dipper@utastro.UUCP (Debbie Byrd) (09/30/84)
Today's new moon is special for two reasons. We'll tell you about them -- right after this. September 24 New Moon Some observers on the east coast Monday morning may have tried to glimpse a very old moon. That's a moon about to disappear into the glare of dawn -- on its way to becoming a new moon, located directly between the Earth and sun. Monday morning's crescent moon was only 17 hours away from new moon, for observers on the east coast. The moon would have risen later as seen from the west coast -- from there, just before dawn on Monday, it would have be only about 14 hours from new. So this particular moon may have been glimpsed by careful observers as an incredibly slim crescent, seen just before sunrise. It's special for that good timing -- and also for being new -- or between the Earth and sun -- on the same day that the moon reaches perigee -- its closest point in orbit to the Earth. A new moon at perigee can create unusually high ocean tides, which are sometimes called spring tides. The moon's gravitational pull causes the tides -- and its pull is even stronger at new or full moon, when the sun, Earth and moon make a line in space. The reason is that now the gravity of the sun and moon reinforce each other. Add that to the fact that the moon is now closest to the Earth -- and you have the reason for some unusually high "spring" tides. By the way, in this case the word spring has nothing to do with the season. It comes from an ancient verb springen, meaning "to leap up." Script by Deborah Byrd. (c) Copyright 1983, 1984 McDonald Observatory, University of Texas at Austin