We see a meteor shower when Earth passes through the debris-strewn path of a comet.
Space is very big, and comets are very small in contrast to the streams of debris they leave behind.
So it's millions of times more likely that we'll enjoy many future years of a particular meteor shower than suffer a collision with that shower's parent comet. What's more, the orbits of comets are constantly being perturbed by the gravitational pull of the planets. So any meteor stream the Earth passes through this year is likely to miss the Earth completely within the next millennium. And as if that isn't enough, Dr. Binzel adds that orbital calculations of all of the known meteor showers show no chance of a future collision between Earth and their parent comets. David, thanks for your question.