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Ephemeris: 04/16/2026 – The Moon’s Far Side isn’t dark!

April 17, 2026 Leave a comment

This is Bob Moler with Ephemeris for Friday, April 17th. Today the Sun will be up for 13 hours and 35 minutes, setting at 8:30, and it will rise tomorrow at 6:53. The Moon is new today, and won’t be visible.

When I hear discussions about the Artemis 2 missions, some people who ought to know better still refer to the far side of the moon as the dark side. Officially we have the two faces of the moon: the near side and the far side. I’ll even accept front side and back side. Until 1959 no one had ever seen the far side of the moon so it was dark, in the sense that we could not see it. Not dark because of the lack of light. I’ve been thinking about it. The far side sees more light from the sun, so maybe we should call it the bright side. It certainly has fewer maria or seas, those dark patches that we see on the near side of the Moon. There’s only one on the far side, it’s called the Moscow Sea since the Russian spotted first. Mare Orientale, subject of much study by the Artemis 2 crew, straddles the near side-far side line. It’s closer to the sun when it’s fully illuminated than the near side by about half a million miles, and it doesn’t suffer solar eclipses to darken it like the near side, being already in night, like it always is, at full moon.

The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.

Addendum

Photograph of the crescent Earth setting behind the limb of the Moon by the Artemis 2 crew.
The far side may seem to be the dark side in this photograph of earthset by the Artemis 2 crew. It is as bright as the brightest parts of the near side. These are the crater filled highlands, so it is the exact same brightness as the highlands on the near side. And indeed in traveling to the Moon, when it was seen half near side and half far side, there was no difference in the brightness of the highlands between the two. So the moon is really dark gray in brightness, on average. It reflects something like 12% of the sunlight it receives, while the earth is more than twice that reflectance. Astronomers call that quantity albedo. So the Moon has an albedo of 12% while the Earth has an albedo of something like 29% on average. So the reason the full moon is so bright at night is due to lack of competition from something that’s actually much whiter. Credit: NASA/ESA/CSA -The Artemis 2 crew.
Categories: Astronomical fact, The Moon Tags: ,