Think how lucky the dinos were, they had no knowledge of asteroids or collisions, just lived along until Whammo, death from the sky. BTW, if we are hit every million years then it has skipped many, many millions of years. The dinos lived for far more than a million(about 185 million)before being smacked(if that is what actually happened) and reptiles were around for serveral hundred million before the Dinos came along. As the article points out it has been 70 million years since the Dinos went under.
So that begs the question: If only one major Asteroid has hit earth over the last 500 million years or so, how do they come up with the "once every million years" figure? BTW, I believe there was one other major extinction of life they didn't mention here, after the Dinos.
Right, this article is a badly edited version of a longer talk Hawking gave. A link to that talk is on the Daily Galaxy website. Haven’t read it yet, myself, so I don’t know if he was more careful than the editor, BUT I’m pretty sure he’s talking about asteroids measuring one kilometer or more in diameter. Those do hit us about once every million years. The 10 kilometer monsters, like the one that got the dinosaurs, hit about every 100 million years.