Tropics, Zones, and Meridian Lines?"
So the Bellman would cry: and the crew would reply
"They are merely conventional signs!"
--Lewis Carroll, The Hunting of the Snark
While in Greenwich last week, attending a concert of only minimal interest to me, I was conscious that I was sitting upon -- or very near to -- the "prime meridian." The British Empire, in all its narcissistic glory, determined in 1851 that longitude at any point across the entire earth should be determined with respect to its rotational distance from Greenwich, a suburban area of London that happened to have the Royal Observatory.
On a prior visit to London, sometime in the distant past, I had visited the observatory, and had enjoyed the pleasure of stepping back and forth between the Western Hemisphere and the Eastern Hemisphere, between Longitude West and Longitude East. I was eager to learn my longitude, east or west, while sitting at the concert, and knew that it was possible to determine it from my iPhone, but -- alas! -- was unable to locate the proper app to make the determination.
Only a day or so later did I discover that the longitude and latitude are to be found on the Compass app -- or, more precisely, on my phone, on the Compass sub-app within the "Extras" app.
I at least can tell you that my present longitude and latitude, as I type this post, are Latitude 47° 38' 7" North, Longitude 122° 18' 1" West. How much fun it would have been to walk a few steps and watch my phone as my longitude switched from 1" East to 1" West.
Right? Such are the joys of nerd-dom.
I am reminded of all this as I read Eric Newby's account of his 1938 apprenticeship, at age 18, on a steel-hulled, four-masted sailing ship, carrying ballast from Belfast to Australia, in preparation for a return trip with a hold full of Aussi grain. The book, The Last Grain Race, was Newby's first book, and is a finely told record of a form of commercial shipping that ended with World War II.
The book is full of technical data that are now, sadly, of only historical interest. But among the data, the constant recording of latitude and longitude, as read from the ship's navigational instruments, speaks the same language that we speak today. Newby's narrative is full of reports such as
The upper topgallants and the mainsail were reset and by midday we were in 36° 39' 3" S, 14° 15' 1" W, having made 320 miles by log in the 24 hours.
The overall effect is fascinating; the repeated details perhaps less so. We sympathize with certain of the crew whose navigational skills were minimal, or even based on fantasy. Such as Yonny Valker, who maintained, despite all argument to the contrary, that longitudinal lines did not meet at the poles; in fact, he maintained, they were strictly parallel and met nowhere. As proof, he offered a Mercator projection of the world map, showing parallel longitudinal lines disappearing into space off the map. When told that, if he believed that longitudinal lines were parallel, he must believe that the world is flat, "Yonny looked cunning but did not answer."
Nor would he agree with Caroll's crew of the Snark that longitude and latitude were merely conventional signs.
Yonny. You do understand that the lines of latitude and longitude aren't real, don't you? That they're only on maps?
"Yeth they are," said Yonny with absolute finality. "They are real. AND THEY NEVER MEET."
The Last Grain Race is a fascinating narrative of a time not so long ago, but still very much over, when men sailed great ships, a narrative told with skill and humor by the writer who later described his mountain climbing adventures in A Short Walk in the Hindu Kush (which I discussed in July 2011).
In conclusion, I just re-checked my latitude and longitude on my phone. The latitude is constant. The longitude has moved to 122° 17' 60" W. Either the tectonic plates have shifted beneath my seat, even as I type, or my iPhone app isn't infallible. In either case, this bizarre discrepancy does not support Yonny's view of reality.
Longitude lines are just "conventional signs." And they do meet at the poles.
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