But given enough time, like a few million years, it does happen occasionally, even in Iowa. Anyhow, we can worry all we want and it won't do any good. There is nothing we can do about asteroids with our present technology. The best computer models that predict the motion of heavenly bodies are not without some degree of error. And trying to blow up a threatening asteroid, as some have suggested, is equally chancy.
Chaos forbids a lot of accuracy in predicting the outcome of galactic snooker.
What people need is a healthy dose of skepticism, not sensationalistic hype and fear-mongering. In our collective ignorance we pose a greater threat to ourselves than any asteroid. As we near the year 2000 there is an unprecedented amount of cultism, fear of technology, rejection of science, religious terrorism and alien-invasion films. All the ingredients for Armageddon. The turn of the millennium is a profitable time for the soothsayers of doom with their prophecies of Biblical wrath.