John Harrison and the Solution to the Longitude Problem

To grandmother’s house I go—eventually. I’m not sure how this happened, but once again, I’m lost. I’m quite certain that I’m going the wrong way. I don’t doubt that I’m not where I’m supposed to be, but I have no idea where I am.

I’m not surprised. In fact, I’ve planned to be lost—I always do on road trips. I’ve been lost on the road, lost in translation, and lost in my thoughts, but I’ve never been lost at sea.

In the interest of full disclosure, I should mention that I’ve never been to sea, but that is entirely beside the point. I’ve also never been an early 18th century mariner, and that is very much nearer to the point. The point is longitude.

Longitude is, of course, the complement to latitude and is used to measure an object’s distance east or west of the prime meridian, which is currently placed at Greenwich, England.

Although the prime meridian is the zero point for longitude, its position—unlike that of the equator, the equivalent point for latitude—is completely arbitrary. Feel free to choose your own for private use—just don’t become a cartographer. Seriously, that would be monumentally impolite.

Impolite as it may be, various people, Ptolemy arguably the most famous, have taken it upon themselves to select a prime meridian for the rest of us (Ptolemy’s was in the Canary islands).

For most of human history, it was impossible to accurately measure longitude at sea. The “longitude problem,” as it came to be known, was a complicated one. So complicated, in fact, that King George I of Britain formed a Board of Longitude composed of A-List scientists, sailors, and other notables to issue a £20,000 prize to anyone who could find a way to measure longitude within half a degree of a great circle. Half a degree of longitude is equivalent to 34 miles of lateral distance at the equator.

As of this writing, £20,000 in 1714 is equivalent to about $1,000,000 (I’m not an economist; any economists out there who take issue with my estimate are free to leave angry comments). The board also offered second and third place prizes for slightly less accurate solutions.

The solution to the “longitude problem” depended upon knowing local time on a ship in relation to a home port. One hour of time difference is equivalent to 15 degrees longitude, so the center of the central time zone, which is six hours behind Greenwich Mean Time, is separated from Greenwich by 80 degrees of longitude.

Serious contenders for the prize were divided into two camps: astronomers and clockmakers.

Article Author: Brian Burns

Brian Burns is a Professional Writing student at the University of Oklahoma. In the summer, he lives with his family in Fort Worth, Texas.

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