Moon's dark side not synonymous with far side
Comment Print Me Email to FriendTonight's Sky for Sunday, May 11 2008
As the moon, stars and planets pop out at nightfall tonight, look for the planets Mars and Saturn on opposite sides of the moon. We elaborate on today’s Earth & Sky radio show. (Outside the sky chart, Mars shines to the west – or right – of the moon, near the Gemini stars, Castor and Pollux.)
As seen from North America this evening, the moon reaches first quarter phase at 10:47 p.m. Central Time (11:47 Eastern Time; 9:47 Mountain Time; 8:47 p.m. Pacific Time). At this juncture, the lunar disk is half-illuminated in sunshine and half-engulfed in shadow. The first quarter moon well illustrates why the far side of the moon is not the same thing as the dark side of the moon.
The near side of the moon – the side that we see from Earth – is always half lit and half in darkness at quarter moon. But the moon’s far side – the half that we don’t see from Earth – is also half lit and half in darkness at quarter moon. In fact, the far side of the moon is only the dark side of the moon at full moon.
The terminator – the shadow line on the moon that divides day from night – shows you where it’s sunrise on the moon when the moon is waxing from new moon to full moon.
