RISING MOON
The jagged shadow land
TOWERING TURRETS and chains of pointy peaks span the day-night divide of the First Quarter Moon on March 29. The parade of rugged crater walls continues night after night. In the north, the large, round, undulating Sea of Serenity suddenly gives way to a huge arc of mountains: the outer ring of the Mare Imbrium basin.
The massive impact threw out an incredible amount of material, much of which was subsequently buried when lava floods erupted through the cracked floors. You can see a load of excavated terrain chaotically dumped just on the southeast side of the grand Apennine chain.
Inside the arc lies the attractive oval form of Archimedes. Farther north, in the multiringed Mare Imbrium, look for the remains of an inner wall: It’s the large number of isolated yet grouped peaks sprouting out of this Sea of Rains. The long daggers of darkness knifing westward into the terminator shorten with each passing hour of observation and almost disappear in a couple of nights more.
Relive the shadows on April 27. Acting as a canvas, the smooth floor of Archimedes displays the remarkable saw-toothed shadows of the crater rim. But it’s all trickery due to the low-angle light from the Sun, which exaggerates apparent height.
At the next sunrise or sunset around your home, try finding a smooth garden wall or guardrail:
The low-angle light will cast a shadow that makes them appear covered with dangerous spikes.
Reversed light occurs on the 13th. If you’re up at 6 A.M., take in the black teeth biting eastward across the lunar soil.