you do have to worry about…and this is actually a problem Mars has in its future; it’s going to get bombarded with one of its moons in the future, so we’d want to have moons far enough out that they’re tidal effects cause them to keep going further out, rather than to come closer in, which would just be a bad thing, but as long as they’re small enough to not wreak gravitational havoc on our planet, then they simply serve as a protector that helps eat things headed our way.

Fraser: But you would get weird tides, right?

Pamela: It depends on the size. I mean, you can imagine if we had a much smaller moon in addition to the one we have now, it would be sufficiently small that the tides that it rose up (assuming it’s further away) would be so minor that they’d be washed out in the noise of the tides that are there. It’s sort of like if you’re at a rock concert, your phone ringing — you might notice, but barely.

Fraser: Right. I know that we get things lining up. We get the Moon and the Sun lining up — you get much bigger tides.

Pamela: Right, and you would see things like that, but it doesn’t mean that it would affect life.

Fraser: Oh! What if we had two stars?! What if we were in a binary system? I forgot to ask that. I wanted to ask that.

Pamela: We’ve actually seen solar systems like this. There’s lots of them out there.

Fraser: Yeah, this was thought to be impossible, right? And now, well, not so impossible.

Pamela: We have this one extremely endearing, old professor who keeps wandering through, and he’s like, “what about planets with more than one sun?’ And we’re like, “they exist!” and he’s like, “no!” He’s very cute and very, very old. So anyway, 61 Cygni B, it’s one of them. We see things like this: there’s the star Tau Boötis A, that has planets, and its companion Tau Boötis B (don’t say that one too fast with elementary school audiences) — all of these systems generally have widely-separated stars, and the beauty of these widely-separated stars is you end up with all the planets gathered around one of the stars, and the other one sort of hangs out, shining beautifully in the distance.

Fraser: So, it all depends on the distance?

Pamela: Yeah.

Fraser: If they’re too close, things won’t work out. If it’s really far away, things work out a lot better.

Pamela: If they’re close, then the planets start to experience what’s called a three-body problem, and those fling things, again, so any time you’re getting gravitationally interacting with three different objects, flinging occurs. So you need two things close together that you can treat as one thing, and then something else further away.

Fraser: I think that’s the whole theme of this whole episode, when you think about it, is it’s really about 3-body interactions.

Pamela: That’s entirely true.

Fraser: You know, that is, if it’s too much gas, too many galaxies, too many moons, too many planets, too many stars, then you get these 3-body interactions that wreak havoc. One last thing that I wanted to bring up is the mass of the Earth, right? I mean, the mass of the Earth that we have is…

Pamela: …kind of awesome.

Fraser: Kind of awesome, well sure! Yeah, but I mean, would things be different if the earth had double the mass? …half the mass?

Pamela: So if you adjust the amount of mass we have, assuming that the density doesn’t change, as we adjust the mass that we have, you run into things like well, if we get small, we don’t have enough mass to hold on to atmosphere.

Fraser: Like Mars…

Pamela: …like Mars. Now, if we get big, we kind of end up with too much atmosphere, so if you can imagine having a much thicker atmosphere, life’s still possible, but you’re going to develop entirely differently, and as you increase the pressure more and more, you can imagine needing exoskeletons to protect yourself. It starts to be much more like the situation life has at the bottom of the ocean, where life always finds a way given that it has the proper stuff, but it takes on a very different shape.

Fraser: Right, so I think in that situation I’d almost prefer to have more gravity.

Pamela: Yes, more gravity is good; less gravity is less atmosphere, which is bad.

Fraser: Which is bad…cool! Alright, and while this episode is running out, I was looking through some questions from people, so that’s kind of cool. Cool! Well, thanks a lot, Pamela! And thanks to everybody who watched this live episode of AstronomyCast. Your thoughts and ideas were very helpful — I stole them all.

Pamela: Thank you for joining us, and stay tuned – more of these are to come.

Fraser: And more good stuff…yeah. Absolutely. Alright, well, thanks a lot Pamela and we’ll talk to you next week.

Pamela: My pleasure. Thanks, Fraser.

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

Ep. 245: Calendars

admin — Tue, 10 Jan 2012 23:37:58 +0000

Our lives are ruled by calendars. And calendars are ruled by astronomy. As we near the end of 2011, and get ready to ring in the new year, let’s discover the astronomy underlying the days, weeks, months and years that segment our lives.

Ep. 245: Calendars
Jump to Shownotes
Jump to Transcript

Show Notes

Explantatory Supplement to the Astronomical Almanac
For all types of calendars, see The Calendar Zone
Calendars Through the Ages website
The Oldest Lunar Calendar on Earth – Environmental Graffiti
Leap years explained
Leap seconds explained — USNO
The Y2K Scare
Mayan calendar explained – Calendars Through the Ages
2012 Reality Check — NASA
Series of articles on 2012 by Ian O’Neill on Universe Today
From “The Truth About 2012: The End is NOT Near” by Dr. Ed Krupp from the Griffith Observatory:
- “The Mayan calendar is not spooling up the thread of time. It is coming to the end of a particular cycle in an unending sequence of cycles. According to the rules of the Maya calendar system, a primary interval, Baktun 13, for all practical purposes ends on the winter solstice, 2012. Although pseudoscientific claims have linked this calendrical curiosity to a Maya prophecy of the end of time, there is no evidence for ancient Maya belief in the world’s end in 2012 or even in any unusual significance to the cycle’s completion.The Maya calendar relied on multiple cycles of time. In Maya tradition, these cycles of time run far into the future, and there are ancient Maya hieroglyphic inscriptions that project time into the future well beyond 21 December 2012. At the end of Baktun 13 (a period of 144,000 days or 394 years), a new baktun will begin. There is no Baktun-13 end of time. The notion of a Baktun-13 transformational end of time is modern. It originated in Mexico Mystique, a book published in 1975 by an American writer, Frank Waters, who made computational errors.”

Transcript: Calendars

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?

Fraser: Good. I see you’re rested from your exotic cruise.

Pamela: I’m not sure I’d say rested. The thing about vacations is there’s so much to do that you just come back a different form of tired.

Fraser: I think your body is so used to travel that it can’t tell the difference between holidays and going to some astronomy conference.

Pamela: No, that’s entirely true.

Fraser: So for anyone who wonders, we’ve taken our Google plus experiment to the next level, and we’re now recording this episode as a Google plus “hang-out on air,” which means that it’s just Pamela…me and Pamela in this recording, but we’ve got anyone who wants can actually watch us record the episode on Google plus, and then when we’re done, we’ll open it up and let people join us, and we’ll ask questions, and we’re going to record the whole thing, and we’re going to put it on YouTube or something, and so, you know, hopefully, try and make the whole thing a little more interactive because one of the coolest things about doing these hang-outs on air, or the “hang-outs” is that we get to answer questions and meet with the fans. We’re trying to sort of take that to the next level. So in the future, if you miss this one, we’re going to try to move to a regular schedule now where you can know that at a certain time you’ll be able to join and watch us record AstronomyCast, or you can just wait until it pops up in your audio player just like normal. Nothing’s going to change, just more – more better.

Pamela: But this means people can subscribe to our YouTube channel as well as our itunes feed.

Fraser: Yeah, right. It’s going to be very confusing.

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Fraser: OK, well let’s get cracking. So our lives are ruled by calendars and the calendars are ruled by astronomy, so as we near the end of 2011 and get ready to ring in the New Year, let’s discover the astronomy underlying the days, weeks, months, and years that segment our lives. So… I was really worried when I was doing that intro because I was thinking you know this almost starts to sound like astronomy, like, our lives are ruled by the motions of the stars. You know, it’s very “astrology sounding,” so not astrology, but astronomy runs everything.

Pamela: Right, so I mean, if you think about it, there are so many different things — mostly related to agriculture, admittedly — that without knowing exactly what dates the Sun is where, you’re going to end up freezing your vegetables, or not harvesting your wheat on time. So at the end of the day, our nearest star, our sun, rules how we should set up our calendar if we want our calendar to make sense for agricultural purposes, and if you get agriculture wrong, everyone dies of starvation.

Fraser: Right so getting some kind of calendar set up and in place is critical. Some of the things that happened, such as the day and night cycle, are just hardwired right into our evolution, but other things clearly are human constructions. So when did calendars first start to happen?

Pamela: As near as we can tell, there’s always been some sort of a calendar system, but there haven’t always been sensible calendar systems, and the problem that we run into is the Moon doesn’t politely orbit the Earth in an integer number of times every year, and so the easiest way to set up a calendar is to set it up based on the lunar cycles, based on full moon to full moon, or new moon to new moon, but if you do that, your year ends up being about ten days too short and so there’s this problem of “Oh, (insert expletive of choice)! How do we keep our year cycled with the planting season?” So then you have to start inserting leap months, but even if you just come up with some mathematical equation to try and tie it strictly to the Sun, even the planet’s rotation about its own axis isn’t an integer number of days per year, so you still end up with this leap-cycle problem, so basically we’ve always had calendars and they’ve never worked.

Fraser: Always had calendars, and they’ve never worked [missing audio]. So then what are some of the calendars? I mea, what are some of the early ones that people started to use? Because I guess the point being that because they never worked, people have needed to come up with some invention or some solution to solve the problem that Mother Nature doesn’t…you know, didn’t nicely match up the lunar cycles to the solar cycle.

Pamela: So pretty much looking across all the different calendars, you want to look at…we find over and over and over that early calendars tended to be built on the 19-year cycle because the number of lunar cycles it takes to line back up so that you have a full moon with the Sun in place “X,” and you have a full moon again with the Sun in place “X” is about (within a few hours) nineteen years. So culture after culture after culture built a 19-year calendar that was based on mostly having 12 lunar months, but then every few years sticking in some sort of a leap month, so this is just one of those things that everyone seemed to settle down upon in some point in their calendar.

Fraser: And so can you give me some examples? I mean, were there some cultures that used that?

Pamela: Well, we see it, for instance, in the Chinese calendar. This is one of the cultures that continues to use this type of calendar today, where they look at the lunar cycle, but it’s not built purely off the lunar cycle. The Islamic calendar is built purely off the lunar calendar. The Hebrew calendar is sort of-mostly-kind of built off the lunar calendar. And they look at where the Sun is, they look at where the Moon is, and really they’re all kind of complicated — and crazy math.
?

Fraser: [missing audio]

Pamela: Well, I mean, really they just sort of have to do things along the lines of, “OK, so the Sun made it most of the way across this particular constellation, we have a new Moon, so since it didn’t actually make it out of the constellation, we’re going to make this a leap month.” Or with the Arabic or Islamic calendar – it’s based on the first sighting of the crescent Moon each month. And it has to be a physical sighting of it on the 29th, or they assume it’s there on the 30th, and so whether a given month in a given country is 29 or 30 days depends on whether or not somebody saw the moon on the 29th day of the month, and so you end up with all of these things built in that are…it’s kind of head-scratching to try and put it all together.

Fraser: So if you were going to try and develop a calendar, what are the problems, as you say, you know, the problems that needed to be solved? Let’s sort of iterate through them.

Pamela: The primary problem that needed to be solved is each of the different cultures — and this really is a cultural problem — wanted to find a way to have their religious holidays fall at roughly the same time in the solar cycle from year to year. So in the Christian church, it was a problem of trying to figure out how to get Easter consistently about the same time every spring. With the Jewish calendar it’s the problem of trying to get Rosh Hashanah at roughly the same time in the fall. The Arabic calendar…they gave up. They simply cycle through so that every year Ramadan falls in a completely different month compared than the calendar used by the Western world. But many of these other calendars were trying to solve the problem of, “how do we have key celebrations fall during the same seasons that often somehow relate to the holidays being celebrated?” Even our own transition in the Western world, going from the Julian calendar, which dates back from the early 300s — that calendar wasn’t perfect, and Easter was drifting and this was a problem, so they came up with the Gregorian calendar to try and solve the problem of Easter.

Fraser: And so you’ve got this disconnect, right? Between the Sun takes – it doesn’t even take 365 days – it takes somewhere between 365 and 366, the Moon takes 29-ish days to go around, right? So each one of these is some kind of mathematical problem, right?

Pamela: Right, and so with the Moon being 29-ish days, the problem was solved by having months that alternated in lunar-based calendars from 29 to 30 days, and a lunar calendar loses about ten days on the solar calendar every year, so if you throw in an extra month every three years, you can sort of stay on cycle, but that still means that you have that month-long swoosh back and forth for holidays like Easter, so when they tried to come up with a calendar that didn’t have as much movement in it, that was when they took the, “OK, for religious reasons we have a seven day week. OK, so we have a 365-day year, mostly, but it’s actually 365.256363. How do we make up for that?” Well, .25 means, well, the first good mathematical calendar, it meant that every four years you have a leap year, so we developed, initially, the first really good calendar was a 365-day year with a leap year every fourth year, and that made the average year 365.25 days, and so now you’re just missing that .006363 part of the year. Now, while that doesn’t sound like a lot, over a couple thousand years, it caused the calendar to drift enough that Easter was misplaced by about 10 days, or at least the part of the year that was a valid part of the year to put Easter in started to drift, and so they decided in the late 1500s, “Crud! We need to figure out how to fix the leap days so that the year is an even more accurate representation of that 365.256363.”

Fraser: And they had to do some pretty radical surgery to their calendar at that point, didn’t they?

Pamela: Well, it wasn’t that radical except in terms of they had to figure out how to get the two calendars aligned. So the change to the calculation went from being 365-day year with one leap day every four years to a 365-day year with a leap year every four years, unless the year was a multiple of 100 in which case it was a leap year only if it was a multiple of 400. So for instance 1900 wasn’t a leap year, but 2000 was a leap year, so mathematically it didn’t change that month, but the problem was they were off by those 10 days. And so they had a couple of options: they could either have a leap day every year for several years, or they could just suck it up and move the entire calendar, and that’s actually what they decided to do.

Fraser: And that’s what I meant, was they just said, “OK fine, you know, let’s just shift the whole thing ten days. Everybody agree? OK, let’s do it.” You can just imagine the coordination that was involved.

Pamela: The thing was not everyone agreed. This was something that came out of the Catholic church, and when they were sorting all of this out in the late 1500s, it wasn’t a Catholic world, and so when they made the jump, initially only the Catholic European countries made the jump. It took until, well, very recently, actually, before all the nations of the world had finally, mostly, kinda, sorta given in to using the Gregorian calendar.

Fraser: Are there still people that don’t use the Gregorian calendar?

Pamela: Well, so you have to look at, well, what are they using the calendar for? So you still have…the Chinese have the Chinese calendar, the Arabic world still has the Arabic calendar, and all of those different nations are slightly off from one another as well, but for the most part, we finally do have all of the major countries have, at least for financial purposes, adopted it. Turkey was one of the last countries to adopt it, as was China; China adopted it in 1929, and Turkey adopted it in 1926.

Fraser: Are there other motions of the…like of the Earth, like, I know the Earth’s axis kind of wobbles a little bit; it precesses. Would that over long terms as well have an impact on our calendars?

Pamela: Well, the precession isn’t so much of a problem as the fact that the length of the day is actually changing, so as our Moon slowly moves further and further away from the Earth, we’re getting longer and longer days, so we can look back in the historical record, and within the fossil record start getting down to days that were many hours shorter than the current day. So this is where we keep having to add in leap seconds now and then because, well, our rotation rate is changing.

Fraser: And it’s at a level that…I mean, I guess the modern scientific timekeeping devices are so accurate that they actually can do that. And so do they actually do that? Do they actually modify the length of the day every year?

Pamela: Well, they don’t modify the length of the day, but they have been working to try and keep the calendar tied to the Sun, but they forfeited that in 2012, and there’s actually recently an announcement saying that there would be no more leap seconds starting in 2012. The problem that we run into is: modern-day timepieces are accurate enough to notice, “Crud! The Sun didn’t line up with the stars on the exact moment it was supposed to relative to my perfectly precise Atomic clock. Let’s fix this.” But every time they add a leap second in — that wreaks havoc with operating systems the globe over, so trying to push that out to all the cell phones, all the laptops, all of the…every electronic device out there, they gave up. And this is actually starting many different people to try and say, “Well, maybe it’s time to reconsider our calendars yet again.” In fact, there was recently a call put out at an international meeting to change our calendar yet again. Keep the seven day week because people realize there’s just some things that aren’t going to change, and the seven-day week is one of them. But what if we redo the calendar in such a way that every year Christmas is on a Sunday, every year your birthday is on the same day of the week, and we simply re-jigger the year, and where the leap years fall so that we can have this perfectly lined-up perpetual calendar? And the justification that they do for this is, if you think about it, if you work in academics, or if you work in a business that has lots of holidays, just trying to figure out, “Oh, crud! This year Fourth of July falls on day “X.” What day do you give people off? Oh, crud! This year Christmas falls on a Sunday, so we have a different number of vacation days compared to last year.” Lots and lots of time goes into figuring out how to schedule work holidays, how to schedule a lot of different things, so maybe if we re-jigger our calendar so that holidays are always the same day of the month, so that the year always starts on the same day of the week, we can save time on having to re-jigger our work schedule every year.

