Slashdot Mirror
John Harrison: Inventor and Longitude Hero
szczys writes: Here's an interesting fact: when at sea you can't establish your longitude without a reliable clock. You can figure out latitude with a sextant, but not longitude. Early clocks used pendulums that don't work on a rocking boat. So in the 1700s the British government offered up £20,000 for a reliable clock that would work at sea. John Harrison designed a really accurate ocean-worthy clock after 31 years of effort and was snubbed for the prize which would be £2.8 Million at today's value. After fighting for the payout for another 36 years he did finally get it at the ripe old age of 80. The methods he used to build this maritime chronometer were core to every wrist and pocket watch through the first third of the 20th Century. One of his timepieces, designated Clock B, was declared by Guinness to be the world's most accurate mechanical clock with a pendulum swinging in free air' more than 250 years after it was designed.
Please, read Dava Sobel's book, Longitude, about the trials and travails of Harrison -- it's a tremendous read. And if you ever get to the Royal Observatory in Greenwich (England), look at the Harrison models, they are amazing.
This is a guy who was a Maker -- self taught and more.
Here's an interesting fact: when at sea you can't establish your longitude without a reliable clock.
Not true. You can use GPS.
You do not need a clock to determine longitude. In fact, a sextant can be used, as long as you have the appropriate tables that map various celestial angles to the correct date and time. These tables were originally overseen by Nevil Maskelyne, one of Harrison's rivals to the longitude prize. The two methods are an early instance of the closed-tech vs open-tech argument we're so used to now. Maskelyne argued that mariners should not depend on Harrison's (closed) bespoke clocks. Instead, he said that open information (the Royal Observatory's tables) should be used with open tech (the sextant) to solve the problem. But Harrison's clocks were so easy to use that his solution won the prize. Sound familiar? Do read Dava Sobel's excellent book on the subject; it's excellent.
He didn't just design them. He built them. An earlier post mentions the museum where they're displayed.
I do not fail; I succeed at finding out what does not work.
If the clock could be produced using 1700's machining and metallurgical technology, only then would it prove Harrison's contemporary critics incorrect.
Harrison built his clocks in the 1700's (although apparently Slashdot only just heard about it). They were incredible machines for their time and, after much wrangling with the astronomers of the time (who thought that schemes like making detailed observations of the moons of Jupiter through a telescope on the heaving deck of a ship in the mid-atlantic were better ideas) he won 1700's X-prize equivalent for inventing a machine to accurately measure longitude. You can actually see the clocks he made in the old Royal Greenwich Observatory building in London.
"when at sea you can't establish your longitude without a reliable clock"
But you could on land?
Imagine if you were in the middle of the prairie in the early 1800's - is it any easier to find your location than at sea.
He didn't just design them. He built them. An earlier post mentions the museum where they're displayed.
Really? Did you even RTFA?
Then why does the article linked to the slashdot entry state:
As a result, his ideas for his super-accurate pendulum clock were forgotten until the 1970s, when interest in the clockmaker and his remarkable timepieces was re-awakened. The artist and clockmaker, Martin Burgess, – working on attempts to decipher Harrison’s plans – produced two versions of his great clock. It is the second of these, Clock B, that has been the focus of attempts to bring it to its maximum accuracy in the past year. “Essentially we have been fine-tuning the clock so that we can bring it to its full potential and accuracy,” said McEvoy.
The article is about the SUPER-ACCURATE PENDULUM CLOCK, not about this shipworthy chronometers. Sure sounds like Harrison never built his super accurate pendulum clock.
So I decided to do some googling/binging/altavistaing/meh myself and not just take the word of slashdotters like you that post no references... and surprise, surprise, what did I find?!? The answer to my question, which just so happens to contradict your statement... The clock that was tested was built using modern materials, and most likely using modern manufacturing techniques.
According to this article: https://www.theverge.com/2015/...
Martin Burgess, a master clockmaker, used Harrison's mechanism and design along with modern materials like duralumin to construct the Martin Burgess Clock B,
And according to this article on the Greenwich Royal Museum website: http://blogs.rmg.co.uk/longitu...
