A marine chronometer is a timekeeper precise enough to be used as a portable time standard, used to determine longitude by means of celestial navigation. A time scale specifies divisions of time. ... Longitude, sometimes denoted by the Greek letter λ (lambda),[1][2] describes the location of a place on Earth east or west of a north-south line called the Prime Meridian. ... Celestial Navigation is the 15th episode of The West Wing. ...

The term chronometer is also used to describe watches tested and certified to meet certain precision standards. In Switzerland, only timepieces certified by the COSC may use the word 'Chronometer' on them. A wrist watch A clock (from the Latin cloca, bell) is an instrument for measuring time. ... Contrôle Officiel Suisse des Chronomètres // Founded in its current structure in 1973, the COSC (Contrôle Officiel Suisse des Chronomètres) is the Swiss Official Chronometer Testing Institute. ...

History

Bréguet twin barrel box chronometer.

Until the mid 1850s, navigation at sea was an unsolved problem due to the difficulty in calculating longitudinal position. Navigators could determine their latitude by measuring the sun's angle at noon. However, to find their longitude, they needed a portable time standard that would work aboard a ship. The purpose of a chronometer is to keep the time of a known fixed location, which can then serve as a reference point for determining the ship's position. Conceptually, by comparing local high noon to the chronometer's time, a navigator could use the time difference to determine the ship's present longitude. Since the Earth rotates 360 degrees every day (24 hours, 1440 minutes), the time difference between the two points reveals how many degrees separate them. With the degrees of difference in hand, locating the position on a map was a relatively simple matter of spherical trigonometry. (In modern practice, a navigational almanac and trigonometric sight-reduction tables permit navigators to measure the Sun, Moon, visible planets, or any of 57 navigational stars at any time that the horizon is visible). Image File history File links Download high-resolution version (1402x1406, 211 KB) Work by Rama File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Chronometer 1893 ... Image File history File links Download high-resolution version (1402x1406, 211 KB) Work by Rama File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Chronometer 1893 ... A Breguet Classique watch with tourbillon Breguet is a manufacturer of fine watches, founded by Abraham Louis Breguet in Paris in 1775. ... Table of geography, hydrography, and navigation, from the 1728 Cyclopaedia. ... Sea as seen from jetty in Frankston, Australia Look up maritime in Wiktionary, the free dictionary. ... Latitude, usually denoted symbolically by the Greek letter phi, , gives the location of a place on Earth north or south of the equator. ... Longitude, sometimes denoted by the Greek letter λ (lambda),[1][2] describes the location of a place on Earth east or west of a north-south line called the Prime Meridian. ... Noon is the time exactly halfway through the day, written 12:00 in the 24-hour clock and 12:00 noon in the 12-hour clock. ... A pocket watch, a device used to tell time Look up time in Wiktionary, the free dictionary. ... The Sun is the star at the center of the Solar System. ... Apparent magnitude: up to -12. ... The eight planets and three dwarf planets of the Solar System. ...

The creation of a seaworthy timepiece was difficult. Until the 20th century, the best timekeepers were pendulum clocks, and the rolling of a ship at sea rendered the ordinary, gravity-based pendulum useless. John Harrison, a Yorkshire carpenter, invented a clock based on a pair of counter-oscillating weighted beams connected by springs whose motion was not influenced by gravity or the motion of a ship. His first two sea timekeepers used this system, but he became rightly convinced that they had a fundamental sensitivity to centrifugal force, which meant that they could never be accurate enough at sea. His third machine replaced one headache with a bigger one, and he eventually abandoned the large machines. Harrison solved the precision problems with his H4 chronometer, essentially a large five-inch (12 cm) diameter pocket watch, which he submitted for a £20,000 prize offered by the British government in the early 18th century. His design used a fast-beating balance controlled by a temperature compensated spiral spring. This general layout remained in use until microchips reduced the cost of a quartz clock to the point that electronic chronometers became commonplace. A pendulum clock uses a pendulum as its time base. ... John Harrison John Harrison (March 24, 1693–March 24, 1776) was an English clockmaker, who designed and built the worlds first successful chronometer (maritime clock), one whose accuracy was great enough to allow the determination of longitude over long distances. ... Centrifugal force (from Latin centrum center and fugere to flee) is a term which may refer to two different forces which are related to rotation. ... A die in the context of integrated circuits is a small piece of semiconducting material on which a given circuit is fabricated. ... A quartz clock A quartz clock is a timepiece that uses an electronic oscillator which is made up by a quartz crystal to keep precise time. ...