Fraser: Well, of course, though, I mean, our Thanksgiving here in Canada falls in a completely different month than yours does in the States, so you can imagine it’s a whole other level of coordination and cooperation. Have there been other… I mean, more radical ideas for your calendars? Things that…I mean, do we need to have seven-day weeks, do we need to have…?

Pamela: Well, we don’t need to have seven-day weeks, although it seems to be the right length of period that people are actually willing to work it. If you think…would you want to really work more than five days at a time without getting time off?

Fraser: I’ve been known to.

Pamela: Yeah well, we’ve both been known to, but imagine if that was the expectation.

Fraser: Yeah, exactly. Yeah.

Pamela: But there have been people who’ve moved to say, “perhaps its time we moved to a decimal system, perhaps it’s time to get rid of this whole 12-month thing altogether,” and then the Mayans they took the approach of “we’re just going to number every day.” They have months and all of that stuff as well, but their “Long Count” calendar… they just simply number the days; that’s how they handle it.

Fraser: We can’t talk about calendars in 2012 without talking about the Mayan calendar. How did the Mayan calendar work, then?

Pamela: The thing that’s hard to wrap your head around is their way of looking at numbers wasn’t a base-10 system like we’re used to. Instead they did things in base-18 and in base-20, so their “long calendar” is actually made of looking at all of these different, crazy cycles that take thousands of years to get through, and they just count the days from the beginning of all of it until today, and so the beginning of all of it, we think – it’s always hard looking at archeological records…we think the beginning of everything was 3114 B.C., August 11, 3114 BC if you want to be specific, and it’s simply been counting forward ever since then. And it’s built on a system where they have days, so there’s a one day, and then they have a month-like period which is 20 days, they have a full circle which is 360 days, they have a (I’m going to mispronounce this)…they have a “k’atun,” which is the cycle of all of these days, which is then 7200 days, and all of these cycles come together into the “b’ak’tun” (which I know I mispronounced), which is the culmination of all of these days cycling through, and that longest cycle is 144,000 days long, so there’s 20 days in the first cycle, then there’s 18 cycles of 20 in the second cycle, there’s 20 cycles of the previous one and so it’s…the entire thing is 1 x 20 x 18 x 20 x 20 to get to their calendar.

Fraser: Right. And 144,000 days from when the calendar started happens to sync up, probably, with December 21, 2012.

Pamela: It’s actually 14 times that.

Fraser: 14 times a hundred and…OK

Pamela: Right, and so this is where their myth starts to come in because their myth is: on the 14th of these cycles starting is the day when it goes to the next “b’ak’tun” and so that’s…

Fraser: …the end of the cycle.

Pamela: Yeah.

Fraser: Yeah. Right. And, in our equivalent, that’s because they numbered every day right from the beginning right until now…you know, this would be day 123,692, or something like that, right? That would be the way they would describe a day. That would get very…that would take up a lot of paper, a lot of stone.

Pamela: Well, they actually…because they’re using an almost base-20 math system, it actually ends up being number-number-dot, number-number-dot, number-number-dot, number-number-dot, number-number, which is still a pain, but it starts to…it’s the equivalent of saying the 5th day of the 13th month in the 24th year of the 15th cycle of the 30th cycle of cycles.

Fraser: And so then when this calendar…and so this calendar theoretically runs to an end. Would they…I guess the point is they never planned to be around that long; they never really thought about it, like, it was just…would they just…the whole system would just start again the next day?

Pamela: This is one of those things that we just don’t have the records to tell us. I mean, it’s a cycle, so yes, it does just start over, but I don’t think they’d ever really plan for it to start over, but we don’t really know, and that’s the crazy thing is they don’t have any “world ending” lore tied to this; they don’t have any “everyone’s going to die” lore tied to this — it’s just the calendar, and so it’s…

Fraser: You think about the fact that how, like, computer scientists didn’t really think through the implications of the year 2000, and they only wrote their code 20 years before the end of the century. They never expected that their software would get used for 20 years, or 25 years, “Oh yeah, no, we’ll just put in, you know, ‘87, ’89” — that never really occurred to them. As you can imagine, again going back to the Mayans building this calendar, “Well, are we going to need this in 5000 years? Nah,” you know? It just never came up, so…

Pamela: It’s the millennium bug.

Fraser: It’s the millennium bug, yeah, exactly…so now we’re having to deal with the millennium bug. Thanks, Mayans.

Pamela: It’s just kind of funny that the software programmers and the Mayans only have a 12-year difference in their failure to think through their calendars.

Fraser: To think through the long duration of that…yeah, that’s good. So then, what things would change our calendars? Would there be events? Would there be things that will happen in the far future, maybe, that would change our calendar dramatically?

Pamela: So, we do have slight changes in the equinox positions that do occur, not due to the precession of the pole, but because our entire orbit – it’s not circular, and so as our orbit slowly rotates in combination with the precession of the pole, we end up with changes in equinox, we end up with slight changes in the solstice dates and the spacings of those, and so the slight things add up over time to, again, leap seconds here and there which will eventually, given enough millennia, turn into leap days. So it’s just a matter of our planet isn’t fixed in space; its axis is turning, its date of perihelion is changing, its date of date of aphelion is changing, and as all these things slowly change, they affect our calendar.

Fraser: But that is something that’s going to happen over the course of…

Pamela: Millennium…

Fraser: But that’s still going to be a cycle, but it would be a, yeah, but it would be a bigger cycle. You just end up with the movement of our orbit sort of slowly rotating around the Sun. What about the fact that our rotation is slowing thanks to the Moon? Will we get to the point where days last a very long time?

Pamela: Well, the rate at which things are slowing is such that, yes, it will happen. Our Sun will probably destroy the Earth before we have to worry about it too much. So you can imagine over the remaining course of humanity we might see a five-hour change, but I think that’s the type of thing…there’s already human beings that quite happily run on 30-hour cycles as they work on shift work, so that’s the type of thing we can deal with over time.

Fraser: Evolution can deal with that. And then would there be something that would perhaps, you know, when the Sun turns into a red giant, and…?

Pamela: Yeah, we’re going to have to be on a different planet by then.

Fraser: …the planet’s center of gravity changes, we’ll spiral outward, that’ll make the years longer, right?

Pamela: Yes. Again, we’re likely to be on a different planet, or dead by then, so I’m not particularly worried about the calendar.

Fraser: Right. OK. Alright, alright…just checking. OK, cool! Well, thanks a lot for the calendar info, Pamela. And thanks to everybody who watched us as we did the recording.

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

Ep. 244: Io

admin — Wed, 21 Dec 2011 20:51:17 +0000

If you want to see one of the strangest places in the Solar System, look no further than Io, Jupiter’s inner Galilean moon. The immense tidal forces from Jupiter keep the moon hotter than hot, with huge volcanoes blasting lava hundreds of kilometres into space.

Ep. 244: Io
Jump to Shownotes
Jump to Transcript

Show Notes

Google+: Fraser, Pamela
End of the World — Not! Cruise
Images of Io — NASA’s Photojournal
Io, Galileo and Simon Marius — Gish Bar Times
Controversy over the discovery of Haumea – Mike Brown’s Planets
Io exploration overview — NASA
Io in mythology — Wiki
Voyager spacecraft and Io
Galileo spacecraft and Io
Magma Ocean Flows Under Io’s surface — Universe Today
NASA’s Plutonium Production Predicament – Universe Today
Juno Mission

Transcript: Io

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: Good. And again, we’re recording well into the future. It’s early December, but we’re recording this for late December because you’re going to be cruising somewhere.

Pamela: Yeah, something like that.

Fraser: Not doing anything?

Pamela: I’m going to be off exploring the planet.

Fraser: You’re going to have a holiday? Sounds good…but once again, we’re recording this as a Google plus hang-out, and so if you want to participate, all you have to do is circle either me or Pamela and then we will give an announcement when we’re going to do the recording, and then you can just jump into the hang-out and we stick around for half an hour or an hour after the recording and answer questions, and it’s a really good time. So I highly recommend it — just circle one of us. And this is kind of cool because we’re recording at a really weird time, and so it’s an opportunity for our Australian listeners to join us on this one.

Pamela: And it just occurred to me we’re recording this a year before we’re going to be on a cruise together celebrating the world not ending.

Fraser: That’s right, or the end of the world — one or the other.

Pamela: Well, yeah…either way, we’ll be together.

Fraser: We’re pretty certain it’s not going to end. Yeah, and so you can go and find out about that at astrosphere.org/endoftheworld?

Pamela: Just go to astrosphere.org. It’s the lead story right now.

Fraser: And there’ll be a link to that. So once again, December 2012, we will…we’re going to be doing a cruise with a bunch of other people, David Brin, astronauts, astronomers… It’s going to be a really good time. So you can check that out on our astrosphere website. We sell it so well. We’ve got a whole year to nag you about this. Actually, you know, I think it’s going to fill up, and we haven’t really publicized it outside of just the AstronomyCast shows, so I’ll probably start talking about it more on Universe Today, so and then it will sell out. I highly recommend you go with us. OK, let’s get on with it.

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Fraser: So if you want to see one of the strangest places in the Solar System, look no forward than Io, Jupiter’s inner Galilean moon. The immense tidal forces from Jupiter keep the moon hotter than hot, with huge volcanoes blasting lava hundreds of kilometers into space. And, Pamela, before we get into this, I have to let you know my daughter proposed tonight’s topic.

Pamela: Yes, she is the one who text messaged me to find out if we could do this.

Fraser: That’s right. So she texted…“Can I text message Pamela?” I’m like, “Yeah, OK.” “I think you guys should do a show on Io.”

Pamela: And I was really confused because I thought she’d written “lol” and lost the second “l” because it was an iphone.

Fraser: No, no, no, she’s ligit. She knows her science; she loves Io.
OK, so then, you know, we got a whole episode to just talk about this moon and, you know, there are so many really interesting things about Io. Let’s get started — and I think, you know, we gotta get started with the discovery. When did we find out about Io?

Pamela: Well, finding out about it…there’s always this lag between discovery and publication. So here we have this interesting…the first dude was too slow, so according to anything you’re likely to read, it was Galileo who discovered Jupiter’s moons in January of 1610. The first night he looked, he probably saw Europa and Io pretty much stacked on top of each other and couldn’t separate them, but then on January 8, he clearly saw the two of them as two distinct objects, and he went on to publish this just a couple of months later in March of 1610. Now the thing is, Simon Morris, another person who’d already figured out how to use telescopes to look up, claims that he saw them in December of 1609. And that would have been one month earlier.

Fraser: Well, where are the photos?

Pamela: Well, yeah, that’s the thing. And he didn’t bother to publish his results, so here’s a clear case of: if you don’t share what you see with the world, you didn’t actually see it.

Fraser: And that has happened even recently with Mike Brown, [missing audio] killing Mike Brown from Cal Tech. You know, people discovering objects and then wanting to gather more science, and then other people figuring out what he’d done and trying to break the news before him, so that still happens. If you discover it, the race is on.

Pamela: Yeah. Publish, publish, publish!

Fraser: So then, I mean, do people have an opinion about whether he really did see it? I guess it really doesn’t matter, right?

Pamela: History gives all the credit to Galileo. And you know Galileo suffered enough for his good work — might as well allow him to keep all the Galilean moons for himself.

Fraser: And so what was he able to see?

Pamela: He saw a small star that appeared to move back and forth beside Jupiter — it was very unexciting. In fact, if you go out with a good pair of binoculars, or a Galileoscope (you can still buy Galileoscopes at Galileoscope.org)…with a Galileoscope, they actually have a lens that allows you to see exactly what Galileo saw, and it’s basically this little, itty-bitty, tiny field of view, where Jupiter is a smudge that you can just make out bands, sort of, on a really clear, perfect night, and then you see the Galilean moons dancing back and forth along a straight line like balls attached to a string.

Fraser: Right, and we’ve talked in other episodes — that was a mind-bending discovery because the previous thought was that everything orbited around the Earth, and here was something orbiting around Jupiter.

Pamela: And Kepler actually proposed that maybe these should be referred to as Jupiter’s moons, and Io being the closest in of the four Galilean moons, that was almost planet #1 orbiting Jupiter.

Fraser: So, then it was just stars and that’s all that anyone could see for years and years and years, right?

Pamela: Yeah, and the thing is all we had was this boring object; it had a great story behind it. While Simon Morris wasn’t credited with his discovery, he did get to name it, and it was named after one of Zeus’ mistresses. This is one of the neat things about the moons of Jupiter is for the most part, they’re people that Zeus seduced at one point or another in mythology. And Io, contrary to the look of the object, Io is named after a female that Zeus seduced and then when Hera, his wife, caught him, he quickly turned poor Io into a white heifer to try and hide what he had done, and there’s all sorts of myths about either the heifer ended up one of Hera, Jupiter’s (Zeus’) wife’s, basically, animals, and all sorts of crazy things, but basically you have this passive little white cow that we eventually found out was anything other than a passive white little moon.

Fraser: Right, right, but then even with better telescopes, over the centuries, we didn’t get much better of a view.

Pamela: No. In modern times, or at least within the past 150 years or so, we were able to make out as we looked at it that, well, it appeared to have slight changes in color across the two hemispheres, and by watching it over time, seeing how the colors varied over time, people were able to figure out that it’s not pear-shaped. Because that’s the thing — when the north and south hemispheres don’t give off the same amount of light, it could either be because, well, the one hemisphere is smaller than the other, like a pear, or it can be, as the case actually is with Io, that you simply have dark splotches, and by watching it as it rotated, they were able to figure out that this is a little, tiny, splotchy something going around and around Jupiter.
?

Fraser: But they didn’t know why.

Pamela: They didn’t know why. That actually took until the 1970s, and the first time we figured that out was when the two Pioneer spacecraft made their way out and in December of ’73 and ’74, respectively. They flew by and it just wasn’t quite what they expected. They found high radiation, they found all sorts of weird materials — it was a silicate world, rather than an icy body. All the other moons that we were looking at, at that point, they were just big old blocks of ice, or big old ice balls, literally, but here they had a silica planet, and…or a silica moon, as the case would be. But the thing was, the Pioneers didn’t actually catch any of the volcanoes going off. For that we’d still have to wait another five years.

Fraser: Right, but I know that the Pioneer spacecraft were fairly low-tech for spacecraft. They didn’t have great instruments; they, you know, they didn’t probably make that close of a fly-by, so we just got a glimpse of what was going on, but I know that it was future spacecraft that really pulled things together.

Pamela: Right, so the next missions where things started to get interesting is actually a pair of missions that I’m just able to remember. Back in 1979 in March, Voyager I flew past Jupiter, and my parents made me take naps so I could stay up to watch the data coming back from the mission. And what was amazing is when they started when Voyager started sending back images, the scientists saw this planet that was covered in these weird pits and discolorations and these mountains and clear volcanoes, and as they went through the data, they were able to catch this amazing, basically, volcanic plume rising up over the edge of this small otherwise unassuming moon when you’re watching it from as far away as Earth, and it turned out this is the most geologically interesting thing that we have in the entire Solar System.

Fraser: And were astronomers, like, at all expecting anything like this?

Pamela: No. No. We had no clue anything like this was out there. It was just one of those things. I mean, there was a prediction from the Pioneer stuff. When Pioneer got there, there was absolutely nothing. So let me step back. From Pioneer there’s absolutely nothing weird anticipated. We’d gotten hints that there was stuff going on from Pioneers, and there had been a theory paper published that predicted that maybe tidal heating could cause some sort of a volcanism, but the level at which this was seen, the amount of sulfur and sulfur-dioxide getting thrown up, the arcs of material going between Jupiter and Io, none of this was predicted ahead of time. And it was like someone had taken every Dark Ages painting idea of Hades and turned it into a moon orbiting Jupiter. All that sulfur, all of that suddenly became real.

