We talk about sunrises and sunsets, despite it being the Earth, not the sun, that is moving. The misnomer aside, this pattern has a profound effect on us. A day is twenty-four hours because that’s the time it takes for the Earth to rotate on its axis once. Our biology, our circadian rhythms, link us to the way we move in space. For most of our history we had no clocks and no calendars, but we always had night and day. There is something profound about doing something, anything, to mark this rotation. And far and wide, we have.
