Corpus Clock

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The Corpus Clock at Corpus Christi College, Cambridge Corpus clock pol.jpg
The Corpus Clock at Corpus Christi College, Cambridge

The Corpus Clock, also known as the Grasshopper clock, is a large sculptural clock at street level on the outside of the Taylor Library at Corpus Christi College, University of Cambridge, in the United Kingdom, at the junction of Bene't Street and Trumpington Street, looking out over King's Parade. It was conceived and funded by John C. Taylor, an old member of the college.

It was officially unveiled to the public on 19 September 2008 by Cambridge physicist Stephen Hawking. [1] The clock was named one of Time's Best Inventions of 2008. [2]

Appearance

The Corpus Clock with two people for scale, looking down Bene't Street at night Cmglee Cambridge Corpus Clock night.jpg
The Corpus Clock with two people for scale, looking down Bene't Street at night

The clock's face is a rippling 24-carat gold-plated stainless steel disc, about 1.5 metres (4.9 ft) in diameter. It has no hands or numerals, but displays the time by opening individual slits in the clock face backlit with blue LEDs; these slits are arranged in three concentric rings displaying hours, minutes, and seconds.

Video

The dominating visual feature of the clock is a grim-looking metal sculpture of an insectoid creature similar to a grasshopper or locust. The sculpture is actually the clock's escapement (see below). Taylor calls this beast the Chronophage (literally "time eater", from the Greek χρόνος [chronos] time , and εφάγον [ephagon] I ate). 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. [3]

The Chronophage is affectionately known by students variously as "Rosalind", a name coined by the college's Prælector, or "Hopsy".[ citation needed ]

Below the clock is an inscription from the Vulgate 1 John 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. [4] The rest of the time, the pendulum 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". [5]

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." It has been described as "hypnotically beautiful and deeply disturbing". [6]

Mechanics of the clock

Simplified animation of the escapement, and "second" and "minute" discs. For clarity, each "minute" is divided into only 10 "seconds", each 6 times longer than an ordinary second, and the "minute" disc is folded to the right. The green lines represent slots in the rotating discs, while the blue lines represent fixed slots. Corpus Clock principle.svg
Simplified animation of the escapement, and "second" and "minute" discs. For clarity, each "minute" is divided into only 10 "seconds", each 6 times longer than an ordinary second, and the "minute" disc is folded to the right. The green lines represent slots in the rotating discs, while the blue lines represent fixed slots.
Opened to show its interior Cmglee Cambridge Corpus Clock open.jpg
Opened to show its interior

The Corpus Clock is a product of traditional mechanical clockmaking. It features the world's largest grasshopper escapement, 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, 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" [7] so that the escapement, and the escape wheel it turns, would be his clock's defining feature.

The Corpus Clock's clockwork is entirely mechanically controlled, without any computer programming, and electricity is used only to power a motor, which winds up the mechanism, and to power the blue LEDs 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 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 slows the action to a realistic pace. [8]

The Corpus Clock is expected to be able to run accurately for at least two hundred years. [9]

Funding and realisation

The Taylor Library and the Corpus Clock on the northwest corner of Corpus Christi College TaylorClock.JPG
The Taylor Library and the Corpus Clock on the northwest corner of Corpus Christi College

Taylor invested five years and £1 million in the Corpus Clock project, and two hundred people, including engineers, sculptors, scientists, jewellers, and calligraphers, were involved. The clockwork incorporates six new patented inventions. The rippling gold-plated dial was made by explosive forming–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. [6] The graticule, or measuring dish, for the Corpus Clock was designed and created by Alan Meeks of Visitech Design. [10] It was machined in aluminium and silver before being plated with gold and rhodium. Matters relating to the Corpus Clock are dealt with by the Custodian of the Corpus Chronophage Clock, a post currently held by Dr Ewan St. John Smith. [11]

There are sisters to the Corpus Chronophage, the Dragon Chronophage that Taylor installed in the eccentric oval mansion Arragon Mooar House he built on the Isle of Man Also a further chronophage clock on loan and in display outside bar 1886 in Regent Street in the city of Douglas in the Isle of Man . [12]

The clock is featured in the Hindi movie Paa , the associated music video "Mudi Mudi", and is shown briefly in the third episode of the television series Zero Hour and in the fifth episode of the Chinese television series Here to Heart . The clock is also featured as a plot element in the alternate history novel "The Quantum Curators and the Fabergé Egg" by Eva St. John.

Related Research Articles

<span class="mw-page-title-main">John Harrison</span> English clockmaker (1693–1776)

John Harrison was an English carpenter and clockmaker who invented the marine chronometer, a long-sought-after device for solving the problem of how to calculate longitude while at sea.

<span class="mw-page-title-main">Pendulum clock</span> Clock regulated by a pendulum

A pendulum clock is a clock that uses a pendulum, a swinging weight, as its timekeeping element. The advantage of a pendulum for timekeeping is that it is an approximate harmonic oscillator: It swings back and forth in a precise time interval dependent on its length, and resists swinging at other rates. From its invention in 1656 by Christiaan Huygens, inspired by Galileo Galilei, until the 1930s, the pendulum clock was the world's most precise timekeeper, accounting for its widespread use. Throughout the 18th and 19th centuries, pendulum clocks in homes, factories, offices, and railroad stations served as primary time standards for scheduling daily life, work shifts, and public transportation. Their greater accuracy allowed for the faster pace of life which was necessary for the Industrial Revolution. The home pendulum clock was replaced by less-expensive synchronous electric clocks in the 1930s and 1940s. Pendulum clocks are now kept mostly for their decorative and antique value.

<span class="mw-page-title-main">Pendulum</span> Mechanism for regulating the speed of clocks

A pendulum is a device made of a weight suspended from a pivot so that it can swing freely. When a pendulum is displaced sideways from its resting, equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the equilibrium position. When released, the restoring force acting on the pendulum's mass causes it to oscillate about the equilibrium position, swinging back and forth. The time for one complete cycle, a left swing and a right swing, is called the period. The period depends on the length of the pendulum and also to a slight degree on the amplitude, the width of the pendulum's swing.

<span class="mw-page-title-main">Grasshopper escapement</span> Low friction clock escapement

The grasshopper escapement is a 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 gives the clock's pendulum periodic pushes to keep it swinging, and each swing releases the clock's gears to move forward by a fixed amount, thus moving the hands forward at a steady rate. The grasshopper escapement was used in a few regulator clocks built during Harrison's time, and a few others over the years, but has never seen wide use. The term "grasshopper" in this connection, apparently from the kicking action of the pallets, first appears in the Horological Journal in the late 19th century.

<span class="mw-page-title-main">Escapement</span> Mechanism for regulating the speed of clocks

An escapement is a mechanical linkage in mechanical watches and clocks that gives impulses to the timekeeping element and periodically releases the gear train to move forward, advancing the clock's hands. The impulse action transfers energy to the clock's timekeeping element to replace the energy lost to friction during its cycle and keep the timekeeper oscillating. The escapement is driven by force from a coiled spring or a suspended weight, transmitted through the timepiece's gear train. Each swing of the pendulum or balance wheel releases a tooth of the escapement's escape wheel, allowing the clock's gear train to advance or "escape" by a fixed amount. This regular periodic advancement moves the clock's hands forward at a steady rate. At the same time, the tooth gives the timekeeping element a push, before another tooth catches on the escapement's pallet, returning the escapement to its "locked" state. The sudden stopping of the escapement's tooth is what generates the characteristic "ticking" sound heard in operating mechanical clocks and watches.

A grandfather clock is a tall, freestanding, weight-driven pendulum clock, with the pendulum held inside the tower or waist of the case. Clocks of this style are commonly 1.8–2.4 metres (6–8 feet) tall with an enclosed pendulum and weights, suspended by either cables or chains, which have to be occasionally calibrated to keep the proper time. The case often features elaborately carved ornamentation on the hood, which surrounds and frames the dial, or clock face.

<span class="mw-page-title-main">Movement (clockwork)</span> Mechanism of a watch or clock

In horology, a movement, also known as a caliber or calibre, is the mechanism of a watch or timepiece, as opposed to the case, which encloses and protects the movement, and the face, which displays the time. The term originated with mechanical timepieces, whose clockwork movements are made of many moving parts. The movement of a digital watch is more commonly known as a module.

