University Place Space Science & Engineering Jan Smit, David Grinspoon, Bill Nye, "Impacts, Planetary Climates and Venus!" 8/31/2010  UP 477   cc >> Sanjay Limaye: That we have such a stellar collection of scientists in Madison and surprisingly all of them interested in Venus. (laughter) And I will not go into which Venus we are talking about. (laughter) But it's a real pleasure for me to welcome all of you here today. We've been meeting here in this beautiful convention center since yesterday and we'll go on for a couple more days to discuss Venus exploration. My name is Sanjay Limaye. I'm a scientist at the Space Science and Engineering Center on the University of Wisconsin campus just down the street for those of you from out of town. And I chair a group sponsored by NASA which is called Venus Exploration Analysis Group. The group is charged with discussing exploration of Venus in the future, not just next year and beyond, but really for the next few decades. So I have a very wonderful job and I get paid for it. And I'm delighted that many of my colleagues came to this workshop. 

We have colleagues from Japan, Russia, India, France, Germany, Belgium, Canada, all over. And we've been discussing Venus. So on the occasion of that, because Venus is exciting and so is exploration, we want to promote awareness of space exploration and especially address the young audience. Encourage them to go into issues that will matter more to them when they grow up. So we arranged this public event and without too much delay I would like to introduce our speakers. First one is Professor Jan Smit from, I'm going to try to get this right, from Vrije University in Amsterdam or VU University in Amsterdam. I didn't get that right. I just can't get that guttural "Vrije" out right. (laughter) Professor Jan Smit, okay. Vrije, Vrije, sorry. 

It gets confusing, it means "Free University" in English. He's going to be speaking on the Chicxulub impact He is an expert on that event that happened many, many years ago and you'll hear more from him. He actually came here the first time I asked him, "Would you be able to come?" He said, "Oh, can I go to Sudbury?" Why Sudbury? Well, that's the biggest nickel mine. But that's not why he wanted to go there. That's because of the Sudbury Impact. I said, no, it's too far. He said, "Okay, I'll go to Upper Michigan where --" and I think maybe he brought a piece of -- and maybe he'll show it, I don't know. Our next speaker is David the Science Dude, who's sitting right up here. Come on up, David. He's the curator at the Denver Museum of Nature and Science, a colleague I've known I think since your graduate student days. 

So you're a few years younger than I am, I think. He's been to Madison before and maybe some of you have heard him. He gave a talk on alien planets or alien life, I don't remember, but he's the author of "Alien Planets" and also, much before that, "Venus Revealed," which is a wonderful book. It talks about the history of Venus exploration. And then finally, the Science Guy. And I know you all came to hear him. (laughter) And there's no way for me that I'm going to do justice to introduce him. He doesn't need an introduction. The only thing I will say, he's an engineer and I guess what I'll say is, for an engineer, he knows an awful lot of science. (laughter) (cheers and applause) And I say this because I am a scientist and I'm proud to be a scientist. 

And I'm a third generation scientist. My grandfather was a research chemist. My father was a research chemist. My sister's a scientist. So science is not new to me. I was born in a scientific environment. But I've had debates with engineers and technologists about, what is more significant, science or technology? I'm not going to go into a debate, but basically I said, if I know what the problem is, I can always invent a technology. But if I don't know or understand the problem, no technology will solve it. So without delay, please join me. Jan Smit. 

(applause)  Just a quick one. The format is going to be, Jan will speak first about impact, then the Science Dude and then Bill, and then all of them will be here on the dais, and then they'll take questions. Thank you. >> Jan Smit: Good evening, ladies and gentlemen. Here's another Science Dude, so you'll have to endure two of them before you have the Guy. (laughter) I'll tell you something about impact, extinctions, Venus, and something. And let's have a look at our two planets, Venus and Earth. They're so alike. How do you know they're alike, and how do they behave? Well, that's what a nuclear scientist does. He smashes atoms by smashing other atoms to it. 

That's what I like to do. I'm smashing the Earth with meteorites and see what happens. And one of the things that happened was the extinction of the dinosaurs, and I hope to convince you that something like that may happen in the future, but as the space telescopes in Arizona have shown, in the next 10,000 years, we'll not have to endure another big impact. So, Venus and the Earth. How are they smashed by meteorite impacts? Well, here are a few examples. The big ones. They're all on the same scales, from Venus. They're rare images because you cannot see through the thick clouds of Venus. They're big ones. And the only ones which you can see are different from the Earth is that the ejecta blankets, we call them, the ring around them, are relatively small compared to what you see on the moon or on Mars. 

And that's because Venus has such an extremely dense atmosphere, say 19 bars or the equivalent of a layer of water of 900 meters. On the Earth, we have our share of craters as well. Here you see the three largest ones. Two of them are very old, the Sudbury crater, where Sanjay was talking about. The Vredefort crater, sitting underneath Johannesburg, and I'm going to talk about the -- crater. Here are a few images of those. This is the crater of Sudbury. You see it's halfway cut in two because of some mountain building event just crossed it through. Here is Johannesburg, here you see the Vredefort crater. They're both about 2 billion years old, so we don't have to worry about those. 

But we worry more about what happened 65 million years ago. The Chicxulub crater on the edge of Yucatan in Mexico. So what did it do? Well, here you can see, we have a large database from the crater. It sits here in Mexico and it has thrown out a lot of material all over the world. And we can safely divide them into what we call proximal, close to the crater, proximal around the Gulf of Mexico, intermediate in North America, and surroundings in the distal part everywhere else in the world. And each of them has a group characteristic. So let's go back to Italy, where in the 1970s it started with the discovery by the -- of a layer of iridium between the two periods. Because here we are at the ancient bottom of the sea with lots of teeming life in them, and we see here the last 500,000 years of the --, what we call the latest Cretaceous. And the first 2.5 million years of the following period, and they're both separated by a very thin cleft in the rock here, but there were so many scientists who were greedy and they all want to sample the iridium, so they took their screwdrivers. I think about a ton of material has been sampled right now. 

But I've been there before all of them, and I sampled it before it was all destroyed. And when you blow it up and the scale is about 6 centimeters here, you see the old period here with all the old fossils in there, the new period with the new fossils, and the layer in between which is highly enriched in iridium. What's so significant about iridium? Well, as you can see, it sits safely in the core of the earth. That's our allotment on the Earth, and it's plentiful, available, in any sort of meteorites and comets. So when you find a peak of iridium like this right at the moment that dinosaurs and all other sorts of life in the ocean disappeared, you know something is wrong there. So let's look what happens. I blew it up a little further. Here you see what I like to call the dinosaurs of the sea. Big, how big? One millimeter. Highly diverse fauna of Cretaceous foraminifers. 

Unicellular organisms which float on the surface of the sea, live happily for a hundred million years, and all of a sudden disappear. And they're followed up by a new stock of much smaller guys. And they're not related. These ones are not related to the other ones, so we know they're going more or less extinct at this level where we find the iridium. And the iridium, we know, is extraterrestrial. Well, while the Alvarezes were working in Italy, and I'm good friends of Walter Alvarez, we share a house in Italy, I was working in Spain. And as you can see, it's not just a skinny, half a centimeter thick layer. It's a juicy 10 centimeter thick layer. So the resolution goes up by a factor of 20. And that's why you can see what happens. 

And we see a very thin layer, which is very significant, followed by a black clay layer for about 10 cm, overlaying the old rocks on the bottom of the ancient sea here in Spain. And lo and behold, at the bottom of this clay layer we find again a thin layer rich in iridium. So that's the boundary where we have to look for. And what else is there? Well, if you blow it up you see all sort of round furrows in there. Not a few of them, if you calculated. And I found a whole layer over the entire world, you'll find, well, you can quickly calculate it. 2 mm thick layer over the entire world, how much is that? High school knowledge, math? (laughter) It's about 800 cubic km, which is Mt. Everest squared in the form of those --. So it's not --, it's a lot. And that's why it's so important. And of course, I have to slip in some dinosaurs because I see a lot of young people in the audience and they want to know what happened to them, because they're gone and they're the favorite tools, of course. 

And this is the typical landscape where I hunted as a student. You see coal layers here, sandstone layers, river flowing there, and what they call the Missouri Breaks in Montana. They're nice dinosaurs, as found a skeleton of them here and the mammal fossils which are much smaller, which are up there. And there is again an iridium layer within a --. Okay, no problems here. So you would think, but if you read the literature, you know that a lot of paleontologists don't agree with this picture, because they think the dinosaurs dwindled out and the mammals happened again. But all before the impact of the meteorite. But there's a problem there. There's a river channel there, and in the river channel are the fossils of the mammals, and as you can see, it makes a huge difference if they're here or there. So if you place them in the channels and put them together with the dinosaurs, you get a totally different picture and everything is jumbled together. 

So I was able to un-mix it and I can tell you the dinosaurs died out just before the iridium levels and the first new mammals of which we all are descendants from started after the iridium --. So what happened? To summarize, here is another blow-up. The Chicxulub impact layer is a 2-mm thick layer over 800 cubic kilometers, separating the old period with all the old fossils in the sea from the clay layer, and you see there is barely any sediment in between. It's a smash --, mass extinction. So anything that caused a mass extinction has to do with the impact, and how. I'll try to tell you. Let's first have a hunt for whatever comes out of the crater. And you see it's very varied. I've talked about the ejecta blanket, which is close to the crater. We have accretionary lapilli. 

Well, that's a difficult term to say, they're hailstones and they form like hailstones, so they accumulate in a cloud, not of water, but in a cloud of silicon in the hot vapor cloud which rises out of the impact. We have melted ejecta, which are these. We have condensates, because due to the conversion of the kinetic energy of this huge impact, we see a huge vapor cloud under tremendous pressure, which expands and then it cools. And when it cools like a rain cloud, it forms condensates. It condenses like a raindrop. And here you see lots of tiny raindrops. And then again, the last ones, we have shocked solids. If they're not melted, they're not vaporized, but they are in the zone in between and they are still ejected out of the crater. This is a little bit complicated, but here's the crater just being formed. The yellow zone is vaporized, the orange zone is melted, and the green zone is sort of shocked, but not properly melted. 

And they each form different pathways and are deposited at different distances from the crater. So I'll go through a lot of them, I'll see how they go. This is more sketchy. This is the crater with the thickness of the atmosphere. We see the hailstones, we see the melted forms, we see the condensed forms, and you see they each are more or less away from the crater. And that's a question mark. What happens if a similar thing happens on Venus? The atmosphere is extremely thick, so those ejecta have a problem getting through the thick atmosphere and we don't know where they land. But maybe -- the Earth will help us interpret future missions to Mars. So first ejecta blanket. Close to the crater. 

