dipper@utastro.UUCP (Debbie Byrd) (03/29/85)
Tonight's first quarter moon has half its day side and half its night side facing in our direction. More -- after this. March 29 Day and Night on the Moon The moon is at first quarter today. It shows a face toward Earth that's precisely half-illuminated. Of course, one complete half of the moon is always illuminated by the sun. Tonight, the first quarter moon shows us half of that lighted half -- or a quarter of the whole moon. Half the moon's dark side also faces us tonight. But, against the dark sky background, we can't see it very easily. The lighted half of the moon is called its day side -- and the dark half is called the night side. On Earth, the cycle of day and night takes 24 hours. That's how long Earth takes to rotate once on its axis. But the moon rotates only once a month. Its day and night each lasts two weeks. As you look at the first quarter moon tonight, remember that it's really facing half its day side and half of its harder-to-see night side in our direction. Surface temperatures on the day side soar to about 220 degrees Fahrenheit, slightly higher than the boiling point of water. Meanwhile, on the night side of the moon, surface temperatures plunge to about 250 degrees below zero. With no lunar atmosphere to absorb heat, a shadow on the moon is treacherous. On the sizzling day side, within the boundaries of a shadow cast by an overhanging rock, temperatures drop to nearly as low as on the moon's night side. If you stood still on the moon with your left foot in sunlight and your right foot in shadow, after awhile your left foot would be broiling, and your right foot freezing. Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin