Joe, you are correct. Talking about the odds of an impact occurring during a specific interval is, well, pointless, but the geologic cratering impact record does give us an idea of how often these things happen on earth over enormous timescales. I think Daniel and Rodger are correct in reasoning that the chances of it happening anytime soon, or even out to imaginable times in the future as measured in human terms, can't be predicted. There have even been recent computer model studies demonstrating that the inner planets orbital integrity isn't robust over very long timescales, and the earth has a not insignificant chance of being hit by an errant Mercury or Mars one day. Personally, I am more worried about getting hit by someone texting while driving, than an asteroid. I would welcome a near-miss by a very small meteorite, however. On Thu, Jul 23, 2009 at 9:28 PM, Joe Bauman <josephmbauman@yahoo.com> wrote:
Asteroid impacts probably happen at random intervals, but over time, there's a likelihood verging on certainty that another one will hit. There's a difference between frequency and the chance that it eventually will happen. A look at how many such events have happened in the last 10,000 years at least gives us something to go on as far as predicting the odds of its happening in the next 10,000. If our world had never been hit we probably wouldn't worry about it. If it was hit by a big asteroid every century, that might give us more concern. -- just a thought.