We found it fortunately. Kevin Pope and Adrianna Ocampo are at NASA. They found a quarry, which is used for cement. And you see there is a layer of older cretaceous stuff, with all the fossils we've got extinct. There is a separation line there and there is a thick blanket with house-sized or even larger blocks which come out of the crater, and this is already 300 km away from the crater. And in between, we see the melted blebs with all vesicles which occur between all the blocks in the mess which is created there. So that's a thick blanket, which ranges close to the crater, a couple of kilometers, and where we found it we are still -- thickness, and it sort of pinches out in the leaves. So that's the blanket. Well understood, we have it on Venus, we have it on the Earth. And what next? We have the hailstones, the siliceous lapilli and calcareous lapilli. 

We call them accretionary lapilli or hailstones, and they occur in a wider zone around the crater. The siliceous ones closer and the calcareous ones a little bit further out. That's how they look like, concentric-looking hailstones. And we found them in Belize and we found them a little bit farther out in El Guayal. These were siliceous ones, and how they are produced, they're sort of new. They're found just not so long ago and scientists don't really understand how they form. But we know they form like hailstones, but where and what, and what are the circumstances, we don't know yet. But they seem to be a product of really large impacts, because as Sanjay told you, I went to Sudbury not so long ago and I tried to find similar sorts of accretionary lapilli, sort of hailstones there. And lo and behold, they are found by Canadian scientists. So here is the Sudbury crater, the same radius around it. 

The Sudbury crater is slightly larger and indeed here you see a thick layer of accretionary hailstones in the forests of northern, of Michigan's peninsula. This photograph I took three days ago in the field. So they're there, and they're a product of large impacts. And do we find them elsewhere? Yes, we do. Because if you look at pictures from NASA on Mars, you see that they find sort of blueberries all over Mars, the same size as the ones here on the Earth. You pick them out, oh, they're just guessing that they are concretions. They are sort of forming in the soil of Mars. Well, I submit the alternative, and I'm sure I'm wrong... (laughter) But who knows? We have to go to a future mission to Mars. They may be produced by the same sort of large impacts in large quantities and assembled there on the surface of Mars. 

So who knows? It's very intriguing. Then the next one out, we have the accretionary lapilli, the hailstones, and then there's a zone around them of stuff that has been melted and squeezed out underneath the meteorite and landed somewhere else. You see they have splashforms in them. They are made of glass with bubbles in them, very intriguing. One of the bubbles sits here in the middle of one of those glassy spheres, and I tried to find out what the gases are inside them, so I squeezed them in a liquid under a microscope and a video camera, and when it squashed, the liquid completely filled the bubble. So what you see here is a perfect, 65 million years old, vacuum in nature. So what happens? Those guys went out of the atmosphere as molten, solidified, and went back to the Earth. So they're very typical and a very typical forms. Here's another example from Wyoming. And they decrease in size from wherever you go. 

In Haiti close to the crater, to somewhere in Wyoming, to in Spain where I work, where you see the smallest ones. But they all form melted, and they form splashforms, so they're spinning in flight and drawn out in droplets and other stuff like that. And one of the last one, condensates. We call them microkrystite, because they're completely crystalline. They occur in large quantities all over the world more or less. And here you can see, I think they're a global phenomenon. And -- once calculated that the vapor cloud expands so rapidly that part of it reaches escape velocity and ends up in the moon or on Mars. So on the next flight on the moon, I will be there to collect the microkrystites from the crater. (laughter) So here we are, tiny globules of different composition, black ones, white ones, etc. They occur in large quantities, but they're not like hailstones, like droplets, solidified in flight. 

And here you see the crystals, and they always form a layer. This is from different areas in the world, always indicating boundary. They're even graded. The larger ones are at the bottom, the smaller ones are at the top, so we know they fell down on the Earth. And they're an intriguing part of the whole story. And they're different because the splashforms are like this, and these are round and they're not splashforms, so you can tell them by just finding them, what kind they are. These are condensates and these are splashforms. Then again, the third zone is the non-melted but shocked ones. All those -- in there, the lines you see in there, are caused by the shock waves which passed through these tiny crystals. They also are entrained within the vapor cloud, and they land on the Earth, the largest ones in North America, the smaller ones in Europe, and lots of them in the Pacific. 

So that's a whole suite of those. Now, how do they relate to ejecta on Venus? Well, here's a small crater with an ejecta blanket. You see clearly there's a halo of lighter stuff around them and they're bent one direction because the winds on Venus are so fierce, hundreds of kilometers an hour, that they will blow anything which is blown out of the crater in a certain direction. So this is the ejecta blanket, this is the inner circle, and as you look closer, there's a black circle around them as well. What are those? So you can have a guess, and the future missions to Venus will prove that, are these splashforms, lapilli? Are those tektites or condensates? Nobody knows how. So we need a return mission to Venus to find out. And I'll tell you, it's very expensive, so you would probably never do that. So finally, let's go to the crater itself, why it's so important and why it's so important that it landed there. When it landed halfway in the Gulf of Mexico, these are the ejecta blanket, they send out tremendous tsunami waves. And we find those tsunami waves all the way, you see the green against the yellow, is where the boundary is between the two periods. 

And you find plenty of evidence for that. So an enormous wave crests, and I'm sure these dumb dinosaurs didn't know how to surf. (laughter) So they probably expired right due to the waves. And these are all the locations where you can find evidence for the tsunami wave. And it's impressive. Here's just near Monterey. You see these impressive mountains in the desert there, and there's a thick layer of tsunami-related. Here's a colleague of mine and here are house-sized blocks inside a tsunami layer. And what do you find in a tsunami layer? We find the bones of those extinct animals. Here is the backbone of a mosasaur within the tsunami layer and there is a small tooth of a smaller dinosaur in the tsunami layer as well. 

So these are the last remains of the last dinosaurs ever seen alive. And mosasaurus, for that matter. Here in other parts you see the slowly laid down sediments of the upper cretaceous interrupted by the tsunami layer and they're followed by dark sediments of the next period. And what you can see also if you blow it a little bit up, you can see the ejecta, the glassy ejecta area at the bottom and the iridium is at the top. Why is that? Well, that's because the coarse grained ejecta, they fly out and they land a little bit earlier, and the iridium is vaporized and does not condense, so it goes a little bit slower, falls on top of it. And the tsunami waves happen to go in between. They're a little bit slower than the ejecta, a little bit faster than the iridium, and the iridium dwindles on top of that. So it all fits very nicely. And then the crater itself. It happened, we know where it is. 

It took a while to discover it because it's completely covered by sediments, so it's completely filled the crater. And people found it by way of gravity anomalies and magnetic anomalies, and they sort of cover up the Gulf region. This is a computer animation. You see clearly the concentric rings of such a crater. And even if you look, if you can pull up Google Earth, I guess you can see where the crater is. Especially if I pull a trick. I put the crater right there, and as it disappears, you can see the crater. Maybe that's in your retina, I don't know, but it's definitely there. You can follow it by way of a series of sinkholes. There is a notch in the coastline there and there is another one there with a lot of stuff. 

So that was important, and a couple of years ago, we decided to drill it. So here's the crater, and it landed as you can see on a very thick, deadly target. The target of 3 km, limestone, anhydrite, with sulfur. 3 km thick, overlying the basement. So all that stuff was vaporized and happens to end up in the atmosphere. What happened when that happens? Well, first, let's see what the crater itself does. It subsides a little bit, so it fills slowly by marine sediments, clays, etc. And we decided to drill it right here, which was not too deep so we had to pay too much money, and shallow enough so we could reach all three targets we wanted. The filling, the crater, ejecta, and the stuff underneath it, because that's important. So here's the drill hole, somewhere in the outer edge of the crater, and this is what we got. 

A nice 1500m thick crater. The ejecta fall back, and a large pile of sediments which were there before and which were vaporized by the impact. This is why you can't find it. So that is important. And what did we find? 7% anhydrite, which is calcium sulfate and carbonate. Why is that so important? Well, if you vaporize sulfur, it ends up in the atmosphere. And as we can see, the largest volcanic eruption in the last century ejected 20 megatons into the atmosphere. This impact, by way of calculations, we guess three orders of magnitude more. Ends up as an aerosol layer in the atmosphere. And what happens if that happens? Well, you have heard many talks. 

If you have aerosols of sulfur in the upper atmosphere, it will bounce back the rays of the sun, the light rays, and it will suddenly cool off probably. It will cool severely off. And we have evidence for that. Because, besides the calcareous plankton, which I studied, which got extinct, we have a whole group of organisms, which sometimes form red tides to make your mussels inedible, you get those signs on the beach you shouldn't eat them. Because they multiply so fast that they get poisonous. And they're built to survive because they make sturdy cysts, and whenever they go at the end of their living season, they make a capsule that sinks down to the sea floor. And when, for instance, winter is over they start to get back to the surface again. So they're there, none of them gets extinct, so they're happily waiting for the circumstances to get better after the impact. And that's what they do. The cold ones in Denmark and Holland migrate towards Tunisia, Africa, for a very short time, maybe less than 50 years. 

And then the opposite happens. We see the warm water species from the tropics migrate toward Denmark. So it's a sort of double whammy. We see first a strong cooling and then a much longer warming. And the warming is probably due because if the sulfur rains out, we are still left with all those greenhouse gases like methane and CO2, which warm up the atmosphere. So if the dinosaurs aren't frozen, they probably get it by being warmer. So what happens? First, large amounts of dust cool, make it very cool, and then it makes it very warm. And that's because it's so special. So the meteorite was not only very big, but it also chose a very unfortunate area to land on. It vaporized all the sulfur and cooled off the Earth for a very short time. 

And that's what we know, and that's why I think the dinosaurs got extinct. So thank you very much. (applause)  (quiet talking, fixing microphone)  >> Limaye: You might wonder what the connection is between what David is going to talk about. We heard the impact and now David's going to talk about planetary climates. David. >> David Grinspoon: Thanks. Ordinarily, I go by the title of Curator of Astrobiology at the Denver Museum of Nature and Science, but this thing works. Tonight, I'll be the Science Dude. (laughter) And we just heard about perhaps one of the ultimate catastrophes that happened in the history of Earth, although, of course, catastrophes are also opportunities and we wouldn't be here without the extinction event that killed the dinosaurs and led to the rise of the mammals. I'm going to talk in a more general sense about climate catastrophes in the solar system and how we can learn a little bit about some useful knowledge about climate change on Earth by studying the other planets. 

Why do we explore the planets? Are we just blasting money up into space? Maybe sometimes it seems that way, and everybody who works in the field of space exploration is used to confronting this question of, "Why are you guys spending all that money up there when we've got all these problems down here?" You know, it's a fair question. I think those of us who get public money to work on the esoteric seeming questions, we should be confronted with this question. But the fact is, there are a number of reasons why we explore the planets, and granted, some of them are things like, "Well, it's fun." It really is, by the way, kids. (laughter) And we're naturally curious. Human beings are curious and we can't help but explore, it's part of our nature. But also there are other reasons why we explore. I mean, I think, not to get too whoo-whoo on you, but it is kind of a spiritual quest. It connects us with the wider universe and it give us meaning. But also, there are some very practical reasons for exploring the planets, especially these days. It's very important for us to understand how planets work, because we need to understand how our own planet works so that we can survive, and that's becoming increasingly clear. 

So yeah, it's fun and we have curiosity, but there are also practical reasons and it's ultimately about survival. We are at the point now where our civilization is capable, clearly, of changing the earth and so it's incumbent upon us to understand what that means, and understand how planets work. You can't understand how planets work by just staying on one of them. You have to compare them and get a larger perspective. And that is, perhaps, these days, the most compelling reason to keep exploring. There's this supposed Chinese proverb. I think it's actually, I was looking it up, I don't think it's actually a real Chinese proverb, but it's a supposed Chinese proverb, but it's still a good one. "May you live in interesting times." And it's actually supposed to be a curse. But I want to briefly mention two current developments in science, which make the times we live in very interesting. One of them is the imminent discovery of new Earths. 

We are clearly on the edge of discovering planets which are at least Earth-like in many respects. And as you probably know, the last decade or so has been a revolution in terms of discovering that, in fact, there are many planets out there. 15 years ago, the only planets we knew about were the, depending on who you listened to, the eight or nine or thousand, in our own solar system. But now we know that in fact almost all the planets, as we long suspected, most of the planets, of course, are out there. And when you look up at the stars tonight or some night that's clear, almost all of those stars have planets around them, we now know. We didn't know that, we suspected it, but we have the technology now to discover planets around other stars and we're just on the edge. It's easier to discover big ones, and it's harder to discover small ones, so we've discovered lots of other Jupiters and we're just on the edge of discovering the new Earths and in fact there's a spacecraft that's up now called Kepler that's going to tell us how many Earths there are out there. And it's really going to be announced any day now. The spacecraft is up there, it's working, it takes a while to get this data and sort it out. And the way Kepler works, it stares at 150,000 stars very intently and watches for the slight dimming as planets cross in between us and those stars. 

It's very, very sensitive to the slight dimming of light when a planet orbits in front of that star. It can notice that and if it happens rhythmically, periodically, then we say, ah, there's a planet orbiting that star. And we are just on the edge, certainly any year now, possibly even any day now, we are going to know something a lot more about how many Earths there are out there. And Kepler, this is just a diagram. It stares in one particular direction off into space. It doesn't cover most of space, but that's just a random direction and presumably it will give us a representative sample and we will soon know how many Earth-like planets there are up orbiting the stars. But what do we mean when we say "Earth-like"? How Earth-like are they really? What Kepler will tell us is if there are planets the same size as Earth orbiting stars that are similar to our Sun. But are they really Earth-like? Well, we don't know because that involves a lot more that's going to be hard to observe. But ultimately that really depends on how their atmospheres have evolved. And so it becomes interesting to us not just thinking about the atmospheres on the planets in our own solar system but how they represent, possibly, the atmospheres of these Earth-like planets out there all around the galaxy. 

But it's going to be very hard for us any time in the foreseeable future to really examine those atmospheres close up. So in a sense, when we examine the atmospheres of Earth and Mars and Venus, sort of the Earth-like planets in our own neighborhood, we are looking at representative planets that might tell us what may be happening on all those billions of planets out there that we are just on the edge of discovering among the stars. So that's one of these two revolutions I wanted to mention. The other one, and I will try to connect the two, is the possible, we've got the imminent discovery of new Earths, and the other one is the possible imminent destruction of the old Earth. Not to be too much of a downer, but I'm not breaking the news to you. You've heard about this. We are doing things to our planet, if you will, the old Earth, that are possibly not too safe for our descendants and so this is another reason why we really want to understand how planets work. And of course, I'm talking about AGW, anthropogenic global warming, the human effects on the atmosphere that are to some degree warming the Earth and threatening other species as well as potentially our own ability to maintain our civilization on our planet. Each of these revolutions causes us to question what we know about how the Earth functions and evolves. And each one gives new urgency to our efforts to explore and understand the other Earth-like planets in our own solar system and in particular to understand what leads a planet to habitability, that is, I mean the ability of a planet to support life. 

We're interested, of course, in this as an intellectual, even, if you will, spiritual question. Are we alone in the universe? Are there other planets out there that can support life? We want to know that because we're curious. It's important to who we are and how we fit into the universe. But also, this question of habitability is very important right now for our own Earth. What are the limits to how a planet can change and still support a biosphere? And of course, there are clues to that in not just the ancient history of our own planet, but the current states and histories of the other planets in our solar system as well. We've all heard a lot about climate models and these projections of possible environments of the Earth into the future. What's the temperature going to be, how much is the sea level going to rise, how much is the atmosphere going to change? Well, how can we really know the answer to these questions? We don't have a crystal ball. How can we see into the future? Well, we don't have a crystal ball, but we have these tools called climate models. What are climate models? Well, they basically, they are sets of equations in computers where we break the atmosphere into a grid, depending on how big your computer is and how sophisticated your model is, maybe 30, 50, or 100 layers deep. And then lots of different little bins of latitude and longitude. 

You're basically breaking the atmosphere into these cubes and then modeling their behavior, all the different things that could happen. The radiation, how they get heated and cooled, how they move around and how each cell affects its neighboring cells. And you put as much physics, as much information as you can into this model with this grid and you basically hit the button and say "go" and you watch how the atmosphere behaves. And if you've got all the physics right and you have all the equations right, then you can accurately model and predict and project into the future what's going to happen to the atmosphere. Well, we've got a lot of really smart physicists and a lot of really smart  atmospheric scientists, but how do we know we're doing it right? We've got a lot depending on this now. In a sense, we are all banking on the climate modelers knowing what they're doing, right? But how do we know they know what they're doing? It's a really tough problem. And it's not the kind of science where you can do an experiment, where you've got a beaker sitting on the laboratory and you say, "I'm going to predict that if I pour this chemical in it's going to turn blue." And then if it does, you say, I was right. You can't really do that with climate change. By the time we can test whether we were right or not, it might be too late. So what do we do? Well, one thing we can do is we can ask the other planets. 

Because if our models are right, they should work for the other planets and those are very different situations. It's not like a minor change on the Earth. It's like, let's take a really different situation, let's put in the same physics and if the model works, we should get the right answer. So this is, in a general sense, how the other planets are very useful in increasing our self-knowledge, in a sense, or our own planetary knowledge about the Earth. So here's a modern family portrait of the planets. Notice how Pluto keeps - hey, Pluto, get out of there! Hey! (laughter) Oh well. I'm not going to argue, fine. If it makes you feel better, you can stay, Pluto, for now. But anyways, this is the modern family portrait of the solar system. This is emblematic of our times. 

If you had lived a couple generations ago, we wouldn't know what any of these places looked like, other than just points of light up in the sky or fuzzy images in telescopes. Maybe a couple of generations from now, this'll be old hat. But this is kind of new information for us, and what we can do is compare and contrast and we're starting to really learn the histories of these planets and see how our own Earth fits in this larger set of family histories. And in particular, when thinking about climate change, it's very useful to think of the comparison between Venus and Earth and Mars because these are the three nearby examples of rocky planets with thick atmospheres. All the planets are useful for exploring in different ways, but these three, Venus, Earth, Mars, are a very convenient trio because this is the local neighborhood and all three of them are sort of variations on the same kind of planet. They're rocky and they have thick atmospheres. So I'm going to focus for the rest of my little time that I have here tonight on the comparison between these three planets and what we know about climate on these worlds and how that illuminates in general the question of climate change. These are landscape pictures of Venus, Earth, and Mars. A typical place on Earth, you think about it, Earth is something like 70% ocean, so if you landed on a random place on Earth it would look like this. A somewhat typical place on Mars. 

This is from the Viking I lander. This was in fact our first landscape picture of Mars and I think it's still one of the most beautiful ones. You can see Mars is a dry, desolate planet with rocks and sand dunes and an ancient dry desert world. And this is one of the few landscape pictures we have of Venus. This is from one of the Russian Venera landers and the camera's sort of pointing down, so you're mostly seeing the foreground, but you're seeing a little bit of sky up here in the corner. It's very hard to land something on Venus because it's 900 degrees there, everywhere, all the time. And that has to do with the main topic I want to drive home tonight, which is that planets have very different environments that are the result of their atmospheres and climate is something that is a signature of a planet's total environment that has to do with not just the physical size of the planet and where it is in relation to the sun, but the atmosphere. It's the atmosphere that determines the climate. And the interesting thing about Venus, Earth, and Mars, is that as far as we can tell, Venus and Mars both used to look like this. The evidence that we have, which we're still trying to improve upon and that's why we keep exploring, but the evidence we have suggests that all three of these planets were more Earth-like. 

They probably all had liquid water on their surfaces. And then something happened to the climates of Mars and Venus, two very different things happened to them, which I'll get to in a second, but they both diverged from these Earth-like conditions. So climate can change. A stable climate is not something we should take for granted. Venus and Mars both have atmospheres of almost all CO2, carbon dioxide. And you know about carbon dioxide because it's a trace gas in Earth's atmosphere. Carbon dioxide in Earth's atmosphere is about 300 parts per million, and even at that level, we're worried about it, not because carbon dioxide is inherently bad, but because it's increasing because we're driving our cars and running our factories and burning coal and all that stuff. As you know, you've heard about this, it's not news to you, it's a greenhouse gas and as the carbon dioxide of Earth's atmosphere increases, it's becoming warmer. Well, Venus is a planet where the atmosphere is essentially all carbon dioxide. It's over 96% carbon dioxide. 

And it's really, really, really hot there. 900 degrees everywhere all the time. Now, it's not just that it's all carbon dioxide, but the atmosphere of Venus is very, very thick. It's almost 100 times as thick as Earth's atmosphere. So it's not just that the air there is mostly CO2, which is a greenhouse gas. There's a lot of air. Really efficiently traps heat. The interesting thing is that Mars is also almost all CO2 in its atmosphere, more than 95% carbon dioxide. But Mars is quite cold. Not just because it's farther from the Sun than Earth, but also the atmosphere of Mars is very, very thin. 

It's in contrast to the atmosphere of Venus, which is 100 times the atmospheric pressure of Earth. The atmospheric pressure of Mars is only about 1% of the atmospheric pressure of Earth. So you'd have to multiply it by 100 times even to get to one Earth atmosphere of pressure. So Mars has a very thin CO2 atmosphere and so consequently it does not have much of a greenhouse effect and consequently is it not only really, really cold there, it averages about -70 or -80 degrees Fahrenheit, but the temperature fluctuates widely there with the seasons and even between day and night because the atmosphere is so thin it just can't hold any heat. So Mars is sort of closer to being an airless body. Earth is somewhere in between, and Venus has a really thick, solid greenhouse of almost pure CO2. So that's the current states of these atmospheres. And then the next question we ask is, how did they come to be so different when the geological and other evidence we have tells us that apparently they were all much more similar when they were young? Well, one thing we do to try to answer this question is to look at the deep history of the Earth. The long term climate history of the Earth. And when we do that, we encounter something that we call the "faint young Sun paradox." What do I mean by that? Well, the Sun, we know, was less bright when it was young and when the planets formed. 

