Ensconced in our tiny solar system and warmed by the Sun, the Earth seems safely removed from the vast dangers and unpredictability of outer space. However, in Fire on Earth, authors John and Mary Gribbin explain that every so often, comets and asteroids from the depths of space collide with the Earth, wreaking havoc on its inhabitants and altering the course of history.Satellite photographs of the Earth taken from space show that the surface of our planet is pockmarked, evidence of numerous cosmic impacts that have occurred for millions of years. In 1990, one such crater was discovered in Mexico's Yucatan peninsula, and was determined by scientists to have been caused by a huge asteroidal collision that led to the extinction of the dinosaurs.More recently, astronomers have discovered a giant comet beyond the orbit of Jupiter that is hurtling towards the Sun and that will provide a spectacular astral display as it shoots across the sky in 1997. Although it will not strike the Earth, it is similar in size and structure to the comet that did collide with our planet sixty-five million years ago, ushering in a devastating ice age that caused dramatic environmental changes the world over.In Fire on Earth, renowned science writers John and Mary Gribbin argue that such events have been instrumental in shaping the course of natural - and thus human - history.Tracing the history of these unpredictable and violent collisions, from prehistory to the present, the authors paint a sobering picture of the many dangers our fragile planet faces, and discuss the disastrous environmental consequences that may ensue. Explaining that these impacts and close encounters occur far more frequently than we believe, the Gribbins address the unsettling but vital question of what we can do when an Earth-bound comet is discovered. Read Less