Telling Time
Since prehistoric days, humans have measured time by watching the arc of the Sun across the horizon. Ancient Egyptians used shadow-clocks to show the Sun’s movement during the day, while at night, they tracked the stars using sophisticated charts such as the Ramesside Star Clock. By the time of the Ancient Greeks, sundials, waterclocks and sand-timers provided more accuracy. But – perhaps strangely to us – timekeeping still mirrored the changeable seasons, so, during the Roman Empire, an hour was longer (about 75 minutes) in the summer than in the winter (45 minutes) because there was more daylight in June than December. Even then, these figures weren’t set in stone. The standardized 60-minute hour only arrived in the 14th century, possibly thanks to Arab scientist Ibn Al-Shatir, who calibrated his sundial to the Earth’s polar axis.