As a star like the Sun evolves, it slowly gets hotter over its lifetime, and it was significantly, about 30% or 40% dimmer when the Earth formed. And this is kind of a complicated looking graph, but let me lead you through it. This is time, so this is now, because it's billions of years before the present, so this is now, this is a billion years ago, 2 billion years ago, 3, 4, 4.5 billion years ago when the planets formed. And this curve is solar luminosity, in other words, how bright the sun was. And this is now, it's 1, this is the present day brightness of the Sun, and how much energy it's been putting out. And if you go back in time, the sun is much, much less bright, 4.5 billion years ago. And given that, we can calculate how hot the Earth should have been. And these two curves, this is the actual surface temperature of the Earth now, right here, TS is surface temperature. And TE is equilibrium temperature. This is how hot the Earth would be without any atmosphere. 

So if you took the Earth today and took the atmosphere away, it would be below the freezing point of water, the temperature. And that would be bad. We probably wouldn't be here. But this difference, between the equilibrium temperature and the actual surface temperature, this is the greenhouse effect. This is the amount by which the atmosphere heats up the Earth today and it gets us into this nice, healthy temperature range above the freezing point of water where we're comfortable. So that's fine, but the weird thing is, given this dimmer Sun in the past, if you go back in time and you calculate how hot the Earth was in time, you come to a point early in the history of the Earth when the surface temperature you calculate was below the freezing point of water. The Earth was completely frozen over. This is given the current amount of greenhouse effect projected into the past. Well, okay, that's what the physics tells us, but the problem is the geology. If you look at the history of the Earth, you can find rocks from back at this time which tell us that the Earth was not frozen over. 

You find sedimentary rocks that were made by flowing water moving sediments around. So that's why it's called the "faint young Sun paradox." Because just the physics tells us the Earth should have been frozen over, but the geological record tells us it wasn't, that the climate was more steady. So something must be wrong with these calculations. When the Earth was young, the Sun was much less bright, so why wasn't the early Earth frozen over? Well, the greenhouse effect must have been stronger then. And that tells us that in some way, the atmosphere evolved. This calculation is for if we have today's atmosphere in the past, the Earth would have been frozen over. So something changed. Was there more carbon dioxide? Maybe, or maybe there was some other gas. But clearly, things were not just constant the way they were because the Earth wasn't frozen over and it should have been with today's atmosphere. Well, in order to understand why the Earth's climate has been so constant, even with this changing Sun and with other kinds of changes, we need to start really thinking about the evolution of climate. 

And an important thing to understand when we're thinking about how climate changes is the concept of feedback. It's positive and negative feedbacks. These are situations where, feedback is an element of a physical system where something either magnifies or diminishes because of the way different parts of the system interact. A really good example of a negative feedback is a thermostat. For instance, in this room, presumably, I hope there's a thermostat. So when the temperature's cool, it exceeds a certain limit and the cooling is switched on. And the temperature begins to fall. And when the temperature drops below this limit, the cooling switches off again and a steady room temperature is maintained so there's an element in the system which is sensing another element in the system and leading to a behavior which stabilizes the system. That is negative feedback. And there are examples in climate of negative feedbacks and you could also have a positive feedback. 

If you wired your thermostat wrong, so that every time it got below a certain temperature the cooler switched on instead of off, then it would just keep getting colder and colder and colder. If you wired it wrong, that would be a positive feedback, that would be unpleasant. Now, there are examples of negative and positive feedbacks in climate. So an example of a negative feedback is clouds. If you heat up the surface of a planet, you get more water vapor because it evaporates. That makes more clouds. Clouds block sunlight, they reflect sunlight and that cools things down. So a hotter surface leads to a physical effect which creates a cooler surface. That is a negative feedback. It stabilizes the system. 

It tends to keep the system within a certain temperature range. Now, an example of a positive feedback is ice feedback. So if you have a hotter surface, it tends to melt ice. Less ice means there's less sunlight reflecting surface. Water absorbs more sunlight and reflects less sunlight than ice and that means you will absorb more sunlight and things will get even hotter and the ice will just keep melting. So ice feedback is a positive feedback, in fact, something like this might be happening to Earth today and it's something we're concerned about. So feedbacks can work in both directions, and that's one of the tricky things about understanding climate change and modeling climate change, is putting in all of these feedbacks correctly because they lead to behavior that we call nonlinear behavior and that tends to make the equations kind of complex and unpredictable. So why has Earth's climate been so stable over all those billions of years, even with the warming Sun? Well, there is a climate thermostat that operates over the long term on Earth. It's what we call the carbonate silicate cycle. And it works like this. 

It has to do with the natural cycle of CO2 in the atmosphere. Volcanoes are always putting out CO2 no matter what. Sometimes it's a little more, sometimes it's a little less, but they don't really respond to the climate, there's just always a volcanic source of CO2. So why doesn't CO2 just build up in the atmosphere since it's always being pumped in by volcanoes? Well, it's also being removed from the atmosphere by what we call weathering reactions. That is, carbon dioxide is dissolved in rainwater and ultimately it goes through some chemical reactions and it ends up being deposited as carbonate rocks. Ultimately, those carbonate rocks get subducted, they get dragged inside the Earth by the plate tectonics, by the churning of the Earth and they end up, the carbon gets broken down and ultimately pumped out again as volcanoes. That's the cycle of CO2 in about 500,000 years or so, half a million years. The CO2 gets cycled through the whole Earth. So the reason why it's a negative feedback or a thermostat is because volcanoes are always pumping out CO2, but this removal of CO2 by these chemical reactions depends on the climate. When the climate is hot, that weathering speeds up. 

The CO2 is removed faster because there's more rainfall and rainfall is what's washing the CO2 out of the air and dissolving it. When the climate is cold, that removal of CO2 by weathering reactions slows down. And when the Earth gets frozen over, which it has a few times in its history, it stops completely. Because when it's just ice here, you're not having rainfall and these chemical reactions stop. So when that happens, when the Earth gets cold or frozen over, this removal part of the cycle isn't happening and the CO2 builds up in the atmosphere. And that eventually makes it get hotter again. So that is why it's a thermostat. If it's hotter, the system removes CO2 and cools it down. If it's colder, the system builds up CO2 and heats it up. So over the long term, Earth's climate is stable. 

Now, this isn't to say, hey, don't worry about climate change, no problem. Because this is something that corrects itself after about a million years. After a million years, we could all be dead. The Earth might be just fine, but this doesn't help us with our short term climate problems, but it's a reason why over the long term, the Earth's climate has been stable. Now these same processes occurred early on Venus and Mars. You had volcanism, you probably had weathering and liquid water. But this climate thermostat appears to have broken on Venus and Mars early on. And it broke in different ways on each of those planets and that's what I'm going to talk about next. This climate thermostat that's worked so well over the entire history of Earth seems to have broken on Venus and Mars. What happened? Well, on Venus, Venus lost its liquid water early on in a process called runaway greenhouse that I'll describe in a second. 

And with no liquid water, then you didn't have this silicate weathering and didn't have any way to remove the CO2 and all the CO2 ends up in the atmosphere and it just gets stuck. It's like that thermostat that's wired wrong and there's no way for it to cool off. On Mars, most of the volcanism stopped early for reasons I'll describe in a minute, so this part of the thermostat turned off. There wasn't any more CO2 coming out so there was no source of CO2 and the CO2 ultimately was lost to space, for reasons that I'll also describe. So this part of the thermostat broke on Mars, this part of the thermostat broke on Venus and only on Earth has this system apparently been running smoothly for 4.5 billion years. Now just a little bit of comparative planetology. Looking at the bulk properties of Venus versus Earth, in some ways Venus is strikingly similar to Earth. It's called Earth's twin or sometimes Earth's evil twin for a reason. Look at this. Look at how similar the two planets are in diameter and in mass. 

These are nerdy units. These are times 10 to the 24th kilograms, but it doesn't really matter what the unit is, the point is, Venus is about 5 and Earth is about 6, so Venus is slightly larger in mass than Earth and almost exactly the same diameter, but if you look at the entire range of planets in the solar system, there are no other two planets that are anything like this similar to one another in terms of mass and size. They really are twins. There's no other pair of planets that we know of that are this similar. And yet, these numbers in red show how strikingly different the environments of these planets are. Venus has, as I said, almost 100 times the atmospheric pressure of Earth. The average surface temperature of Earth is a nice, cool 68 degrees. The average surface temperature of Venus is a nice, warm, not so nice warm 890 degrees. And then these are also nerdy units, but the point of this number is that Earth has 100,000 times as much water as Venus, which is really strange, because Earth and Venus seem to be made out of basically the same stuff, and yet something happened to all the water on Venus. What happened? Well, we think that Venus had what we call a runaway greenhouse effect. 

Basically we think they started out as identical twins, but Venus was born on the wrong side of the tracks. Those tracks in this case being the inner edge of the habitable zone, or the distance from the Sun where a planet can maintain its water. Well, why did Venus lose its water? Well, the runaway greenhouse works like this. If you're like Earth but you've got too much sun, then there's a powerful positive feedback. I've got Jimi Hendrix here to represent feedback. (laughter) If you have a higher surface temperature, that leads to evaporation. And then you've got more water vapor in the atmosphere. More water vapor, water is a very powerful greenhouse gas, water vapor. So if you've got more water vapor in the atmosphere, that leads to what we call more infrared opacity, or just more ability to block the radiation from the planet and that leads the surface temperature to be higher, which leads to more evaporation, and uh-oh, more surface heating and if you get a planet with water hot enough, it's just going to run away. There's no stopping this. 

It's a runaway greenhouse. And ultimately, you get a steam atmosphere and then when you've got that much water up in the atmosphere, it's very vulnerable to being lost to space. Basically what happens is that the water vapor gets broken up by sunlight into hydrogen and oxygen. The hydrogen, being a very light gas, sort of streams off into space. They hydrogen escapes, and the result after billions of years of this is that today Venus has only 1/100,000 times Earth's water inventory. In other words, Venus has almost no water compared to Earth. And this in a nutshell is how we understand this strange divergence in conditions between Venus and Earth. That's sort of the cartoon version. We're still trying to work on the details. Venus is a hard place to explore because it's so hot. 

