we know this happens. the risk of -- specially like what they are talking about an extinction-level events these are millions of years apart, the likely for it to happen in your lifetime and mine is minuscule. if you really want to understand what we are up against, you really want to understand what we can do about it to protect ourselves, the things you do are actually the same -- bill: drill down on that? what do you do, what are the ideas? >> first of all, you want to know what's out there. it's very hard to see a comet coming because they come out of the dark. you want a really good set of survey telescopes, watch all the asteroids and comets coming in. this is great science. this will tell you about the solar system at the same time that you're learning a lot about what are the risks that you have early warning system at the same time. that's part one.