Shannon Borges, age 10, of Visalia, California,for his question:

Could the lunar astronauts see the earth rotating?

Standing on our side of the moon, the earth is seen as a huge and magnificent object in the lunar skies. It hangs there in a fixed position, 13 times bigger than the moon appears in our skies. Its beauty is breath taking and its major features of lands, seas and drifting clouds can be seen clearly. The lunar astronauts also saw our great, big beauteous globe rotating on its axis. Every 24 hours, they saw daylight and darkness creep across its surface. From the moon, every 24 hours the earth goes through changing phases, like the changing phases of the moon.

From the far side of the moon, astronauts could not see the earth rotating through its phases. That side is forever turned away from us and the earth cannot be seen at all. But from the side facing us, the rotating earth provides a reliable clock, marking off each earth day.