After Harrison's work proved the possibility of portable precision timekeepers, making them practical by perfecting simpler and more affordable designs was the next problem. Pierre Le Roy and Ferdinand Berthoud in France, and Thomas Mudge in England successfully produced marine timekeepers. Although none of these makers discovered a path to simplicity, they did encourage others by proving that Harrison's design was not the only answer to the problem. The greatest strides toward practicality came at the hands of Thomas Earnshaw and John Arnold, who developed simplified, detached, "spring detent" escapements, moved the temperature compensation to the balance, and improved the design and manufacturing of balance springs. This combination of innovations served as the basis of marine chronometers until the electronic era. Thomas Earnshaw (born on February 4, 1749 in in Ashton-under-Lyne - died March 1, 1829 in London) was an English watchmaker who first simplified the process of chronometer production, making them available to the general public. ... London watchmaker John Arnold (1736–99), was one of the true master clockmakers from what was unarguably England’s golden age of horology. ... A simple escapement. ...

Although industrial production methods began revolutionizing watchmaking in the middle of the 19th century, chronometer manufacture remained craft-based much longer. Around the turn of the 20th century, Swiss makers like Ulysse Nardin made great strides toward incorporating modern production methods, like fully interchangeable parts, but it was only with the onset of World War II that the American Hamilton Watch Company succeeded in mass production of chronometers in quantity for the US Navy. Despite Hamilton's success, chronometers made in the old way never disappeared from the marketplace during the era of mechanical timekeepers. Mercer, in St. Albans, England, for instance, continued to produce high-quality chronometers by traditional production methods well into the 1970s. Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki Tōjō Casualties Military dead: 17,000,000 Civilian dead: 33,000... Hamilton pocketwatch, ca. ... Mass production is the production of large amounts of standardised products on production lines. ... The United States Navy (USN) is the branch of the United States armed forces responsible for naval operations. ...

The most complete international collection of marine chronometers, including Harrison's H1 to H4, is at the National Maritime Museum, Greenwich, England.

Mechanical chronometers

A chronometer mechanism diagrammed (text is in German). Note fusee to transform varying spring tension to a constant force

The crucial problem was to find a resonator that remained unaffected by the changing conditions met by a ship at sea. The balance wheel harnessed to a spring solved most of the problems associated with the ship's motion. Unfortunately, the elasticity of most balance spring materials changes relative to temperature. To compensate for ever-changing spring strength, the majority of chronometer balances used bi-metallic strips to move small weights toward and away from the center of oscillation, thus altering the period of the balance to match the changing force of the spring. The balance spring problem was solved with a nickel-steel named Elinvar for its invariable elasticity at normal temperatures. The inventor was Charles Edouard Guillaume, who won the Nobel Prize for physics in recognition for his metallurgical work (the only Nobel that has been granted for work related to horology). Image File history File links Size of this preview: 725 × 599 pixel Image in higher resolution (1355 × 1120 pixel, file size: 156 KB, MIME type: image/png) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Chronometer ... Image File history File links Size of this preview: 725 × 599 pixel Image in higher resolution (1355 × 1120 pixel, file size: 156 KB, MIME type: image/png) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Chronometer ... The spring-powered clock (invented in about 1510 by Peter Henlein of Nuremberg, Germany) did have its problems, that of slowing down when the mainspring unwound. ... Red arrows indicate the balance wheel on this movement. ... Elinvar is the name of a type of metallic alloy with a modulus of elasticity which does not vary with temperature; the name means elastically invariable. ... Charles Édouard Guillaume (February 15, 1861, Fleurier – June 13, 1938, Sèvres), was a French-Swiss Physicist that received the Nobel Prize in Physics in 1920 in recognition of the service he had rendered to precision measurements in Physics by his discovery of anomalies in nickel steel alloys. ... List of Nobel Prize laureates in Physics from 1901 to the present day. ... Horology is the study of the science and art of timekeeping devices. ...