<span class="mw-page-title-main">Anchor escapement</span> Type of mechanism used in pendulum clocks

In horology, the anchor escapement is a type of escapement used in pendulum clocks. The escapement is a mechanism in a mechanical clock that maintains the swing of the pendulum by giving it a small push each swing, and allows the clock's wheels to advance a fixed amount with each swing, moving the clock's hands forward. The anchor escapement was so named because one of its principal parts is shaped vaguely like a ship's anchor.

<span class="mw-page-title-main">Verge escapement</span> Early clock mechanism

The vergeescapement is the earliest known type of mechanical escapement, the mechanism in a mechanical clock that controls its rate by allowing the gear train to advance at regular intervals or 'ticks'. Verge escapements were used from the late 13th century until the mid 19th century in clocks and pocketwatches. The name verge comes from the Latin virga, meaning stick or rod.

<span class="mw-page-title-main">Balance wheel</span> Time measuring device

A balance wheel, or balance, is the timekeeping device used in mechanical watches and small clocks, analogous to the pendulum in a pendulum clock. It is a weighted wheel that rotates back and forth, being returned toward its center position by a spiral torsion spring, known as the balance spring or hairspring. It is driven by the escapement, which transforms the rotating motion of the watch gear train into impulses delivered to the balance wheel. Each swing of the wheel allows the gear train to advance a set amount, moving the hands forward. The balance wheel and hairspring together form a harmonic oscillator, which due to resonance oscillates preferentially at a certain rate, its resonant frequency or "beat", and resists oscillating at other rates. The combination of the mass of the balance wheel and the elasticity of the spring keep the time between each oscillation or "tick" very constant, accounting for its nearly universal use as the timekeeper in mechanical watches to the present. From its invention in the 14th century until tuning fork and quartz movements became available in the 1960s, virtually every portable timekeeping device used some form of balance wheel.

<span class="mw-page-title-main">Galileo's escapement</span>

Galileo's escapement is a design for a clock escapement, invented around 1637 by Italian scientist Galileo Galilei (1564–1642). Galileo was one of the leading minds of the Scientific Revolution. He was dubbed the founder of theoretical physics. He is also credited with the invention of the celatone and the geometric and military compass. Galileo's escapement was the earliest design of a pendulum clock. Since Galileo was by then blind, he described the device to his son Vincenzio, who drew a sketch of it. The son began construction of a prototype, but both he and Galileo died before it was completed.

<span class="mw-page-title-main">Torsion pendulum clock</span> Clock that uses a torsion pendulum to keep time

A torsion pendulum clock, more commonly known as an anniversary clock or 400-day clock, is a mechanical clock which keeps time with a mechanism called a torsion pendulum. This is a weighted disk or wheel, often a decorative wheel with three or four chrome balls on ornate spokes, suspended by a thin wire or ribbon called a torsion spring. The torsion pendulum rotates about the vertical axis of the wire, twisting it, instead of swinging like an ordinary pendulum. The force of the twisting torsion spring reverses the direction of rotation, so the torsion pendulum oscillates slowly, clockwise and counterclockwise. The clock's gears apply a pulse of torque to the top of the torsion spring with each rotation to keep the wheel going. The Atmos Clock made by the Swiss company Jaeger-LeCoultre is another style of this clock. The wheel and torsion spring function similarly to a watch's balance wheel and hairspring, as a harmonic oscillator to control the rate of the clock's hands.

In mechanical horology, a remontoire is a small secondary source of power, 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. It was used in a few precision clocks and watches to place the source of power closer to the escapement, thereby increasing the accuracy by evening out variations in drive force caused by unevenness of the friction in the geartrain. In spring-driven precision clocks, a gravity remontoire is sometimes used to replace the uneven force delivered by the mainspring running down by the more constant force of gravity acting on a weight. In turret clocks, it serves to separate the large forces needed to drive the hands from the modest forces needed to drive the escapement which keeps the pendulum swinging. A remontoire should not be confused with a maintaining power spring, which is used only to keep the timepiece going while it is being wound.

<span class="mw-page-title-main">Riefler escapement</span> Mechanical escapement for pendulum clocks

The Riefler escapement is a mechanical escapement for precision pendulum clocks invented and patented by German instrument maker Sigmund Riefler in 1889. It was used in the astronomical regulator clocks made by his German firm Clemens Riefler from 1890 to 1965, which were perhaps the most accurate all-mechanical pendulum clocks made.