Fraser: I mean, I always imagined seeing, like, video of the volcanoes on Hawaii, or some of the…where you’ve got like these fountains of lava blasting in the air, and you’ve got you know, globs of lava, you know, plopping out of the volcano and landing as, you know, chunks of rock around. I mean, you’ve got this world, but it’s that times, I don’t know, like 1000, like you’ve got these streams of lava blasting out of the moon and, you know, creating these fountains of material. So let’s imagine, you know, that we were, like, standing above Io. What would we see?

Pamela: Well, so standing — that doesn’t even give you enough perspective. So, the thing to think about is the biggest volcanic eruption that most of us are familiar with from the news is the unpronounceable volcano that went off in Iceland in 2010, and that volcano threw material several miles up into the air, but it was still “single digit number” of miles into the air. Well, Io is about a third the radius of the planet Earth, not quite, it’s a little bit less than that, and it’s able to throw material into space roughly 1/3 of its diameter, so…[laughing]

Fraser: Hundreds of kilometers…

Pamela: It’s going hundreds of kilometers into space, and we just don’t have the…

Fraser: Well, it’s even more than that, right? I mean, as you said, it’s trailing away from Io itself and being absorbed into Jupiter.

Pamela: Right.

Fraser: It would be like volcanoes on Earth being blasted off and being, you know, making their way to the Sun.

Pamela: Or imagine having a volcano going off and the material in the volcano becomes part of the Northern Lights because that’s a closer analogy to what’s happening, or even better would be imagine if the Earth’s moon suddenly had a volcano that joined the Northern Lights because that’s essentially what’s happening is when these volcanoes go off — some of the material that gets released into the atmosphere, it gets…or not so much into the atmosphere, that gets released into space, it gets caught up in the magnetic field lines and forms these amazing streams of radioactive material that are kind of dangerous to the spacecraft that go through them. But this is plasma streams writ large, where volcanoes, gravity and electro-mechanics are all interacting in violent and amazing ways I don’t ever wish to calculate.

Fraser: No, or visit.

Pamela: Or visit. Yes.

Fraser: Right. And so, you know, we talked about, like, if you could stand on the surface, what would you see?

Pamela: If you could stand on the surface, you’d simply see a volcanic eruption that streams all the way into space. So if you’ve seen a rocket launch, you know how you can see the stream of material going all the way up into the sky and stretching out over the horizon? Well, this is a volcanic eruption that does the same sort of thing.

Fraser: And you would be standing on recent lava flows — no matter where you were.

Pamela: Pretty much. This is a constantly resurfaced world. There are some craters on it, but very few. So the surface is… we’ve seen areas basically the size of Arizona get resurfaced just in the years that we’ve been watching this planet with spacecraft.

Fraser: Wow!

Pamela: I keep calling it a planet – it acts like a planet! It’s not; it’s a moon. So, this moon…

Fraser: Now, when we see the pictures…we’ve seen the pictures from Voyager (and we’ve seen the updated pictures taken by New Horizons and Cassini), it’s got this strange, like, it looks like a bruised orange, like, it’s got these yellows, and oranges, and browns, and all these crazy colors, so what’s going on there?

Pamela: Well, the yellow is sulfur, so this really is every imagining of Hades turned into a moon. So, you do see when you look at the images some ices, you do see variations of the sulfur, where you get irons and you get different silicas mixed in, but that overwhelming yellow covering the whole moon — that’s just sulfur and sulfur-dioxide.

Fraser: Is it like snow, or…?

Pamela: No, think of it as they talked about with the unpronounceable volcano that went off in Iceland. All of the silica ash that would destroy airplanes if airplanes flew through the ash — well, that yellow-y stuff that you’re seeing is similar sorts of material. It’s all the silica stuff that got thrown into space, all the sulfur ash that got (I don’t know if ash is the right word), all of the sulfurs that got thrown into space, and then, gravitationally, some of it gets pulled back down — a lot of it gets pulled back down, and it’s kind of amazing the size of the arches that some of these plumes make as they go up, and then fall down far away from their volcanoes.

Fraser: And, uh, someone from the hang-out wanted to know: why is there so much sulfur?

Pamela: You know, this is actually one of those things that when I was researching for this show I was trying to find. I couldn’t find a quick answer anywhere. This is a world that has a disproportionately large amount of silicon, a disproportionately large amount of sulfur, and its composition is just different from everything else, so somehow when the Solar System was differentiating, this one rock ended up in a part of the Solar System that for the most part is ice and gas.

Fraser: And, so then what…and then what is causing this? I mean, now those regular listeners to the show will know, but I think it’s quite an amazing story. So what is causing this moon, unlike all the rest, to be so volcanically active?

Pamela: Well, it has an unfortunate location. So, as I was saying earlier, it’s one of the four Galilean moons, which means it is orbiting Jupiter and it’s the inner most of those four, and the others are Europa, Ganymede and Callisto, and the inner three: Io, Europa and Ganymede have orbits that have, over time, settled into what’s called a resonance. So for every two times Io goes around Jupiter, Europa goes around once, so if Io’s at the top of Jupiter and Europa’s at the top of Jupiter and you’re looking down from the north (so that’s kind of a weird way to think of it), you’re looking…you’re hovering above the north pole, looking at the planet, and at the top of the planet, you see Io and then directly above it you see Europa, then the next time Io gets to the top, Europa’s going to be exactly at the bottom. Now, Ganymede is doing this exact same thing, but for every four times, so every time that Io and Europa are lined up, Ganymede’s going to be lined up with them, and this resonance: this 2:1, 4:1, 1:1 resonance between these three moons forces Io to sometimes be closer to Jupiter, sometimes be further from Jupiter, and to undergo constantly changing gravitational pulls, and this constantly changing gravitational pull has the effect of, over and over and over, squishing Io like a stress ball held in the hand of an angry Roman god, which according to mythology it is [laughing], so…or in this case, yeah, I’m not going to go into the mythological connotations on this one.

Fraser: But it’s that squishing, and then un-squishing, and then squishing, and then un-squishing — just heats it up, and there’s, I mean there are so many examples that you can think of something very similar. You can take a rubber ball and squish it and un-squish it.

Pamela: If you have a small child that you want to tire out, hand them a small rubber ball and have them bounce it over and over and over with a paddle, and eventually, it will actually change temperature from doing this.

Fraser: Yeah, I mean, bounce it up and down for a while, and then touch it, hold it, and you’ll feel the warmth coming off of the ball and that’s because it’s the same process.

Pamela: In this case, this constant squishy-squishy-squishy that it undergoes is able to build it up to a temperature of 1200 degrees, and it’s estimated that anywhere from 20% or more of its mantle is melted and that there’s a vast subsurface — basically, oceans of lava. The surface is probably about 7 miles (12 km) thick, or more. It’s at least that thick, but it’s certainly not more than 25 miles (40 km) thick, so this is a world with a very, very thin surface over a rather hot interior of magma, and all of that’s just under pressure waiting to break through and fly hundreds of kilometers into the atmosphere.

Fraser: Right, and so it’s that tidal forces that…well, I guess it’s a mixture, right? The tidal forces are creating huge pockets of this liquid that’s increasing the pressure, and then at some point it has to find a way out, and you get these cracks in the surface, and you get these geysers, and then at the same time it’s a smaller object than Earth and so it’s got less gravity, and so things can just fly further when they blast out.

Pamela: Right, and what’s kind of awesome is not only are there the volcanoes, but there’s also regularly-formed mountains from all of the forces that the crust is undergoing from having all of this squishing, all of these tidal forces, all of the pressure from the magma, and some of the mountains that are forming are actually bigger than Earth’s Mt. Everest. So here again you have something a little less than a third the diameter of Earth, mountains bigger than Earth, volcanoes spewing material up to what on Earth would be the orbital height of the Space Shuttle — I mean, just imagine if one of the volcanoes in Iceland or Indonesia or Hawaii went off and hit the Space Station! That’s the scale that we’re looking at here!

Fraser: And again, like, I think about how you’ve got Europa, which is a little further out, which possibly has, you know, a crust of ice with liquid water underneath, and it’s that tidal flexing has made the water liquid. But with poor Io, it’s the tidal flexing has made the rock liquid. It’s just a different sense of scale. Now, you know, we always think: Europa, Callisto — maybe there could be some life? Enceladus? What do you think are the chances of finding life on Io?

Pamela: You know, I think if we’re going to find something with something more than a few cells inside, Europa’s the place to look. But Io…we find out at Yellowstone, here in America, all of these amazing thermophiles that live in the hot springs, that live in the extremely sulfuric acid-rich pools, that live in these bizarre chemistries, and these bizarre chemistries are at a completely different pressure and gravity than Io, but compositionally, they’re just as toxic, and if stuff can live in those toxic environments on Earth, there’s no reason to think that stuff couldn’t evolve to exist in the similarly toxic environments on Io. You have a thermal gradient, you have presumably some sort of liquid (that part we don’t know for sure), but you’ve got that thermal gradient and that is one of the things that drives the chemistry of life.

Fraser: Yeah. I mean, if you’ve got a source of energy, that goes a long way… You [missing audio] in helping out life, so it’s really interesting. Now are there any plans to re-visit Io?

Pamela: Well, we want to, and this is one of the problems we’re dealing with now.

Fraser: Yeah, you and I want to. We want Io visited, but…

Pamela: [laughing]

Fraser: Are there any plans by you know scientists? Perhaps space agencies?

Pamela: One of the problems we’re dealing with right now is lack of funding, and this gets reflected in two fairly significant ways. One of them is we just don’t have any more of the radioisotope-driven engines that you need to go out and explore these distant locations in the Solar System; we just don’t have the radioactive materials we need to build more of them. And Congress cut the budget to turn on the facilities necessary to manufacture those radioactive isotopes. And then there were plans to explore the moons of Jupiter in greater detail, but that spacecraft doesn’t necessarily look like it’s going to happen anymore. As they cut more and more of the U. S. budget, as we move toward having our own form of austerity measures, we’re losing our scientific dreams, and so I have to say probably not in the next 10 years is anything going to launch to explore these moons. Now, we do have a spacecraft on the way out to Jupiter; this is Juno. Yeah, so Juno’s going to do a great job at what it does. It’s going to be mapping the magnetic fields of Jupiter, and it’s that magnetic field that carries around the radioactive materials. It’s going to be doing a great job measuring the composition of Jupiter’s atmosphere, and mapping out the gravity of Jupiter. It’s going to do some really awesome things, but this isn’t an imaging mission. It does have a camera on-board; it’s a camera designed to take pretty pictures because we want pretty pictures, but it’s not really a science camera. So the science is going to be the type of stuff that makes the scientists happy, but doesn’t necessarily end up on the nightly news. And so Jupiter is going to reveal a few more secrets, but not necessarily a few more pretty pictures.

Fraser: Oh, wow. OK, on that sad note…well, thank you very much, Pamela, and we’ll talk to you after Christmas.

Pamela: That sounds great, Fraser. I’ll talk to you later.

Fraser: Alright. I hope everybody has a great Holiday, and we’ll talk to you again next week.

Pamela: Sounds great. Happy Holidays, everyone.

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

Ep. 242: Torino Scale

admin — Tue, 06 Dec 2011 03:16:35 +0000

When you hear of a looming asteroid strike, do you wonder what to do? Should you go into your underground bunker, evacuate the state, or leave the planet? Fortunately, astronomers have developed the Torino Scale – a handy measurement that incorporates both the risk of a strike with the amount of devastation.

Ep. 242: Torino Scale

Show Notes

Google+: Fraser, Pamela
NASA’s NEO Program info on the Torino Impact Hazard Scale
Current Impact Risks (as of this recording)
Asteroid 2005 YU55 — Universe Today
Richard Binzel: Three Questions on Near Earth Asteroids — MIT
News story from 1999 detailing the Torino Scale — Terradaily
1/2mv^2 — Kinetic Energy
The Torino Scale — Universe Today
Torino Impact Scale Explained — NASA
What Damage Have Meteorite Impacts Done in Human History? – Oberlin College
Chíing-yang Meteorite Shower of 1490
Campo del Cielo Meteorites
Tunguska Impact -- Science@NASA
Barringer Crater (Meteor Crater)
Predicting Apophis’ Encounters in 2029 and 2036 -- NASA
AstroGear

Transcript: The Torino Scale

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?

Fraser: Good! So once again, we’re recording AstronomyCast live as a Google plus hang-out, but we’ve muted them all so you can’t hear any voices. Everyone’s going to wave in silence. So if you want to join us for future recordings of AstronomyCast, all you have to do is join Google plus and then circle me or Pamela, and then when the hang-out is kind of approaching, we will…

Pamela: …warn you!

Fraser: …mention it, warn you, and then we’ll start the hang-out up, and it’s kind of a race to get in, but it’s super-fun, and then we try to leave the hang-out open for another half hour, forty-five minutes after we do the recording, and we answer questions and yak about space and astronomy and photography, dogs…

Pamela: Stuff.

Fraser: Yeah, so it’s awesome and super-fun, and we’d love to have you guys join us. So when you hear of a looming asteroid strike, do you wonder what to do? Should you go into your underground bunker, evacuate the state, or leave the planet? Fortunately, astronomers have developed the Torino Scale, a handy measurement that incorporates both the likelihood of a strike, and the amount of devastation. This is good; this was needed for a long time, you know? The Torino Scale?

Pamela: Well, I’m not sure it’s needed so much as it’s just one of those things of die/not gonna die, and probabilities.

Fraser: I mean, that was my intro, right? Asteroid YU 2005 is going to strike the Earth, you know? I gotta know! Should I evacuate Europe? Should I leave the planet? Or is it sort of no big deal, I’m just going to get out my binoculars and watch it strike the neighboring city, so um, you know? So, I think, now we’ve really got a really precise way to be prepared. So where did this concept come from?

Pamela: Well, back in the 1950s, as we started to realize more and more and more that our planet is kind of covered in asteroid impacts, people started thinking, well, so what do all of these different types of impacts mean?” And, well, any time you get scientists thinking hard about something, they’re going to end up coming up with a numerical way of quantifying all of it.

Fraser: Right, like the Richter Scale…

Pamela: Right.

Fraser: Oh man, what is it? The Fuji…F-Scale for tornadoes? The scale for hurricanes…

Pamela: Right, so we have all these different scales, and it was finally professor Richard P. Binzel, who (he was working at MIT at the time)…it was only in 1995 that he presented this at a conference, and so this is a fairly new way of looking at the Universe and saying this is numerically quantified how it’s going to destroy us, and he gave his presentation, actually at a UN-hosted conference, where they were discussing future destruction of the planet Earth.

Fraser: Right, right I, again, you can just imagine scientists going, “Is there some way we can put a number to this?” You know? So right, OK, so he presented, he sat down and decided he was going to be the one to come up with a name, but it doesn’t have his name.

Pamela: No, that’s actually one of the things about it that, to me, was kind of confusing until I realized it ended up getting revised in June 1999 in the Italian city of Turin, which if we weren’t Americans, we would call the city of Torino. So it’s named after the city where the current version of it, more or less – it got revised again later to make it more press-friendly, but it got named after the city where the current, all-but-final version of it was invented.

Fraser: Right and that sounds like a nice, sort of, way to sort of cap it off, and then we’ve got this nice measurement scale from this point on, and it’s actually taken off pretty well, I mean, I can…that’s in my time. When I started Universe Today back in ’99, I can kind of remember when they started to incorporate that scale, and we’ve been watching it ever since. And now, every asteroid that has any kind of likelihood of hitting the Earth gets, you know, will get a measurement on the Torino Scale.

Pamela: And what’s interesting is you might be one of the reasons why in 2005 they felt the need to re-change some of the wording. So this is a scale that goes…

Fraser: Me? What?! What?!

Pamela: Well, it’s a scale that goes from 0 to 10, and it used to be that objects that were Torino level one, which the official definition is “a routine discovery in which a pass near the Earth is predicted that poses no unusual level of danger.” It goes on a little bit longer than that…

Fraser: We’re going to go through the scale in a second, but yeah.

Pamela: So, this is now called “normal,” so anything Torino level one is “normal.” Well, it used to be that it was “events meriting careful monitoring,” and so many members of the press went a little nuts — not saying you’d go nuts, but you’d probably mention it anytime something got a Torino level of one, that they’re like, “OK we’ve got to rename this so people don’t panic.” So in 2001, it went from “merits careful monitoring” to “normal.”

