Chronometry

Chronometry, also known as horology, is the study of measuring time and keeping track of it. It helps us set standard measurements of time that we use in many parts of daily life and science. While horology often focuses on mechanical devices like clocks and watches, chronometry is broader and also includes studying how living things and even rocks relate to time.

The hourglass is often used as a symbol representing the passage of time.

People who love studying and working with timekeeping devices are called horologists. There are many groups and societies around the world for these enthusiasts, with the National Association of Watch and Clock Collectors being one of the largest.

The idea of keeping track of time goes back to very old times, with early people marking the phases of the moon to measure years. Over time, this led to the creation of written calendars and then mechanical devices. Today, the most precise timekeeping is done by atomic clocks, which help set the international standard for the second.

Etymology

Chronometry comes from two Ancient Greek words: chronos meaning "time" and metron meaning "measure". Together, they mean measuring time.

Chronos, the Greeks' personification of time

In Ancient Greek, chronos was used to talk about time in a straightforward way, like dates and how long things take. It could mean anything from a few seconds to whole seasons or even lifetimes.

There was also another word, kairos, which was more about the right moment for something to happen. It wasn't as exact as chronos and could mean a good time or a time of crisis. Both words helped Ancient Greeks understand time in different ways.

Subfields

Biochronometry

Biochronometry, also known as chronobiology, studies how animals behave and change based on time. It looks at two main patterns: daily rhythms called circadian rhythms and yearly patterns called circannual cycles. Examples include how sea creatures move with the tides, how plants make food, and how tiny living things change with temperature.

These daily and yearly patterns can be seen in all kinds of living things, from simple cells to humans. Scientists study these patterns to learn more about how living things work and how they change over time. This helps us understand things like sleep and health in humans.

An artistic illustration of the tracking of the earth's history through geology

Mental chronometry

Mental chronometry studies how the human mind processes information, looking at how quickly we react and perceive things. It is part of cognitive psychology and helps us learn about thinking and acting. Scientists measure reaction times using different methods, including studying brain activity with event-related potentials.

Geochronometry

Geochronometry is about finding the age of rocks and geological events. It helps us understand the history of places on Earth, like when volcanoes erupted or when oceans changed. Most dating methods use radioactive decay, where certain materials change over time. One method, called thermoluminescence, measures the light given off by heated materials to find their age.

Time metrology

Time metrology, also called time and frequency metrology, is the science of measuring time very accurately. It helps us define the second as the main unit for measuring time. This field also creates and shares time and frequency standards that everyone can use.

Its main jobs are to make the second real as the SI unit of measurement for time and to set up time standards and frequency standards and share them with others. This helps keep clocks and other time tools working right around the world.

History

Early humans used their senses to tell the time of day and their body's natural rhythms to know the seasons. These rhythms were mainly influenced by a system that measures changes in daylight throughout the year, helping them prepare for future events.

Ancient Egyptian sundial splitting daytime into 12 parts

As humans began farming, understanding the seasons became very important. The phases of the moon were not always reliable, especially when weather made it hard to see. This led to the creation of better ways to track time.

The Ancient Egyptians created one of the first calendars, which lasted for a very long time. They noticed that the star Sirius appeared before sunrise every 365 days, which helped them create a calendar with twelve months of thirty days, plus five extra days. These five days were important in their culture, representing the birthdays of their gods.

The Maya also had a complex calendar system, using a zero date and connecting their timekeeping to their beliefs about the heavens and human life.

Museums and libraries

Europe

"Universal Clock" at the Clock Museum in Zacatlán, Puebla, Mexico

There are many places where you can learn about clocks and timekeeping. One example is the Royal Greenwich Observatory, which helped create the Prime Meridian and kept very accurate clocks made by John Harrison. In London, you can visit the Clockmakers' Museum, the British Museum, the Science Museum (London), and the Wallace Collection. The Guildhall Library in London also has many books about clocks.

In Switzerland, the Musée international d'horlogerie in La Chaux-de-Fonds is a big museum about timekeeping. Nearby, the Musée d'Horlogerie du Locle is smaller but still interesting. France has the Musée du Temps (Museum of Time) in Besançon. Portugal has the Museu do Relógio in Serpa and Évora. Germany has the Deutsches Uhrenmuseum in Furtwangen im Schwarzwald, in the Black Forest.

North America

In North America, the National Watch and Clock Museum in Columbia, Pennsylvania and the American Clock and Watch Museum in Bristol, Connecticut are two main places to learn about clocks. The Willard House and Clock Museum in Grafton, Massachusetts is another clock museum. The National Watch and Clock Library in Columbia, Pennsylvania has many books about timekeeping.

Organizations

Several groups around the world study and share knowledge about timekeeping. Some of these groups include the American Watchmakers-Clockmakers Institute in the United States, the Antiquarian Horological Society in the United Kingdom, and the British Horological Institute, also in the United Kingdom. Other groups include Chronometrophilia in Switzerland, the Deutsche Gesellschaft für Chronometrie in Germany, the Horological Society of New York in the United States, and the National Association of Watch and Clock Collectors in the United States.

Glossary

Term	Explanation
Chablon	French term for a watch movement (not including the dial and hands), that is not completely assembled.
Ébauche	French term (commonly used in English-speaking countries) for a movement blank, i.e., an incomplete watch movement sold as a set of loose parts—comprising the main plate, bridges, train, winding and setting mechanism, and regulator. The timing system, escapement, and mainspring, however, are not parts of the ébauche.
Établissage	French term for the method of manufacturing watches or movements by assembling their various components. It generally includes the following operations: receipt, inspection and stocking of the "ébauche", the regulating elements and the other parts of the movement and of the make-up; assembling; springing and timing; fitting the dial and hands; casing; final inspection before packing and dispatching.
Établisseur	French term for a watch factory that assembles watches from components it buys from other suppliers.
Factory, works	In the Swiss watch industry, the term manufacture is used of a factory that manufacturers watches almost completely, as distinct from an atelier de terminage, which only assembles, times, and fits hands and casing.
Manufacture d'horlogerie	French term for a watch factory that produces components (particularly the "ébauche") for its products (watches, alarm and desk clocks, etc.).
Remontoire	French term for a small secondary source of power, typically a weight or spring, which runs the timekeeping mechanism and is itself periodically rewound by the timepiece's main power source, such as a mainspring.
Terminage	French term denoting the process of assembling watch parts for the account of a producer.
Termineur	French term for an independent watchmaker (or workshop) engaged in assembling watches, either wholly or in part, for the account of an "établisseur" or a "manufacture", who supply the necessary loose parts. See "atelier de terminage" above.