The Curious History of Time

We all know there are 24 hours in a day, but would you be surprised to learn that wasn't always the case? We know the Earth rotates on its axis one full turn in approximately the time span we define as a day, but who decided to divide the day into 24 equal increments of 60 minutes? According to this University of Cambridge article by Leo Rogers, hours did not have a fixed length until the second century B.C. when Greek astronomer and mathematician Hipparchus proposed dividing the day into 24 hours. (He is also considered the "Father of Trigonometry," so now you know who to blame for that.)

However, people continued using hours of varying length for centuries, based on the varying length of daylight in a season. It wasn't until the 14th century that mechanical clocks were invented and time as we know it was 'created'. Medieval European towns began building large astronomical clocks like the one in Prague's Old Town that dates from 1410. This clock not only tells time, but also has a series of mechanical figures - from a skeleton to the apostles - who appear on the hour. The skeleton represents death and rings the hour. The apostles engage in an hourly parade. The clock also shows the positions of the sun and moon in the sky. Cool, huh?

However, most people still didn't 'tell time' like we do today. According to the National Museum of American History, the almanac was the main tool used to mark time in the 18th century. Very few people had clocks, but everyone was attuned to the movement of the sun across the sky. Time was local, based on the rise and set of the sun in any given location. In the early 19th century, the possession of a clock became a status symbol (different in appearance but similar in function and status to an Apple watch). A head-on train crash in 1853 stressed the need for accurate and shared timekeeping.

The Creation of Time Zones

The railroads made the first attempt at creating 'standard time,' but had well over 50 time zones that were hard to coordinate. In 1884, Sandford Fleming, a Scottish-Canadian railroad engineer proposed worldwide standard time zones, the choosing of a prime meridian, and use of a 24-hour world clock. Thus, Universal Time (UT) was created. Time is eternal, but time as we mark it is less than 150 years old.

The starting point for tracking time was chosen arbitrarily. Twenty-five nations met in Washington, D.C. to make the decision: Greenwich, England was selected as the Prime Meridian with the designation of Longitude 0º. From there, the earth was divided into 24 lines of latitude spaced equally apart, into one hour time zones. However, as you can see in the graphic below, some states, nations, and islands choose to alter the lines. Who wants to be in a different time zone than their next door neighbor?

Travel Time

Now let's get to the fun part: How does time affect international travel? Most of us realize that other countries lie in different time zones. After all, we have three time zones in the U.S. (Russia has eleven, fyi.) When traveling, we research our destination to discover how many hours ahead or behind they are relative to us. The International Dateline runs halfway around the world (180º away) from the Prime Meridian. It runs through the Pacific Ocean so it's pretty hard to straddle Monday and Tuesday for a selfie.

This is important to realize when looking at flight times as well. For example, my upcoming flight departs from Philadelphia at 10:45 p.m. and arrives in London at 10:45 a.m. This does not mean it's a 12-hour flight; England is five hours ahead of the East Coast, so it's a mere seven hour journey. I'm not even going to attempt to explain Daylight Savings Time, but keep in mind: 1) not all places observe DST and 2) even if they do, they might not change their clocks on the same day we do.

Image courtesy of physioinq

Traveling across time zones causes the well-known phenomenon of jet lag. According to the CDC, jet lag is caused by "a mismatch between a person’s normal daily rhythms and a new time zone...when you travel across more than three time zones." They recommend adjusting your sleep hours before your departure, arriving two days in advance of scheduled events, avoiding alcohol, and eating small meals. I don't do any of those things: I just self-regulate with Tylenol PM and caffeine/energy drinks. Of course, you're welcome to try it the healthy way.

The good news is that jet lag only occurs when traveling eastward or westward (and it's easier on your body to travel west than east.) Do note that a flight from New York to Paris will be shorter than a flight from Paris to New York due to headwinds. It takes longer to fly west. You can travel as many hours as you'd like North-South without jet lag. More good news is that our phones are now smart enough to know where we are and what time it is there. No more winding back the watch.

The Future is Calling 

I am fascinated by time on long haul flights. Once I boarded a plane in Texas on a Monday and landed 16 hours later in Australia on a Wednesday. I have given much thought to that missing Tuesday. Did I pass through it quickly or miss it altogether? On the way home from Australia, I departed on a Friday morning and arrived home 36 hours later on the same Friday evening. Somehow that doesn't bother me as much as the missing Tuesday.

One of my favorite things to do while traveling is to call my family from the future. It never ceases to amuse me to call home from China or New Zealand. Here's a typical conversation:

"This is your mother calling from the future!"

"Hi mom." (I can hear the eye rolling.)

"It's Thursday here!" I exclaim. "What day is it there?"

"You know it's Wednesday here," they grumble.

"How's the past?"

"Great. Want to talk to Dad?"

Maybe it's not as exciting as 'real' time travel, which apparently has been proven to be mathematically possible, but I get a kick out of it.