Fraser: Well, and the thing is if you go through enough of these, you see the way it always plays out, which is that somebody discovers an asteroid, they quickly assign a Torino Scale to it, and then, you know, and then everybody points their telescopes at it and gets careful data on it, and then, always, every time so far, the Torino…it just drops back off the Torino Scale because they now know that it’s not going to be any kind of risk, but there’s this gap where the press goes bonkers, and people freak out.

Pamela: Well, it’s fun!

Fraser: It’s fun?

Pamela: Well, I…think about it. We live in a world where people celebrate death and destruction, and pepper spraying, and all these other crazy things that make it into the news. If it bleeds, it leads, and destroying of the planet counts as bleeding.

Fraser: Right, it is big news. Although people gotten a lot more used to it, I’m still waiting for people to get numb to asteroid discoveries and asteroid risks, and they still don’t. I mean every one of them – we had a huge boost when, what was it? 2005? huge boost of traffic to the Universe Today because everyone was searching for it. OK, so then what is the purpose, like, what does the Torino Scale measure?

Pamela: It’s sort of the planetary risk level for asteroids the way we have a color system to describe nuclear threats, the way we have a color scale to describe airport safety threats, it’s just another one of these three-minutes-before-midnight threat assessments, so if it’s zero, we’re good. It’s going past the Earth, we’re fine, just smile and watch — and ten is we all die.

Fraser: We all die. Right, but the point is when you think about the Fujita Scale (thank you to the people in the hang-out who reminded me of the name), but when you think of the Fujita Tornado Damage Scale, you have like speed of winds, and the size of the tornado itself. When you’re thinking about the scale for the hurricanes, you’ve got, sort of, the speed of the winds, and that’s just it, right? When you’ve got the Richter scale, we’ve got the amount of shaking, so what are we measuring with the Torino Scale?

Pamela: ½MV squared.

Fraser: Right, ½MV…right! So we’re measuring the momentum of it?

Pamela: Well, no, no, no — momentum is mass times velocity. This is energy.

Fraser: Right, total energy.

Pamela: So, we have to worry about what’s its mass, what’s its velocity as it’s coming towards us, and it also has to deal with, in addition to these measurable things, it also has to deal with how likely is it that those measurable things are going to impact their energy, well, on our heads.

Fraser: So Jupiter is going to have a lot of mass and velocity, but it isn’t going to hit us.

Pamela: And at the end of its day, its velocity really isn’t that bad, so… It just has a giant mass that isn’t going to hit us.

Fraser: Right, right. It isn’t going to hit us, and the trick is if they hit us. So, it’s both the velocity and the mass of the object, but also that probability of whether it’s going to hit.

Pamela: So, we have things that have high probability, low mass, low velocity, do zero damage; things with high mass, high velocity that are somewhere else in the Solar System and aren’t going to hit us and thus do no damage, but it’s the things in between with a moderate probability of hitting us, and enough mass and velocity to make it through our atmosphere — those are the interesting things that we like to look at.

Fraser: Right, and I know that the danger on the Torino Scale — it could be a high probability, but not a lot of damage, and it could be the other way – a lot of damage, but a low probability of hitting us, and the Torino Scale nicely accounts for both of those.

Pamela: Right, and the thing that anyone that’s gone out and has looked up for any period of time has realized is we’re constantly getting hit with stuff, but the catch is we’re constantly getting hit with stuff that’s of a size that doesn’t matter, so about every 30 seconds a 1 millimeter object hits our atmosphere – shooting star – little, tiny, probably-not-noticed shooting star. About once a year, an object one meter in diameter hits us, burns up, does no damage, and we notice over and over and over in the satellites that are looking for things being blown up — nuclear assessment and things like that — there are dozens to hundreds, depending on how much energy you’re looking at, massive explosions in our atmosphere, Hiroshima-sized explosions in our atmosphere from things that hit us on a regular basis that no one notices because it’s out over the ocean, or over the prairie or something.

Fraser: So, let’s go through the Torino Scale. Let’s start with the bottom, I guess, zero and walk our way up to ten.

Pamela: OK.

Fraser: So what is zero on the Torino Scale?

Pamela: Uh, nice lightshow, maybe — probably not. This is the YU 55, so things that go past that we know exist, they’re not coming anywhere near us, but we can look at them as they go by.

Fraser: So we are certain that they will not do anything to the planet.

Pamela: We are absolutely, positively certain they will do nothing to the planet.

Fraser: OK, so what is a “one” on the Torino Scale?

Pamela: A one is “the chance of collision is extremely unlikely,” about the same as a random object of the same size striking the Earth within the next few decades.

Fraser: In other words, objects are randomly hitting our…what? hitting our atmosphere every few decades anyway, and so there’s just neither much risk, nor much damage if it does.

Pamela: It actually kind of boils down to, “we don’t know much about this object yet. It’s as likely to hit us as anything else, and anything else is probably not going to hit us.”

Fraser: Right. OK. Let’s move on, I want to hear the next one.

Pamela: OK, so this is number two: “events meriting concern,” yellow zone number two. Number two just says “a somewhat close, unusual encounter, collision is very unlikely.”

Fraser: OK. Three?

Pamela: “A close encounter with a 1% or greater chance of collision capable of causing localized destruction.” This is your neighbor’s house is destroyed.

Fraser: Well, it’s more than that, right? It’s like a city.

Pamela: Yeah, but it’s still confined to a region. So we’ve experienced these things in human memory, so it’s…

Fraser: Would that be like Tunguska?

Pamela: Well, Tunguska, yes. It would also be back in 1490, there was a Chinese village that reportedly had about 10,000 people killed.

Fraser: Right, OK. Yeah, and I know we have lots of these iron meteorites that are found in, like, what is it? Campo del Cielo meteorite? And there’s…so like Tunguska. for example. was like a…what? 1908 asteroid, comet, UFO traveling through a wormhole, um…

Pamela: [laughing] Something blew up in the atmosphere and flattened part of Siberia.

Fraser: Right, so in other words, it didn’t cause any damage to Paris or Moscow, but it sure ruined a chunk of the Siberian forest.

Pamela: Right.

Fraser: OK. Alright, so, that is localized damage. Let’s keep going.

Pamela: OK, so now we move out of yellow into threat level orange, and these are threatening events. And I just sound far too mirthful reading these, but destruction is fun! So number five is “a close encounter with a significant threat of a collision capable of causing regional devastation.”

Fraser: Regional…so when they say regional, are they talking about, like, Europe? Great Britain?

Pamela: Yeah, pretty much.

Fraser: Yeah, OK.

Pamela: Let’s just, like, get rid of Australia.

Fraser: So, in other words, if that happens, and great, it hits Australia, then you and me over here in North America would probably be alright.

Pamela: Right, so here we’re not talking enough material getting thrown into the atmosphere that it causes global cooling. We’re not…we have to worry about things like massive fires being caused, but as long as that doesn’t happen, we’re probably good. As long as it’s elsewhere…

Fraser: And that’s only half way up the scale.

Pamela: It’s only half way up the scale, but these are still probable things, so there’s a significant threat, but not a certain threat.

Fraser: Right. OK, keep going up.

Pamela: So threat level six is “a close encounter with a significant threat of a collision capable of causing global catastrophe,” so this is the dinosaurs dying — perhaps.

Fraser: Right, but I think the key there, and this is really weird, right? Because this is essentially complete destruction of the Earth, of all life on Earth, but we’re still…but maybe, right? That’s the trick.

Pamela: It’s the maybe that’s important. It’s the maybe that keeps it from being a red.

Fraser: So maybe the whole Earth will be destroyed, but maybe not. Who can say? Right. OK. Let’s keep going.

Pamela: OK, so threat level seven is “a close encounter with an extremely significant object capable of a collision causing a global catastrophe.”

Fraser: That’s seven?

Pamela: That’s seven.

Fraser: Well, hold on a second, so that is again global catastrophe, and a very high likelihood of a collision?

Pamela: So we went from “significant threat” at six to “extremely significant threat” at seven.

Fraser: Are we going to be destroying the Universe by the end of this scale?

Pamela: We’re just increasing certainty as we go.

Fraser: OK. Alright, it’s just hard to say with these words, you just want, like, is it a 75% chance? Is it a 33% chance?

Pamela: Yeah, they don’t do that for us.

Fraser: OK, let’s go on to level eight. I’m scared now.

Pamela: OK, so we’re now going into threat level red. These are certain collisions.

Fraser: Aaah…certain. 100% chance, yeah… There’s a 100% chance that an asteroid is going to strike. OK.

Pamela: So at threat level eight, we have “a collision capable of causing localized destruction. Such events occur somewhere on Earth between once per 50 years, and once per 1000 years.”

Fraser: So, this would be astronomers detecting a Tunguska-level event, or maybe meteor crater in Arizona, right? And saying…Barringer Crater? Yeah.

Pamela: Beringer.

Fraser: Yeah, Barringer, and saying, “We are absolutely going to get hit by a Barringer. It’s probably going to hit, you know, Paris. Everybody ought to move away from Paris.”

Pamela: See, I’m not actually sure if Barringer is localized or regional because of all of the stuff it tossed into the atmosphere.

Fraser: Right, right, you know maybe that’s just… Yeah, but what is it? A Tunguska happens every 100-1000 years, so it sounds like that’s sort of in the scale.

Pamela: It’s definitely Tunguska.

Fraser: Well, I mean Tunguska flattened a forest for 1000s of kilometers, right? …square kilometers, so it was a pretty big event.

Pamela: Yeah, it was kind of awesome.

Fraser: …dig out a big crater, but that’s kind of what we’re talking about. I can see maybe Barringer being even worse, but the point being…but it’s interesting, you know, the previous level was, you know, “the Earth is completely toast probably,” and now we’re back to “a very small part of the Earth is toast for certain.” OK.

Pamela: Yes. OK, so threat level nine is “a collision capable of causing regional devastation. Such events occur between once per 1000 years and once per 100,000 years.”

Fraser: Ouch. OK.

Pamela: So this is, “We see it coming. Everyone get on a plane and go somewhere else now, please. That part of the planet is about to end.”

Fraser: OK, and number ten…

Pamela: Number ten: “a collision capable of causing a global climatic catastrophe. Such events occur once per 100,000 years or less.”

Fraser: 100,000 years or less?!

Pamela: Yes.

Fraser: So we’re not even talking about like a KT, you know the one that ruined the dinosaurs 65 million years ago; we’re talking about something much less damaging.

Pamela: Well, so this is where you end up with people arguing over what counts as global catastrophe. So, does it count if it changes the weather patterns? Does it count if you have mass extinctions? because we certainly haven’t had a mass extinction in a while. So, people do squabble over those kinds of things.

Fraser: But we are talking about the end of civilization as we know it.

Pamela: Yes.

Fraser: No matter where you live, civilization is going to come to an end.

Pamela: Yes.

Fraser: Wow! So since the Torino Scale has been developed, how bad has it gotten?

Pamela: Well, we made it up to four once, briefly, but the nice thing about the scale is it’s self-correcting as you get more data because up until you get into that red zone, all you’re really talking about is things that might hit the Earth, and how bad it’ll be if they happen to get to “might,” or happen to get past “might.” So Apophis, which we’ve all heard about in the news, is the big one that everyone freaks out about, and we now know it is a zero. There is no chance that we know of that on its next pass past the Earth — and this is all we’re worrying about is the scale’s looking ten years out into the future. It’s not going to hit us then.

Fraser: Although, there’s a possibility of that in 2029, and a completely unknown possibility in 2036.

Pamela: Yeah, so it currently still has, for the 2036 encounter, a rating of a level one because we need to wait and see what happens in 2029 because its orbit will get changed as it goes past the Earth.

Fraser: So the highest…so Apophis, you know, rose in the charts to four.

Pamela: Yes.

Fraser: Which I think they kind of regretted doing that, but…

Pamela: Yeah, well, it was an honest…you see, the problem is that science is something where we’re constantly learning new things, and… It was an honest level four..

Fraser: Yeah. There was enough uncertainty…

Pamela: There was an object in 2006 that temporarily got a level of two, but it got downgraded quickly, so in general, things don’t make it very high on this scale.

Fraser: And they don’t last long on the scale.

Pamela: Right, and what’s kind of amazing is we have all sorts of surveys that are essentially accelerating the rate at which we discover asteroids, so even as we’re discovering more and more and more and more asteroids on a regular basis, we’re not discovering more Earth-destroyers as we go.

Fraser: Right, and in fact, I think, you know, we mentioned this in another show, we’re finding all of big nasties, and have really ruled out a lot of impacts in the foreseeable future.

Pamela: Right.

Fraser: The size of asteroids is the problem that we’re looking for now, and they’re getting smaller and smaller, which is kind of a relief.

Pamela: And the thing interested me, in researching the show, I went through and I looked up historical accounts of people getting clobbered because you’ve probably seen on TV if you’ve ever watched any of the bad science channel specials, the story of the car that got hit, the story of the lady that had one come through her roof, and bounce off her radio and hit her…

Fraser: The dog that got killed…

Pamela: …the dog that got killed, so there’s all these stories that are always in the news. But the thing that got me that I didn’t know about is there’s a number of different (number being 3), number of different areas getting walloped by basically a rain of solar system gravel, and so there’s this story in 1490 that people argue over how accurate the numbers are, but according to the histories, the Chinese province, that I’m about to mispronounce, Chíing-yang, was hit by a whole bunch of asteroid fragments that killed about 10,000 people, and that’s kind of dramatic. And there was a village in Africa that had a rain of fragments, and there’s just all these stories of places basically getting rained on with shards that damage roofs — it’s like a massive hail storm, usually, but that seems to be the more frequent way of individuals having close encounters with asteroids.

Fraser: And so just as we’re recording the show right now, how many objects are on the scale?

Pamela: Well, everything’s on the scale…

Fraser: Oh, sorry.

Pamela: …because everything gets a Torino level.

Fraser: Sure. How many are above one?

Pamela: Well, we have nothing above one.

Fraser: Wow.

Pamela: So there are two objects that we don’t know their orbits well enough to give them a zero, so there’s two things that we’re still following up on that have a rating of one in the near future. So, we’re doing pretty good. With everything we’ve discovered, we are safe for at least ten years, and for the things that we know, with the exception of Apophis, there’s nothing to worry about.

Fraser: Alright. Wait a minute – that was like a nice, pleasant, happy ending to that.

Pamela: That’s why it allows me to giggle while reading the scale.

That

Fraser: That was good. I like you reading the scale. People should…we should have a separate recording of that and then we could just listen to that show – you doing the Torino Scale. Right? Well, that was great. Well, thanks a lot, Pamela.

Pamela: It was my pleasure.

Fraser: And next week, I think, we’re going to actually specifically talk about Tunguska.

Pamela: Yes.

Fraser: And that will be kind of cool. And that was from a listener who suggested that idea for a topic, so we will…we live only to serve, and we will do that episode next, so….

Pamela: And one side comment before we take off: we are recording this as we enter the Holiday season in 2011, and we just posted a bunch of new stuff in our store, including a new t-shirt design for the Venus transit next year.

Fraser: Cool!

Pamela: So if you’re gearing up in your preparations for the Venus transit, and you want a map on a shirt of where the transit is visible, we have that shirt for you. So, go to Astrogear.org and get stuff for the Holidays for the people in your life, and for yourself while you’re there.

Fraser: Sounds good. Alright, well, thanks a lot, Pamela.

Pamela: Sounds great!

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

Ep. 238: Solar Activity

admin — Thu, 10 Nov 2011 16:56:54 +0000

The Sun looks like a harmless burning ball of fire in the sky: warm, life-giving and forever unchanging. But we know better, don’t we. It’s really a massive ball of churning hydrogen plasma, encased in twisting magnetic field lines, speckled with sunspots, and constantly disgorging vast plumes of radiation and charged particles. The Sun is very active indeed.