‘Clock B’ is one of two clocks made from modern materials, chiefly duraluminium and invar, that follow the perceived format laid out in Harrison’s convoluted text: Concerning such mechanism
You do not need a clock to determine longitude.
Yes you do. Maskelyne's method just uses the moon as a clock and required being able to accurately measure the angular separation between the moon and a bright star near its path to determine the time. Since the moon moves ~0.5 degrees every hour you need to measure the angle to at least this accuracy to get a time. While it worked it required great care measuring the angles, complex tables to convert the angle to a time and a clear view of the night sky. Even with all this extra effort on the one voyage where they were compared directly this method produced an error three times greater than Harrison's clock.
I would also disagree with your open tech argument. Have a look at the 1775 Nautical Almanac. Apart from copyright on the tables you had to have a government license to print them and the calculations on which the tables are based are not given anywhere (although there is some reassurance that the calculations have been checked multiple times). Worse this is a something you had to purchase every year. I don't see how this is any more open than Harrison's clock whose mechanism you could examine and tweak if you though you could do better.
Why is this a Slashdot article, today? Yes, it was interesting when the book was released, and when the documentaries aired, but if Slashdot ran an article each time a reader rediscovered history....
A few years ago I measured my longitude myself, just for fun. I measured the time of local noon, using a portable shortwave radio tuned to WWV. Correct local solar time to mean time with the equation of time, read off my longitude. I would have won the prize. Shows what an accurate clock can do.
I've read Captain Cook's logs and in his time they observed things like the moons of Jupiter to get a time reference. Reasonably accurate, but time-consuming.
...laura
The Jeremy Irons movie is great and its on YouTube.
Seastead this.
It was far too expensive to practically manufacture in the day. The prize authors should have included a clause to limit the manufacturing expense, but they didn't think of it at the time, and were surprised. But, it was not an open society, and monarchies can change the rules on a whim.
Table-ized A.I.
Oh, gee, well excuse me for thinking that if someone says they're on display at a fucking museum that they're on display at a fucking museum!!!
I do not fail; I succeed at finding out what does not work.
Ahem. This.
They are the direct link to the Harrison's sea clocks. Number 1, now in a private collection, belonged to the Time Museum, USA, until the museum closed in 2000 and its collection was dispersed at auction in 2004. Number 2 is in the Leeds City Museum. It forms the core of a permanent display dedicated to John Harrison's achievements, "John Harrison: The Clockmaker Who Changed the World" and had its official opening on 23 January 2014, the first longitude-related event marking the tercentenary of the Longitude Act. Number 3 is in the Worshipful Company of Clockmakers' collection.
and knew his longitude, but it is apparently hard to do and few people were good at it.
I'll bet he could have designed it in an hour if he had a good 3D Printer and access to a Maker Faire. And he could have done a TED talk about it afterwards.
I imagine a 3D printed clock would be approximately as useful as a chocolate teapot. Even if you could control it from your iPhone in a Microbrew pub while combing your beard.
To have a right to do a thing is not at all the same as to be right in doing it
It isn't like observing the angle of the sun on a pitching deck is all that much easier though.
APK likes to ask for responses to the same things over and over. Maybe he just likes the responses?
Chocolate teapots have their uses. Main one is that if you're hungry you could eat it. Also, these guys would have it that you can even use one for brewing tea
A 3D printed clock though - plenty of examples. Usually using other materials for the pendulum, but I imagine nowhere near as consistent or useful at sea as Harrison's clocks.
Several of Harrison's clocks are on display at Greenwich Observatory in London. The more interesting ones to see are the larger ones because the mechanism can be determined. Amazingly the larger clocks are accurate despite being made largely out of WOOD. As well as the rolling of the ship not affecting the mechanism, temperature and humidity are compensated for. Often friction and wear and the need for lubrication are avoided by axles rolling back and forth rather then revolving in a bearing. Dana Sobel's book popularised the prize, the man and the clocks but I think she does not convey properly the engineering achievement. The clocks must be seen.
Paul Beardsell