I subscribed to an online Page-A-Day calendar last year, and for Valentine’s, they gave me a code to subscribe to one for free this year. So I opted for the Fact or Crap calendar. Browsing January, I got the answer to a puzzlement:
Why do you see the whole moon even when it’s new? Y’know, you look up, see that bare line of a crescent, but can also make out the rest of the circle, the rest of the moon. Why isn’t the dark part completely invisible?
Earthshine, that’s why. Just like the moon, the Earth reflects sunlight, too – enough to let you make out the whole moon even when it’s dark. The strength of the earthshine depends on Earth’s cloud cover.
I knew the Earth reflected light, like the moon, if not as well; I just never realized that was why a new moon is visible.
UPDATE: There was a derailment in the comments; two trains of thought couldn’t stay on the same track. My American pop culture references do not extend to TV-series of the 1950’s so Mark had to explain, which he has done here.
A Roll in the Universe 
13 replies on “Oh, is that why!”
Thanks for the link, Keera. i just entered our dog in the calendar contest!
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Being a nerd in disguise, of course I knew this. Yet, I still cannot see that face everyone talks about – I suppose this part of my imagination is non-existent, but then how come I can make shapes of clouds?
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Cool, Mark! Let me know what happens!Tim, maybe you see the rabbit? Some cultures see a rabbit in the moon and not a face. Me, I see the man in the moon just fine, but not the rabbit.
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http://images.google.com/imgres?imgurl=http://ncsdweb.ncsd.k12.wy.us/planetarium/ART/maninmoon.jpg&imgrefurl=http://ncsdweb.ncsd.k12.wy.us/planetarium/manshow.html&h=265&w=247&sz=32&hl=en&start=3&tbnid=Lo4OZbtIoBc4tM:&tbnh=112&tbnw=104&prev=/images%3Fq%3DMan%2BIn%2BThe%2BMoon%26gbv%3D2%26svnum%3D10%26hl%3Den%26sa%3DGThat might help, Tim.
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Nope, no rabbit. I now finally see the face, though it reminds me more of a bowling ball . . . thanks, Mark. 😉
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The bowling ball has exaggerated the dark areas but at least it shows where to look. The rabbit is seen right side up when viewing the moon from the southern hemisphere. http://nzphoto.tripod.com/astro/index.htm#rabbitI still have trouble seeing it. The best picture I\’ve seen, was one taken during an eclipse but that site has disappeared.
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What I want to know is, where\’s Alice???
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Oh, that Alice. Couldn\’t figure what you wanted my friend of the 10,000 Monkeys and a Camera for.You can ask her when she\’s ten feet tall.
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NOOOO! Wrong Alice. Think about it. Think about how sweet it is…
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I must be dense today. This one went right over my head, too (as we say in Norway). I have no idea what you\’re talking about. I\’m assuming this all has to do with the moon.
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http://en.wikipedia.org/wiki/The_Honeymooners
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Oh, no wonder I didn\’t get it. I have never seen The Honeymooners.
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\”two trains of thought couldn\’t stay on the same track.\”Good damn thing. We probably avoided a horrendous head-on. :o)>
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