Ep. 238: Solar Activity

Show Notes

Solar Maximum prediction for 2013 — Science@NASA
The Solar Cycle — Marshall Space Flight Center
Animation of the Sun’s magnetic field lines over time - Windows to the Universe
Earth’s Inconstant Magnetic Field - NASA
Sunspots come in pairs — Universe Today
Stunning aurorae in Oct. 2011 seen at low latitudes (and bright red in some regions.) — Universe Today
Image/video of magnetic field lines on the Sun – Universe Today
Video from the Solar Dynamics Observatory of magnetic field lines snapping and material being flung out from the Sun — Lights in the Dark
Long periods of no sunspots – Science@NASA
Where are the Sunspots? (article from 2008) — Universe Today
Maunder Minimum — Universe Today
Using Ice Cores to Study Solar Influence on Climate — Australian Dept. of Sustainability
Solar activity and climate: is the Sun causing global warming? – Skeptical Science
El Nino Found to Drive Tropical Civil Wars – Scientific American
Solar Flare — NASA
CME –NASA
Magnetohydrodynamics — Wiki
STEREO Mission
Solar Dynamics Observatory
Astronomers Track Flares on a Distant Star — Universe Today
Studying Starspots – Ohio Wesleyan University
AC Episode #163: Auroras
SpaceWeather.com
Aurora Season (aurorae on the equinox) — Science@NASA

Transcript: Solar Activity

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?

Fraser: Good…and we’re once again recording this as a live Google plus hang-out. Hello to all of our Google plus friends. They’re all waving; you can’t see it…joke never gets old. Alright, so we don’t have a lot of time for chitchat; you have an airplane to catch so we’re just going to roll. The Sun looks like a harmless ball of fire in the sky: warm, life giving and forever unchanging, but we know better, don’t we? It’s really a massive ball of churning hydrogen plasma encased in twisting magnetic field lines, speckled with sunspots and constantly disgorging vast balloons of radiation and charged particles. The Sun is very active indeed. And you know what’s cool, Pamela? We are nearing the solar maximum.

Pamela: Well, we hope we are nearing the solar maximum.

Fraser: Yeah, It’s very weird this year, very weird…strange times we live in.

Pamela: Yeah, yeah, so we’re recording this in November of 2011, and they keep changing when they think our current solar cycle is going to peak just cause it’s such a weird one. It’s behaving oddly, and so the Gaussian fits aren’t working so well. We’re currently looking at a maximum probably around May of 2013, which for an 11-year cycle is right around the corner.

Fraser: Right. Alright, so I was getting ahead of myself, so let’s go back, go back. So, the Sun is a ball of plasma hydrogen pulled together by its gravity in a nice state of equilibrium with the light pressure pushing out and the gravity pulling inward, and that would seem to be the sort of state of perfect balance, but the Sun is very active, so what’s going on?

Pamela: Well, on the grand scheme of stars, the Sun is actually very boring and very inactive, but what we’re realizing…

Fraser: Well, the show’s over then. Thank you very much.

Pamela: [laughing] What we’re realizing is when you look at any star, even our boring Sun, in enough detail you start to see all kinds of crazy variations, and our sun’s most notable variation is its sunspot cycle, so if you watch the Sun for 11 years, you’ll see it goes from having no or virtually no sunspots to having those really pocks-mark covered face that’s just covered in sunspots, and what’s interesting is as you watch over time, where the sunspots appear also varies. And this entire cycle repeats every 11 years, and if you have the right tools to watch, you’ll actually realize that what’s happening is for one set of 11 years, you have a north magnetic pole on the top of the Sun and the south magnetic pole on the bottom of the Sun, and then for the next 11 years, that will switch, and so what we’re watching is, over time, the Sun’s magnetic field is tying itself literally in a knot and flipping itself over, and in the process we end up with magnetic field lines poking through the Sun, and those magnetic field lines poking through actually change how much light that we’re getting here on the planet Earth.

Fraser: So just to sort of think of this as an analogy here on Earth, it would be as if your compass pointed north, and then 11 years later it flipped around and started pointing south.

Pamela: That’s exactly what we’re seeing with the Sun, and what’s cool is along the way we see this change in, well, the amount of light that we get that tracks beautifully with the sunspots, so the more sunspots we get, the more energy we get. It’s a very small effect, just a little over a watt per square meter across the planet, but that little variation that we see, that’s enough that, well, it actually slightly changes the temperature on the planet.

Fraser: Well, I guess the part that I find kind of confusing is why does the Sun even have this activity, this cycle? I mean, as I mentioned earlier on, I mean, it’s compressed down, it’s got this balanced state — shouldn’t it have figured out these fluctuations over the course of 4 and a half billion years?

Pamela: So the problem with astronomy is there’s basically two things that we’re trying to get a handle on: one of them is dust, which luckily isn’t a huge problem when looking at the Sun, and the other one is magnetic fields, and that one is a huge problem when looking at the Sun. So, we know that (we think we know, at least) that the Sun’s magnetic field is generated somewhere at the interface between where energy is getting transported via convection, via big blobs of hot material rising, giving off their energy at the surface of the Sun, and then sinking back down, and via radiative transfer, which is where you just have the light radiating through the material and transporting energy along the way, and exactly what causes this magnetic field to arise at this particular point in the Sun, we don’t fully understand. What causes it to turn itself inside out and flip over on a not-precisely-but-pretty-close-to 11-year cycle, is also something that we haven’t quite figured out. I mean, we know in big brush strokes that it has to do with differential rotation of the Sun. This is where you have giant ball of, well, plasma gas; that’s not a solid. Here on the Earth, the equator, it rotates in lockstep with Massachusetts, in lockstep with Siberia, in lockstep with South Africa…

Fraser: Right, cause it’s a solid.

Pamela: No matter where you are, because it’s a solid, everything rotates together. Sun’s not like that. With the Sun you end up with different parts of the planet rotating at different velocities and as a result, well, different parts get carried ahead while others lag behind, and this seems to be partially if not fully responsible for the magnetic field becoming a tangled mess over time, and as the magnetic field tangles itself up, it ends up turning itself inside out, and we don’t fully understand the details — we just know it happens. I love observational astronomy; theorists have a challenge.

Fraser: Yeah, and I’ve seen some really interesting animations, maybe it was on a Nova episode… We’ll try to link to something in the show notes where you can see these animations of, or simulations of what the magnetic field lines look like over time. And you start with these nice, clean magnetic field lines from the top to the bottom, and then over time they get all twisted and turned out and not connecting sort of top to bottom. And then you get this point where it’s all jumbled, then it flips over and balances back out again. It’s quite amazing, and it’s…a lot of this kind of theory, this only came together fairly recently, I mean, we’re in modern history and the people really figured out what’s causing this cycle, the sunspot cycle, and how it connects the field lines and really what’s going on. It’s quite a fascinating process. And, I mean, there’s a version of it that happens here on Earth, although it’s different.

Pamela: Now, we don’t fully understand the time scales for the Earth. We just know the Earth does flip occasionally, but the Sun’s pretty much like a confused clock that is sometimes ahead and sometimes behind, but averages out to on time in the end.

Fraser: And so this is the situation that we talked about. So we are nearing the solar maximum in 2012/2013, and what does the solar maximum mean?

Pamela: Solar maximum is that point when the Sun’s magnetic field is its most tangled, when you have field lines that are poking through the surface, and when you see sunspots. The sunspots often come in pairs, and one of them is the point where the field line is coming through the surface, and other one is the point where the field line is going back into the surface, and as the field line twists itself around, it actually channels plasma, and so these footprints can be connecting plasma loops, they can be the cause of giant coronal mass ejections…all sorts of activity is associated with these places of magnetic entanglement. And when the field lines break, as they sometimes do, and rearrange themselves into lower energy configurations, that energy can get flung straight at us here on the planet Earth, so we actually really have to pay attention during solar maximum because, well, sometimes we get lucky we just end up with amazing northern and southern lights – the aurora borealis that you can…well, last week there was one that was visible as far south as Arizona. You only get that with big solar flares, but if you get unlucky, you’re not paying attention, when all that energy, when all those ionized particles hit the Earth’s magnetic field, they generate electricity in the Earth’s power grid, and this is something we’ve talked about in “Various Ways to Destroy the Earth” shows, and that excess energy in the Earth’s power grid isn’t exactly free energy. It is actually sometimes a cause for lack of energy because it can, well, overwhelm the system and take down the grid.

Fraser: And there’s, you know, those magnetic field lines coiling out of the sun – it’s a really powerful analogy in my mind, and you can see these amazing videos taken by some of the recent spacecraft — the SDO mission, right? You can see these videos, time-lapse videos of the surface of the Sun. And you see the solar material following the field line from one sunspot to another sunspot, and you can see how it’s sort of wriggling, like writhing, like snakes on the surface of the Sun, and then you can see them snap like someone has coiled up too far, and the, you know, the coil just can’t handle it anymore and it just snaps and releases, and you see this material flung out like the end of a whip, like a bullwhip, is being sprayed out into space, and then you can see the sunspots disappear. The videos, the time-lapse videos of the Sun, of the solar activity is just mind blowing. Some of those beautiful space-related video, like, time-lapse footage that you’ll ever see…I could just watch that stuff all day. So that’s the solar maximum. The solar minimum is this opposite situation, right? Where there are no sunspots, the magnetic field is not coiled. Is there like a great big sunspot at the north and south poles of the Sun where the magnetic field lines are coming out?

Pamela: [laughing] No. What’s actually kind of amazing is that during solar minimum, you end up with most of the sunspots at the equator, of all places, so as you hit solar maximum, you end up with sunspots towards more southern and northern latitudes of the Sun. They really only get as far north and south as about 30 degrees, but it’s still neat to watch them back and forth. And we’re talking averages here — sunspots can poke out anywhere they please.

Fraser: And you can have times where there’s not a single sunspot on the surface of the Sun.

Pamela: You can actually have months, occasionally years, with no sunspots at all, and this is one of the things that we’ve recently been dealing with. This was kind of the solar minimum that refused to end, and we’re still trying to figure out what causes this to happen sometimes. As you look at long-term maps of solar cycles, you see that there’s amazing variation, and sometimes the Sun just stops, and we don’t know why – for twenty thirty, fifty years. And one of the problems that we deal with is things like the modern minimum from 1650 to about 1700. That was a period of negligible sunspot activity. There were sunspots, but very, very few. And during that period, we actually had a mini-ice age where planetary temperatures dropped, where one of the problems associated with this is you end up with much stronger winter storms in New England and in northern Europe; you end up with much hotter seasons in the central regions of America and in Canada. Southern Europe is also hot. We don’t have as good of records for some other parts of the planet, and so when we see the Sun going into quiet times, it’s sort of a warning that, “Wow! We could have severe northern storms.” So looking at things like last year and the year before where it decided to just snow in England on a regular basis, there are those who attribute that random, non-normal snowing in England to it actually being a really quiet sunspot time.

Fraser: Hmm…interesting. I wonder if there is a larger cycle that could last over thousands of years, and maybe…that sits on top of that 22-year cycle of the sunspots coming, coming, going away, coming back that has these highs and lows, you know, more modern minimums, but the problem is that we’ve only been observing sunspots for the last few hundred years, and so we just don’t have any accurate observations before that.

Pamela: We do have hints at longer-term cycles, and the hints come from ice cores. One of the things about the sunspot cycle is it’s tied to the whole magnetic behavior of the Sun, and so when you have a really active Sun, you actually have the solar winds and other factors pushing past the planet Earth, and actually making it harder for things like cosmic rays to hit our upper atmosphere, and with fewer cosmic rays hitting our atmosphere, we end up with fewer aerosols. There’s also various chemical productions that we see in our own atmosphere as a result of interplay with space weather, and so when we take ice core samples, we can actually look back in time and get a feel for what the Sun has been doing over, well, thousands of years, and so there are those who study this and are saying that we’re actually heading back towards a cooling cycle with the Sun, where perhaps for the next 500 years, we’re going to slowly work ourselves down to a point where the planet cools off to a lot like it was during the Holocene period before it again begins to warm back up where we’re looking at a much longer, 1000s of years cycle.

Fraser: So isn’t the rise and fall of the solar activity what’s driving, like, things like the ice ages?

Pamela: In the past. Um, right now we have to worry about the effects of man on the atmosphere, and that’s a whole can of worms for an independent show.

Fraser: And that makes the whole thing more complicated, which is that you’ve got the inputs of man pushing against the activity of the Sun, and the whole thing is super-complicated and takes, you know, people who specialize in it to argue about it, so definitely not a can of worms we’re going to open on today’s episode, needless to say…you know, we understand that it’s complicated, so we’ll move on. So I guess there’s like a longer-term variation in climate that can be attributed to the solar activity, the solar maximum, the solar minimum and some kind of cycle over a long period of time.

Pamela: Right. So what we do see is due to solar activity, which is just one of many effects, but there are specific points, such as the mini-ice age during the modern minimum that can be tied directly to the sunspot cycle. What’s interesting is we can also see planetary heating tied to the sunspot cycle, and that has some interesting sociological impacts.

Fraser: I’m intrigued! Please tell me more about the sociological impacts.

Pamela: [laughing] So I have to admit I need to do more research on this because there’s statistics, and then there’s statistics that are really, well um, couched in what is the differentiation between this and random.

Fraser: Yeah, but you found some really cool research.

Pamela: I did find some really cool research. So one of the things that I think all of us know is that when you’re hot, you’re grumpy, and it turns out that when the planet is hot, societies get grumpy. And so there was a recent study coming out of the Earth Institute at Columbia University in New York that found that there appears to be a link between El Nino, which is a warming of the oceans that’s tied to warmer seasons, that, well, when there’s El Nino, there’s also a lot of world conflict, so they were able to tie roughly a fifth of world conflicts to warmer temperatures, so, yes, if you want a civil war, wait for an El Nino and it may just happen on its own.

Fraser: Right, so we’ve talked about sunspots and twisting magnetic fields, but there’s a lot of other really cool stuff that the Sun throws at us, like, we hear about flares, and coronal mass ejections, and solar storms, and proton storms, and things like that, so what are all these? Let’s kind of run through these. What are the kinds of things that the Sun can emanate during these periods of solar activity?

Pamela: So, solar flare is usually nothing more than…it’s a energetic outburst that probably isn’t going to destroy anything, or cause astronauts to have to go into hiding, or anything particularly exciting, but it’s just when a field line breaks, and a bunch of material is released into space, so this is…

Fraser: That’s that snapping that we talked about earlier…

Pamela: It’s that snapping, and all of that material that’s tangled up inside of that magnetic field, well, it just keeps going in a straight line along whatever direction it was heading in originally.

Fraser: But why do we see a blast of x-ray radiation?

Pamela: There’s some things we’re still trying to figure out. One of the things that has amused me in recent years is at the American Astronomical Society meetings, about every two years there’s a major press release on, “We have now figured out why…” and it’s going to be either coronal mass ejections, or why some parts of the Sun’s atmosphere are hotter than they logically seem to be, or any number of different things, and the x-ray emission comes from the high-energy particles that are tangled up in the magnetic fields, but that doesn’t explain all of the high energies that we see, so we’re still figuring this out. It’s awesome to have the stars so close to study, but when something gets studied in sufficient detail, you realize it’s a much uglier problem than you thought.

Fraser: Well, didn’t you say that solar hydrodynamics is the most complicated science and mathematics that you could possibly envision, that trying to understand how plasma works in three dimensions…?

Pamela: Yeah, it’s hydro-magneto dynamics.

Fraser: Hydro-magneto dynamics.…sorry, I forgot the magneto part.

Pamela: It’s just nasty.

Fraser: If you want to choose the most complicated path in science, in astronomy, there’s your career path.

Pamela: So the broad brush strokes answer is the magnetic field lines have a whole lot of energy in them, and when they break its because they’re rearranging into a lower energy state, and all that energy has to go somewhere and sometimes it gets thrown straight at us.

Fraser: [laughing] Right. Right. And so the solar flare is that momentary release of energy that is a blast of radiation. Um, the coronal mass ejections are these particles that are thrown out in some random direction — sometimes right at Earth.

Pamela: Now, so coronal mass ejections are basically the big, angry brother of solar flares. So solar flares are fairly well understood; they’re tied to magnetic field lines, they’re rearranging. Coronal mass ejections we’re still trying to sort all the things that trigger them. They’re also triggered at times by breaking the field lines, breaking the tangled up field lines, clusters of sunspots, and when these go off, we also can get a blast of particles heading towards us at various different velocities. So sometimes we’ll only get half a day’s warning that there’s this cloud of particles heading toward us, and sometimes it’s a couple of days, and these are the things that we do have to worry about because, well, all of those ionized particles, those can pose danger to astronauts. All of the high energy radiation tangled up with this –that can pose danger, well, to just about everything on orbit. Luckily, the light gets to us before the particles, so thanks to spacecraft like STEREO and SDO that are watching the Sun for us… SDO actually takes an image of the Sun every 10 seconds. These spacecraft are allowing us to do better modeling, are allowing us to see the stuff on our way, and as we continue to watch these things, it’s a matter of building up models, of “if we see this, then this is going to occur; if we see this, then this other thing is going to occur.” And between STEREO and SDO’s constant vigilance, we’re getting better at predicting when large solar flares are coming our way.

