Clock of the Long Now
The Clock of the Long Now, also called the 10,000-year clock, is a proposed mechanical 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...

 designed to keep time for 10,000 years. The project to build it is part of the Long Now Foundation
Long Now Foundation
The Long Now Foundation, established in 1996, is a private organization that seeks to become the seed of a very long-term cultural institution. It aims to provide a counterpoint to what it views as today's "faster/cheaper" mindset and to promote "slower/better" thinking...


The project was conceived by Danny Hillis
W. Daniel Hillis
William Daniel "Danny" Hillis is an American inventor, entrepreneur, and author. He co-founded Thinking Machines Corporation, a company that developed the Connection Machine, a parallel supercomputer designed by Hillis at MIT...

 in 1986 and the first prototype of the clock began working on December 31, 1999, just in time to display the transition to the year 2000. At midnight on New Year's Eve, the date indicator changed from 01999 to 02000, and the chime
Chime (bell instrument)
A carillon-like instrument with fewer than 23 bells is called a chime.American chimes usually have one to one and a half diatonic octaves. Many chimes play an automated piece of music. Prior to 1900, chime bells typically lacked dynamic variation and the inner tuning required to permit the use of...

 struck twice. That prototype, approximately two metres tall, is currently on display at the Science Museum
Science Museum (London)
The Science Museum is one of the three major museums on Exhibition Road, South Kensington, London in the Royal Borough of Kensington and Chelsea. It is part of the National Museum of Science and Industry. The museum is a major London tourist attraction....

 in London.

As of December 2007, two more recent prototypes are on display at The Long Now Museum & Store at Fort Mason Center in San Francisco.

The first full-scale clock's manufacture and site construction is being funded by Jeff Bezos
Jeff Bezos
Jeffrey Preston "Jeff" Bezos is the founder, president, chief executive officer , and chairman of the board of life and background:...

, who has donated $42 million, and is located on his Texas land.


The clock is one of several projects through which the foundation intends to promote long-term thinking. In the words of Stewart Brand
Stewart Brand
Stewart Brand is an American writer, best known as editor of the Whole Earth Catalog. He founded a number of organizations including The WELL, the Global Business Network, and the Long Now Foundation...

, a founding board member of the foundation, "Such a clock, if sufficiently impressive and well-engineered, would embody deep time for people. It should be charismatic to visit, interesting to think about, and famous enough to become iconic in the public discourse. Ideally, it would do for thinking about time what the photographs of Earth from space have done for thinking about the environment. Such icons reframe the way people think."


The basic design principles and requirements for the clock are:
  1. Longevity: The clock should be accurate even after 10,000 years, and must not contain valuable parts (such as jewels
    A gemstone or gem is a piece of mineral, which, in cut and polished form, is used to make jewelry or other adornments...

    , expensive metals, or special alloys) that might be looted.
  2. Maintainability: Future generations should be able to keep the clock working, if necessary, with nothing more advanced than Bronze Age
    Bronze Age
    The Bronze Age is a period characterized by the use of copper and its alloy bronze as the chief hard materials in the manufacture of some implements and weapons. Chronologically, it stands between the Stone Age and Iron Age...

     tools and materials.
  3. Transparency: The clock should be understandable without stopping or disassembling it; no functionality should be opaque.
  4. Evolvability: It should be possible to improve the clock over time.
  5. Scalability: To ensure that the final large clock will work properly, smaller prototypes must be built and tested.

No clock can have a guaranteed lifetime of 10,000 years, but some clocks are designed with guaranteed limits. (For example, a clock that shows a four-digit year date will not display the correct year after the year 9999.) With continued care and maintenance the Clock of the Long Now could reasonably be expected to display the correct time for 10,000 years.

Whether a clock would actually receive continued care and maintenance for such a long time is debatable. Hillis chose the 10,000-year goal to be just within the limits of plausibility. There are technological artifacts, such as fragments of pots and baskets, from 10,000 years in the past, so there is some precedent for human artifacts surviving this long, although very few human artifacts have been continuously tended for more than a few centuries.

Power considerations

Many options were considered for the power source of the clock, but most were rejected due to their inability to meet the requirements. For example, nuclear power
Nuclear power
Nuclear power is the use of sustained nuclear fission to generate heat and electricity. Nuclear power plants provide about 6% of the world's energy and 13–14% of the world's electricity, with the U.S., France, and Japan together accounting for about 50% of nuclear generated electricity...

 and solar power
Solar power
Solar energy, radiant light and heat from the sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies. Solar radiation, along with secondary solar-powered resources such as wind and wave power, hydroelectricity and biomass, account for most of the available...

 systems would violate the principles of transparency and longevity. In the end, Hillis decided to require regular human winding of a falling weight design because the clock design already assumes regular human maintenance.

Timing considerations

The timing mechanism for such a long lasting clock needs to be reliable and robust as well as accurate. The options considered but rejected as sources of timing for the clock included:

Self-contained clocks

Most of these methods are inaccurate (the clock will slowly become less correct) but reliable (the clock will not suddenly stop working). Others are accurate but opaque.
  • 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...

     (inaccurate over the long term, and requires lots of ticks, which creates wear
    In materials science, wear is erosion or sideways displacement of material from its "derivative" and original position on a solid surface performed by the action of another surface....

  • torsion pendulum
    Torsion spring
    A torsion spring is a spring that works by torsion or twisting; that is, a flexible elastic object that stores mechanical energy when it is twisted. The amount of force it exerts is proportional to the amount it is twisted. There are two types...

