There are relatively few big ideas that have changed our concept of the universe. Examples include the atomic theory and the theory of evolution. Another is the concept of uniformitarianism. Put forth by Hutton and made respectable by Lyell, the concept holds that the same processes at work today were responsible for the shaping of the past. Thus rather than great mountains being raised overnight, they arose by intermittent earthquakes lifting them by inches or feet at a time. Rather than miles-deep sediments laid down in a single, great, world-wide flood, everyday erosion deposited them over long periods of time.
As often is the case with new ideas, Lyell went a bit overboard and
tended to insist that these processes had to occur at the same rates as today. Now we
know that rates vary with a number of conditions and that occasional severe events fit
with uniformitarianism, but were unanticipated by Lyell because they're so widely
scattered through time. Thus asteroid impacts had no part in early thinking, but are
very much on the mind of modern scientists.
Listen to the Audio (mp3 format) as recorded by KTEP, Public Radio for the Southwest.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
Asteroid Ida and its moon, photographed by the spaceship Galileo from a distance of 6,755 miles. The asteroid is about 35 miles long, and its moon has a diameter of about 1 mile. Photograph courtesy of NASA.