Corpus Clock

Corpus Clock

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The Corpus Clock is a large sculptural clock
A clock is an instrument used to indicate, keep, and co-ordinate time. The word clock is derived ultimately from the Celtic words clagan and clocca meaning "bell". A silent instrument missing such a mechanism has traditionally been known as a timepiece...

 at street level on the outside of the Taylor Library at Corpus Christi College
Corpus Christi College, Cambridge
Corpus Christi College is a constituent college of the University of Cambridge. It is notable as the only college founded by Cambridge townspeople: it was established in 1352 by the Guilds of Corpus Christi and the Blessed Virgin Mary...

, Cambridge University
University of Cambridge
The University of Cambridge is a public research university located in Cambridge, United Kingdom. It is the second-oldest university in both the United Kingdom and the English-speaking world , and the seventh-oldest globally...

, at the junction of Bene't Street
Bene't Street
Bene't Street is a short but historic street in central Cambridge, England. There is a junction with King's Parade to the north and Trumpington Street to the south at the western end of the street. Free School Lane leads off to the south. To the east, the street continues as Wheeler Street.The...

 and Trumpington Street
Trumpington Street
Trumpington Street is a major historic street in central Cambridge, England. At the north end it continues as King's Parade where King's College is located...

, looking out over King's Parade
King's Parade
King's Parade is a historical street in central Cambridge, England. The street continues north as Trinity Street and then St John's Street, and south as Trumpington Street. It is a major tourist area in Cambridge, commanding a central position in the University of Cambridge area of the city...

. It was conceived and funded by John C. Taylor
John C. Taylor (inventor)
John Crawshaw Taylor OBE is a British inventor, entrepreneur, horologist and philanthropist best known for his extensive research into electric kettles.- Career :...

, an old member of the college.

It was officially unveiled to the public on 19 September 2008 by Cambridge physicist
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...

 Stephen Hawking
Stephen Hawking
Stephen William Hawking, CH, CBE, FRS, FRSA is an English theoretical physicist and cosmologist, whose scientific books and public appearances have made him an academic celebrity...


The clock was one of Time
Time (magazine)
Time is an American news magazine. A European edition is published from London. Time Europe covers the Middle East, Africa and, since 2003, Latin America. An Asian edition is based in Hong Kong...

s Best Inventions of 2008. It also features in the Indian
Cinema of India
The cinema of India consists of films produced across India, which includes the cinematic culture of Andhra Pradesh, Assam, Gujarat, Haryana, Jammu and Kashmir, Karnataka, Kerala, Maharashtra, Orissa, Punjab, Tamil Nadu, and West Bengal. Indian films came to be followed throughout South Asia and...

 movie Paa
Paa (film)
Paa is a 2009 Indian film directed by R. Balakrishnan starring Amitabh Bachchan, Abhishek Bachchan, and Vidya Balan. The film is based on a rare genetic condition known as progeria and places emphasis on a father-son relationship...

 and the associated music video Mudi Mudi.


The clock's face is a rippling 24-carat
Carat (purity)
The karat or carat is a unit of purity for gold alloys.- Measure :Karat purity is measured as 24 times the purity by mass:where...

Gold plating
Gold plating is a method of depositing a thin layer of gold onto the surface of another metal, most often copper or silver , by chemical or electrochemical plating...

 stainless steel
Stainless steel
In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass....

 disc, about 1.5 metres (4.9 ft) in diameter. It has no hands or numbers, but displays the time by opening individual slits in the clock face backlit with blue LEDs
Light-emitting diode
A light-emitting diode is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting...

; these slits are arranged in three concentric rings displaying hour
The hour is a unit of measurement of time. In modern usage, an hour comprises 60 minutes, or 3,600 seconds...

s, minute
A minute is a unit of measurement of time or of angle. The minute is a unit of time equal to 1/60th of an hour or 60 seconds. In the UTC time scale, a minute on rare occasions has 59 or 61 seconds; see leap second. The minute is not an SI unit; however, it is accepted for use with SI units...

s, and second
The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock....