The escapement serves two purposes. First, it allows the train to advance fractionally and record the balance's oscillations. At the same time, it supplies minute amounts of energy to counter tiny losses from friction, thus maintaining the equilibrium of the oscillating balance. The escapement is the part that ticks. Since the natural resonance of an oscillating balance serves as the heart of a chronometer, chronometer escapements are designed to interfere with the balance as little as possible. There are many constant force and detached escapement designs, but the most common are the spring detent and pivoted detent. In both of these, a small detent locks the escape wheel and allows the balance to swing completely free of interference except for a brief moment at the center of oscillation, when it is least susceptible to outside influences. At the center of oscillation, a roller on the balance staff momentarily displaces the detent, allowing one tooth of the escape wheel to pass. The escape wheel tooth then imparts its energy on a second roller on the balance staff. Since the escape wheel turns in only one direction, the balance receives impulse in only one direction. On the return oscillation, a passing spring on the tip of the detent allows the unlocking roller on the staff to move by without displacing the detent. A simple escapement. ...

Chronometers often included other innovations to increase their efficiency and precision. Hard stones such as diamond^{[citation needed]}, ruby, and sapphire were often use as jewel bearings to decrease friction and wear of the pivots and escapement. Until the end of mechanical chronometer production in the third quarter of the 20th century, makers continued to experiment with things like ball bearings and chrome-plated pivots. ruby jewel bearings used in an Omega mechanical watch movement A jewel bearing is a bearing which allows motion by running a shaft slightly off-center so that the shaft rolls inside of the bearing rather than sliding. ...

Marine chronometers always contain a maintaining power which keeps the chronometer going while it is being wound, and a power reserve to indicate how long the chronometer will continue to run without being wound. In horology, a maintaining power is a mechanism for keeping a clock or watch going while it is being wound. ... Types of power reserve indicator Power Reserve Indicator - originally called French: - is a function of the watch, which is meant to show how long the watch is going to work until the next winding. ...

Today

Quartz clocks and atomic clocks have made mechanical clock-chronometers obsolete for time standards used scientifically and/or industrially. A quartz clock A quartz clock is a timepiece that uses an electronic oscillator which is made up by a quartz crystal to keep precise time. ... Chip-Scale Atomic Clock Unveiled by NIST An atomic clock is a type of clock that uses an atomic resonance frequency standard to feed its counter. ...

• Clock
• Clockmaker
• Chronometer watch
• Horology
• Jewel bearing
• Railroad chronometers
• Watch
• Watchmaker

A wrist watch A clock (from the Latin cloca, bell) is an instrument for measuring time. ... A clockmaker is an artisan who makes and repairs clocks. ... Horology is the study of the science and art of timekeeping devices. ... ruby jewel bearings used in an Omega mechanical watch movement A jewel bearing is a bearing which allows motion by running a shaft slightly off-center so that the shaft rolls inside of the bearing rather than sliding. ... Railroad chronometers (railroaders watches) were critical to the safe and correct operation of trains in the United States. ... A wrist watch Pocket watch with chain TIMEX Ironman Triathlon A watch is a timepiece or clock that displays the time and sometimes the day, date, month and year. ... A watchmaker is an artisan who makes and repairs watches. ...

External links

• National Maritime Museum, Greenwich