
Clockmaker John Harrison vindicated 250 years after ‘absurd’ claims - agd
http://www.theguardian.com/science/2015/apr/19/clockmaker-john-harrison-vindicated-250-years-absurd-claims
======
nmjenkins
What 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
200 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
Harrison 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
At 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
This 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

      > The Harrison clocks had no pendulums.
    

The clock referred to in the article does have a pendulum.

~~~
magicalist
Oh, 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.

------
Animats
Here'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)

------
boyter
I 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
Being 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
Well the iPod was getting savaged by MP3 playing featurephones anyways.

~~~
clarky07
Yeah that's simply not true. iPod didn't decline until after 2009.
[http://www.huffingtonpost.com/2014/01/28/ipod-
sales_n_468000...](http://www.huffingtonpost.com/2014/01/28/ipod-
sales_n_4680000.html)

~~~
digi_owl
Would love to see a pr model breakdown of that. Do they put the iPod Touch in
with the rest of the iPods, or in with the iPhone?

~~~
clarky07
iPod touch is counted with iPods.

------
pcrh
Some more information on this site:

[http://www.frodsham.com/burgess-regulator/](http://www.frodsham.com/burgess-
regulator/)

------
Tloewald
Was 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).

------
zokier
Why didn't Harrison build the clock and demonstrate the accuracy to counter
the criticism?

~~~
mapt
I 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.

------
rat87
Discussions of Clock accuracy remind me of

Thief of Time (from the Discworld series by Terry Pratchett)

------
deanclatworthy
The 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.

~~~
DanAndersen
I don't mean to sound critical here, but I find it interesting that, quite
often, discussions like this assume that who the speaker likes or the
ideologies the speaker accepts are the ones that will be vindicated in the
future.

I'm reminded of AskReddit threads, where people ask "what will people 100
years look back on our time and think was crazy?" and the top responses are
always relatively uncontroversial (e.g. "people will look back and wonder how
we could have banned gay marriage").

I wonder if there have been any good discussions, on HN or Reddit or
somewhere, that focus on that question from the perspective of "what kinds of
things will people believe in in the future, things for which I'll be on the
'wrong side of history'?"

~~~
CJefferson
This is something I've tried really hard to think about, and it is indeed very
difficult.

I'm a meat eater, and don't intend to stop. That's the best thing I can think
of where I expect to be seen as horrible 100 years from now.

In the case of current online communities, I hope the current habit of picking
one comment someone made, or one photo they took, and the whole internet
attacking them for it, will be seen as unacceptable. (I'm not talking about
people doing things genuinely terrible, but doing things which lots of people
do every day, but then one person, for some reason, gets into the public
sphere for it).

