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Clockmaker John Harrison vindicated 250 years after ‘absurd’ claims
- nmjenkins 12y agoWhat I don't get is, why did they dismiss the plans out of hand 200 years ago when the guy that wrote them was literally famous for producing a revolutionary clock? I mean, with that kind of track record, you'd have thought someone would give it a go.
- leecb 12y ago200 years ago, how would you validate his claim? You would have to have a more accurate time reference, and I'm not sure exactly what that would be.
- ColinWright 12y agoHarrison measured the accuracy of his clocks by observing eclipses of stars by chimneys. We know that for a given star such eclipses happen every 86164.09056 seconds. For those who might be wondering why it's not every 24 hours, or 86400 seconds, look up "Sidereal Day"[0][1][2]. [0] https://www.google.co.uk/search?q=sidereal+day https://www.google.co.uk/search?q=sidereal+day [1] http://simple.wikipedia.org/wiki/Sidereal_day http://simple.wikipedia.org/wiki/Sidereal_day [2] http://en.wikipedia.org/wiki/Sidereal_time http://en.wikipedia.org/wiki/Sidereal_time
- dllu 12y agoAt that level of accuracy, however, you will find that the rotation of the Earth itself doesn't keep time that well. The Shortt-Synchronome clock [0] was the most accurate pendulum clock, known to have an error of less than 1 second per year. It was used in 1926 to detect tiny seasonal changes in the Earth's rotation rate. An evaluation of the clock in 1984 revealed it was even more accurate than thought --- it was in fact accurate to within 1 second per 12 years, the discrepancy being due to "the slight changes in gravity due to tidal distortions in the solid Earth caused by the gravity of the Sun and Moon." Harrison's claim of 1 second error in 100 days is clearly in the same order of magnitude as the Shortt-Synchronome's known error rate of 1 second per year in 1926, and thus would have been also affected by the tiny seasonal changes in the Earth's rotation rate. [0] https://en.wikipedia.org/wiki/Shortt-Synchronome_clock https://en.wikipedia.org/wiki/Shortt-Synchronome_clock
- magicalist 12y agoThis is why we talk about mean time and still have to account for discrepancies as leap seconds. That's not an issue with the clocks, just the earth. However, the situations are actually pretty different. If you look into the study of the Shortt-Synchronome clock, you'll see it's actually talking about the gravitational effects of the sun and moon on pendulums. The Harrison clocks had no pendulums. The Shortt-Synchronome is still a pretty amazing clock, though.
- ColinWright 12y ago> The Harrison clocks had no pendulums. The clock referred to in the article does have a pendulum.
- magicalist 12y agoOh, I see, I thought they were asking how you would validate his claim of the "revolutionary clock"(s) he was famous for in the first place.
- dmurray 12y ago> At that level of accuracy, however, you will find that the rotation of the Earth itself doesn't keep time that well. If the main purpose of the clock was to measure longitude by observing the position of the stars, "only as accurate as the Earth's rotation is consistent" is as good as you could possibly need.
- abecedarius 12y agoEyeballing the figure at http://en.wikipedia.org/wiki/Fluctuations_in_the_length_of_day#Observations http://en.wikipedia.org/wiki/Fluctuations_in_the_length_of_d... it looks like you could expect stellar time to be off proper time by not more than around 0.1 seconds in 100 days, since the width of the band of fluctuations is around 1 ms. (I'd say 0.01 seconds since in a random walk the error grows with the square root of time, not linearly.) Maybe this fluctuation graph has subtracted out seasonal variation?
- mpweiher 12y agoAs long as you're at a fixed location, how about a sundial?
- lostlogin 12y agoTo the second? I'm not a sundial expert but have seen a few and those that I have seen have been vaguely useful for telling which hour it is. Maybe even which half hour. I assume you could just lengthen the vertical to get a longer and more accurate shadow. But it's still a bit hard to see this being a reference. Edit: here is a link to some accuracy measurement. I have no idea what the record is, but these ones were getting down to 30 seconds ish. http://www.sage.unsw.edu.au/currentstudents/ug/projects/o%27brien/o%27brien.htm http://www.sage.unsw.edu.au/currentstudents/ug/projects/o%27...
- pcl 12y agoThat part is easy: you just compare it to local solar noon. Earth's rotation is considerably more accurate than this clock's target. For more info about the number of seconds in a solar day, see this awesome Wikipedia page: http://en.wikipedia.org/wiki/Leap_second http://en.wikipedia.org/wiki/Leap_second
- stromgo 12y agoFor more info about the number of seconds in a solar day, I would rather recommend the table at http://en.wikipedia.org/wiki/Solar_time#Apparent_solar_time http://en.wikipedia.org/wiki/Solar_time#Apparent_solar_time . The Leap_second article discusses a much smaller variation (~2 ms) on top of the big cyclic variation (~20 s).
- jacobolus 12y agoThe most obvious way would probably be to build two of them and see how accurate they were against each-other. Alternately, you could use astronomical angle measurements. You can get quite accurate measure if you don’t move around. (The reason determining time was difficult on ships is that you need to know precisely where the ship is to figure out the time from the stars, or precisely what time it is to figure out position.)
- deleted 12y ago[deleted]
- zkhalique 12y agoYou could simply build 10 of them and test them against each other. Even though statistical significance hadn't been discovered yet, I'm sure someone could have worked out the math.
- gaius 12y agoBecause the ideas were buried in a book that was mainly about dissing his rivals, and no-one saw past the scandal. Its worth noting that this recreation uses materials and fabrication techniques not available at the time, too. So there is still no definitive proof that it would have worked.
- thret 12y agoSo to really prove his claim someone would have to create the clock according to the design, using only the technology available 250 years ago? That would be impressive. Perhaps now that the design has been validated someone will attempt it.
- fnordfnordfnord 12y agoSomeone did. Martin Burgess. It is mentioned in OP's link. And here: http://www.clockmakers.org/wp-content/uploads/2014/05/Decoding-Harrison.pdf http://www.clockmakers.org/wp-content/uploads/2014/05/Decodi...
- maxerickson 12y agoNeither link is clear about the methods used to manufacture the clock.
- keithpeter 12y agoIn addition to the other replies to your post which make valid points, you have to remember that Harrison was a self-educated carpenter and clockmaker. The Longitude Committee was composed of the great and the good, and preferred the lunar distance method for getting the longitude at sea. Edit: child post points out the Longitude Board's examination of Harrison's watches for finding the longitude at sea was much earlier than the publication of Harrison's book. Wikipedia page has the time-line.
- gaius 12y agoYou've got your timeline mixed up - by the time the book was published, the committee had fully accepted the clocks and showered Harrison with awards.
- keithpeter 12y agoThe watches? I recollect that Harrison was in dispute with the committee for decades, resolved only by the direct intervention of the king? He never received the full longitude prize that I am aware of. Would welcome correction.
- iwwr 12y agoHowever, clocks were expensive to manufacture and few ships had them. The lunar distance method was a mainstay of navigation until the latter 19th century.
- scrollaway 12y agoHijacking your comment to recommend those fascinated by time (and those that aren't!) to look into this year's FOSDEM main track dedicated to time. I especially recommend the talk "Precise Time", which goes in depth about how to track time, what tracks time, to what level of accuracy, how to measure inaccuracies etc. It's not a very technical talk, you can watch it with any layman: https://video.fosdem.org/2015/main_track-time/ https://video.fosdem.org/2015/main_track-time/
- fnordfnordfnord 12y agoThanks for posting the link. Is anyone having trouble viewing the videos? I can watch them from my browser plugin, but from VLC or mplayer the video is buggy. In all cases the audio amplitude is very low.
- cauterized 12y agoThere would have been no way to validate it because they couldn't measure the accuracy of a timepiece to within even a few seconds.
- deleted 12y ago[deleted]
- zachalexander 12y agoCan you support this claim? I'm not skeptical so much as curious. How did people keep more or less consistent time back then?
- analog31 12y agoThe only option was to compare the reading of a clock, to an astronomical observation such as the zenith of the sun.
- cauterized 12y agoRight. And the zenith can be identified by eye or using a sundial to within an accuracy of a minute or so, but not to a matter of a second or two AFAIK. Maybe using a sundial the height of the Eiffel Tower?
- analog31 12y agoIt does seem pretty daunting. A tall sundial would not have enough mechanical stability to be accurate, especially due to wind loading. AFAIK at least one of the people who measured the circumference of the earth, did so by observing a shadow at the bottom of a deep well. Still, a shadow would be pretty washed out over the span of, say, 15 meters, unless some sort of focusing optic were involved.
- cauterized 12y agoA tall cliff? A building with a spire on top? An obelisk? Guess now I'm going to have to go and find a tall building with a spire and check how recognizable the shadow of that spire is!
- pg_is_a_butt 12y agowhat if elon musk said he could power a car to haul 5 tons 500 miles with a tablespoon of spit?
- pcrh 12y agoSome more information on this site: http://www.frodsham.com/burgess-regulator/ http://www.frodsham.com/burgess-regulator/
- deanclatworthy 12y agoThe classic tale of hindsight, undoing the wrongs of the past where labelling progressive and forward thinkers "insane" was commonplace. I wonder if we will look back on the forward thinkers of today (Stallman, Assange et. al) in 50 years and regret the scepticism which we throw their way today.
- vacri 12y agoThere is considerable selection bias here. Lots of crazy ideas are pooh-pooh'd because, well, they're crazy. Have a look at a random assortment of patents, for example.
- ColinWright 12y agoRelevant: But the fact that some geniuses were laughed at does not imply that all who are laughed at are geniuses. They laughed at Columbus, they laughed at Fulton, they laughed at the Wright Brothers. But they also laughed at Bozo the Clown. -- Carl Sagan
- zkhalique 12y agoI'd say Bozo was a genius! http://www.sfgate.com/news/article/Larry-Harmon-the-real-genius-behind-Bozo-the-3205801.php http://www.sfgate.com/news/article/Larry-Harmon-the-real-gen...
- rodgerd 12y agoAlso, there are no shortages of examples of people who have great ideas in one domain (DNA, polio vaccine) who have terrible ideas in others (racism, vitamin C as a cureall).
- soup10 12y agoBoth Stallman and Assange's philosophies are hugely well known and influential. Most of the criticism thrown their way comes from how they court controversy for attention.
- rat87 12y agoDiscussions of Clock accuracy remind me of Thief of Time (from the Discworld series by Terry Pratchett)
- zokier 12y agoWhy didn't Harrison build the clock and demonstrate the accuracy to counter the criticism?
- cauterized 12y agoAccording to TFA he died not long after. Also, it probably wouldn't have been possible to validate his claims at the time because you'd need another way to measure the current time to within an accuracy of one second (even if that method had to be recalibrated daily).
- mapt 12y agoI only know what I saw on the film adaptation of Longitude, which was a one-note perseverance story that may not be the most objectively accurate: http://www.imdb.com/title/tt0192263/ http://www.imdb.com/title/tt0192263/ Harrison apparently spent his whole life building these clocks and fighting to secure the prize given a hostile council of astronomers who had pre-decided that an astronomical method put forth by some learned man would win, not some pathetic carpenter. Every demonstration he made, they would decide they required some higher standard of proof, or some rule had changed which invalidated the demonstration. He became extremely bitter at the process. His son spent much of his life attempting to validate the timepieces in naval voyages. Harrison was only awarded part of the prize on his deathbed after intervention by a sympathetic sovereign and also the death of some of the strong personalities on the Board.
- boyter 12y agoI think the greatest thing we can learn from Harrison is being able to throw away a great deal of work for something new if it will produce a better result. The fact he did this himself with his orginal large sea clocks in favour of the smaller ones really speaks of dedication to the idea over implementation.
- seanmcdirmid 12y agoBeing able to disrupt your own work is a sign of greatness, that you aren't satisfied with resting on your laurels. Unfortunately, many companies don't get this (Apple being a notable exception with the classic iPhones killing iPod sales).
- digi_owl 12y agoWell the iPod was getting savaged by MP3 playing featurephones anyways.
- andrewflnr 12y agoThat doesn't seem to affect the common protective instinct corporations have for their products. If you have a failing product, you want to rescue it somehow, not join in the beating.
- digi_owl 12y agoWell they kinda rescued it, remember that alongside the iPhone came the iPod Touch. Basically an iPhone without the radio. Also, the iPhone was tied directly to the existing iPod infrastructure via iTunes etc.
- uxp 12y agoLike the largely unsuccessful Motorolla Rokr?
- clarky07 12y agoYeah that's simply not true. iPod didn't decline until after 2009. http://www.huffingtonpost.com/2014/01/28/ipod-sales_n_4680000.html http://www.huffingtonpost.com/2014/01/28/ipod-sales_n_468000...
- Animats 12y agoHere's more technical data about the clock, including pictures.[1] The basic issues in high-accuracy clock design for fixed clocks in air are 1) providing the same amount of energy to the pendulum on each beat, 2) sensing the completion of each beat while withdrawing a fixed amount of energy, and 3) dealing with variation in temperature, air pressure, and humidity. 1) and 2) are the hard design problems. The general idea is that the drive train lifts up a tiny weight by a fixed distance, which is then released to power the pendulum. The pendulum impulse is thus isolated from variations in the rest of the drive train. See "grasshopper escapement". Dealing with 3) generally involves bimetallic strips and other self-adjusting mechanisms. Temperature variation is the big problem. There have been clocks with mercury barometers in the pendulum to compensate for air pressure, but this isn't one of them. Harrison designed this clock, like most of his clocks, to run without lubrication, eliminating another source of variability. It's a beautiful piece of mechanical design. The Smithsonian Institution used to have a very nice collection of important high-precision clocks, which they kept set and running. They seem to have been retired from public display. [1] http://www.frodsham.com/burgess-regulator/ http://www.frodsham.com/burgess-regulator/ [2] http://en.wikipedia.org/wiki/Grasshopper_escapement http://en.wikipedia.org/wiki/Grasshopper_escapement
- Tloewald 12y agoWas the clock that was tested made with contemporary tools? It may be that Harrison was right (his design was correct) but so were his critics (it couldn't be executed as designed at the time).