Today the first quarter moon rises out of the east in the early afternoon. It will look like a half moon; the part of it we can’t see is in shadow – it’s still nighttime on the eastern half of the moon. Just as we experience day-lit and dark periods on earth, so the moon has both day and night. But the moon’s rotation is slow; a lunar day lasts two weeks, followed by two weeks of night. As the moon orbits the earth, its rotation speed as it spins on its axis matches its revolution about the earth, so it rotates once for every orbit. This is called a synchronous or tidal lock, an effect of the earth’s tidal pull on the moon, which has slowed down its rotation to be in synch with its revolution. Because of this we can see only one side of the moon, called lunar nearside; the far side of the moon (sometimes mistakenly called “the dark side,”) can never be seen from earth. Or as Pink Floyd tells us, there is no dark side of the moon; matter of fact, it’s all dark!