It's hard to send spacecraft there, and even we send orbiters there, but Venus is completely shrouded in clouds, and so we're studying it, but there are aspects of it that are very challenging to study. What we have learned is that Venus has a very dynamic climate. It seems to have ongoing volcanism, volcanoes on the surface. We're still trying to confirm that, but we've got some tantalizing evidence recently telling us that we think Venus does have active volcanoes. And those volcanoes put out gases, which make the clouds. And the clouds are blocking radiation and the radiation is also affecting things on the surface. So what you have is this complex cycle of gases and clouds and volcanoes on the surface, and it's really, it's turning out to be a very difficult place to understand. But in exciting ways, because it has this complexity of its behavior and this ongoing evolution that in a way mirrors the Earth in complexity, and we don't know of too many other places like that that have ongoing geology that's affecting the climate. And so you've heard of the expression Earth system science, which is how people have come to think of Earth science, where you can't just study the oceans or the clouds or the icecaps or the geology, but you sort of try to understand the whole system. Well, now we're trying to do Venus system science where we've learned that in order to understand any part of this system and understand the climate, we have to study the surface, the atmosphere, the interior, the clouds, and sort of all of these pieces of the system we study. 

We have to try to figure out the interactions. Well, how do we do that? Well, we have spacecraft that are helping us crack these mysteries. And there's a spacecraft that's at Venus right now called Venus Express, and here's some nice images from one of the cameras on board that spacecraft. And Venus Express is a European Space Agency orbiter that's now been at Venus for several years and it's really sort of our first weather satellite at Venus and is teaching us a lot about the climate of that planet. And in addition now there's another spacecraft, a Japanese spacecraft called Akatsuki, which is on its way to Venus. It was successfully launched and will get there this winter and so we will have two spacecraft at Venus and in addition, we have a lot of plans and proposals we're hoping for future missions and there are actually several proposals now for new American missions to Venus. We want to send orbiters, we want to send balloons, we want to send landers, and we've got lots of ambitious plans. All we need is funding. (laughter) So if there's one take-home lesson from this lecture, write your congressperson. (laughs) No, no, no. 

But anyways, we've got some exciting ongoing exploration and we've got big plans for future missions and it's all in the service of trying to crack this mystery, trying to understand the climate system of Venus and how it compares to the climate system of Earth. And now let me talk just a little bit, I'm going to switch gears and talk about Mars for a second. On Mars, there's lots of evidence for ancient surface water. Mars is a cold, dry desert now, but we see evidence for dried up rivers. We see evidence for layered sediments. This could be some place in Utah where sediments were laid down in ancient seas. We see evidence even for river deltas. Here's a river delta, and you can see this river. I'm going to show you now. This is sort of like the Mississippi delta, where a river has flowed out and laid these sediments and then I'm going to show you a close-up of this. 

There's a meander in this river. You can even see where this river spilled its banks and wandered. And this tells us that there was a sustained period of liquid flow. This wasn't just a temporary flood that had this kind of meandering behavior. So there's lots of evidence from orbit of an ancient climate on Mars that was warmer and wetter. And in fact, when we go to the surface of Mars, which we've now done beautifully with the Mars exploration rovers, which are still functioning there many, many years after the end of the supposed 90-day mission, we can actually go up to the rocks and scratch and sniff and ask the rocks questions. And the rocks answer us, and they say, "Go home." (laughter) Sorry. What they actually say is, there was water here once. These rocks are pay dirt. These particular rocks here are sulfate minerals that when we go up with those instruments and we knock and say, "Hello, tell us your story" and we look at the chemical composition and we look with a microscope and understand the structure, these rocks very clearly were laid down in ancient pools of acidic, sulfur-rich water long ago on Mars. 

And we even see some sections, some very deep sections of these sediments telling us that there were long periods of time where Mars was water rich. So that's interesting, but it creates a puzzle. What happened to Mars? Mars was clearly once much wetter and warmer than it is today, so what was so different? Well, when Mars was young, it seems to have had a lot more air. And therefore a stronger greenhouse. So where did it go, what happened? Well, for one thing, Mars lost its ability to replenish its air because the volcanoes died out young. There's a lot of volcanoes on Mars, but some basic physics tells us that small objects cool off faster than large objects. You know this if you've ever taken potatoes out of the oven and after a few minutes the small ones are cool and the big ones are still hot. It's what we call the surface-to-volume ratio. That's the nerdy term. But basically, the interior of these small potatoes has more access to the exterior. 

It's easier for them to radiate away their energy, whereas the bigger ones, the interior can't cool off as easily. The same thing is true of planets. And Venus and Earth are both fairly large for rocky planets and they're still hot on the inside. They still have active geology. Mars is substantially smaller and it lost its internal heat early and its volcanoes died. And so it lost its source for CO2. The other thing, Mars is sort of doubly damned because since it's so small, it also has smaller gravity, weaker gravity, which makes it harder for it to hang on to its atmosphere. And there's something we've learned called impact erosion, where the Martian atmosphere was blasted off into space in large impact events. The kind of events that Jan talked about were very common when the planets were young. They were getting hit all the time. 

We know this because we look at the surface of Mars and it's covered with big craters, especially the southern hemisphere, which is older. And you can count the craters on Mars, and we have some idea of when they all hit. And if you model that and you look at when the craters occur over time and you model the effects of that on the atmosphere, each one of those big impacts blows a little bit of air out into space. And over time, the models show us that most of the atmosphere of Mars was lost very early on. So the ancient greenhouse was much stronger and we believe that helps us explain why Mars was once warmer and wetter than it is today. So both Venus and Mars experienced radical climate change from more Earth-like conditions to their current uninhabitable states. I'm going to wrap up now and Bill Nye's going to come up and talk to you more specifically about climate change on Earth. I want to leave you with this question. Is there another Earth out there? Well, it's probably true that soon Kepler will announce the discovery of planets that are similar to Earth, and it's going to be very exciting. There are going to planets, I mean, in science we don't know anything until we have proof because this is science, it's not fake, but I can tell you, as sure as I am about any future scientific result, I pretty much know, I'd put money on it, that very soon we're going to know about other Earth-sized planets because things are going very rapidly in that direction. 

But is there another Earth out there? I would say no, because one thing we've learned by studying Venus, Earth, and Mars is that planets are all individuals. They have complex histories and there will be planets that have some of the same qualities of Earth, but we're not going to find another Earth. We're not going to find another planet that's just like ours. So is there another Earth out there, no. (laughter) Anyways, in conclusion, planetary climate is complex. And it's uncertain. Radical climate change does happen to planets, don't let this happen to your planet. Earth has been remarkably stable, but that is no guarantee of future performance. We need all the help we can get, including data from other planets. Earth is unique, but planetary observations and modeling give us a reality check on our assumptions about climate modeling, and they provide indispensable perspective on the uniqueness, on the deep past, and on the long term fate of Earth. 

And in memory of Jack Horpenheimer, I will say, I will end with the words, "Keep looking up." Thank you. (applause)  >> Limaye: Thank you, David. So you can see there is a reason, I just want to say that The Onion, which is printed in Madison, it started in Madison. I was shocked because when that story that David showed, that picture, NASA is flying $5 bills and $1 bills? Well, that came very shortly after NASA had selected the mission to Jupiter, Juno, which is due to be launched. And the price tag of that mission was $700 million. (laughter) And now I can tell you that the price tag of that mission is twice, $1.5 billion. You're all paying for it. So thank you for paying your taxes. If you don't like how they are being spent, write to your congressperson, Russ Feingold, whoever's running against him. I don't know, I'm not speaking, but be active. 

I think what I'm saying is that what we do as scientists, especially with NASA and I've got some of my colleagues here, a project scientist sitting up front here. --, please stand up. (applause) He's taken us to Venus and we are very grateful, because NASA has not flown a mission to Venus. We've been trying for the last 15 years. So we are grateful for the ride the Europeans have given us. We are working with that mission which is why we are here. And I would like to recognize another scientist, --, who built the camera along with his colleagues, the movies that you saw here. (applause) And let me take this chance to recognize a few of my colleagues. Jan Helbert, who's working with the infrared data from the same mission. And next to him is Sue Smickar, who... 

(applause) ...has worked on Venus for many years and is active in pursuing - I'm sorry, I shouldn't have said "many years." (laughter) But anyway. I'll zip my lips. And next to her is Ellen --, who has worked on Venus before and they're all very active. And then in the front row there are some up and coming young Venus scientists. I don't want to take time. Where is Bill? Bill, where are you? Oh, come on up here. I'm killing time here. (applause)  >> Bill Nye: Sanjay, Sanjay, greetings! >> Limaye: Greetings. Bill's ready and Bill will tie this all together and tell us what we can do with Earth. >> Nye: It'll be perfectly clear, yes. 

Sanjay, thank you. (applause) Greetings, greetings. Let's see, we just take this and put it in here. (laughter) Still fresh for me, still hilarious. (laughter) All right. So, not to speak ill will of the fastest growing computer company in the northern hemisphere, but none of these are - every two weeks, there's a new one. (laughter) This is about a month old, so it doesn't fit. Now, hey, what's your name, sir? >> Matthew. >> Nye: Do you know what gaffer tape is? >> Yeah. >> Nye: I have some. 

Let's secure this.  No jokes? That's it? Now, if they come unplugged, it changes, it's hard to see.  (laughter) This is my first trip to Madison. I will be back, it's beautiful. Fabulous place. (cheers and applause)  How fast this happens usually depends on the age of the projector. No, the younger the projector, the less messing around there is to get it to work. Oh, you see, this is not what we hoped for. Let's try this. Wait, don't watch, no looking, no looking, here we go. 

All right, boom. Yes. (applause) The drag of this is, we're not quite at what we want. We'll fake it. We'll fake it, what's the worst that can happen? Bad example, that's a bad example. (laughter) Please wait, don't tell me what to do. I was feeling great about this lecture until just a few minutes ago. Just really, it was until just a few minutes ago. I think he's a Badger. Came up to me and said, "Is Bill Nye your real name?" And I said, "Well, it's William Nye." (laughter) And then the guy said, "Well, why did you change it?" (laughter) And then I got a little anxious right there. 

Just to review. Greetings. Greetings, earthlings! And tonight, for a little while, we are Venusians. We are studying Venus, we are thinking Venusian-ally. Now, just to review. >> (inaudible) >> Nye: We'll get to that. How many people here - oh.  What's this little dog doing back here? Ignore that man! (laughter) All right. Kids, this is really - I mean, don't get me wrong. It's really good even without the "N," but it's really better with the "N," so let's just - let's sit down and think some thoughts, shall we? We'll go to preferences and... 

We'll maybe detect some displays or something. It's gonna be fun. Let's detect some displays. Oh, look at all that, huh? Let's see if this does it. (laughter) No, no. Let's... You know, and so what happens normally - have you guys ever done lectures? The audio guy normally comes to your hotel room two days before to put the microphone on because they want to make sure you have the microphone. They can't let go of that thing. But this part is sort of secondary. Let's see. 

There's a whole bunch of information here. But we have another problem that you guys, you really have to be on the other side of my face to experience. Oh wow, oh look, there's a whole world down here! (laughter) Let's try this. I'm sorry, you guys. I'm not just fiddling. I'm making the point that - we did detect. You're absolutely right. We don't want to mirror, no mirror. No mirror, people, that would be madness. Let's try this. 

Three, two, one! (laughter)  Okay, that's good, that's not bad. Now what we've got to do, just got to do this. Now, four, five, six... And soon we should have - yes! (cheers and applause)  Yes! So, Sanjay, when did this - where'd he go? When was this lecture hall built? >> Limaye: 1997. >> Nye: In the 20th century. (laughter) So we have some crossover. You've just seen time travel. That projector from the 20th century, this machine, early in the 21st. There we are. Now, who is from the space generation? Does anyone know? Here's what you have to do to be in the space generation. 

You have to be born after the 4th of October, 1957. Anyone? Yes, a few of us. This means you are born after Sputnik flew, and Sputnik was a big deal. I will tell everybody, if you weren't here, it was crazy! All the grown-ups were talking about it, it was turned up to 11. This is the first object humans put in space and people were, like, totally freaked! Because it meant then that humans had the ability to create satellites. And this changed the world, and it became quite commonplace. It became so commonplace, we all love, a big rocket, very cool. Here's the game "Rockets to the Moon." These are very common. If you're not familiar with the game, let me point out that despite its appearance it is a timely game. (laughter) And it is fun to play. 

(laughter) Just want to point that out so everybody knows it's fun to play. So let me just review. There's been a lot going on here this week. Let me point this out. Let's say that this picture of the Sun represents the Sun. (laughter) Then the Earth is what we call 1 Astronomical Unit, the distance from the Sun to the Earth in round numbers, we call it 1. Mars is 2.5 times farther away. Mercury is not even half as close, and Venus, then, is 3/4 as far, 0.7, yeah. So you might expect, shooting from the hip, that Mercury would be hotter than Venus. If you stand closer to the fire, you expect it to be hotter. 

But no, my friends, just to review, this is not the case. Just to go back over it. This is too hot. This is way too hot. Mars is too cold, but the Earth is just right, and this is a good thing. And the reason all of this is, is because of the air on each place. It's the atmosphere. On Mars, they, if there are any of "them," have hardly any. On Venus they've got a lot more than we do, 90 times as much, Mercury, none. Not enough gravity, blew off, long gone. 

But this has made the world the way it is. With all this, all these atmospheres, I just want to remind everybody. You're in the space generation. You know space pictures. These are routine. This is a day at your space office. This is nothing. Cover of USA Today. Cover of... New York Times, whatever. 

You'll see this picture. But notice that the Earth's atmosphere is really very, very thin. Crazy thin. Thinner than most of us can imagine. And it is this thinness that has made the world, made us be alive at a time when our world is changing. Now there's probably a few people in here who still wonder whether or not our planet, the Earth, is going through climate change. If you are wondering, if you are concerned, you should do what I did. I went to the Ice Core Lab in Glendale, Colorado. Glendale, Colorado is quite different from Glendale, California, if you ever go. So in the Ice Core Lab in Colorado, it's 37 Celsius below zero. 

It's almost -40 Fahrenheit. And I said to Todd Hinkley, the guy who runs the Ice Core Lab, "Todd. Hinkley." (laughter) I probably said, "Dr. Hinkley. Why did you choose -37? Is that your tectic point for evaporation of certain isotopes of water and interaction with sulfur?" "No, no, we didn't pick it. We took the thermostat and turned it all the way down." (laughter) "It's as cold as it will go, dingbat." When you go in there, it is cold. Even by Wisconsin standards, I'm sorry. It is cold. So what we have done, people have gone all over the world, drilled a hollow drill bit pipe into the ice. In Siberia, in Greenland, in Antarctica, and you pull out these big tubes, these big cylinders of ice. And then you take them into the Warm Room, where it's only 27 below! Which in Fahrenheit's like 15, 17 below. And I will admit, it feels warm. 

You guys live in Wisconsin, what am I telling you? (laughter) Take off your fourth pair of mittens, wow, this is great! I see your face is exposed, my goodness, it must be very warm. Anyway, what happens there, if you don't know this, they look at the ice very closely. And I've seen it. You can count the layers of ice just like rings on a tree except it's quite a bit easier. The layers of ice are about this wide, 10cm, across the palm of your hand. And they are a result of the layers of snow that fall every year and then the tines of the snowflakes get smushed by snow that falls in later years and smushed and smushed and they break. And that mechanical breaking causes them to melt a little bit and, fabulous word, they re-gel. Regelation. Come on, that's a good word. (laughter) Regelation. 

And they turn almost clear. And then trapped between the tines of snowflakes are these tiny bubbles... (singing) § Of ancient atmosphere § trapped in these slices of ice. So I saw Don Ho, by the way, older reference. He died, he doesn't, as far as I know, he doesn't sing much anymore. (laughter) But he started that song, "Tiny Bubbles," which, for the young people, is about champagne and the bubbles that occur. They give off carbon dioxide, this gas we like. And he started singing that song and he said, "I've sung that song every night for 34 years... I hate that song." (laughter) He was very funny. He was very funny, he was a good guy. 

Big supporter of science education, by the way. Those little sand grains are Asian desert. They blew to Greenland from the Gobi, from the desert in China. And we can identify that by looking at them the way Jan and the guys do with their mass spectrometers, and we can determine exactly where the dust came from, very cool. So those of you who are unfamiliar with this, I look like nobody, but the other day I met Michael Mann, and he was one of the first guys to compile these kinds of graphs. And this is where you take, you look at the tiny bubbles trapped between the snowflakes and you can figure out very well how warm the world was. When it's warmer, more lightweight oxygen evaporates than heavy oxygen with an extra neutron. And you can figure out, they can compare how many neutrons you've got in your air with how many neutrons evaporate off the sea surface using fantastic data from crazy organizations like the British Navy, where even thermometers made in the 1700s are just dead-on accurate. They're just, craftsmen, made in the 1800s, really good thermometers. They can compare the recent data, the last few decades, with data from centuries ago. 

And they get the method working really well, they're really confident about it. So this, then, is where you see the Earth having - the Earth's temperature's changing, but it's going along pretty constantly for a long time. The oldest ice cores go back over 100,000 years. But then when you get near where we are alive today, here's the year 2000, it goes way up. The temperature of the world goes way up. And this is what Michael Mann and those guys call the "hockey stick" graph, which in Wisconsin must be very clear to you. (laughter) So there's a hockey stick, that's what the graph looks like. So, for many, many of you in the audience today, you are not only members of the space generation, you are members of what I call... (deep voice) The climate generation! Dun-dun-dun! Now, to be a member of the climate generation, you know what you have to do. You have to be born, but there's a little more to it, there's a rule. 

You have to be born after the 23rd of June, 1988. Anyone? Yes, way to go. About half of us, right on. I'm not in that "us," sorry. I had nothing to do with it. Nobody asked me. I just showed up some time ago. Anyway, this was the day that Jim Hansen, James Hansen, who was Sanjay's thesis advisor, how about that? What was he? >> Limaye: (inaudible) >> Nye: "Post-doctoral thesis advisor." For his, what, your fourth degree? Your fifth? (laughter) Anyway, he went before the US congress and said, "Hey, the world seems to be getting warmer, carbon dioxide seems to be a big part of this. And you know why I know that? 'Cause I've studied Venus." That's what he told congress. This would be 20-something years ago. 

And people thought he was crazy. But now everybody's in on it. Now, if you haven't seen these pictures, I'll refresh you. This is the Upsala glacier, these are famous types of pictures. Upsala glacier, 1928. This is in Patagonia in South America. And my old roommate's been climbing there, he says it's the most beautiful place. Anybody from there, been there? I've never been. A spectacular place, he says, and he's quite the outdoorsman. Anyway, this is that same area today, or a few years ago, and it's no longer an ice sheet. 

They call this, in mountain climbing, this is called an ice sheet because it's a sheet of ice. (laughter) Now there is no ice sheet. And these are infamous or notorious pictures taken from just about the same place and this huge amount of ice and snow has melted away. And this, I hope, gives you pause for thought. So here's me. Well, actually, it's a picture of me, I'm over here. (laughter) And this is at Mt. St. Helens, and Mt. St. Helens is in Washington state. We used to do the Science Guy show in Washington state. I lived in Seattle for a long time. I mean, it's not Wisconsin. 

It's all right, it's okay. It's no Wisconsin. But there we are on the rim of Mt. St. Helens. And you say, "Why are you lazy people lying down? What kind of climbing is that?" Because right there is about 500 meters. It's like almost 1500 feet straight down! And so you can be a hard dude, macho guy, "Oh yeah, I'm gonna stand right here." It's really hard, I'll tell ya. It's really hard, 'cause it's crumbly, you know. It's scree, it's gravel. Anyway, it's a volcano and volcanoes I found quite cool. This is another representation of the temperature of the Earth from the Intergovernmental Panel on Climate Change, the IPCC. This then, when things are cool, are blue. 

When things get warm, we go orange. 'Cause that's how we humans think, we're fire people. And so this is another, this is further evidence of climate change. So what we've got here - oh boy, is it just washed out? Here we go. So when Krakatoa volcano blew up in 1880, the Earth cooled off a little bit. Although carbon dioxide was thrown into the air, a lot of carbon dioxide, all this dust, all these particles, and you saw at Mt. St. Helens, the particles are gray. It's ash, people use the word "ash," but it's just powdered rock. And the Earth cools off. Santa Maria, 1900s. People were alive. 

This is not ancient history. People recorded the volcano eruption. They estimated how much volume of stuff got tossed in the atmosphere. And this is another thing where scientists correlate, or connect, the eruption of volcanoes with the cooling of the Earth. Now, here's Mt. St. Helens. And it's just a tiny bit there, because Mt. St. Helens is not in the tropics. If you're a volcano and you want to cool the Earth off, you've got to be in the tropics. So I don't know what you're doing, I don't know if there are any volcanoes here, Wisconsin's not going to do it. If there were a volcano, we would notice, wouldn't we? I mean, I don't know about that guy who asked me why my name was Bill, but... (laughter) We would notice. 

Anyway, people project, and you've probably seen these, people project what will happen to the world's temperature if we don't do anything. It'll get warmer, warmer. If we do everything all at once, it'll stabilize. If we do somewhere in between, it'll do somewhere in between. And these are the kind of data that, if you're a scientist and build this computer model, as David referred to, and you get this result, where you're able to show that volcanoes in 1880, looking at, for example, ice cores, for example the amount of pollen of certain weeds that grow a lot when it's warm and not so much when it's cool. And the width of tree rings when it's a warm season or a cool season. When you're able to correlate all those data, and then you see this in the future, you get concerned. If you're like me, you get, if I may, like, totally freaked. It is really serious, serious business. And it seems impossible. 

