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 was a slow annual process to which bodies could easily adapt.
Back then, coordinating time with your neighbor was straightforward as long as your sundials had the same orientation. Even when more advanced timekeeping pieces came along, they would be recalibrated using sundials. Wherever you went in the world, time continued to be local.
When the steam engine appeared and allowed people to travel faster than the sun’s progress across the sky, time coordination became a problem that needed solving. If you left Chicago by train at 1pm and spent two hours traveling, you should expect to arrive at your destination at 3pm. But if you traveled west, you would often arrive earlier than 3pm. And if you traveled east, you would often arrive later. The clocks in those destinations were set to their local time, and local time across continents varies, as does the position of the sun at any given instance. At Chicago’s latitude, there is one hour difference according to the sundial every 800 or so miles you travel east or west. Einstein’s realization that time is relative depending upon an observer’s location and speed percolated as he pondered the phenomenom of train travel.
Coordinating time between distant points has become a fixation as civilization enters the era of globalization. Whose clock will set the standard? How can we be sure all our clocks are coordinated? If someone in New York has a zoom call with someone in Australia, their clocks must be synchronized even though they are on opposite sides of the earth (and their sundials are way out of sync). We rely on our computer networks to maintain this coordination.
Computers communicate with each other electromagnetically, almost at the speed of light. But variations in hardware and programming prevent their clocks from easily syncing. Computer programs rely on a set sequence of events. If we’re trying to have a video conference, or execute a stock trade, or hold choir practice remotely, or play Fortnite with our neighbors, our computer clocks need to be synchronized. Time coordination is still a dilemma for civilization, even these days.
We probably won’t be going back to sundials any time soon, but taking a vacation and unplugging from work and play this week might help us ease our corporeal selves through the daylight saving time shift.