It’s the third night of Chanukah! So, to celebrate, here are eight facts about the earth and Moon:
1) There is no dark side of the moon. The moon is in a synchronous orbit with the earth, which means its rotates in the same amount of time as it takes to orbit. This is why the same side of the moon always faces the earth. The far side is not dark at all; it gets the same amount of sunlight as the near side—the side we see.
2) The earth is the only planet in the solar system with exactly one Moon, it’s the only big moon in the inner solar system, and that moon is the largest one relative to the size of its parent planet. It’s the fifth largest overall. Neptune’s moon Triton is the second largest moon relative to its parent planet.
3) Seen from the moon, the earth goes through the same set of phases that the moon does, but they’re opposite. For example, if the moon is in its waxing gibbous phase as seen from Earth, the earth is in its waning gibbous phase as seen from the moon.
4) Almost all of the famous photos of the Apollo 11 astronauts taken from the moon are of Buzz Aldrin. There’s only one full-body photo of Armstrong from the surface, and you can see it below (via NASA).
5) Even though the moon is the second brightest thing in the sky, after the sun, it only reflects about 7% of the sunlight that hits it. That’s only a little bit brighter than asphalt or black paint.
6) One of the biggest problems for the Apollo astronauts was the lunar dust, which covered their suits when they came back in from their moon walks. It is very fine, and very rough. It clung to equipment, jammed parts of their suits, which made it even harder to move in them, and got into their lungs. Plus, it smelled like gunpowder.
7) Three astronauts flew to the moon twice: Jim Lovell on Apollo 8 and Apollo 13; John Young on Apollo 10 and Apollo 16; and Gene Cernan on Apollo 10 and Apollo 17.
8) The moon’s pull is slowing the earth’s rotation by about 2 milliseconds every hundred years. The energy taken from the earth, in turn, speeds up the moon and moves it about an inch and a half farther away each year. As the moon drifts away, its pull on the earth will get weaker but it won’t escape. Given enough time, though, the earth would slow enough so that the two will be locked with the same sides facing each other, like Pluto and Charon are now. This will take about 50 billion years. By that time, though, the sun will have grown into a red giant, burned and consumed the earth and moon, and died. Um… Happy holidays!