Last week, after taking a few moments to praise an astute employee of Perry County and lambaste the state of Montana for its alleged role in stealing Shermans Creek, I wrote about the history of latitude and longitude.
Actually, I only got as far as latitude before I ran out of space.
I mentioned that latitude — one’s distance north or south of the Equator — is fairly easy to find, using even pretty crude tools. By way of explaining the relationship of latitude to the earth’s axis of rotation, I made a somewhat grotesque analogy involving an obese bureaucrat, a spinning desk chair, and a gloomy overhead fluorescent light. I may have used the phrase “horizon of blubber.”
Not that I’m apologizing.
If you missed out on last week’s exciting installment, I cordially invite you to the “My Op-Eds” area of www.matthewolshan.com.
Latitude, as I explained, was pretty well understood by the so-called Age of Discovery. Christopher Columbus would have used latitude to help estimate his position.
Longitude, on the other hand, is much harder to determine. The problem of longitude was so great that for centuries, even to try to find it was considered the act of a fool or madman. By 1714, ignorance of longitude was such a constraint on maritime trade – not to mention international exploration – that an Act of Parliament was passed in England establishing a prize of £20,000, the equivalent of about $3.5 million today, for any practical method that would provide longitude within half a degree of accuracy.
Prizes to stimulate technical innovation often work quite well. They’re still in common use. Think of the recent Ansari X Prize, which awarded $10 million to the first team that could send a privately built rocket to the edge of space and back.
The quest for longitude was the space race of its day. Nations were competing to be master of the seas. The might, wealth, and talent of England were brought to bear on the longitude problem. No less a scientific celebrity than Sir Isaac Newton was asked to help judge the contest.
The main challenge was that longitude is based on a measurement of time. It’s useful to think of longitude in terms of time zones. Modern time zones divide the earth into segments, like sections of an orange. As you move east or west, you move into a new time zone. If it’s noon in Landisburg, I know that it’s 9AM in San Francisco. Those three hours in time difference correspond to a distance of about 2,750 miles.
Longitude works along very similar lines. All you need to know to determine your longitude are two crucial times: the time of day where you happen to be; and the time of day at that very moment in the port you departed from.
Knowing the time of day where you are is fairly easy. You can always ask someone. Or consult a local clock. Or calculate it yourself the old-fashioned way, using the position of the sun or the stars.
The hard part, the part that stumped mariners for hundreds of years, was knowing the time of day back at their home port, after they’d been at sea for a week, or a month, or a year.
Remember: this is the early 18th century. It’s not like you can just pick up the satellite phone, make a long-distance call, and ask your wife to check the clock on the microwave.
So why not just take a clock with you aboard ship? You’d have to keep it wound, but otherwise, you could just leave it alone. That way, you’d always know what time it was at home, even if you sailed halfway around the world.
Easy, right? There was just one tiny little wrinkle. In order to find an accurate longitude – accurate enough, anyway, to collect the Longitude Act’s grand prize – your clock would need to gain or lose no more than three seconds per day.
This, in an era when the only timepieces that could deliver that kind of accuracy were huge pendulum clocks bolted to a wall. The technical challenge of building a clock capable of keeping accurate time aboard a ship that was pitching and rolling — not to mention subjected to wild temperature swings, another mortal enemy of accuracy — was so great as to be considered impossible.
In fact, the preeminent scientists of the day thought that developing a marine timekeeper with sufficient accuracy was a pipe dream. They favored a method of finding longitude based on very precise observations of the moon. Unfortunately, making that method work required compiling a table based on thousands of fantastically complex calculations. How complex? Well, by the early 1780s, after about fifty years of blisteringly difficult work, the mathematicians were finally closing in on a first draft.
Enter John Harrison, a humble woodworker and would-be clockmaker from Lincolnshire, a rural area not unlike Perry County, who somehow got it into his head that he was the man to make the impossible clock that would solve the longitude problem.
More on Mr. Harrison and his fascinating clocks next week.
This column was published in the Perry Co Times on 03 June 2010
For more information, please contact Mr. Olshan at writing@matthewolshan.com
