02 January 2018

The far side of the moon is dark, but not in darkness

Photo taken from a spacecraft, showing the side away from the earth fully illuminated by the sun.

It's amazing how many people think the far side of the moon is in eternal darkness.

Via the Space subreddit, where the discussion thread includes these nuggets:
"I love how this photo shows how dull the moon really is. It's about as luminous as asphalt. It just looks so bright because it normally sits in an inky black sky." "The moon albedo is only 0.12, that is, only 12% of incident light gets reflected. Asphalt and coal have similar albedos." "The moon is one of the darkest (least reflective) bodies in the solar system. It just looks bright and white to us because it's so close."
There's also a discussion there about "tidal locking."


  1. When I was in junior high in the early 60's, the science teacher showed us (IIRC) a Disney film about a flight to the moon. They didn't land, just looped around it to take pictures. Of course, the "important" part was to take pictures of the "dark side". They dropped flares(!) to illuminate it and take the pictures.

    After the film was over, I asked the science teacher why they just didn't wait a couple of weeks so that it would be in the sun and they wouldn't need those flares; his answer was that it's the dark side. Duh!

  2. When photographing the moon, you can use the “sunny 16” rule for objects illuminated by bright sunlight, because that’s what it is. But it is necessary then to open up a couple of stops, to keep it from coming out a dull gray—because that also is what it is.

  3. it is not the 'dark side' of the moon. the moon rotates on its axis, but that rotation is synchronous rotation. to us, it seems to be standing still and always showing just the one face.

    https://www.space.com/24871-does-the-moon-rotate.html Does the Moon Rotate?

    https://www.youtube.com/watch?v=OZIB_leg75Q Synchronous Rotation of the Moon



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