Fraser: That’s really cool. STEREO, you know, particularly has this 3-dimensional view of the Sun, so one of the big problems with a lot of the spacecraft before now was they took a picture of the Sun and they could see a coronal mass ejection, but they wouldn’t know if it was actually directed right at Earth, so they would say, “Well, we kind of probably think that maybe this one’s coming toward Earth,” but STEREO sees it in 3-D, so it can see the alignment of the coronal mass ejection and tell with a lot more accuracy exactly where that gun was pointed, and…

Pamela: And the way it’s seeing in 3-D is one of the two spacecraft is in an orbit that’s slightly bigger than the Earth’s, and the other one is in an orbit slightly smaller than the Earth, so this is causing them to lag behind the planet, and move in front of the planet and actually look at that space between the Sun and the Earth. Now, unfortunately…

Fraser: It’s binocular vision of the Sun.

Pamela: Exactly. Now, unfortunately, they’re eventually going to pass behind the Sun, which isn’t a useful place for them to be, but they come back around, and assuming these spacecraft are still healthy, once they come back around we’ll be able to use them again.

Fraser: Yeah, that’s amazing. And so we get this binocular view, so you get this chain, right? You get an X-ray flare, the spacecraft can spot the direction that the coronal mass ejection has been blasted out, and then predict that a storm of particles is going to pass by the Earth within “x” minutes because the light from the Sun takes 8 minutes to get here; the particles take only a little longer than that, and so the astronauts have a few seconds or minutes to get into cover before they sweep past the Earth.

Pamela: And most of the time the particles do take hours to days to get here, so that’s a good thing.

Fraser: But some of them can be really energetic and can get here really fast, and they’re worst ones, right?

Pamela: Yeah, it’s a difficult situation because the more dangerous, the less warning.

Fraser: So, we’re kind of running out of time, but I just wanted to compare and contrast what we see with our Sun with some other stars out there, and maybe this is a whole other show on its own where we can talk about solar activity or the star activity on other stars are, but how does our Sun compare to other kinds of stars? If we could get up close and watch, you know, Betelgeuse or a red dwarf star, or…you know what I mean?

Pamela: Right, so we do see other stars, Betelgeuse being one of them, that have much larger sunspots that – well, we don’t know for certain if it’s individual sunspots that are much larger, but have large percentages of the side facing us covered in sunspots, so we’re able to map over time using interferometric telescopes the patterning of the sunspots. This is one of the amazing things that we’ve started to be able to do by linking together multiple optical telescopes is actually tell how sunspots appear on the surfaces of stars that were just able to resolve. We’re also able to look at minor variations over time, and using high-speed imaging start to get hints at, well, this is actually a variation that goes with the rotation period of the star. Well, that’s likely sunspot behavior as well. We also see violent, violent flares from some types of stars. The type of flares that would just casually destroy our atmosphere on a regular basis, so we both have more run-of-the-mill sunspots; we also have much less flare activity, and all of this makes our planet a fairly safe place to be. Now, this has a lot to do with where we are on the diagram of stars — we’re not too cold, we’re not too hot, we are happily burning hydrogen…all of these things are good things to be doing.

Fraser: Right. But we could have things a lot worse …

Pamela: We certainly could.

Fraser: …as far as stellar activity goes, but then we wouldn’t be here to talk about that, so there you go. Alright, awesome! Alright, well thank you very much, Pamela, and…Oh, just one last thing just to mention is one of the big side effects of all this solar activity is the auroras that we see here on Earth, and so we’ve done a whole episode just on auroras that you can listen to that gives you a lot more information on exactly what’s going on, exactly how the interactions are with the Earth’s magnetic field, and how you can see them, and so on…So we are, as we said, we’re entering this period of high activity and over the next few years, we’re going to have multiple opportunities to see auroras, and if we’re lucky they’re going to be fairly far south, so stay tuned to spaceweather.com. They probably have the most comprehensive alerts, and anything that’s going to be really interesting, we’ll mention it on Universe Today, but definitely try to go out and see some auroras over the next couple of years because then you won’t be able to see them again for a long time.

Pamela: And in general, the best aurora curve, for whatever reason, of the alignment of the magnetic fields around October and March of each year, around the equinoxes, and so in the couple of months around equinox, that’s when you really need to stayed tuned to, “Oh, there’s a solar flare! Oh, there’s a coronal mass ejection!” Good chance of good aurora.

Fraser: Yeah, get outside, take some hot chocolate, stare into the sky and hope that you’ll be able to see it because if you do see an aurora, it’s one of the most amazing things that you’ll have ever seen in your life so, and you know, some of them have gone really far south; I mean, I remember hearing with a storm people were seeing them in like Florida, so it’s not impossible with this solar cycle.

Pamela: And one of the amazing things is you can actually see them from spacecraft, so if you’re flying Trans-Atlantic or trans-pacific where the airplane is likely to cut near one of the poles, try to sit on the side of the aircraft that’s going to put you on the pole-facing side, so Chicago to London sitting on the north side of the plane, Cape town to Sidney sitting on the south side of the plane, and you’d be surprised. I saw some absolutely amazing aurora a couple weeks ago on a flight over to London.

Fraser: Cool pro tip! I love that! OK, well, thanks a lot, Pamela. I know you’ve got to run to a flight. Thanks again, and we’ll talk to you next week.

Pamela: Sounds good. Talk to you later, Fraser.

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

Ep. 237: Spooky Sounds From Space

admin — Wed, 02 Nov 2011 15:23:06 +0000

To help you out with your halloween parties, we’ve collected together the spooky sounds of space. Every piece of audio we’re about to play might sound like it comes from a terrifying nightmare dimension, but it’s really just a natural space phenomena.

Ep. 237: Spooky Sounds From Space

Show Notes

Radio Echos off of meteors

The colorful tail consists of ionized air that can reflect radio waves from TV, radar, and AM/FM radio transmitters.
Reference: http://science.nasa.gov/science-news/science-at-nasa/1998/ast22dec98_1/

Aurora on Earth

Recorded by Stephen P. McGreevy.
Recorded at Grass River Provincial Park in central-western Manitoba, Canada on 30 August 1996 at 1652 UTC during the McGreevy Summer 1996 Solar-Minimum ELF-VLF Recording Expedition in the auroral-oval region when aurora can be frequently seen overhead
Reference: http://www-pw.physics.uiowa.edu/mcgreevy/#latest
Audio: http://www-pw.physics.uiowa.edu/mcgreevy/30a1652.wav

Aurora on Saturn

The radio waves are closely related to the auroras near the poles of the planet.
Reference: http://www.nasa.gov/mission_pages/cassini/multimedia/pia07966.html
Audio: http://www.nasa.gov/wav/123163main_cas-skr1-112203.wav

Lightening on Saturn

Reference: http://www-pw.physics.uiowa.edu/space-audio/cassini/cas-sed-06-023-2hr/
Audio: http://www-pw.physics.uiowa.edu/space-audio/cassini/cas-sed-06-023-2hr/cas-sed-06-023-twohour.wav

Lightening on Earth (Whistlers)

Whistlers are produced by lightning and travel along Earth’s magnetic field line from one hemisphere to the other, as shown in this illustration. In the ionized gas that exists in this region of space, the high frequencies travel faster than the low frequencies, thereby dispersing the wave from the lightning stroke into a whistling tone that decreases in frequency with increasing time, hence the term “whistler.”
Reference: http://www-pw.physics.uiowa.edu/space-audio/sounds/EarthWhistlers/EarthWhistlers.html
Audio: http://www-pw.physics.uiowa.edu/space-audio/sounds/EarthWhistlers/ewhist.wav

Hitting Saturns Bow Shock

The Cassini spacecraft crossed the bow shock of Saturn at 09 hr 45 min Universal Time on June 27, 2004, at a radial distance of 49.2 RS (Saturn Radii) from Saturn. The bow shock is a discontinuity that forms in the solar wind when the supersonic solar wind encounters the magnetic field of a planet
Reference: http://www-pw.physics.uiowa.edu/space-audio/cassini/bow-shock/
Audio: http://www-pw.physics.uiowa.edu/space-audio/cassini/bow-shock/t2004_179_oneshock.wav

Voyager Crossing Termination Shock

Reference: http://www-pw.physics.uiowa.edu/space-audio/voyager/termination-shock/
Audio: http://www-pw.physics.uiowa.edu/space-audio/voyager/termination-shock/vgertermshock4.wav

Jupiter Cyclotron Emission

Jovian electron cyclotron emissions are intense narrow-banded emissions, generated by energetic electrons spiraling along the magnetic field lines of Jupiter and its magnetized moons.
Reference http://www-pw.physics.uiowa.edu/space-audio/descriptions/JovianECE.html
Audio: http://www-pw.physics.uiowa.edu/space-audio/sounds/jcyclo.wav

Transcript: Spooky Space Sounds

Pamela: Happy Halloween! How are you doing today?

Fraser: Doing really good. We’re going to go into a whole pile of trick-or-treating tonight, but uh…or I’m imagining in the future; we’re actually not recording this on Halloween, but to get into the setting…but yeah, our kids are at that age now where Halloween is a competitive sport.

Pamela: That is awesome!

Fraser: It’s all about speed and endurance and starting time, and uh, yeah….

Pamela: That is very cool. I live in a small town, and we actually do a town Halloween parade, where it’s a bunch of, basically, take someone’s old hay trailer and build a float on top of it and pull it down the street with a tractor or a pick-up truck — and it’s really endearing, and they throw candy at the kids, not to the kids, at the kids.

Fraser: Wow, Halloween’s a big deal, then?

Pamela: Oh yeah, totally. We actually have a neighborhood email list to get competitive on who gave away more treats.

Fraser: [laughing] That’s awesome! Alright. To help you out with your Halloween party, we’ve collected together the spooky sounds of the Solar System. Every piece of audio you’re about to play might sound like it comes from a terrifying nightmare dimension, but it’s really just a natural space phenomenon right here in our own solar system. Alright, Pamela, so this show’s going to be a little different in that we’re going to play a bunch of audio clips, and then we’re going to explain the science that’s going on. So why don’t we just listen to our first clip?

Pamela: OK.

[audio clip]

Fraser: That was really weird. That kind of sounded like an underwater depth gage, like a submarine sound…so what were we hearing there?

Pamela: So the background hissy static — that’s just the sound of the sky. It’s the exact same thing you see when you turn on a television, not a new digital television, you have to find one of the old, regular televisions, and you turn it to someplace where there’s no channel. It’s that background radio photons that are coming from space, that are coming from electrons trapped in the atmosphere, just the hum of electrons changing energy levels and in the process giving off radio light. Now, that high-pitched UFO noise you heard, that was actually the sound of a meteor reflecting back off of its ion trail, reflecting back sounds from an earth transmitter. Our planet’s covered in, well, radio-transmitters; they’re giving off your radio signals, they’re giving off your television signals, and as a speck of rock comes through our atmosphere, it heats up, it charges the atoms around it as it goes through the atmosphere and it leaves this trail of excited atoms behind it, and that trail of excited atoms acts like a mirror and sends back some of that radio emission, and creates that UFO noise that you hear above the background hiss.

Fraser: And so if they were recording for a whole night, you would be able to hear every meteor that was going across in the sky.

Pamela: And what’s kind of awesome is that clip was from the Geminid storm — and you can actually do this for any meteor storm, you can go out, get a radio receiver that’s tuned to the proper station (and there’s instructions for how to do this on-line that we’ll link to in our show notes), and you can sit there and you can watch the sky for the shooting stars, and at the same time, listen to the noise they make as they reflect back bits of radio signal.

Fraser: And so it’s science that regular people could do with a little bit of investment and some time and work. It’s not…you don’t need a huge radio dish.

Pamela: No, this is the perfect science fair project if you’re looking for a science fair project for your kid and you have a Radio Shack nearby. It’s really something awesome that everyone who has a kid who likes to tinker should do at least once while their kid is growing up.

Fraser: That really sounds like a UFO. That was great! OK, let’s do the next one.

[audio clip]

Fraser: Alright, so that sounded to me like a bit like sirens off in the distance, police sirens off in the distance, a whole bunch of them, or people playing the saw — you know, that sound, you know, when you play the saw, or a bit like crickets, like cicadas at night. So what was that?

Pamela: That was actually the solar aurora. That was magnetic interactions between our Earth’s magnetic field and particles from the Sun that if you could go out and look at them would probably paint the sky in fabulous dancing curtains of green, but auditorily, when you take the radio emissions and you play with them to get them down to where a human can hear them, those particles from the Sun when they hit the Earth’s magnetic field, they change velocity and that change in velocity is a change in energy, and that energy has to go somewhere, and that energy goes into creating radio signals, release of photons in the radio frequencies, and we’re able to detect those using very special, not-so-cheap-and-easy-to-build-in-your-backyard, using special radio receivers, and what’s neat was the person who recorded this, Stephen McGreevy, he actually he went on a trip up to Grassriver Provincial Park in the central western Manitoba area of Canada and this was during normally solar minimum, but there was a really nice light show back in the summer of 1996, and as he looked at the aurora straight overhead, he was able to capture the sound coming from the aurora at the same time.

Fraser: That’s pretty amazing and it’s interesting that it happened during the solar minimum so I wonder if someone’s going to be doing that now that we’re nearing the solar maximum.

Pamela: Well, what gets me is so you can have solar flares at any time, but the type of sound that you get from them captured in the radio signals – that traces out how the particles are interacting with our magnetic field, and if you have a whole lot more particles coming from a really big flare, like the flares we’re starting to get right now that are causing auroras visible as far south as Arizona, they’re going to be even more spectacular to listen to, and I look forward to seeing those posted on the internet — they’re just not there yet.

Fraser: OK, so let’s move on to the next one, and it’s kind of related…

[audio clip]

Fraser: That’s a haunted house.

Pamela: That’s totally haunted house. This is the one [missing audio] sent me. It’s totally haunted house!

Fraser: It is amazing! Alright, now we’re getting into it. I mean, that was a haunted house sound. That was really scary! What is that?

Pamela: That’s Saturn!

Fraser: What part of Saturn?

Pamela: It’s an aurora on Saturn. It’s basically the big brother to the previous sound clip that we listened to. So the Cassini spacecraft is approaching Saturn; it was able to listen in on the Sun’s, well, solar storms wreaking havoc, or at least wreaking beautiful noise on Saturn’s magnetic fields. So as waves of particles went in and moved up and down the field lines, their changes in velocity and other interactions were able to produce these changing pitch radio frequencies and the change in pitch, that actually corresponds to the different energy levels, where as you’re hearing higher pitched notes, those are higher energy, higher frequency photons, and as you hear the lower pitches…so you’re essentially sliding up and down the energy spectrum. Think of it as particles sliding down the magnetic field and gaining and losing speed depending on which direction their whipping along the field lines.

Fraser: Right, and it’s…I mean there was something in common with the Earth aurora, but it definitely sounded otherworldly. Is it just like the instruments that were used to measure the two different aurora?

Pamela: It is a matter of: this is a much better instrument. It has much better frequency coverage, which is where you get the sliding up and down, so if you imagine a difference between a slide whistle that is two inches long and a slide whistle that is twenty inches long that allows you to detect different things. It’s a difference in, well, you’re not getting all the background hiss that you get from being within the Earth’s atmosphere. And then it was just they managed to take a much longer time and they cheated. In that particular audio clip they seriously cheated. Every 73 seconds of audio corresponds to 27 minutes, so they sped things up a little bit, which helps as well.

Fraser: Right. That’s what I was wondering is: was that over a long period of time? OK, so let’s move on to the next one, and just give people a hint: this is also on Saturn, but something different.

[audio clip]

Fraser: That sounded like hail hitting like a tin roof, but a little more muffled, or like you’re walking on chunks of ice, or walking on snow, like icy snow.

Pamela: Or, so I don’t know if you’ve had this where you are, but here in southern Illinois, and back growing up in Boston, we’d sometimes get these snowstorms that would cover the roof and everything else in 5, 6, 10 inches of snow, and then we’d get an ice storm afterwards, so you end up with this layer of ice on the top of the snow, and the sound of the ice balls hitting the snow sounded a lot like this as well.

Fraser: I mean, we never get anything like that, but… So what is it then?

