The relatively calm features of day-to-day life on Earth mask the truth that the history of nature includes many disasters. In 1908 in Siberia, for example, a giant fireball was seen in the sky, and eyewitness accounts show that it impacted the Earth with spectacular and dramatic results. Various theories have been proposed to explain the event, but the only one that makes sense is that a piece of a comet hit the Earth. A repeat of such an event without a proper understanding might be mistaken as a nuclear attack and perhaps set off a nuclear war.

The spectacular visual of shooting stars or meteor showers actually comes from very small particles in space. However, in the past, comets “have always evoked fear and awe and superstition” (78). Sooner or later, comets collide with planets. The impact craters on the moon and throughout the inner solar system (including on Mercury, Venus, and Mars) offer evidence of a time billions of years ago when collisions of matter in our own solar system were far more violent and regular. Collisions among asteroids happen frequently, and the result can be the meteorites that fall to Earth and are now found in museums the world over.