I was sad to hear of the recent passing of Umberto Eco, one of my favorite contemporary novelists. Due to his long career as a professor of “semiotics”, his novels drew on a wide variety of historical, mathematical, and scientific ideas from throughout the past millennium. One that I read relatively recently was “The Island of the Day Before”, his 1994 story of a soldier marooned during the 1600s, the historical period during which the governments of Europe were desperately searching for a reliable way to measure longitude. You may recall our discussion of this multi-century quest back in episode 108. The key plot twist is that the main character, an Italian soldier named Roberto Della Griva, gets marooned on a ship that is trapped within sight of the International Dateline, and an island which sits beyond it.
Della Griva attaches a mystical significance to this line, as is implied by the book’s title. He somehow convinces himself that if he could just cross it, it would mean he was traveling back in time. If he will manage to swim across the line tomorrow, would it mean that today he should see himself swimming in the distance? Here is one amusing passage from the book:
“Indeed, as he sees it distant not only in space but also (backwards) in time, from this moment on, whenever he mentions that distance, Roberto seems to confuse space and time, and he writes, "The bay, alas, is too yesterday," and ,"How much sea separates me from the day barely ended," and even, "Threatening rainclouds are coming from the Island, whereas today it is already clear . . . .”
While these speculations are rather absurd, this discussion got me curious about the actual history of the International Dateline. It has been recognized since ancient times that the time of day is slightly different as you travel to the east or west, but the idea that you might travel all the way around the world and gain or lose a day was only really conceivable in relatively recent eras of human history. The real history of the Dateline can probably be properly said to have started with Magellan’s circumnavigation of the globe. When the handful of survivors of that three-year voyage arrived home in 1522, they were surprised to discover that despite careful logging of their travels, they had lost a day. Here is a description from one of them:
On Wednesday, the ninth of July , we arrived at one these islands named Santiago, where we immediately sent the boat ashore to obtain provisions. [...] And we charged our men in the boat that, when they were ashore, they should ask what day it was. They were answered that to the Portuguese it was Thursday, at which they were much amazed, for to us it was Wednesday, and we knew not how we had fallen into error. For every day I, being always in health, had written down each day without any intermission. But, as we were told since, there had been no mistake, for we had always made our voyage westward and had returned to the same place of departure as the sun, wherefore the long voyage had brought the gain of twenty-four hours, as is clearly seen.
As you can see, even though they were caught by surprise at first, the sailors were able to quickly realize their fallacy. Because they were traveling in the same direction as the sun, they had experienced one less day, but each day they had experienced was slightly longer. So there was no actual time travel, just an accounting error. A similar phenomenon was observed later by other circumnavigators, such as English explorer Francis Drake. This incident also inspired the famous surprise ending of Jules Verne’s “Around the World in 80 Days”. Even though the reasons for the gain or loss of a day upon circumnavigation were well known, I suppose it is vaguely possible than an uneducated sailor like Eco’s character could have attached a more mystical significance to the effect.
But even these odd experiences of sailors were not really common enough to motivate standardization of time zones and an international dateline, until the era of trains came along in the 19th century. Suddenly it was possible to move quickly and continuously between areas with different local times. Finally in October 1884, representatives from 25 nations met at an international conference in Washington, DC, and came up with the system of time zones we know today, based on longitudinal lines starting from the Greenwich meridian, and times derived by adding or subtracting from the Greenwich Mean Time, or GMT. To increase the chances of universal adoption, it was agreed that local islands and nations can move the timelines for convenience, which is why we see those squiggly time zone boundaries today instead of simple longitudinal lines. Amusingly, the French seemed to be insulted by the idea of a location in England defining the time zones: until 1911, instead of referring to Greenwich Mean Time, they referred to Paris Mean Time minus nine minutes and 21 seconds, which was equivalent.
Unfortunately, since these meridians and zones are all artificial labels, I’m afraid Della Griva’s dream of somehow using them for time travel would never quite pan out. Some modern writers ponder this idea as well, but I think they are mostly tongue-in-cheek. For example, travel author Bill Bryson has written:
“I left Los Angeles on January 3 and arrived in Sydney fourteen hours later on January 5. For me there was no January 4. None at all. Where it went exactly I couldn’t tell you. All I know is that for one twenty-four-hour period in the history of earth, it appears I had no being. I find it a little uncanny, to say the least. I mean to say, if you were browsing through your ticket folder and you saw a notice that said, ‘Passengers are advised that on some crossings twenty-four-hour loss of existence may occur’…, you would probably get up and make inquiries, grab a sleeve, and say, ‘Excuse me.’”
But somehow I don’t think Bryson really believes he lost a day of his life due to the shifting of a few time labels. I would be more concerned about the portion of my existence that is wasted while crammed into a tiny airline seat for half a day.
In a more serious vein, there was a solar eclipse last month that started on March 9 and ended on March 8, but it was actually traveling forward in time the whole way, although it achieved its peculiar timeline by crossing the International Dateline as it travelled. Also, you shouldn’t completely lose hope— one form of time travel across the dateline is possible. Remember that under the theory of relativity, if you travel by airplane at a high speed, you really do lose a tiny fraction of a second, as time slows down for you in relation to your friends on the ground. However, that works across any line, not just one artificial one.
And this has been your math mutation for today.
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