Around The World In 79 Days

 

Norene and I are toying with the idea of a trans-Pacific cruise next year, Seattle to Australia/New Zealand.  If we go, we will cross both the Equator and the International Date Line and this got me to thinking — always a dangerous situation.

In Jules Verne's Around The World In 80 Days, the plot twist hinges on the fact that Phileas Fogg travels eastward from London.  As a result, each day's sunset is a little earlier than yesterday's.  In the days before time zones, local time was established by local noon, and it was customary for travelers to set their timepieces to that local standard.  When in Rome...

Because each of Fogg's 'days' was shorter than the canonical 24-hours, he actually arrives back in London a full day ahead of his deadline — but doesn't realize it because he has seen 80 sunsets (in 79 days), although, realistically, when he got to San Francisco, he must certainly have wondered why Thursday's newspaper was being published on Friday...

(Aside: the phenomenon is said to have been discovered by the 17th-century Norwegian explorer, Andersrag, who named it after himself: the Alex Andersrag Time Band...)

In the modern world, we accept that crossing the International Date Line west-to-east involves crossing into yesterday, and crossing east-to-west into tomorrow.  Why should this be so?  Let's perform a little thought-experiment:

We start with two observers in London at 8am on a Tuesday, both with clocks set to GMT and we send both on a high-speed trip (able to cross vast distances in the wink of an eye), one westward to American Samoa, and the other eastward to Tonga.  They are instructed to change their clocks backward or forward as appropriate for the time zone they're currently in.  The one traveling eastward to Tonga will constantly set the clock forward from 8am to 9am to 10am until arriving at Tonga 12 time zones later at 8pm Tuesday.  The other travels west to American Samoa inching his clock backward to 7am and 6am until arriving in American Samoa 11 time zones earlier at 9pm Monday.  At this point, the two observers are a (reasonably) short flight from each other and their clocks say different days.  One of them must be wrong, right?  No, they're both right.

They're both right because neither has crossed the date line.  If the observer in American Samoa travels to meet his partner at Tonga, he will be forced (by convention) to adjust his clock from 'Monday' to 'Tuesday'.  If the observer at Tonga travels to American Samoa, he will be forced to adjust his clock from 'Tuesday' to 'Monday'.  This is what Phileas Fogg didn't realize: at some point during the trip, convention says he stepped across the line from Tuesday into Monday.  Of course, we all know how that worked out: he realizes his error just in time to complete the trip according to the wager he made 80 days prior.

(If we go on that cruise, we will 'lose' a day just after leaving American Samoa — then gain it back and lose it again as the ship weaves back and forth across the line — and not get it back until we return to the U.S. at the end of the cruise.)