It seems impossible to many people that I've met over the last few years. It just doesn't seem like humans could change the climate of a whole planet. I mean, my goodness. I ride my bicycle to campus, for crying out loud. How could I be changing the world? Well, from the same vantage point at Mt. St. Helens, this is the next year actually. That's Mt. Rainier, that you see off in the distance. Mt. Rainier is famous, a big mountain out there and it's on the license plate of Washington state and stuff. But this is not a problem with the camera. That's a layer of smog, and I've drawn it in a little bit. There's a layer of smog right there. 

And just to help you see it, I've put a line on it. But this is 80 nautical miles from Seattle. It's 30 nautical miles from Portland, Oregon. And the smog just sloshes in. And so the reason this is happening is, there are a lot of people in the world. I captured this from the web right before I left Los Angeles the day before yesterday. There are now 6.8 billion people on Earth. When I was young and I went to the World's Fair in New York in 1965... Yes, climate generation people, we had the Beatles. We did not have disco yet. 

We did not have New Wave. And we got, I mean, we got by, even though we didn't have Lady Gaga. (laughter) We managed. Hey, she's a musician. I'm a fan. I have no problem, she's good. Anyway, when I was at the World's Fair, I was very disappointed. I was with my dad and my family. We had missed this board depicting the world's population, changing from 2,999,999,999 people, changing to 3 billion. We missed that. 

My father and I went, "Doggone it!" That wasn't that long ago. The world's population has more than doubled, and that is how humans are changing the world. There are just a lot of us. And some of my best friends are humans. (laughter) I'm a fan of humans. But this is the problem. So people talk about, David made reference to the amount of carbon dioxide in the air. And if you've never done this, I encourage everybody to do this. I'd do it up here, but it's more compelling if it's big. So you can do this yourself. 

I have two containers of clear water and I put fountain pen ink in it. And this is blue ink, but after a few minutes it turns this amber color. In the year 1750, using the ice and other means, people agree that there were about 250 parts per million of carbon dioxide in the Earth's atmosphere. A part per million doesn't sound like much, it's 0.025%. It's not even a tenth of a percent. Doesn't sound like much. But if it's ink in water, or if it's, pick your poison, arsenic in water, you would notice it. Now, sort of this spring, a lot of people agreed on 389 ppm. Almost 400 ppm of carbon dioxide. And you with your eye can tell, even though it's parts per million, which sounds like a tiny amount, it is enough to, dare I say it, change the world! Now, what I want you guys to do, the young people here, I want you to change the world and I want you to save it. 

Now, bear in mind, the world is going to be fine. Cockroaches, sea jellies, apparently there's some squid that eat each other, that just are going to do great. They're going to have a great time. What we want to do is save the world for me. For us! And so I want you to get on that. Here's an example. I was in New Orleans for the Science Teacher Convention last year. This was a gas station in New Orleans. It's not there right now, 'cause they had it wash away when this hurricane came. Oh, don't worry, we'll build a drugstore right across the street in the last four years. 

You guys, really? You've thought this through? So here's a house that's built on sticks, and this would be a great idea, and it's your buddy Brad Pitt. Way to go, very cool. It's for a Category 4 hurricane. This dyke, which is a little ways away, is for a Category 5. Now, I'm not a civil engineer or expert on water management. It's not that far. It's going to happen again, everybody. Come on, people. I want you to change the world. The water level here was Category 5, the house was Category 4. 

And so I asked the spiritual question, "Are we sure about this?" (laughter) And what I mean is, this is not rocket surgery. (laughter) This is just making decisions. This is being a voter and taxpayer, just thinking about things. Now, you may have noticed that it has been very warm this year. Well, let me tell you, the last ten years have been the warmest on record. The warmest anybody who's been keeping track has noticed. And furthermore, the year that we're in now, which is 2010 by the common reckoning, is on track to be yet warmer. So it will be at least as warm as 2005, which was very warm. These data from the Union of Concerned Scientists, this is from the Australian Ministry on Climate Change, and I can tell you that when we do the reckoning for 2010, it will be the warmest year on record. It will be the warmest year in the last 131 years, which is how long these particular records have been kept, since 1879. 

So if you like to worry about things, this is a good time. You're in the right place. So what I'm saying to the climate generation, it's about making decisions. It's about, if I may, keeping your head in the game. I know that this year was the first time NASCAR came to Wisconsin, in many, many years. Anybody go? Nobody? (laughter) It is very exciting, I mean, the cars go really fast. It's very exciting. However, for those of you race fans - I thought there'd be a couple race fans. These cars get five miles to the gallon and they use leaded gas! People, it's the 21st century, for crying out loud. I have a Prius, okay? We could have a little contest. 

When I was young, by the way, car racing was where technology was developed, where new engines were created. Everybody who's got a fuel-injected car, it was all developed in auto racing. Well, this particular style of car operating is the celebration of the past. They have mechanical fuel pumps, which no car has, they've got a carburetor, which you can't even find. People can't even spell that word anymore, not that you need it. And let's have a contest. Me and four of you will get in my Prius, and we've changed one rule at NASCAR. We've changed one rule. You only get, let's pick a number, 50 gallons of gas to go 500 miles. We could win! (laughter) We would drive, we could stop and have pizza. 

(laughter) 'Cause those guys couldn't finish! And it's not, people make a lot of cars. I'm a mechanical engineer, people think about cars a lot. And yet, we have this weird celebration of doing things the old way. People, we can change this. I am very excited about my next vehicle, which I'm pretty sure will be a blank slide. (laughter) No, just a second. Will be the Nissan Leaf. I got to drive it the other day, it's all electric. And those of you who have never driven an electric car, it's so cool. It's so much fun. 

You can hate cars and you can hate people, but like cars, you can hate everything. But this car, the Chevy Volt, is sexy. Okay, I'm sorry. It's just fun to drive. So these cars depend on their batteries. And if things go really well in a car like the Leaf, you'll go 150 km, you'll go 100 miles. Things go really well in the Volt, you'll go 40 miles. The key is the batteries. Right now, everybody, our batteries have electrons that jump between big molecules, like through this goo, the battery electrolyte. This is a fuel cell developed by Toshiba that will run a laptop like this for a couple of days. 

The trouble is, you can't move it. You can't shake it, it'll mess it up, so it's in development. But my friends, young people, climate generation people, if you could invent a better battery, whether in yuan, Euros, or dollars, you will get rich. (laughter) You will get crazy rich! You will be Richie Rich Rich! (laughter) You'll be head-of-IKEA rich! (laughter) You'll be, like, out of control. I want you to do this and change the world. Now, this is the Golden Gate Bridge. Well, it's a picture of the Golden Gate Bridge. If we had the Golden Gate Bridge here, I think you'd know right away. (laughter) There's no fooling you. This bridge is state of the art, and it's held up with steel. 

I had the great privilege of meeting a guy named Rick Smalley, who unlike many of us here, has a Nobel prize. And he got his Nobel prize with a couple other guys for discovering buckminsterfullerenes, and Buckminster Fuller was an architect who developed the geodesic dome, and he named this molecule after him. By the way, Rick Smalley was working in the astronomy department at Rice University. They were looking at molecules in space and couldn't figure out what they were. At the spectral light going through molecules in space. And he realized, he told this story, it was very compelling, very good, it was really good, on camera - that he woke up at three in the morning and had figured it out. That it was this pattern on a conventional soccer ball, old-style soccer ball, football. Hexagon, pentagon, hexagon, pentagon, hexagon, pentagon. So if you could take these molecules and stretch them this way and allow more carbon to grow in between, you get material that is 10,000 times stronger than steel. "I'm sorry, Bill, I thought you said..." I did. 

I said "10,000." 10,000 times stronger than steel, and they would weigh about 1/6 as much as steel. This material only exists in 30 billionths of a meter lengths, 30 nanometers right now, 50 nanometers. But somebody in here, some climate generation person, could work this out and change the world! So Rick Smalley was the guy, he was very well-spoken, and he said, "What we have to do is not do less." See, traditional environmentalists like me and my neighbor Ed Begley, we were brought up, "You gotta do less." We want you to drive less, use less clean water, so wear dirty clothes. (laughter) And then really, if you can, just don't eat. (laughter) Because humans are bad, humans should not be here, just don't even eat. But that turns out, that's not very popular. People don't go for that. (laughter) And what we have to do, as Rick Smalley said, I call him Rick, we have to find ways to do more with less. My friends, if you can solve this problem, you will change the world. Meanwhile, the world is changing. 

If you told my father, this is a guy I knew pretty well. (laughter) If you told my father we could use unbelievably faint pulses of radio from outer space to plant seeds in a field so precisely we could spell words, he would think you were crazy. Well, in my case, he thought that anyway. (laughter) This is remarkable. This is done with global positioning satellites directing tractors on where to plant seeds to within considerably less than a meter. This is rye grass in a wheat field, which was done for a hilarious thing, and this work, you can do this. This is doing more with less, because you can grow more wheat, or more of anything, on the same amount of land more efficiently. Now, everybody. I just want you to think about this, climate generation people. I took these pictures here at a world-famous restaurant. 

Hamburgers are 49 cents US. A salad, which I admit has some protein in it, is $5, $4.99. Now, I think, you're in Wisconsin, you've seen farms. You don't have to know that much about it. Growing what it takes to make a salad has got to take less energy, less water, less everything than raising a cow, feeding a cow, getting water to a cow, killing the cow, cleaning it up, grinding it up, cooking it, putting it with a bun - it's got to take less energy to make a salad than a hamburger! But what has happened, by the great accident of democracy, compromises have been made for well over a century into a thing we call the Farm Bill. And now beef production for the sake of hamburgers is now cheaper than making a salad. You've got to, it can't be that hard. That has to be a solvable problem. This is not really an engineering problem. It's not a science problem. 

It's a human interaction problem. It's your lawyers and such. So I want you guys to figure this out and change the world. Now, when you fertilize fields, you use fertilizer normally made by the Huber process. A guy in Germany figured this out at the turn of the last century. And this is an oil refinery where they also have a fertilizer plant. I like it because it's colorful, it's happy. (laughter) Now, you might be able to figure out that taking nitrogen, which in chemistry is written N2, right out of the air to make fertilizer takes a lot of energy. That's why they put the fertilizer plants by the oil refineries. But we have another source of nitrogen. 

These are pigs. And they make nitrogen fertilizer like crazy. (laughter) But we have gotten in a situation, largely by accident, really, by the evolution of our technology where we have made it about the same amount of money to make fertilizer through a hugely energy intensive process instead of taking it in the old fashioned way from pigs. So what we want to do is get you guys in the climate generation to move away from the old confined feeding operation, or CAFO, to what we like to call the smart pasture operation. The SPO! (laughter) And if you could do this, you would change the world, and if you did it right, you would also what? Get rich, that's right. (laughter) 'Cause fertilizer's almost free. This is a nuclear power plant. Well, once again, it's a picture of a nuclear power plant. And I took these from an airplane. Well, I was in the terminal in Harrisburg, Pennsylvania, which is where Three Mile Island is. 

