The total lunar eclipse last Sunday night (Jan. 20) sent me to visualizing how the changing aspects of the Moon are matched by how the Earth looks from the Moon, but in reverse. When the Moon is full and at its brightest, the Earth is new and darkest - except during a total lunar eclipse when the Moon is darkened as well!
That of course is when the Moon plunges into the dark umbra shadow of the Earth, and is cast into a shade of red or orange, its hue and depth varying from eclipse to eclipse. Did you get to see the eclipse?
It was really cold out there as seen from northeastern Pennsylvania, feeling below zero with the wind chill. Still, it was a grand sight to peek between my head scarves and hood, at the narrowing, bright crescent of moonlight until the Moon was orange like an apricot.
We often hear about the “dark side of the Moon” meaning the side turned away from Earth. Actually, only at full Moon is the far side almost completely dark, facing only the stars without the Earth or Sun in the lunar sky.
I said “almost” completely dark because it may be surprising how much light comes from the brightest area of the Milky Way, the part in the direction of constellations Sagittarius and Scorpius, looking towards the galaxy’s central hub.
The near side of the Moon, facing us, is much brighter, even when the Moon is at new phase, with the Sun behind it (directly behind it during a total solar eclipse). The Moon’s near side is then bathed in “earthshine,” which is sunlight reflecting off the full face of the Earth.
You can readily see earthshine when the Moon is a slim crescent, in the twilight sky. It’s a beautiful sight in binoculars.
When the Moon is a crescent, the Earth is in gibbous phase, appearing more like a football than a baseball. There is a corresponding slice of Earth on one side in darkness.
Similarly, when the Moon appears gibbous, the Earth, from the Moon, is a crescent.
When the Moon is at last quarter phase (which it is on Jan. 27), halfway from full Moon to new Moon, the left half of the Moon (as seen from northern latitudes) is shining in the sunlight. From the Moon, the Earth is also in quarter phase, with the right half lit up.
The night portion of the Earth is also never fully dark; the moonlight reflects off the land, clouds and seas. This “moonshine” is what you see when the bright Moon is up and illuminates the rural landscape. It’s not nearly as bright as earthshine would be for as astronaut on the lunar surface.
Remember, the Earth is approximately four times bigger than the Moon. Imagine four full moons, end to end.
China made history, Jan. 3, 2019, when its unmanned probe, Chang’e 4, successfully made soft landing on the far side of the Moon. The mission includes a rover vehicle and an experiment to grow plants in an enclosed chamber, an important study for long term human space voyages. A satellite has to relay the signals from the lander to the Earth since the Earth is out of view.
The Russians were the first to loop around the Moon in 1959, when Luna 3 sent back historic but grainy far side pictures. Twenty-seven human beings, to date, have seen the far side. All were Americans abroad nine Apollo missions that orbited the Moon (1968-1972). Six of the missions also landed.
Did you know, the far side does NOT include 50% of the Moon? In fact, only 41% of the entire lunar globe is forever turned away from us. That’s because the Moon has wobbles as it orbits the Earth. Known as “libration,” the effect is as much as 59% of the Moon can be viewed from Earth, over time.
The far side of the Moon is quite different from the near side, as it almost completely lacks the dark lava plains called “maria” that make up the familiar “Man in the Moon” pattern. Indeed, the far side, one can muse, is the back of the head of the Man of the Moon so of course it lacks a “face”!
Keep looking up!
Peter Becker is Managing Editor at The News Eagle in Hawley, PA. Notes are welcome at email@example.com. Please mention in what newspaper or web site you read this column.