Pamela: That is lightning on Saturn.

Fraser: Are all those pops like lightning strikes?

Pamela: That’s lightning bursts. Yeah, so you have, basically, you’re catching all of the lightning strikes across a large section of the planet. You hear all of these little tiny pops that are all different frequencies, and they’re occurring over time (again this is one that’s sped up 20 seconds in this case is 2 hours, so you can imagine each of those little blips is lightning that occurred over two hours). But this was a massive lightning storm, and we can also detect the Earth’s lightning, but it doesn’t sound like much when you add in the Earth’s noise that we also receive, so this was just much more amazing. And we don’t really think of Saturn as having lightning storms — it’s not like we see lightning bolts when we look at pretty, astronomical images of Saturn, but this is a stormy planet that has lightning going off all the time, and we can detect it from its radio signals.

Fraser: Alright, let’s move on to another one and this one is still — like we’re following a theme — it’s lightning, but it’s somewhere else. Listen.

[audio clip]

Fraser: I’m hearing a video game. It’s sounds very familiar. I think I’ve played that game.

Pamela: Either that, or like a bad 1980s sci-fi battle scene.

Fraser: Yeah, exactly! Perfect. So, I said it was lightning. So where is this?

Pamela: This is here on Earth, but we’re listening to something else now. We’re not listening to the individual bleeps of lightning like we were on Saturn. These are what’s called whistlers, and what ends up happening is when you have the lightning go off, it can produce ionized gas, and that ionized gas as it gets caught up and travels along field lines, produces this whistling noise. So again, lightning, but you’re hearing a different aspect of the lightning, and this is just one clip of many that we could have chosen from. You get them that they sound sometimes like an entire arcade of video games because you get different ones going off at different frequencies all layered on top of each other. So here is ionized gas that is created by lightning and produces radio signals as it travels along magnetic field lines.

Fraser: But it’s the same phenomenon — that’s really neat! Alright, let’s move on to another one.

[audio clip]

Fraser: Right, so that one sounded similar to the haunted house sound, but then there was like this crash halfway through.

Pamela: Right, so it’s sort of like you’re going along, they’re trying to creep you out, they’re trying to creep you out, and then they attack you with everything all at once! In this case, it’s the Cassini spacecraft again traveling through space, listening to radio waves, listening to radio waves, everything’s fine, suddenly hits the edge of Saturn’s magnetic field, and that place with the solar wind hits the edge of the magnetic field. This is the bow shock region around Saturn and everything goes nuts at that particular place. One way to think of this is it’s almost like the sonic boom that’s created when you start traveling faster than the speed of sound, and it booms through. This is the radio in the magnetic field equivalent of that, so you have supersonic solar wind suddenly gets decelerated rather rapidly and creates this pulse of radio emissions across the entire frequency band.

Fraser: It’s the same instrument that captured the sounds of the aurora, which is why it sounds familiar, but it’s capturing a different phenomenon at this point. I mean, we’ve all seen those pictures of a bow shock. Usually we see it around the Earth; we see these illustrations of it. It almost looks like there’s a comet around the Earth, where on one side of the Earth, it’s rounded — and this is our magnetic field, and then on the other side of the Earth, the one that’s away from the Sun, it’s stretched out into this big, long tail because that’s the side that’s not being impacted by the charged particles from the Sun, and that’s the thing that’s protecting us, and I guess protecting Saturn, and this is that moment where Cassini crossed into that force field around Saturn, right?

Pamela: And it wasn’t the fact that Cassini crossed it so much that caused the sound, as Cassini was able to hear all the solar particles that were traveling along with it have the “Holy expletive!” moment of changing velocity, and this is something that we keep kind of saying as though everyone understands it, but all of these noises come from some sort of a particle: an electron, a proton, an atomic nuclei that doesn’t have as many electrons attached to it as it should. It comes from one of these charged particles traveling through space and interacting with a magnetic field in a way that changes what direction it’s moving in, it changes what speed it’s traveling at, and all of these different changes represent a change in the energy of the particle. And when you change the energy of a particle, that energy that it lost has to go somewhere, and where it’s losing the energy is into creating radio light, and so if you think of it in terms of: if you get something going really fast, it has to take energy from somewhere – that’s the gasoline, and then when you slow it down really fast, slam on the brakes, the tires get really, really hot from all of that energy that had been the motion of the car getting expelled against, well, the asphalt as the tires try and screech to a slow-down, so what becomes hot tires, when it’s a slowing down particle, becomes radio energy instead.

Fraser: Right, or to use another analogy, right, if you’re not wearing your seatbelt and you run into something and you come smashing out the front window, you’re the radio emissions being given off by the car, which is the particle, so…alright well, the next one then is similar, but a different spacecraft.

Pamela: Yep.

[audio clip]

Fraser: That one was a little more subtle. What were we hearing there?

Pamela: Those were what are called electron plasma oscillations, which is a fancy way of saying there’s a whole lot of charged particles out there, and as those charged particles from outside of our Solar System hit the termination shock of the solar particles pushing against them, they end up getting driven into oscillations, and the Voyager spacecraft, as it’s trying to leave the Solar System, has had this weird experience of the solar termination shock. Where it ends depends on how active the Sun is, so it goes back and forth like where the shoreline is on a beach. As you’re walking along, sometimes your feet are dry, sometimes your feet are wet. Well, sometimes Voyager for a while was within the termination shock and sometimes it was beyond, and as it was traveling along, it got to pick up all of these little electronic plasma oscillations along the edge of that, well, termination shock to our Solar System.

Fraser: And so the termination shock is sweeping past Voyager and then coming back in.

Pamela: And beyond the termination shock is where there’s a region of electron plasma that is oscillating, and those little blips of noise that you hear — those are the plasma oscillations. Now, the reason it doesn’t sound quite so sexy as the other ones is — it’s Voyager.

Fraser: Right, it’s a very old spacecraft, very far away, not able to send a lot of data, not a lot of power…

Pamela: [laughing] Right.

Fraser: You can barely hear it…yeah.

Pamela: Yeah, so it’s several hours worth of data…collapses down into like six seconds of audio, and the frequency range that we were listening to was a lot less than some of the other clips.

Fraser: So, when Cassini…well, Cassini will never get a chance to leave the termination shock, but if it could it would sound different. We would hear a more high fidelity version of this.

Pamela: So hopefully someday we will get to send an instrument with the fidelity of Cassini out there, but it’s not in the budget right now.

Fraser: So, let’s do our last piece of audio.

[audio clip]

Fraser: I heard a saw going, you know, going through metal really far away, or some bird, some exotic bird in the middle of a rainforest making its sad call, but what are we hearing?

Pamela: What I heard actually was a 1980s synthesizer pretending to either be a piccolo, or a bird and failing miserably in the process. The reality is we were listening energetic electrons at Jupiter caught up in its magnetic fields. Jupiter is one of the most complex magnetic fields in the Solar System in terms of…well, it has a nice, normal magnetic field that has moons embedded in the side of it, and those moons spew up particles that get caught in the magnetic fields, and some of them have their own magnetic fields and, well, to the hapless electrons out there, they can what are called cyclotron emissions as they move through the magnetic fields and spiral rapidly around and around the field lines, and in the process they give off radio emission that sounds rather like you wish you were wearing earplugs.

Fraser: Well, this is Jupiter’s equivalent of a particle accelerator.

Pamela: Exactly, and it’s one of the biggest particle accelerators in the Solar System. It’s just not useful for doing, well, Higgs Boson-type science.

Fraser: Yeah, um, the power would be there, we just can’t control it. Right. So that was great. Now, that’s actually only about half of the spooky sounds that are out there. We just covered the ones that we have in the Solar System, so maybe next year, we’ll cover the spooky sounds around the whole universe because there’s pulsars…

Pamela: Blazars, and quasars …

Fraser: Quasars and all kinds of great stuff, so I hope you enjoyed this, and I would love to hear if anybody wants to turn this into a haunted house background sound. People could play it in their homes, “What’s that weird sound?” The sounds of space…

Pamela: And we have to give kudos to the University of Iowa for putting these up on their website. This show was made much easier to put together thanks to the hard-work of the folks there just archiving these noises and making them not sound horrible to the human ear.

Fraser: And I know you kind of curated this one with your friends on Twitter, so thanks to everybody on Twitter who responded to you and pointed you towards cool, spooky space sounds.

Pamela: So one final announcement before we disappear. I was asked by Andy Shaner at the Lunar and Planetary Institute down in Houston, TX if I could let all of you know about a project called “My Moon.” They’re actually trying to provide jobs to people 18-25 who are interested in the Moon, and are interested in helping them out with the Moon, and if you want to find out more, we’ll be tweeting about it and we’ll post a link up on the website, or you can just Google “my moon street team” and find out how you can be a part of, well, helping everyone know more about the Solar System.

Fraser: Sounds really great. OK, well, thanks a lot Pamela! We’ll talk to you next week, and Happy Halloween!

Pamela: Happy Halloween!

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

Astronomy Cast at Dragon*Con 2011: Strange Stuff in Space

admin — Sun, 16 Oct 2011 04:06:24 +0000

This is an impromptu episode of Astronomy Cast that we recorded during Dragon*Con 2011. Pamela was scheduled to speak with a panel about strange things in space, but she ended up being the only person there. So Fraser jumped in, and this was what we did. We mostly talked about unusual things in the Solar System, but a few things in the rest of the Universe.

Strange Stuff in Space

Show Notes

Diamond Planet — Universe Today
Mimas — NASA
Liquid Lake on Titan Confirmed — Universe Today
Cassini Captures Sunshine Gleaming Off lake on Titan – Universe Today
Chris McKay – What is Consuming Hydrogen and Acetylene on Titan — NASA
Europa Analog Deep Sea Vents Found in the Caribbean – Universe Today
Hot Jupiters
Coolest Brown Dwarf Discovered — Universe Today
Complex Molecules in Space — BBC
Polycyclic Aromatic Hydrocarbons
Buckyballs in Space — Universe Today
Cepheid Variables — Imagine the Universe
Bright Star by John Keats
Binary Stars — Cornell
The Great Attractor — Imagine the Universe
Enceladus internal heat and ice — Universe Today
Astrogear Store (Support Science Education!)
Sunspot Cycle Could be Going on Hiatus – Universe Today
Iapetus — Universe Today
Ice Hunters
Other citizen science projects in the Zooniverse

Ep. 234: Lunar Phases

admin — Tue, 11 Oct 2011 15:15:22 +0000

The Moon is a stark reminder that we actually live in a Universe filled with stars and planets and moons. The changing phases of the Moon show us the relative positions of the Earth, the Sun and the Moon as they interact with one another. Let’s learn about the different phases, the geometry of the whole system, and some of the interesting science wrapped up with our fascination of our only natural satellite.

Ep. 234: Lunar Phases

Show Notes

Google+: Fraser, Pamela
Astrogear
Surley Amy Astronomy Cast pendant
Galileo’s observations of the Moon – Rice U
Phases of the Moon demos — NOAO
Moon and Earth Phase Viewer
New Moon astrophoto — Universe Today
How Can You See the Sun and the Moon at the Same Time? — Universe Today
Understanding Waxing Crescent Moon Phases — EarthSky Blog
Moon Illusion — Universe Today
Eclipses, Episode #160
Waning Moon — Universe Today
Understanding the Gibbous Moon — EarthSky Blog
Quarter Moon — Universe Today
Video: Libration and phases of the Moon: One Year of the Moon in 2.5 Minutes — Universe Today
SuperMoon Illusion — Universe Today
Phases of Venus and Mercury
Annular eclipse for May 2012
The Moon at Perigee and Apogee — Inconstant Moon
Just to be Clear: The Moon Did Not Cause the Earthquake in Japan — Universe Today
Moon Phases 2011 — Universe Today
Moon Phases 2012 – Universe Today

Transcript: Lunar Phases

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: Good. So once again, we’re recording this episode of Astronomy Cast as a Google hang-out, and so all of the…our eight closest friends who are listening to this episode — you can all wave, but keep your microphones silent. So…if you want to participate with us, probably the best thing to do is to go onto Google plus, add me and/or Pamela to your circle, and then you get the notifications on when we do them. Right now, they’re completely random, and I apologize for that, but that’s just sort of our schedule, so it’s sort of like if you happen to notice that we do the recording, and it fills up fast, and I apologize for that, and so if anyone from Google’s listening, let us get on to the Google hang-outs on-air — that would be awesome, and then we can broadcast it to a larger audience. So now, did you have any more…anything else to update this week?

Pamela: Um, no. I have absolutely nothing. It’s boring.

Fraser: You’re plugless?! What?! You?

Pamela: I…well, we need donations — we always need donations, but we have to restock our store, so go in there. You can buy lanyards, but you know, by the time people listen to this, we are going to be selling “Surlys,” so there may be “Surly Amys” available if you go in and check out Astrogear.org.

Fraser: These are cool little ceramic necklaces that have our logo on them among other things. OK, well let’s get rockin’ then. So the moon is a stark reminder that we actually live in a universe filled with stars and planets and moons. The changing phases of the moon show us the relative positions of the Earth, the Sun and the Moon as they interact with one another. Let’s learn about the different phases, the geometry of the whole system, and some of the interesting science wrapped up with our fascination of our only natural satellite. Did you like that? Was that a nice intro?

Pamela: You’re getting good!

Fraser: So I think that, you know, but I mean, when I look out and I see the Moon, and I see the phases, it’s…for me that’s the reminder that we live in the Universe and that we have this ball of rock orbiting around the Earth. So how did the early astronomers and philosophers and stuff try to come to grips with what they were seeing in orbiting the planet, or not even orbiting the planet, just in the sky?

Pamela: Yeah, it was a god. It was not actually attributed as the source of the tides until remarkably recently. That’s something that continues to confuse me is how did Galileo not realize, among everything else he realized, that the Moon is responsible for the tides? But it was seen as a god for a while… They realized that it was part of the Solar System and along with the planets and the Sun was originally put on an orbit going around and around the Earth, and it was a holy object and a celestial object, but they didn’t realize it was a rock until Galileo came along and that was actually kind of a complete change in paradigm. Before that Aristotilian philosophy had said that the Moon was a perfect sphere – it wasn’t a perfect color, but it was a perfect sphere, and when Galileo looked at it through a telescope, he realized there’s mountains. They didn’t have the concept of crater, but there were mountains, there were differences in coloration, he could see shadows, and that was when they finally realized 400 years ago: it’s a rock. And since then we’ve been trying to understand it from a geologic point of view, trying to understand it as another object a lot like the Earth in many ways.

Fraser: Right. So when we see the moon, when we see the phases, when we describe it as “phases,” what are we really seeing?

Pamela: We’re just seeing differences in geometry, basically, between us, the Sun and the Moon. As the Moon goes around and around the Earth, you can imagine there’s this line connecting the center of the Earth and the center of the Sun, and when the Moon is on that line between us and the Sun, all of the Sun’s light hits a side of the Moon we can’t see. Now, most of the time, the Moon isn’t actually on that line in particular. It’s above or below the line, such that it doesn’t come between us and the Sun. The Moon’s orbit is tilted relative to the Earth, and this a good thing, otherwise we’d get monthly lunar eclipses, and that would get really un-exciting after a while.

Fraser: Right, and I think the way to do this right, of course, is to go into a really dark room with like a tennis ball, and hold…and then turn a really bright light on or a flashlight on from one source, and then hold the tennis ball at arm’s length. Your head is the Earth, and that’s what we see, and then if you put the tennis ball right in between us and the…you know, you and the flashlight. You can’t see the illuminated side of the Moon, and that’s the new moon. Now, you could still have the tennis ball a little above or below the flashlight itself, so you could still actually see the flashlight, but you’re not going to be able to see the lit side of the tennis ball — and that’s the new moon.

Pamela: And the way it works is it’s actually a couple days’ orbit to either side of the new moon before we can start to clearly make out the crescent moon, and exactly how long depends on how good your eyes are. And holidays like Ramadan are actually tied to: when is it that you first see that crescent moon reappearing as the Moon comes out and starts to show its illuminated side again? And I know for me, in particular, my favorite views of the moon are these amazingly thin crescents that you can sometimes see in the twilight.

Fraser: And there’s some really neat astrophotos that I’ve seen as well, where photographers will catch the moon — you know, they’re trying to break the record for the newest moon that they’ve been able to image. They’ll try to image the moon hours or even minutes after it’s passed the new moon phase, and try to get the littlest sliver of sunlight.

