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Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
The geological implications of the Earth’s collisions with other bodies in space have become fully evident only since the opening of the Space Age. In the early eighteenth century, most western natural philosophers accepted the view, inherited from Aristotle and confirmed on mechanistic grounds by Isaac Newton, that interplanetary space is empty of solid matter. In the final decade of that century, two books, one by Ernst F. F. Chladni of Wittenberg and one by James Hutton of Edinburgh, contributed to the rise of meteorite studies and uniformitarian geology, respectively. Although they arose almost simultaneously, these two branches of science, one of which postulated the fall to Earth of solid bodies from space while the other endorsed only strictly endogenous processes acting upon the Earth, evolved separately over the next 200 years. This paper traces the long estrangement between mainstream geology and the science of meteorites. The two disciplines collided head-on in 1980 when a team of scientists headed by the physicist, Luis Alvarez, of the University of California, hypothesized that the massive extinctions at the end of the Cretaceous were triggered by the hypervelocity impact of a large body from space. Many geologists rejected outright such an exotic cause. More recently, as evidence has accumulated for the K-T impact as well as for many other crater-forming impacts, we are beginning to realize that unpredictable collisions have played a role of fundamental importance throughout the history of the solar system.
