Feeling groggy? Is your circadian rhythm off? Wouldn’t be surprising since many of us just readjusted our clocks again during our civilization’s dance with daylight. From the beginning we’ve organized our days by watching the sun’s movement and by noting how shadows shortened and lengthened. Early Mediterranean cultures divided daylight into 12 hours, or 12 divisions on the arc of a sundial. The length of the hour there varied according to the season. In the winter, an hour could be as short as 45 minutes. In the summer, it could be as long as 75 minutes. Days lengthening and shortening […]