Dark Side of The Moon

First of all, a great album. And more than being a figure of speech, the actual phenomenon of the moon’s dark side is pretty interesting. The moon is tidally locked — it’s orbital period (how long it takes for one thing to orbit another thing) matches its rotational period (the rate at which the moon rotates around its own axis). This is reason we only ever see one side of the moon during its 29 day orbit.