Marine chronometer

chronometerchronometersChronoscopemarine chronometersmarine timekeepersnautical chronometeraccurate clockchronometrykeeping time on a ship at seamarine clock
A marine chronometer is a timepiece that is precise and accurate enough to be used as a portable time standard; it can therefore be used to determine longitude by means of accurately measuring the time of a known fixed location, for example Greenwich Mean Time (GMT) and the time at the current location.wikipedia
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John Harrison

H-4H4H4 and H5
The first true chronometer was the life work of one man, John Harrison, spanning 31 years of persistent experimentation and testing that revolutionized naval (and later aerial) navigation and enabling the Age of Discovery and Colonialism to accelerate.
John Harrison (3 April 1693 – 24 March 1776) was a self-educated English carpenter and clockmaker who invented the marine chronometer, a long-sought-after device for solving the problem of calculating longitude while at sea.

Greenwich Mean Time

GMTGMT+4UTC±00:00
A marine chronometer is a timepiece that is precise and accurate enough to be used as a portable time standard; it can therefore be used to determine longitude by means of accurately measuring the time of a known fixed location, for example Greenwich Mean Time (GMT) and the time at the current location.
As the United Kingdom developed into an advanced maritime nation, British mariners kept at least one chronometer on GMT to calculate their longitude from the Greenwich meridian, which was considered to have longitude zero degrees, by a convention adopted in the International Meridian Conference of 1884.

Chronometer watch

chronometerchronometerscertified
It has recently become more commonly used to describe watches tested and certified to meet certain precision standards.
The term chronometer is also used to describe a marine chronometer used for celestial navigation and determination of longitude.

Longitude

WestlongitudinalE
A marine chronometer is a timepiece that is precise and accurate enough to be used as a portable time standard; it can therefore be used to determine longitude by means of accurately measuring the time of a known fixed location, for example Greenwich Mean Time (GMT) and the time at the current location.
John Harrison, a self-educated English clockmaker, invented the marine chronometer, the key piece in solving the problem of accurately establishing longitude at sea, thus revolutionising and extending the possibility of safe long distance sea travel.

Lunar distance (navigation)

lunar distance methodlunar distancemethod of lunar distances
The lunar distances method, initially proposed by Johannes Werner in 1514, was developed in parallel with the marine chronometer. (Time balls became redundant around 1920 with the introduction of radio time signals, which have themselves largely been superseded by GPS time.) In addition to setting their time before departing on a voyage, ship chronometers were also routinely checked for accuracy while at sea by carrying out lunar or solar observations.
The method was published in 1763 and used until about 1850 when it was superseded by the marine chronometer.

Jeremy Thacker

The term chronometer was coined from the Greek words χρόνος (chronos) (meaning time) and meter (meaning counter) in 1714 by Jeremy Thacker, an early competitor for the prize set by the Longitude Act in the same year. Attempts to construct a working marine chronometer were begun by Jeremy Thacker in England in 1714, and by Henry Sully in France two years later.
In the work, the claim is made that Thacker created and extensively tested a marine chronometer positioned on gimbals and within a vacuum, and that sea trials would take place.

Navigation

nauticalnavigatenavigational
When first developed in the 18th century, it was a major technical achievement, as accurate knowledge of the time over a long sea voyage is necessary for navigation, lacking electronic or communications aids. Until the mid-1750s, accurate navigation at sea out of sight of land was an unsolved problem due to the difficulty in calculating longitude.
Reliable marine chronometers were unavailable until the late 18th century and not affordable until the 19th century.

Chronometer

Chronometer (disambiguation)
The term chronometer was coined from the Greek words χρόνος (chronos) (meaning time) and meter (meaning counter) in 1714 by Jeremy Thacker, an early competitor for the prize set by the Longitude Act in the same year.

Henry Sully

Attempts to construct a working marine chronometer were begun by Jeremy Thacker in England in 1714, and by Henry Sully in France two years later.
He invented a marine clock to determine longitude accurately, a sophisticated pendulum clock.

Sea

maritimemarineat sea
Until the mid-1750s, accurate navigation at sea out of sight of land was an unsolved problem due to the difficulty in calculating longitude.
The longitude (a line on the globe joining the two poles) could only be calculated with an accurate chronometer to show the exact time difference between the ship and a fixed point such as the Greenwich Meridian.

Balance spring

hairspringisochronousbalance spring or "hair spring
In 1675, Huygens, who was receiving a pension from Louis XIV, invented a chronometer that employed a balance wheel and a spiral spring for regulation, instead of a pendulum, opening the way to marine chronometers and modern pocket watches and wristwatches. The greatest strides toward practicality came at the hands of Thomas Earnshaw and John Arnold, who in 1780 developed and patented simplified, detached, "spring detent" escapements, moved the temperature compensation to the balance, and improved the design and manufacturing of balance springs.
The balance spring is a fine spiral or helical torsion spring used in mechanical watches, alarm clocks, kitchen timers, marine chronometers, and other timekeeping mechanisms to control the rate of oscillation of the balance wheel.

Balance wheel

foliotbalancecompensation balance
In 1675, Huygens, who was receiving a pension from Louis XIV, invented a chronometer that employed a balance wheel and a spiral spring for regulation, instead of a pendulum, opening the way to marine chronometers and modern pocket watches and wristwatches.
Until the 1980s balance wheels were the timekeeping technology used in chronometers, bank vault time locks, time fuzes for munitions, alarm clocks, kitchen timers and stopwatches, but quartz technology has taken over these applications, and the main remaining use is in quality mechanical watches.

Pendulum clock

regulator clockClock pendulumregulator
Until the 20th century, the best timekeepers were pendulum clocks, but both the rolling of a ship at sea and the up to 0.2% variations in the gravity of Earth made a simple gravity-based pendulum useless both in theory and in practice. Christiaan Huygens, following his invention of the pendulum clock in 1656, made the first attempt at a marine chronometer in 1673 in France, under the sponsorship of Jean-Baptiste Colbert.
These precision instruments, installed in naval observatories and kept accurate within a second by observation of star transits overhead, were used to set marine chronometers on naval and commercial vessels.

Time ball

balltime-balltimeball
It was common for ships at the time to observe a time ball, such as the one at the Royal Observatory, Greenwich, to check their chronometers before departing on a long voyage.
It consists of a large, painted wooden or metal ball that is dropped at a predetermined time, principally to enable navigators aboard ships offshore to verify the setting of their marine chronometers.

Galileo Galilei

GalileoGalileanGalilei
Observation of regular celestial motions, such as Galileo's method based on observing Jupiter's natural satellites, was usually not possible at sea due to the ship's motion.
For sea navigation, where delicate telescopic observations were more difficult, the longitude problem eventually required development of a practical portable marine chronometer, such as that of John Harrison.

Bimetallic strip

bi-metallic stripbimetallicbi-metallic
Construction of his third machine, designated H3, in 1759 included novel circular balances and the invention of the bi-metallic strip and caged roller bearings, inventions which are still widely used.
He made it for his third marine chronometer (H3) of 1759 to compensate for temperature-induced changes in the balance spring.

Arniston (East Indiaman)

ArnistonArniston'' (ship)
The new technology was initially so expensive that not all ships carried chronometers, as illustrated by the fateful last journey of the East Indiaman Arniston, shipwrecked with the loss of 372 lives.
Controversially, the ship did not have a marine chronometer on board, a comparatively new navigational instrument that was an "easy and cheap addition to her equipment" that would have enabled her to determine her longitude accurately.

Thomas Earnshaw

Earnshaw
The greatest strides toward practicality came at the hands of Thomas Earnshaw and John Arnold, who in 1780 developed and patented simplified, detached, "spring detent" escapements, moved the temperature compensation to the balance, and improved the design and manufacturing of balance springs.
Thomas Earnshaw (4 February 1749 in Ashton-under-Lyne – 1 March 1829 in London) was an English watchmaker who, following John Arnold's earlier work, further simplified the process of marine chronometer production, making them available to the general public.

Gemma Frisius

Frisius, GemmaGemma Frisius, Reiner
The Dutch scientist Gemma Frisius was the first to propose the use of a chronometer to determine longitude in 1530.
Twenty years later, in ~1553, he was the first to describe how an accurate clock could be used to determine longitude.

Time signal

time serviceradio time signaltime
(Time balls became redundant around 1920 with the introduction of radio time signals, which have themselves largely been superseded by GPS time.) In addition to setting their time before departing on a voyage, ship chronometers were also routinely checked for accuracy while at sea by carrying out lunar or solar observations.
Accurate knowledge of time of day is essential for navigation, and ships carried the most accurate marine chronometers available, although they did not keep perfect time.

Ulysse Nardin

Around the turn of the 20th century, Swiss makers such as Ulysse Nardin made great strides toward incorporating modern production methods and using fully interchangeable parts, but it was only with the onset of World War II that the Hamilton Watch Company in the United States perfected the process of mass production, which enabled it to produce thousands of its Hamilton Model 21 and Model 22 chronometers of World War Two for the United States Navy & Army and other Allied navies.
Ulysse Nardin is regarded as a top-tier Kering brand, and is best known for manufacturing highly accurate marine chronometers.

Thomas Mercer Chronometers

Thomas Mercer chronometer
Thomas Mercer Chronometers still makes chronometers to the present day.
Thomas Mercer Chronometers is a British company specialising in the design and production of bespoke chronometers.

Royal Observatory, Greenwich

Royal Greenwich ObservatoryRoyal ObservatoryGreenwich Observatory
It was common for ships at the time to observe a time ball, such as the one at the Royal Observatory, Greenwich, to check their chronometers before departing on a long voyage.
Notable exhibits include John Harrison's sea watch, the H4, which received a large reward from the Board of Longitude, and his three earlier marine timekeepers; all four are the property of the Ministry of Defence.

Longitude rewards

Longitude prizelongitudeprize
The term chronometer was coined from the Greek words χρόνος (chronos) (meaning time) and meter (meaning counter) in 1714 by Jeremy Thacker, an early competitor for the prize set by the Longitude Act in the same year.
The winner of the most reward money under the Longitude Act is John Harrison for sea timekeepers, including his H4 sea watch.

Christiaan Huygens

HuygensChristian HuygensChristiaan Huyghens
Christiaan Huygens, following his invention of the pendulum clock in 1656, made the first attempt at a marine chronometer in 1673 in France, under the sponsorship of Jean-Baptiste Colbert.
Huygens motivation for inventing the pendulum clock was to create an accurate marine chronometer that could be used to find longitude by celestial navigation during sea voyages.