<span class="mw-page-title-main">Turret clock</span> Large prominently located clock used as a public amenity

A turret clock or tower clock is a clock designed to be mounted high in the wall of a building, usually in a clock tower, in public buildings such as churches, university buildings, and town halls. As a public amenity to enable the community to tell the time, it has a large face visible from far away, and often a striking mechanism which rings bells upon the hours.

<span class="mw-page-title-main">Marine chronometer</span> Clock used on ships to aid in navigation

A marine chronometer is a precision timepiece that is carried on a ship and employed in the determination of the ship's position by celestial navigation. It is used to determine longitude by comparing Greenwich Mean Time (GMT), and the time at the current location found from observations of celestial bodies. When first developed in the 18th century, it was a major technical achievement, as accurate knowledge of the time over a long sea voyage was vital for effective navigation, lacking electronic or communications aids. The first true chronometer was the life work of one man, John Harrison, spanning 31 years of persistent experimentation and testing that revolutionized naval navigation.

<span class="mw-page-title-main">History of timekeeping devices</span>

The history of timekeeping devices dates back to when ancient civilizations first observed astronomical bodies as they moved across the sky. Devices and methods for keeping time have gradually improved through a series of new inventions, starting with measuring time by continuous processes, such as the flow of liquid in water clocks, to mechanical clocks, and eventually repetitive, oscillatory processes, such as the swing of pendulums. Oscillating timekeepers are used in modern timepieces.

In horology, a wheel train is the gear train of a mechanical watch or clock. Although the term is used for other types of gear trains, the long history of mechanical timepieces has created a traditional terminology for their gear trains which is not used in other applications of gears.

<span class="mw-page-title-main">John Taylor (inventor)</span> British inventor, entrepreneur, horologist and philanthropist

John Crawshaw Taylor is an English inventor, entrepreneur, horologist and philanthropist best known for his extensive research into electric kettles.

<span class="mw-page-title-main">Ahasuerus Fromanteel</span> English clockmaker

Ahasuerus Fromanteel was a clockmaker, the first maker of pendulum clocks in Britain.

References

  1. ↑ "Hawking unveils 'strangest clock'". BBC . 19 September 2008. Retrieved 19 September 2008.
  2. ↑ "48. The Time Eater Clock: TIME's Best Inventions of 2008". Time . 10 November 2008. Archived from the original on 2 November 2008. Retrieved 18 November 2008.
  3. ↑ "Time to unveil Corpus Clock". University of Cambridge. 19 September 2008. Retrieved 20 September 2008.
  4. ↑ Bannerman, Lucy (19 September 2008). "Cambridge reveals the time-eater, Chronophage, devourer of hours". The Times . London. Retrieved 20 September 2008.[ dead link ]
  5. ↑ "Cambridge's fantastical new clock even tells time". Associated Press. 19 September 2008. Archived from the original on 24 September 2008. Retrieved 20 September 2008.
  6. 1 2 Kennedy, Maev (18 September 2008). "Beware the time-eater: Cambridge University's monstrous new clock". The Guardian . London. Retrieved 20 September 2008.
  7. ↑ Highfield, Roger (14 September 2008). "Stephen Hawking to unveil strange new way to tell the time". The Daily Telegraph . London. Archived from the original on 19 September 2008. Retrieved 20 September 2008.
  8. ↑ Taylor, John. "The Corpus Clock". The Pelican, Corpus Christi College alumni magazine. No. Easter Term edition. pp. 20–21.
  9. ↑ "Hawking unveils new £1m Cambridge clock". Cambridge Evening News . 20 September 2008. Archived from the original on 20 September 2008. Retrieved 20 September 2008.
  10. ↑ "Visitech Design – UK Design Consultants in Hampshire and Sussex". Archived from the original on 14 October 2001. Retrieved 25 January 2009.{{cite news}}: CS1 maint: unfit URL (link)
  11. ↑ "Dr Ewan St. John Smith". Corpus Christi College University of Cambridge. 22 December 2016.
  12. ↑ "Savills instructed to sell the 'most complicated house ever built' for £30m". Property Industry Eye. 26 January 2023.
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