dipper@utastro.UUCP (Debbie Byrd) (11/09/84)
In our universe, everything is always moving. We talk about the movement of rotation -- right after this. November 9 Rotation In our universe, everything moves -- or rotates -- spins on its axis usually slowly and ponderously -- but sometimes in a twinkling of an eye. A few tiny, ultra-compact stars whirl around once in only a matter of seconds -- or less. Other stars -- like our own sun -- take days, weeks or months to rotate once. And not just stars -- whole galaxies also rotate. When you consider the rotation of one of these vast systems of stars -- you can think of each individual star as a molecule in a single body. As the body-galaxy rotates, each star is in motion around the galactic center. The whole gigantic assembly spins on a timescale of hundreds of millions of years. So things rotate -- but why? To answer, think back to a time many billions of years ago, when the universe was in its infancy. All matter was an expanded gas. The galaxies coalesced from this gas -- and later also the stars. In each case, separate clouds pulled apart from the rest -- and the matter in these clouds was in motion. As gravity made the cloud collapse, each particle of matter moved faster -- just as a spinning skater moves faster when she draws in her arms. Eventually the clouds had collapsed to their current states. Each particle is still in motion -- only now much of that motion shows up as the rotation of galaxies and stars. If you could stand back from the universe, you would see everything engaged in its own particular cosmic dance. Script by Deborah Byrd. (c) Copyright 1983, 1984 McDonald Observatory, University of Texas at Austin