The dominating visual feature of the clock is a sculpture of a grim-looking, devouring, metal insect similar to a grasshopper
The grasshopper is an insect of the suborder Caelifera in the order Orthoptera. To distinguish it from bush crickets or katydids, it is sometimes referred to as the short-horned grasshopper...

 or locust
Locusts are the swarming phase of short-horned grasshoppers of the family Acrididae. These are species that can breed rapidly under suitable conditions and subsequently become gregarious and migratory...

. The sculpture is actually the clock's escapement
In mechanical watches and clocks, an escapement is a device that transfers energy to the timekeeping element and enables counting the number of oscillations of the timekeeping element...

 (see below). Taylor calls this beast the Chronophage (literally "time eater", from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 χρόνος [chronos] time
Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....

, and φάγω [phago] I eat). It moves its mouth, appearing to "eat up" the seconds as they pass, and occasionally it "blinks" in seeming satisfaction. The creature's constant motion produces an eerie grinding sound that suits its task. The hour is tolled by the sound of a chain clanking into a small wooden coffin hidden in the back of the clock.
The Chronophage is affectionately known by students variously as 'Rosalind', a name coined by the college's Prælector, or 'Hopsy'.

Below the clock is an inscription from the Vulgate
The Vulgate is a late 4th-century Latin translation of the Bible. It was largely the work of St. Jerome, who was commissioned by Pope Damasus I in 382 to make a revision of the old Latin translations...

 1 John
First Epistle of John
The First Epistle of John, often referred to as First John and written 1 John, is a book of the New Testament. This fourth catholic or "general" epistle is attributed to John the Evangelist, traditionally thought to be the author of the Gospel of John and the other two Epistles of John. This...

 2:17: mundus transit et concupiscentia eius ("the world passeth away, and the lust thereof").

The clock is entirely accurate only once every five minutes. The rest of the time, the pendulum
A pendulum is a weight suspended from a pivot so that it can swing freely. When a pendulum is displaced from its resting equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the equilibrium position...

 may seem to catch or stop, and the lights may lag or, then, race to get ahead. According to Taylor, this erratic motion reflects life's "irregularity".

Conceived as a work of public art, the Chronophage reminds viewers in a dramatic way of the inevitable passing of time. Taylor deliberately designed it to be "terrifying": "Basically I view time as not on your side. He'll eat up every minute of your life, and as soon as one has gone he's salivating for the next." Others have described it as "hypnotically beautiful and deeply disturbing".

Mechanics of the clock

The Corpus Clock is a product of traditional mechanical clockmaking. It features the world's largest grasshopper escapement
Grasshopper escapement
The grasshopper escapement is an unusual, low-friction escapement for pendulum clocks invented by British clockmaker John Harrison around 1722. An escapement, part of every mechanical clock, is the mechanism that causes the clock's gears to move forward by a fixed distance at regular intervals and...

, a low-friction mechanism for converting pendulum motion into rotational motion while at the same time giving back to the pendulum the energy needed to maintain its swing. The grasshopper escapement was an invention of the renowned eighteenth-century clockmaker John Harrison
John Harrison
John Harrison was a self-educated English clockmaker. He invented the marine chronometer, a long-sought device in solving the problem of establishing the East-West position or longitude of a ship at sea, thus revolutionising and extending the possibility of safe long distance sea travel in the Age...

, and Taylor intended the Corpus Clock to be a homage to Harrison's work. Since "no one knows how a grasshopper escapement works", Taylor "decided to turn the clock inside out" so that the escapement
In mechanical watches and clocks, an escapement is a device that transfers energy to the timekeeping element and enables counting the number of oscillations of the timekeeping element...

, and the escape wheel it turns, would be his clock's defining feature.

