There seems to have been a lot of talk about navigation lately — Tesla’s self-driving cars are getting a lot of publicity, and not the kind they’d like and then there was the Chinese Balloon’s path; the news media sometimes listed its location by latitude and longitude. Latitude and longitude are how we navigate the globe. Our car’s GPS only knows where it is by latitude and longitude coordinates. It just displays the map for all of us too stupid, or lazy to to navigate by coordinates.
The quest for an accurate gauge of longitude is an interesting story — and finding an accurate gauge of longitude literally opened up the world.
Think back to maybe the fourth grade — when you learned about latitude and longitude. Now if you can find one, look at a globe. On the globe, you’ll notice it is sliced by a bunch of lines going two separate directions. The horizontal lines are called “latitude.” They tell you how many degrees you’re north or south of the Equator. That means the the vertical lines are longitude.They tell you how far east or west you are using the longitude line that runs through Greenwich, England (for no really good reason) as the prime meridian. By using longitudinal and latitudinal coordinates, you can find any spot on the globe.
But finding your longitude is much harder than finding your latitude. Latitude is set by the equator — a fixed point. That means, even out at sea, it’s simple to gauge your latitude by the length of the day or the position of the Sun. But longitude is more dynamic — it moves as the Earth rotates. Every four minutes, longitude shifts one degree. So — determining longitude, especially at sea, long ago was considered a problem as insoluble as finding the fountain of youth or turning lead into gold.
Just knowing your latitude, or where you were in a northerly or southernly sort of way was perfectly adequate for a time, but as humans and their ships navigated farther and farther from the shore, it became apparent that there was a need for accurate positioning data. Traditional methods of measuring longitude were laughably inaccurate. One scheme worth mentioning is the method in which distance was measured by counting how many rope knots, spaced about 50 feet apart, slipped out of a sailor’s finger in 28 seconds (this is where the nautical term for speed, “knots” came from.) This would be fine as long as you traveled in a direct straight line and were constantly gauging your speed. But no one on a ship ever did either one of those things — the former because of waves, cross-currents, and winds. The latter, just because — maybe the sailors were busy singing sea shanties and playing the hornpipe. Anyhow, this way of measuring distance was known as “dead reckoning,” because a navigator deduced the ship’s position based on speed and direction of travel — and the time elapsed since the last known position.
While latitude only required the knowledge of the date and ability to determine the angle of the Sun, longitude required another measurement — the knowledge of the exact time at a place that was not where your were…. let’s call that place Greenwich, England. Due to the rotation of the Earth, noon comes at different times at different places east and west on the Earth. If you spotted the Sun at high noon wherever you were, and then noted the time difference between you and Greenwich, you could determine your longitude distance from that point. But what you need is a clock set to Greenwich mean time — and — it must keep excellent time.
This was a much easier problem if you were on land. By the 17th century clocks were reasonably accurate thanks to the principle of the pendulum. However, pendulum clocks aren’t practical on sailing ships — especially the rickety ones that people used to cross the seas back in the early days. You just can’t use a pendulum clock on a ship that’s rocking and rolling on the waves.
The longitude problem haunted sailors for centuries and captains of ships had to rely on dead reckoning, which essentially meant they were guessing, or steering the ship by the seat of their pants. Ships were forced to stick to the few safe routes everyone knew.
Finally, in 1714, merchants and sea captains banded together and brought a petition to the British Parliament to solve the longitude problem. The government paid attention and offered a reward to anyone who could solve it. The Longitude Act, issued on July 8, 1714, offered a prize for a practical and useful method to determine longitude to an accuracy of half a degree.
As you might guess, this led to some really stupid ideas being submitted. One suggested stationing warships in permanent positions across the Atlantic — at midnight Greenwich time, they’d send up fireworks that could be seen for 100 miles around. Ships at sea could take their reading from there. Of course, this solution assumes there was a practical method for the “fireworks ships” to know when it’s Greenwich time… obviously if that were the case, there would be no need for the ships at all. The entries became so cockamamie that the “quest for longitude” became a shorthand phrase for insanity.
Finally, a guy named John Harrison, a self-taught clockmaker and carpenter, came to the rescue. Harrison did three things. First, he replaced the pendulum with balance springs. Second, he made the springs with a combination of metals to compensate for shrinkage and expansion. And finally, for the wood casings and other wood parts of his timepiece, Harrison used a tropical wood that was self-lubricating to reduce friction. What this all meant is that John Harrison had created the first timepiece that could keep accurate time at sea.
Harrison created four versions of his timepiece — he took the first version, the H1, on its maiden voyage to Lisbon in 1734 and got so violently seasick that he never sailed again. His final version, the H4, was taken on a voyage from England to Jamaica — a trip that took more than 80 days — and his “clock” only lost five seconds.
So Harrison not only came up with the means to establish accurate positions at sea, he also gave the world the most accurate time measurement it had ever seen. It turns out that to know where you are, you must also know when you’re there.
I’ve always heard that timing is everything — I guess that’s true if you’re looking for your place in the world.
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