How likely is an NEA impact?
Maybe more than you expect. (But not so high that you should spend your retirement savings early!) The current best estimate is that impacts large enough to cause a global catastrophe occur on average every few hundred thousand years. These impacts are the ones large enough to cause significant global climatic disruption, widespread crop failures and probable societal collapse. This translates into a probability of a little less than one chance in a few thousand of such an impact occurring during a typical human lifespan. Smaller objects, of course, are more numerous, and impact more frequently. Impacts capable of causing severe local or regional disasters occur once every few hundred years, depending on how you define “local” and “regional.” Fortunately most of the Earth is uninhabited so the likelihood of a impact near a populated area is far less. What would happen if there was an impact? If an object were to penetrate the Earth’s atmosphere, the type of impact at the surface would
