dipper@utastro.UUCP (Debbie Byrd) (01/13/85)
The last quarter moon can point you in the direction of Earth's movement in orbit around the sun. More -- after this. January 13 The Last Quarter Moon The moon can help you take a mental journey. It can help you imagine the direction that Earth moves in its orbit around the sun. The best time to use the moon in this way is when it's at last quarter -- which it will be Sunday night. The last quarter moon rises around midnight -- and will be high in the south at dawn on Monday. It looks half illuminated -- like half a pie. If you get up early Monday, and look toward the last quarter moon, you'll also be looking in the direction that Earth moves around the sun. In other words, you'll be standing there looking up at the moon. And the sun will be near the horizon, just risen or about to rise. Take a moment to imagine the moon in orbit around the Earth -- and the Earth/moon system in orbit around the sun. When the moon's at last quarter, it's located approximately in Earth's orbital path, in the direction of forward motion. So, at dawn, Earth's motion in orbit is carrying you toward the place where the moon is. If the moon weren't moving, too, if we could somehow anchor it to the spot where we see it at dawn, Earth would reach the moon in a very small amount of time. Earth hurtles through its orbit at about 18 miles per second, and the moon is only about 250 thousand miles away from Earth., We can't anchor the moon -- but, if we could, we'd reach it only about three and a half hours. Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin