We left off last week in the middle of the great space race of the 18th century: the international competition to solve the problem of finding longitude at sea, kicked off by an Act of Parliament in England in 1714 that established a huge cash prize for anyone who could provide a practical method of finding longitude within half a degree of accuracy.
With £20,000 on the line, or about $3.5 million today, the kooks really came out of the woodwork. The long-suffering judges on the Board of Longitude sifted through mountains of hare-brained schemes.
For instance, a “solution” that proposed the creation an archipelago of anchored waystations across the Atlantic that would fire off artillery shells at precise intervals.
Impractical, but at least not crazy.
Unlike another famous entry that was based on a mystical substance called “the powder of sympathy.” The first step in this plan was to stab a dog – but not fatally! — and stash the poor wounded beast on the departing ship. The knife, however, would stay in the home port. According to the inventor’s theory, every time the knife was dipped into his magical powder, the dog would yelp with pain, even if he was halfway across the ocean. So by dipping the knife in the powder of sympathy, say, every day at noon, sailors would be able to set their clock very precisely.
By dog’s yelp.
Of course, the real solution to the problem of longitude lay in one of two directions: either by making a fantastically complicated chart of lunar movement for sailors to consult; or by developing a marine timekeeper that was accurate to within 3 seconds per day.
Let me digress for a moment about the accuracy of clocks. In the modern era, we’ve grown accustomed to the incredible accuracy of atomic clocks. The GPS system in your car or truck is a good example. GPS satellites have atomic clocks on board. Your precise position on earth is determined by how long it takes the signal from three or four of these satellites to reach the GPS receiver on your dashboard. By measuring the lag times of the different signals, your receiver can fix your position within, say, 20 feet.
So you see, even today, navigation depends on the link between time and distance.
How accurate are today’s atomic clocks? A really good one will be accurate to about one second in thirty million years.
That’s right. Thirty million years.
Some of you may have seen the little clocks that keep time using a radio signal from one of the official U.S. atomic clocks. You can get them for about $20 on Amazon. About ten years ago, I gave my grandfather one of these so-called “atomic clocks.” I had the idea that I was giving him the most accurate clock he’d ever own.
Not so! It turns out that the pokey radio signal that beams the atomic time to your little Amazon clock reduces its accuracy by about 11 billion times: from one second in thirty million years all the way down to one second per day.
Even so, accuracy of one second per day isn’t so bad. It certainly would have won you the Longitude Prize back in the 18th century.
But it’s not so great, either.
Enter John Harrison, the humble Lincolnshire clockmaker who eventually claimed the Longitude Prize, although not without enduring a lot of misery first.
Harrison’s background was as a woodworker and joiner, not a scientist. In fact, he had scant formal education.
But clocks fascinated him. He approached them with a somewhat naïve and open mind, which led him to some surprising solutions. For instance, lubrication was a problem in early clocks. The oil was based on animal fats, which broke down and migrated in ways that interfered with a clock’s accuracy.
Rather than try to come up with a better oil, Harrison simply did away with oil altogether by using a special wood called lignum vitae in his clocks. Lignum vitae is very dense, which makes it excellent for turning small clock parts. It also has a kind of waxiness that provides natural lubrication.
Just doing away with lubricating oil was a big improvement. But Harrison wasn’t content to stop there. He set out to solve one of the great clock-making challenges of the day: how to compensate for wide swings of temperature.
Harrison’s brilliant solution to the problem was to join different kinds of metal into a single strip. The two metals were carefully chosen so that their rates of expansion and contraction precisely offset one another.
These so-called “bimetallic strips” are still in use today. Until the advent of digital thermostats, there was a bimetallic strip in every household thermostat in America. They’re still common in toaster ovens and water heaters.
By the 1720s, Harrison was making extremely fine pendulum clocks, accurate to one second per month.
In other words, 30 times more accurate than those atomic radio clocks from Amazon!
But a pendulum clock wouldn’t work aboard a ship. He was still a long way from a design that could take the Longitude Prize.
Like many inventors, Harrison was a man obsessed. He drew ceaselessly. He experimented day and night. He built prototype after prototype. He’d solve one problem, only to find himself at the threshold of much larger one.
In his 40s and 50s, he spent 19 years on one clock that in the end, just wasn’t good enough.
Throughout the long, lonely years, he kept innovating. One of his ideas was a special bearing, a round “cage” with tiny brass rollers inside, designed to reduce friction in the clock’s mechanism.
This was the grandfather of a useful little device we call the “ball bearing.”
Harrison’s greatest stroke of genius, the one insight that really cracked the problem wide open, was that a marine timekeeper needed to be quite small — not much larger, in fact, than a normal pocket watch.
By scaling down the works, he was able to negate the chaotic changes in gravity and momentum that bedeviled the accuracy of large sea-born clocks.
Unfortunately, it took Harrison so long to develop his marine chronometer that by the time it was finally ready, he was an old man. His influence had waned. The scientific community had all but given up on him — and on a clock as the solution to the longitude problem.
He fought fiercely for the Longitude Prize, but never managed to claim it fully, or with the universal acclaim he so richly deserved. He was awarded the prize in dribs and drabs, and only through the intercession of powerful friends, including King George III, who was an admirer.
John Harrison died in the revolutionary year of 1776. He didn’t live to see the revolution in navigation that his chronometer would enable, or the great expansion of the British Empire that came the following century as a direct result.
This column was published in the Perry Co Times on 10 June 2010
For more information, please contact Mr. Olshan at writing@matthewolshan.com
