our atmosphere all the time but has to be larger and get them lower in the sky to explode to do some lasting damage. do you think we re going to go through a period or does this stuff cycle in pers where that is a possibility? no. it s a random occurrence. and the odds are not huge. but they add up. and so you don t know. right now we don t know when the next major impact will be and we d like to find out. neil: seems like a lot of the ones that have been noteworthy in the pass, like the one that hit siberia in 1908. largely unpopulated region, but had the same meteor hit, for example, london, i m told that london would be gone. so that when these things do hit, they hit over largely unpopulated areas. not all the time. that just the mathematical odds