dipper@utastro.UUCP (Debbie Byrd) (08/18/85)
The farther away you look in space, the deeper you are looking into the past. More -- after this. August 18 A Time Machine With your eyes, you possess a time machine. Look out into space any clear night -- and you are looking back in time. The light you'll see from the stars tonight has been traveling toward us for hundreds or even thousands of years. Not that light travels slowly. In fact, light is the fastest moving stuff in our universe -- it whips along at a speed of 186 thousand miles per second. If you could move at the speed of light, you could circle the Earth seven times in one second. A trip to the moon and back would take just three seconds. And the sun -- ninety three million miles away -- could be reached in about eight minutes. Astronomical distances can be measured in terms of light travel time. In one year, a beam of light travels six trillion miles -- one light-year. The next nearest star beyond our sun -- in the star system Alpha Centauri -- is about four light-years away. Most of the stars visible to the naked eye are tens or hundreds or thousands of light-years away. With the largest telescopes, astronomers can study objects at distances of billions of light-years. Light from these objects began its journey when the universe was young. So when we look billions of light-years away, we see objects not as they are now -- but as they were billions of years ago -- before our own sun was born. With the "time machine" of their eyes and instruments, astronomers can study the processes which shaped our universe in its early history. Script by Wayne Wyrick. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin