'Dark side' is really a misnomer. The entire moon experiences daylight and night time, just as earth does. However, a full day (analogous to earth's 24 hour day) is an entire lunar cycle long on the moon. The side of the moon that faces away from earth might be more properly called the 'far side'.Many believe that the moon does not turn on its axis, but this is a completely geocentric (and inaccurate) assumption. It is not unlike the belief of centuries past that the sun, moon, planets and stars must orbit around earth; after all, that is how it appears.In order for the same face of the moon to orient toward earth all of the time, while the moon orbits around the earth, then the moon must turn on its axis exactly once for every orbit that the moon makes around earth.It was named the 'Dark side' because until the Luna 3 probe in 1959 nothing was known about it. (Dark being used as meaning 'unseeable' or 'mysterious') Now days it is more commonly known as the Far Side.