Pamela: Right, and yeah, it’s really amazing, particularly when you can start to get it close to planets and things like that. There’s been a few cases where you’ve had the Moon right next to Venus, the Moon right next to Mercury in the sky, and one of the things I love is watching how often people get the crescent moon completely wrong in artwork because you need to think of the illuminated side of the Moon as chasing the Sun across the sky, so as the Moon gets closer and closer to the Sun, you end up with a thinner crescent and it’s curved so that the illuminated part is toward the Sun, and the non-illuminated part is away from the Sun. And as the Moon goes past the Sun, it switches to keep the illuminated side always closer. Now, this has the effect that as the crescent moon gets low on the horizon following a sunset…so you have the sunset first and then the Moon setting later, you should have basically horns poking up where the Moon is doing an imitation of a longhorn for all you UT alumni, and occasionally you’ll see crescent moons drawn so they’re perpendicular to the horizon, and that geometry just does not happen.

Fraser: That doesn’t happen. Right. OK, so let’s imagine that we’re going to sort of take one full circle – again, go to your imaginary dark room with your tennis ball held at arm’s length, and so you’re seeing this thin sliver of light on the edge of the tennis ball, and as you turn, you’re seeing that grow and grow and grow. Now, which way are you turning?

Pamela: So, the way I always remember it is you take your right hand, put it over your heart, and the direction of your fingertips — that’s the direction the Moon orbits, so it’s going from the right toward the left around your head if the North Pole is at the top of your head and the Sun is in front of you.

Fraser: So I’m turning left…is that right?

Pamela: Yes.

Fraser: In the room…OK, so I’m arm out, tennis ball, and I’m turning left, and so I’m seeing more and more light on the tennis ball; I’m seeing this wrap around and I guess that’s the indication…and that should have been the indication that the Moon is a sphere is that you’re seeing this crescent shape wrap around, this light on the Moon, that should have just been like, “Duh, everything’s a sphere, even the Earth. And they’re all orbiting one another, and the Sun’s probably a ball…” and you know, like, it’s funny that that didn’t sink in.

Pamela: Well, the Greeks were pretty good about understanding that the Moon is a sphere. It was the everyday people of Europe in the times of Columbus that weren’t so keen on the “round planet” thing going on. So it’s interesting how knowledge doesn’t always filter through and, um, yeah, yeah…so smart people did figure it out: it is a sphere based on the pattern of the shadows moving.

Fraser: And so now I’ve turned 90 degrees, and so you can imagine now that before my arm was stretched out pointing towards that flashlight. Now, I’ve turned left so that my, sort of, right shoulder is facing the light and I’m holding this tennis ball out, and now I guess I’m going to see half the ball illuminated?

Pamela: You have a first quarter moon, and the first quarter moon actually can do some really neat tricks. It’s a moon that you have a chance to see both during the day and during the night. It’s one that rises at noon, it’s high in the sky at six p.m., setting around midnight. This is a moon that people really like to have around for star parties, so a lot of groups will schedule their star parties specifically for first quarters, so they can show people the shadows that Galileo saw.

Fraser: Right, of course. I mean, the best time to look at the Moon with a telescope is this halfway point. You know, at a new moon you can’t see anything, at a full moon everything washes out, but when you have this quarter moon you have these nice, long shadows across the surface of the Moon and the craters are just highlighted, and you can really see them, so a lot of the times when you have this full moon, people are like “Oh, can we look at it with a telescope?” but that’s actually the worst time. It’s much better when it’s this quarter moon. Oh, and we actually got this…we did an article recently in Universe Today about this. People were wondering, “How can we see the Moon and the Sun at the same time?” — and this is it. I mean, if you are near the equinox, you’ve got these, sort of, night and day having roughly the same length of time, so you can absolutely have both the Sun and the Moon in the sky at the same time. So, it’s all geometry. Right, so now I’m holding this tennis ball, and I see it sort of half on and so now I’m going to keep turning, and so now my back is to the light, my…I’m holding the tennis ball, but the tennis ball’s not in my shadow, so I’m not actually blocking the light from the light to the ball, and so now I can see a full moon, so I can see the whole tennis ball that I can see is completely illuminated by this light.

Pamela: So, you’ve now watched the moon do what’s called “wax.” So “wax on, wax off”– the Moon does that. You’ve seen the Moon wax toward full, you now have a Moon that if you end up with a full moon precisely at the equinox, some really neat things can happen. So if you traveled to the Equator and it’s one of those special equinox days (September, March), you can have the Sun setting at 6 p.m. in the west at the exact same moment that that full moon is starting to peek itself up above the horizon in the east. This is a kind of magical thing to get to see. Even if you don’t live on the Equator, you still get to see the same effect. It’s just not quite as dramatic when you’re elsewhere on the planet. The full moon is the washed-out, hard-to-see-interesting-features Moon, but it’s still pretty impressive when it’s down low on the horizon, and this actually leads to “the Moon illusion.”

Right. “The Moon illusion” — this is where people always think the Moon looks way bigger when it’s close to the horizon. It’s the Moon is just rising, “Look how big the moon is!”. It’s hilarious if you go onto Twitter, and you do a search for Moon around the time of the full moon, you will see tweet after tweet, post after post, people going, “Why does the moon look so big? Look how big the moon looks!” and I’m often…I’ll just jump in and reply to people, I’m like: “It’s not actually big, it’s just an illusion, it’s a trick of your brain,” and I’ll link them to various articles that are happening, but the…and the way that you can test this out, right, is you hold your arms out at full you know at arm’s length, your nail on your pinky finger will cover up the Moon perfectly and then you try it again later when the Moon is really high up in the sky and you’ll see the same thing, so you’re clearly being tricked.

Pamela: And what’s kind of neat if you have a telephoto camera, you can actually magnify this illusion. Get so that there’s some dramatic building off distant on the horizon with the Moon rising right beside it. Well, the distance between you and the Moon hasn’t really changed, but the distance between you and that building has changed significantly enough that it appears really small. Now use that telephoto lens to zoom in on the building and the Moon will appear as big as the building — and this is just an effect of making the building the size of a fingernail so that it’s the same size as the Moon. It’s a great way to make a dramatic photo.

Fraser: And I’ve seen some great time-lapse photos that people have done where they capture the Moon every two minutes or so, and you get just circle, circle, circle, circle, circle, and you can see the transition of colors. The Moon is coming from the horizon up higher in the sky, and it’s getting through the atomospheric haze, and it’s changing its color from this deep red to yellow to white, but the size is exactly the same — it doesn’t change, and so you can really see clearly this is not the case. The Moon does not change in size at all, and yet if you go outside and look at the Moon, it will absolutely trick you every time — and you fall for it, too. Now, we mentioned that back when the Moon was a new moon, and now when the Moon is a full moon that, you know, the Moon is not blocking our view of the Sun, even though the Moon and the Sun are actually roughly the same size in the sky, and yet the shadow of the Earth is not falling on the Moon, so why when you get these…these…this geometry, why is this not happening? Why is the Moon not blocking every time, and why is the Moon not passing into our shadow every time?

Pamela: So we have this double-angle effect. The Earth is inclined relative to the Sun, and then the Moon’s orbit is inclined relative to the Earth and this adds up to have the Moon, most of the time, as much as more than 20 degrees above or below the center line that connects between the Earth and the Sun, and this difference in angle is sufficient to keep that little tiny moon from blocking that little, tiny sun in the sky. So the way to do this is to actually take a hula hoop and connect your tennis ball somehow (cut the hula hoop, drill a hole through the tennis ball), and take that hula hoop and tilt it slightly. And the act of tilting it…you can now see what the orbit does, where that tennis ball is most of the time above the line or below the line, but twice each month, it cuts across the line and we only end up with an eclipse at those two magical times, and it’s not magical, it’s physics, it’s geometry — at those two times of the year when the full moon just happens to occur near the time when the Moon is cutting across that line between the Earth and the Sun.

Fraser: Right, and we’ve mentioned before in our “Eclipses” episode that they often go in pairs — that you’ll get a solar eclipse and a lunar eclipse in…one after the other because the Moon is spending its time…it’s at the point in its orbit, or the point of its inclination where it is actually passing through the shadow, and then blocks the Sun on the, you know, half a month later. OK, so we’re at the point now where we’ve got our maximum brightness, the Moon is washed out, we’re not really seeing anything and then we’re turning, we’re continuing to turn, we’re turning left some more before we were waxing, so now the amount of Moon we’re seeing is starting to decrease again.

Pamela: So now we’re waxing off, or the correct term is “waning,” and a lot of people will mispronounce it as “wanning” so you can…

Fraser: “Wanning”…like you!

Pamela: I’m better now, it’s “waning.” I’ve learned, and…

Fraser: That’s all I’ll say. Just to…not to drag you through the mud, but in a previous episode, that is what you said, and I called you on it, and I did a bunch of research, and I was right, and anyway…who’s the astronomer now?! Anyway, let’s continue… I know, I’m the linguist…

Pamela: Yeah, well, this is what happens when you learn from books. Books don’t teach you how to pronounce things.

Fraser: Right. So the moon is waning and it is…we’re still turning left, the Moon is waning, the amount of light…so now we’re seeing almost like this crescent of darkness starting to appear on the Moon as it’s getting less and less, and the funny thing as well is you’ll still get, as I’ve said I’ve been watching the twitters recently, and people will still for about four days think that the moon looks full.

Pamela: Right, so as the Moon orbits past the position of true full moon, it takes us a while to catch on to the fact that this is now called the gibbous moon. This is any time the moon is less than full, you can have a waxing gibbous, you can have a waning gibbous…and it wanes its way towards what’s called third quarter.

Fraser: Right, so I’m continuing to turn left holding this tennis ball on the hula hoop at arm’s length with its slight tilt, and now, again, I’m seeing the Moon half-lit. The front part is lit from the light, the back part of it is in shadow because I’m seeing it from the side, I’m seeing it half lit, half in darkness, and it is a waning quarter moon now. It’s a last quarter moon? Is that right?

Pamela: Last quarter, third quarter — this is when you see the Moon in the morning. And I know one of the things that stumped me is you’re seeing half the Moon, and we call it a quarter moon, and that was profoundly disturbing! Well, it’s because it’s a 3-dimensional object, and so we’re seeing one quarter of a 3-dimensional sphere illuminated, so a full moon is a half moon.

Fraser: Right, we’re seeing one quarter illuminated; we’re not seeing the quarter that’s also illuminated, we’re seeing one quarter of it that’s dark, and we’re not seeing the other quarter of it that’s dark.

Pamela: Right.

Fraser: OK.

Pamela: So, it’s that silly geometry. Once again, if you want to learn geometry, the Moon offers you everything you ever didn’t know you needed to know.

Fraser: And even more… Right, so you’ve got… and then the Moon continues on in its orbit, day after day, and you get to the point where we approach it being a new moon again.

Pamela: Exactly, and the thing that is interesting about all of this is because the Moon’s orbit isn’t completely circular – it’s slightly elliptical, its speed actually varies as it goes around, sometimes it’s moving a little bit faster, sometimes it’s moving a little bit slower and this causes, since it’s rotating about its axis at a constant rate, this causes, sometimes its rotation gets a little ahead of its movement around the planet, sometimes it gets a little behind its movement around the planet, and this allows us to see a little bit more of the planet than we would get to see otherwise. And since its orbit is inclined up and down relative to the central line, we also get to see a little bit more in the north-south direction as well. So along the way, even though in general the Moon looks the same, if you take photo after photo after photo what you realize through the passing nights, is we’re actually getting to see a little bit extra of the Moon as we get to look over the top look under the bottom, look around to the east, look around to the west, and all these different motions together get referred to as the lunar librations.

Fraser: And there’s an astonishing video that we…we actually posted on Universe Today, so Nancy’s going to be doing our show notes, and she’s going to know exactly the video that she did where you see the Moon move through all of these phases and it just looks…it just looks amazing. You can see the Moon almost — I can’t even describe it, I’m using my hands here, but it looks like it’s sort of oscillating back and forth, it’s like it’s wobbling back and forth over this period. It’s one of the coolest videos you will ever see, so I highly recommend…look for…check our show notes, or do a Google search for lunar libration video, and its just astonishing! The other thing that’s really interesting to see is the fact that the Moon, as you said, it’s on an elliptical orbit, so the times that it’s very close and the times that it’s very far, actually will get out of sync with the full moons and the new moons, and so you will have full moons that are super-full, you know, these “super moons,” and then other times you’re going to have these times when the…even though it’s a full moon, it’s at the furthest point, you know, the apogee of its orbit, and so it looks a lot smaller, and it can be significant. So the Moon when it’s at the perogee and at full moon at the same time, it’s actually quite bright.

Pamela: And this is where we end up with annular vs. full solar eclipses is when you have the Moon, in the case of an eclipse, at new moon when it’s closest to the Earth, it’s much bigger and it’s able to block the Sun for longer; whereas, when you have the Moon at its greatest distance when it’s new moon, and you have a solar eclipse, this is when the Moon can’t even fully block the Sun, and you end up with what is called an annular eclipse. So there’s lots of different things to take into consideration, and one thing, though, that is a myth — there are people who are actually concerned when there’s a full moon with the Moon at its closest to the Earth that this can actually have major geological effects on the planet Earth, and there are people out there who tried to blame the earthquake and tsunami in Japan on a “super moon” that occurred a few days later. That’s just not something you actually have to worry about. The difference between these two things in terms of percent change, is sort of like if you’re in California and you jump east — how much closer are you to New York City at that point? It’s just not a lot to have to worry about.

Fraser: Yeah, again, you feel more gravity from, you know, I don’t know, a table in front of you than the Moon, so and the changes are not going to wrench the Earth’s surface apart, and it doesn’t matter! What does it have to do with the phase of the Moon? The Moon gets that close every month, and so whether it’s illuminated or not illuminated has no difference on the geologic impact on the Earth — so get that out of your heads.

Pamela: Right.

Fraser: So before we wrap this up there’s this one thing that’s kind of neat. So what we see playing out with the Moon going around the Earth, we also see with Venus going around the Sun; Venus goes through phases, too.

Pamela: Right, and so does Mercury; it’s just a lot harder to find Mercury, at least with a pair of binoculars — it tends to get lost in the twilight Sun. So one of the ways we’re able to figure out that Mercury and Venus go around the Sun and not around the Earth is from the phases that we’re able to see. If Mercury and Venus weren’t located where they are, we wouldn’t be able to see them go through essentially a full set of phases. So what happens is as Venus gets ready to pass behind the Sun, we can see it as almost full, or if you can ignore the glare of the Sun somehow, a full Venus. Now, as it comes back around towards us, it gets to a crescent phase as it passes above or below the Sun. We essentially have a new Venus phase if you could find it in the glare of the Sun. It works best if you’re in space and can block the Sun without having the atmosphere get illuminated in the process. And it was Galileo that was able to see Venus go through this full set of phases, and there’s something actually really awesome about seeing a crescent Venus. And you can really see the angular size — how much of your field of view and your eyepiece Venus takes up as it’s closest to you for the crescent phase, and then furthest away from you for the full phase, so you get to see this tall, skinny crescent Venus, and the much smaller full Venus in the greater distance.

Fraser: Yeah, yeah, and it’s actually brighter when it’s in the crescent phase than it is when it’s further away, right?

Pamela: Right.

Cool! Well, thanks a lot, Pamela. Well, so I hope you can all do this experiment in the room, show your kids, really let it sink in, and then never be confused by the phases of the moon again. That was awesome – thanks!

Sounds great! I’ll talk to you later.

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

Ep. 233: Radar

admin — Tue, 04 Oct 2011 01:22:23 +0000

Radar is one of the those technologies that changed everything: it allows boats and aircraft to “see” at night and through thick fog. But it also changed astronomy and ground imaging, tracking asteroids with great accuracy, allowing spacecraft to peer through Venus’ thick clouds and revealing secrets beneath the Earth’s shifting sands.

Ep. 233: Radar

Show Notes

Skeptics Guide to the Universe
SGU24
The story of Pearl Harbor and Radar: Columbus Dispatch
Planetary Radar Astronomy – JPL
Radar Astronomy and Venus — Time
Asteroid Radar Astronomy — JPL
Radar Observations of Asteroid 216 Kleopatra — Science
3-D views of 216 Kleopatra
Haystack Observatory
Doppler Radar – NOAA
Inverse Square Law — GSU
Arecibo Observatory
UARS Satellite

Transcript: Radar