The Corpus Clock's clockwork
A clockwork is the inner workings of either a mechanical clock or a device that operates in a similar fashion. Specifically, the term refers to a mechanical device utilizing a complex series of gears....

 is entirely mechanically controlled, without any computer programming
Digital clock
A digital clock is a type of clock that displays the time digitally, i.e. in cyphers, as opposed to an analog clock, where the time is displayed by hands. Digital clocks are often associated with electronic drives, but the "digital" description refers only to the display, not to the drive mechanism...

, and electricity is used only to power a motor
Electric motor
An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...

, which winds up the mechanism, and to power the blue LEDs
LEDS can be initials for:* Law Enforcement Data System* Link Eleven Display System* Low Energy Dislocation Structure* Land Electronic Defence System * LEDs * Life-Events and Difficulties Schedule...

 that shine behind the slits in the clock's face. The clock has many unexpected and innovative features; for example, the pendulum briefly stops at apparently irregular intervals, and the Chronophage moves its mouth and blinks its eyes. Taylor explains it as follows:

The gold eyelids travel across the eye and disappear again in an instant; if you are not watching carefully you will not even notice... Sometimes you will even see two blinks in quick succession. The Blink is performed by a hidden spring drive, controlled in the best tradition of seventeenth century clockmakers of London. The spring is coiled up inside a housing that can be seen mounted on the large gearwheel visibly protruding from the bottom of the mechanism. As the huge pendulum below the Clock rocks the Chronophage as he steps round the great escapewheel, each backward and forward movement is used by sprag
A sprag clutch is a one-way freewheel clutch. It resembles a roller bearing, but instead of cylindrical rollers, non-revolving asymmetric figure-of-eight shaped sprags are used...

 clutches to wind up the drive spring. A position step prevents the spring from being overwound yet allows the spring to be ready at an instant to drive the Blink. The mechanism is released by a countwheel with semi random spacing so the Blink takes place at any position in the to- and fro- motion of the pendulum. A further countwheel mechanism chooses a single or a double blink whilst the air damper at the top of the gear train
Gear train
A gear train is formed by mounting gears on a frame so that the teeth of the gears engage. Gear teeth are designed to ensure the pitch circles of engaging gears roll on each other without slipping, this provides a smooth transmission of rotation from one gear to the next.The transmission of...

 slows the action to a realistic pace.

The Corpus Clock is expected to be able to run accurately for at least two hundred years. In practice, however, it stopped three times in the first month of its operation.

Funding and realisation

Taylor invested five years and £1 million in the Corpus Clock project, and two hundred people, including engineers, sculptors, scientists, jewellers
Jewellery or jewelry is a form of personal adornment, such as brooches, rings, necklaces, earrings, and bracelets.With some exceptions, such as medical alert bracelets or military dog tags, jewellery normally differs from other items of personal adornment in that it has no other purpose than to...

, and calligraphers
Calligraphy is a type of visual art. It is often called the art of fancy lettering . A contemporary definition of calligraphic practice is "the art of giving form to signs in an expressive, harmonious and skillful manner"...

, were involved. The clockwork incorporates six new patent
A patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....

ed inventions. The rippling gold-plated dial was made by explosive forming
Explosive forming
Explosive forming is a metalworking technique in which an explosive charge is used instead of a punch or press. It can be used on materials for which a press setup would be prohibitively large or require an unreasonably high pressure, and is generally much cheaper than building a large enough and...

–using an explosive charge to press a thin sheet of stainless steel onto a mould underwater at a "secret military research institute in Holland." Stewart Huxley was the design engineer. Sculptor Matthew Sanderson modelled the Chronophage. The graticule, or measuring dish, for the Corpus Clock was designed and created by Alan Meeks of Visitech Design. It was machined in aluminium and silver before being plated with gold and rhodium
Rhodium is a chemical element that is a rare, silvery-white, hard and chemically inert transition metal and a member of the platinum group. It has the chemical symbol Rh and atomic number 45. It is composed of only one isotope, 103Rh. Naturally occurring rhodium is found as the free metal, alloyed...


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