And I am all for nuclear power as long as you guys figure out what to do with the waste. Just make sure you have that figured out. What went wrong, they had this idea, nuclear power was going to be too cheap to meter. But it got complicated, all the rubber gloves and coveralls and all the stuff you need to move radioactive material around has made this low-level, so called "low-level" radioactive waste that's made it really expensive. And of course, it's also dangerous and so on. But if you could figure that out, that would be really good. Now, around the world we have a lot of wind. This is a United Nations and departments of energy from around the world map, there's a lot going on. But you get the idea, especially when you're near the coast of many countries it's very windy where the wind comes off the flat ocean. There is so much wind in North Dakota, North Dakota alone could power all of the United States and most of Canada, if you could get it all. 

The other thing about wind that's charming is, it's free and it's not especially dangerous. I was out in Palm Springs, California, and here's a tower, one of the many wind turbine towers, they're all over the place, that fell down. It buckled. And that's bad, and if you're the guy or gal who owns that tower, you're not a fan. (laughter) That was unfortunate. But the thing is, it's not that big a deal. When something goes wrong with a nuclear power plant, it is a huge big deal. If we have, right now there are 432 nuclear power plants around the world. If we get that to be 4,320 or 14,320, there's going to be a mistake. Something's going to go wrong, in the same way something went wrong with that oil well. 

There's going to be a problem, and we've got to all decide if that's worth it. If you guys can figure that out, I am right there with you. But it's a complicated problem. When you're in China, in the cities, every house, every apartment building has a solar hot water system on top. Everybody does. And the reason they do this is not because they're a bunch of hippies that want to live off the grid. It's 'cause the heat is free. It snows in Beijing, and yet they've got these on every house. It's a very cool, high-technology idea. The heat comes down, it boils this refrigerant, or heat-ant, and it goes up to the top of this pipe, it gives up its heat to that scuba tank-y shaped thing, and then dribbles back down. 

No moving parts, all day, and everybody gets hot water. I want somebody out here to start a hot water company in the US and get rich. Would you get that done? Now I'm going to throw this in, okay, look. Those of you who don't want to acknowledge this, pretend this didn't happen. Suppose we did this, okay? Instead of spending tax dollars to make roads that are big and thick that can hold up big, heavy sport utility vehicles and stuff like this, and then you have to re-pave them every year 'cause of the snow. Instead, what we do is build bike-ways that are covered. And then we would hook up louvers, so whenever the wind blew everybody who went across this tunnel would have a tailwind, and that way we could use the tax dollars to get people moving around on bicycles rather than repairing roads. It's a crazy idea, I just threw it out, you can pretend it never happened. (laughter) (cheers and applause) It's too crazy, it's too crazy, didn't even happen. All right, this is in the United States. 

This is my house in southern California. I have 4 kilowatts of solar panels and my electric bill, they just raised it, my electric bill is $10 a month. It used to be $7. That's The Man, that's The Man. And then in the foreground is my solar hot water system and then this is the sola-tube, that's a brand name, and it has grooves in it that make it a Fresnel lens, and you guys are familiar with them even if you don't use that word. Light comes in sideways and is directed down this tube. And it's much brighter than a skylight. Even now, four years later, I tried to turn off the lights in this room, it's so bright. And this is technology that we hardly use, but we could save a lot. It sounds silly, but we could save a lot of electricity. 

I want you to get into that business. Now then, the future could be the situation where all these buildings which have all this space are used for growing plants, and we could have little gardens all over the place. It sounds crazy unless you think of it ahead of time and you could maybe do that, right? Now, I hearkened to this, I talked about this earlier today. I grew up reading, delivering the newspaper and I remember in the Sunday paper they still have Ripley's Believe It or Not. You come to Los Angeles, you can go to the Believe It or Not Museum, still going. And I read over the years several times versions of this and I called them and they sent me copies of the cartoon. Anyway, "Insects which have been flying for 350 million years defy the laws of aerodynamics!" "The bumblebee, considering its size and shape and wingspan is an aerodynamic misfit and should be unable to fly!" Even as a little kid, I realized the problem was not with the bees. (laughter) The bees have it figured out. It's the theory that's screwed up. So there are dozens, dozens of dozens, hundreds of things in your everyday experience that we think we know, that we're sure of, and we're wrong. 

And I want you guys to discover those things and change the world. 'Cause in the future, a lot of crazy ideas are going to come up. Let's put reflectors in space. Let's throw baking soda in the air and soak up carbon dioxide. (laughter) Let's throw iron in the ocean and grow more algae and then that'll make more oxygen. More algae, what could go wrong? (laughter) What could happen? More zebra mussels, come on, it'll be great. I just want you to know that I, a week from tonight, will have a job. (laughter) Yeah, exactly. "You, Bill, a job? You can't be serious." And I'll be executive director of the Planetary Society and - (cheers and applause)  Right on! We are going to launch a solar sail. Now, this is like science fiction. 

This thing, this is an artist's rendering and gorgeous, it'll look every bit this great, nothing will go wrong. (laughter) Pushed through space by photons. "Wait, Uncle Bill. Light has no mass, how can it have momentum? Have you taken leave of your senses?" Perhaps. (laughter) But this has been around a long time, since relativity was discovered, that light should have momentum. And indeed, certain spacecraft including the ones that go to Venus, interplanetary spacecraft, are tinily affected, but measurably affected by the momentum of light. So this thing is so low mass, how low mass is it? That we'll hope to get it in orbit around the Earth and get a picture of the Earth below with the spacecraft. Earlier this summer, Japanese Aerospace Exploration Agency, JAXA, deployed the first successful solar sail. And it's on its way to Venus and they steer with it and they do cool things. And so we're hoping that this technology gets employed because it's ideal for keeping an eye on the Sun. 

You can have stationed keeping an orbit around the Sun, not have it fall into the Sun, with the solar sail. For years and years and years because the fuel is free. Very exciting. Now here's another crazy idea for you. It might be possible. Do you see how the bubbles in the wake of this boat reflect light? They're white almost. When you look at them closely they're tiny bubbles. (laughter) When you look at them closely, they reflect light in a way that you can't even see with your eye. If you have just 3% of the light being reflected, you kind of have to do so-called A-B. You have to look at the bubbled water and the un-bubbled water to even tell them apart. 

It may be possible to use the bubbles off the back of ships to reflect light into space and we could have the World Bubble Council maintaining the reflectivity of the Earth. Sounds crazy, but it might work. It especially might work to keep ponds and cooling ponds around power plants from evaporating too fast. Seems like a crazy idea, but I ran across this about a year ago and I keep throwing it out. Russell Seitz is the guy, he was at Harvard. I keep throwing his idea out. He told me, "Yeah, tell everybody." So I told you, too. And when you think about climate change, you can get daunted, I have to say. But my grandfather, and that was a long time ago, but, my fellow humans, that wasn't that long ago. My grandfather went into World War I on a horse. 

You'll be shocked to learn my grandfather was an organic chemist. And he put bleach or chlorine in the lister bags in the canteens, 'cause I guess fighting a war when you have diarrhea is really hard. So they didn't want to get dysentery, this miserable parasite. So they killed it with chlorine, so you'd drink a little chlorine so you wouldn't get sick. Wait... (laughter) And he put a gas mask on himself and a gas mask on his horse. And when there was a fire on Berkwood Place in Baltimore, Maryland, the fire truck showed up pulled by horses. But 20 years later, by the time World War II was fought, nobody did anything like that in a big city with horses. Everything changed. Everything changed in just 20 years. 

And so I submit to you, you guys, we can change the world. Those people back then, if you can believe it, didn't even have the internet! (laughter) What did they do all day? (laughter) David and I were in Cape Canaveral, you were there, yes, yes, for the launch of New Horizons, which is on its way to Pluto. Pluto, the last of the traditional planets, now the first of the Plutoids! I just love the word "Plutoid," I think it's fantastic. All right. This launched in 1996, pardon me, hold it, 2006. And it is the fastest object humans have ever launched. When the astronauts went to the moon, it took them three days, or two and a half, half a day to slow down. 'Cause you're going to the moon, you don't want to miss, it's bad. (laughter) This spacecraft went past the moon in nine hours. Going that fast, it will arrive in the vicinity of the Plutoid Pluto in 2015. 

So I just want you to think back. "I remember, I believe it was 2010 and Uncle Bill was here and he was talking about a bunch of technology, I don't know what it was, and he mentioned that Pluto thing." And just think about when the first spectacular pictures of Pluto come back, 2015, think about the world today and how it's changed in five years. Has anything changed? Have you been part of any change? Has climate change been more pronounced? Have you noticed it, have the years gotten even warmer since 2010? Because we need you to change the world. Now, this is a picture of Saturn taken by the Galileo spacecraft. No, the Cassini spacecraft. Spectacular picture where rocket scientists got the camera out beyond the orbit of Saturn pointed back at the Sun, but this is also a picture of the Earth. The Earth is right here. That's it, that's the Earth, which makes the picture for me even more astonishing. Now, if we could go camera right a few thousand kilometers and look back, that's the Earth. That's it. 

This is everybody. And as my old professor Carl Sagan used to say, that's everyone you've ever met. Everyone that's ever lived. Every oak tree, every sea jelly, every emperor, every couple in love, everybody who's ever lived is right there on what he called the "pale blue dot." So it's where we make our stand. There is no cavalry coming over the hill. If what happened on Venus happens here, we are in trouble. And so I used to go to the beach in Delaware. Like you guys watch "Jersey Shore" and stuff. (laughter) It's just south of that, where my family used to go to the shore. And as a little kid I stood there and thought, "Boy, I really don't amount to much." The ocean is trackless. 

If you've ever been out on the ocean, you can't find your way unless you're very, very careful. And so I remember thinking, "I am just insignificant." And Mrs. Cochran, my third grade teacher, had also been my brother's third grade teacher, told us that there were more stars in the sky than grains of sand on the beach. And I remember thinking, "Mrs. Cochran, are you high?" (laughter)  I mean, I couldn't express it, but... (laughter) "Mrs. Cochran, have you ever been to a beach? There's a lot of sand, lady!" You look left and right in Delaware, that's 1500 nautical miles of sand in either direction. The tide goes out a little bit and there's more sand! You shuffle your feet, there's sand! Sand, sand, sand! But apparently there are more stars than all of that. So I remember thinking, "I am nothing. I'm just a speck, standing on the Earth, which really in the cosmic scheme of things is another speck." And it's orbiting the Sun, which is in every way an unremarkable star. I am a speck on a speck orbiting a speck, in the middle of speck-less-ness! (laughter) I am nothing! (laughter) If you'll excuse me, I suck, I am nothing. But then with my brain, which is only this big - in the case of my old boss, of course... (laughter)  But with that brain, you can imagine all of this. 

You can understand the science of climate change. You can do something about it and you can, my friends, dare I say it, change the world! Thank you all very much, thank you. (cheers and applause) Thank you, oh man. (cheers and applause)