Dennis Do herty, age 10, of Cape Elizabeth, Maine, for his question:
What makes the moon change?
The man in the moon is a changeable follow. At full moon he stares at the earth from a face as round as a penny. But night after night that round face shrinks. It becomes a half moon, and two weeks after the full moon we see the thin crescent of the old moon. The next night there seems to be no moon at all. Then the now moon appears, a pale thin crescent pointing the opposite way from the old moon. It takes the man in the moon just over 27 days to go through all his changes.
The golden moon seems first to peep, move around until his full face stares at the earth, then turns around glancing back over his shoulder. But this is not what happens at all. For the face of the man in the moon is always staring at the earth, whether we see it or not. Of course, it is not really a face and there is no real man in the moon. The staring eyes and wide open mouth are low, shadowy holes on the moon's landscape.
The moon is a round ball, but it never turns so that we can see the other side. The same face is always turned towards us. And we see only the part of this face which is bathed in sunshine. When the moon is full, the side facing us is all in sunshine. When we see a crescent moon, sunshine fads only on a thin strip along one side. The rest of the moon’s face is then in shadow, the shadow of night. And we cannot see it.
The earth has a day and night, and so does the moon. One day and night on earth lasts 24 hours because it takes the earth 24 hours to turn around once. It spins on its axis, like a top, and so does the moon. But the moon takes about 27 days to make one turn. One day and night on the moon lasts 27 days. A lunar day is about two weeks and a lunar night is about two weeks.
We see only half of the bier, round moon. We watch the dawn arise on one side. It grows and grows until in two woks our side of the moon is in full daylight. Then night begins to fall along‑one side. The full moon shrinks as the shadows of night creep across its face. When our side of the moon is dark, the opposite side is in sunshine.
The moon rides in a ring around and around the earth. This path is its orbit. Each journey around its orbit takes about 27 days. This is also the time it takes to turn on its axis. It also explains why the same side always faces the earth.
The sun is 93,005,000 miles away from the earth and the moon. It is always shining on half the earth and half the moon. As the moon goes around its orbit, it must pass between the earth and the sun. Then the side facing us is dark, the opposite side facing the sun is in daylight. You see no moon at all. Half way around the orbit, the earth is between the moon and the sun. The side facing us also faces the sun. We see the full moon.
The crescent moons and the half moon occur as the moon moves from dark moon to full moon. We see only the sunny part of the moon, but the big round face always stares at the earth, though some or all of it may be hidden in shadows.