dipper@utastro.UUCP (Debbie Byrd) (12/30/85)
Every one of us is a passenger on the Earth. We'll talk about where we're going -- when we come back. December 30 Passengers on the Earth Just for a moment, stop what you're doing and ask yourself -- how am I moving in space? Imagine yourself in a larger perspective, riding through space on the surface of a planet. The Earth travels in a year-long orbit around the sun, and you travel with it, as a passenger on the Earth. Earth also rotates, or spins like a top around a central axis. It takes you around with it once each day, so that your head points more or less toward the sun at noon and away from the sun at midnight. So you're traveling around the sun, and you're spinning once a day around the central axis of the Earth. But the sun has a motion through space, too, and it carries your planet and you along with it. The sun is one of billions of stars in our galaxy, which is called the Milky Way. And the galaxy also rotates. So the sun, like the Earth, orbits around a center, in this case the center of the galaxy. Unlike the Earth, though, one orbit for the sun takes much longer than a year. It takes about 250 million years so that only 20 such circuits of the galaxy have been made since the birth of the sun. What's more the galaxy itself moves through intergalactic space in ways that aren't completely known or understood. So when you think about how you're moving in space -- remember you're riding on a planet -- orbiting around a star -- orbiting the center of a galaxy -- in a universe that never stands still. Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin