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I have to challenge this as it is incorrect:

You say:-

Remember, Harrison's biggest challenge was not making an accurate chronometer 
(that had been done already) but rather making one that remained accurate 
despite the motion and temperature changes experienced at sea.
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According to Rupert Gould:-

The term chronometer is generally believed was first used in the modern sense 
of a machine specifically designed for the purpose of keeping acurate time at 
sea by John Arnold in his pamphlet " An Account of the going of a Pocket 
Chronometer" published in 1782. Though it does appear to have been first used 
in the same sense by Jeremy Thacker in his description of his "machine for 
the longitude" published in 1714.
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Accurate chronometers had _not_  been made before Harrison (or otherwise they 
would surely have made claim to the longitude prize); and even land-based 
long-case pendulum clocks, so-called "regulators" (the most accurate 
available) were not as accurate as Harrison's regulator - beside the general 
fact they could not be used at sea.  There was NO accurate clock available 
for use at sea - i.e. a chronometer,  before Harrison.

It was considered _impossible_ for physical scientific reasons by all of the 
leading scientists and astronomers of the early eighteenth century to produce 
a clock accurate enough that could withstand the difficult conditions of 
sailing ships of the time. That is the real measure of what Harrison was up 
against.

Harrison was the first to get to grips with the real problems of accuracy. 
He understood the need to reduce friction and was the inventor of various 
methods of reducing it including what we now call needle-roller bearings.
 
He was the first to introduce temperature compensation successfully with 
gridiron pendulum for regulators, and bimetallic stip compensators in his 
chronometers.  This, along with the balanced spring opposing-pendulum 
oscillator were the big breakthroughs.

He was the first to understand the need for balanced mass/spring oscillators 
that could maintain oscillation though subject to external forces - thrown 
around by a sailing ship; and he undestood for the first time the need to 
de-couple the oscillating elements from the rest of the mechanism as much as 
possible and hence understood in principle what we would now call 'Q' - the 
"goodness" of an oscillator.

His 'grasshopper' escapement in his regulator is recognised as the most 
friction free escapement of them all, which affects the motion of a pendulum 
the least and increases accuracy thereby.  Not unitl the Shortt clock came 
into being in the 1920s was his regulator improved upon.

He understood the forces involved in his large rocking balance clocks and 
realised that there was a fundamental underlying physical problem which could 
not be overcome; hence his change after a lifetime of improving his designs 
of the large clocks to small pocket-watch configuration - the one which 
evenually won the longitude prize.

Harrison can rightly be descibed as a genius in my opinon - someone who is so 
advanced compared to his contemporaries they are unique and there is no 
meaningful comparison really possible.  He started his working life as a 
carpenter and joiner, working on a large estate in the service of Sir Rowland 
Winn of Nostell Priory;  but became the world's leading master of horology in 
marine chronometer development.  An astonishing achievement.

His achievement is so huge and comprehensive; the brilliant inventiveness so 
amazing;  and the lifelong dedication in the face of all the opposition, 
including scientific negativity against him in the eighteenth century;  is 
difficult to comprehend today.  It is probably the equivalent of someone 
today converting their motor car into a spaceship capable of travelling to 
the Moon and back!

Douglas Denny.
Chichester. England.

================

Original Post:

Gary:

A fascinating experiment and experimental confirmation of my long-held belief 
that even the cheapest digital watch makes a superb chronometer.

Now a challenge for anyone wanting to repeat the experiment or extend the results:

1.   Take the "watch board" and simulate motion.   Okay, maybe we can't take 
it to sea but maybe drive it around town with us?

2.   Vary the temperature.   Maybe put the board outside in direct sunlight 
(and rain and maybe even snow).

Remember, Harrison's biggest challenge was not making an accurate chronometer 
(that had been done already) but rather making one that remained accurate 
despite the motion and temperature changes experienced at sea.

Whoops, as I write this I'm looking at my digital watch on my wrist and 
watching it bounce around.   Maybe experiment #1 isn't required.   In fact, 
the very nature of digital watches should make them motion-insensitive 
(excluding relativistic effects :-P ).

Lu Abel



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