字幕表 動画を再生する 英語字幕をプリント Thanks. My name is Ed Lu, and I'm building a space telescope, together with the B612 Foundation. (Applause) It's called Sentinel, and simply put, its mission is to protect the Earth. In 2018 we're going to launch this thing, and it's big, by the way, it's about the size of a FedEx delivery van. We're going to launch into an orbit around the Sun. So it's going to be about 500,000 times further from the Earth than the Hubble space telescope. And we are going to find and track threatening asteroids before they find us. How'd we end up on this crazy quest, other than the fact that everybody needs a space telescope? Right? Our organization started out about 10 years ago. We started it with a different goal, we were working with a different project, related. And then something happened about a year and a half ago. Interesting, a guy came up and asked me a question, and it crystallized our thinking. What we realized is that we had to change our course, and that we had no choice but to actually do this, instead. And I want to tell you the story about how we ended up there and what we're doing. Why should you care about asteroids? Well, if you're a scientist, they're very, very interesting, they're parts, left over parts of the solar system from the formation of it. But if you're a citizen of planet Earth, and you all are, I hope, (Laughter) asteroids are important because they hit the Earth. So if you roll this video, anybody here has ever seen an asteroid impact site? They're all over the Earth. These are some of the known ones on planet Earth. An awful lot, it's kind of a surprising lot? But there's way more than this. They hit the Earth all the time. Just look up at the Moon. The Moon is covered in craters, and actually the Earth is hit more often than the Moon. So the reason you don't actually see them on the Earth is because they get covered up by the ocean, or wind and weather, and things like that get rid of them. They sometimes actually hit the Earth, even in modern times. 1908 Tunguska, this is the aftermath. It looks like a bunch of telephone poles laying on its side. This is an impact site called Tunguska. It's thankfully in Siberia, where an asteroid, fairly small, about 40 meters across -- so I would say that's about the size of this room -- it hit in Siberia moving at a velocity of about 20 kilometers per second. Anybody here whoever took High School physics knows that the energy is one half M V squared. When you have a big number and you square it, you get a huge number, and that was an enormous amount of energy. It was about a thousand times larger than the energy in the bomb dropped on Hiroshima. So, it wiped out a huge area. It's about 2,500 square kilometers of total destruction. So, for example, just to put that in perspective, if you drew a circle between the Golden Gate Bridge and San Jose, it took about that size. That's the area that was wiped out. Again, a thousand times larger than the Hiroshima bomb. That was only 100 years ago. These hit the Earth about every 100 to 200 years. So, flip a coin, that's the odds that somewhere on Earth, during your lifetime, it's going to happen again. Random spot, most of the world's unpopulated, but wouldn't it be a shame if it was a populated area? (Laughter) About 10 years ago, we decided that we'd work on the problem of deflecting asteroids. There was a bunch of really bad Hollywood movies out. Armageddon, Deep Impact, we thought we'd be the heroes, we're going to figure out how to deflect an asteroid. And if you roll this little movie, over the last 10 years, we together with a lot of other scientists, have worked on this problem, and now we understand that it's actually not that difficult to deflect an asteroid. What you have to do is either run into it with a spacecraft, like this, and boom! You actually change the velocity slightly. It's like playing billiards. It turns out that with sufficient notice you only need to change the velocity of an asteroid by about a millimeter per second to turn a hit into a miss, if you do it early enough. A millimeter per second. That's about this fast. Okay? So you don't need to change the velocity a lot, you don't need oil miners, and Bruce Willis, and stuff. (Laughter) It turns out that there are actually even controllable ways of doing this. If we take the next video here. This is something that me and another astronaut, named Stan Love, yes he is Doctor Love, invented. It's called a gravity tractor. It's very, very simple. You just hover a spacecraft nearby, and the mutual attraction of gravity between them, very, very tiny, adds up and if you can hover for months, so if you run this, you'll see that you can actually tow asteroids and give them the required fraction of a millimeter per second needed to precisely put this where you want. What we realized after about 10 years of working on this, and the community has realized, is that deflecting asteroids is actually not that hard. We actually have the technology to do things like this. So what's the problem? The problem is, if you don't know where asteroids are, there's nothing you can do about it, right? As my friend Don Yeomans likes to say, "The 3 rules of deflecting asteroids are: Find them early, find them early, and find them early." So let's look at the big picture. What does the Solar System look like? If you could run this... The green circle there is the orbit of the Earth, and then you can see the orbits of the other planets. And these are all the known asteroids, and these are actual real positions. (audience murmuring) The wizards at the California Academy of Sciences put this together, these are real orbits. All of this is real data, those are the locations of all the known asteroids. So the Earth again, look at the green line. You see all the stuff flying around. It's a very crowded place in our Solar System. It's a little deceptive, because you have to make them bigger so you can see it, but very, very crowded. That's the good -- So here's the bad news, though. We know what tiny area of the Solar System we've actually surveyed thus far, we know that it's not very much. There's a hundred times more than you see here. And those are undiscovered right now, and we really have no way to discover them from the ground. So what does the real Solar System look like? Multiply this by 100 and you get what the real Solar System looks like, it looks like this. This is actually the situation -- follow the green line of the Earth, and follow all the things that go whizzing past the Earth. Every time you hear in the news that an asteroid has whizzed past the Earth you should think, "So what, it's happening all the time, 99 out of 100 we don't know about." So that's what the situation looks like in the Solar System, and that's what we want to change. Because if you know where every single one of these is, we can tell you where it's going. Because we understand something called "Orbital Mechanics". It turns out that if you tell me the velocity and the location of each one of these things, I'll tell you where it is any point out in the future. Okay, that's how we send probes to Mars, for instance. We ended up in a situation where we know how to deflect asteroids, but we're not looking for them. We're driving around the Solar System with our eyes closed, essentially. And that seems kind of crazy, right? Because these things do hit the Earth, as evidenced by this guy here. As you all know, an asteroid impact is what wiped out the dinosaurs and we don't want to be like him.