Something that is much more likely to happen and is very dangerous, is for such a sizeable meteorite not to hit a populated city, but hit an appropriately deep part of the ocean, hundred or even more miles from shore. That would give rise to a big tidal wave, tens of feet high, that could sweep inland and do a lot of damage, could happen on the long ocean shores of the United States or, let us say, of Japan. Something of that kind might well happen, not just a hit of meteorite, but a hit of meteorite that costs very many lives, might well happen once in a few thousand years. An unlikely event but its unlikely nature, I believe, is really cancelled by the size of the trouble which may occur with a small probability, and it is probably known by everyone that these things are now known to happen in remarkable places. It happened recently on Jupiter where fragments of a comet have hit and disturbed regions of the size of the Earth. Of course Jupiter with its bigger surface and mass is a much better collector of such dangerous objects, but on Earth itself we have definite knowledge of a catastrophic event of this kind.