     (less frequent ticks, but even less accurate)
  • balance wheel
    Balance wheel
    The balance wheel is the timekeeping device used in mechanical watches and some 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 spring, the balance spring or hairspring...

     (more inaccurate than pendulum)
  • water flow
    Water clock
    A water clock or clepsydra is any timepiece in which time is measured by the regulated flow of liquid into or out from a vessel where the amount is then measured.Water clocks, along with sundials, are likely to be the oldest time-measuring instruments, with the only exceptions...

     (inaccurate and wet)
  • solid material flow
    Pitch drop experiment
    The pitch drop experiment is a long-term experiment which measures the flow of a piece of pitch over many years. Pitch is the name for any of a number of highly viscous liquids which appear solid, most commonly bitumen...

  • wear and corrosion
    Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...

     (very inaccurate)
  • rolling balls (very inaccurate)
  • diffusion
    Molecular diffusion, often called simply diffusion, is the thermal motion of all particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size of the particles...

  • tuning fork
    Tuning fork
    A tuning fork is an acoustic resonator in the form of a two-pronged fork with the prongs formed from a U-shaped bar of elastic metal . It resonates at a specific constant pitch when set vibrating by striking it against a surface or with an object, and emits a pure musical tone after waiting a...

  • pressure chamber cycle (inaccurate)
  • inertial governor
    Governor (device)
    A governor, or speed limiter, is a device used to measure and regulate the speed of a machine, such as an engine. A classic example is the centrifugal governor, also known as the Watt or fly-ball governor, which uses a rotating assembly of weights mounted on arms to determine how fast the engine...

  • atomic oscillator
    Atomic clock
    An atomic clock is a clock that uses an electronic transition frequency in the microwave, optical, or ultraviolet region of the electromagnetic spectrum of atoms as a frequency standard for its timekeeping element...

     (opaque, difficult to maintain)
  • piezoelectric crystal oscillator
    Crystal oscillator
    A crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a very precise frequency...

     (opaque, difficult to maintain)
  • atomic decay (opaque, difficult to measure precisely)

External events that the clock could track or be adjusted by

Many of these methods are accurate (some external cycles are very uniform over huge stretches of time) but unreliable (the clock could stop working completely if it failed to track the external event properly). Others have separate difficulties.
  • daily temperature cycle (unreliable)
  • seasonal temperature cycle (imprecise)
  • tidal force
    Tidal force
    The tidal force is a secondary effect of the force of gravity and is responsible for the tides. It arises because the gravitational force per unit mass exerted on one body by a second body is not constant across its diameter, the side nearest to the second being more attracted by it than the side...

    s (difficult to measure)
  • Earth's rotating inertial frame
    Inertial frame of reference
    In physics, an inertial frame of reference is a frame of reference that describes time homogeneously and space homogeneously, isotropically, and in a time-independent manner.All inertial frames are in a state of constant, rectilinear motion with respect to one another; they are not...

     (difficult to measure accurately)
  • stellar alignment (unreliable because of weather)
  • solar alignment (unreliable because of weather)
  • tectonic motion
    Continental drift
    Continental drift is the movement of the Earth's continents relative to each other. The hypothesis that continents 'drift' was first put forward by Abraham Ortelius in 1596 and was fully developed by Alfred Wegener in 1912...

     (difficult to predict and measure)
  • orbital
    Planetary orbit
    In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...

     dynamics (difficult to scale)
  • human ritual (too dependent on humans).

Hillis concluded that no single source of timing could meet the requirements. As a compromise the clock will use an unreliable but accurate timer to adjust an inaccurate but reliable timer, creating a phase-locked loop
Phase-locked loop
A phase-locked loop or phase lock loop is a control system that generates an output signal whose phase is related to the phase of an input "reference" signal. It is an electronic circuit consisting of a variable frequency oscillator and a phase detector...


In the current design, a slow mechanical oscillator, based on a torsional pendulum, keeps time inaccurately, but reliably. At noon the light from the Sun, a timer that is accurate but (due to weather) unreliable, is concentrated on a segment of metal through a lens
Lens (optics)
A lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam. A simple lens consists of a single optical element...

. The metal buckles and the buckling force resets the clock to noon. The combination can, in principle, provide both reliability and long-term accuracy.

Displaying the time and date

Many of the usual units displayed on clocks, such as hours and calendar
A calendar is a system of organizing days for social, religious, commercial, or administrative purposes. This is done by giving names to periods of time, typically days, weeks, months, and years. The name given to each day is known as a date. Periods in a calendar are usually, though not...

 dates, may have little meaning after 10,000 years. However, every human culture counts days, months (in some form), and years, all of which are based on lunar and solar cycles. There are also longer natural cycles, such as the 25,765-year precession of Earth's axis. On the other hand, the clock is a product of our time, and it seems appropriate to pay some homage to our current arbitrary systems of time measurement. In the end, it seemed best to display both the natural cycles and some of the current cultural cycles.

The center of the clock will show a star field, indicating both the sidereal day and the precession of the zodiac
In astronomy, the zodiac is a circle of twelve 30° divisions of celestial longitude which are centred upon the ecliptic: the apparent path of the Sun across the celestial sphere over the course of the year...

. Around this will be a display showing the position of the Sun and the Moon in the sky, as well as the phase
Lunar phase
A lunar phase or phase of the moon is the appearance of the illuminated portion of the Moon as seen by an observer, usually on Earth. The lunar phases change cyclically as the Moon orbits the Earth, according to the changing relative positions of the Earth, Moon, and Sun...

 and angle of the Moon. Outside this will be the ephemeral
An ephemeris is a table of values that gives the positions of astronomical objects in the sky at a given time or times. Different kinds of ephemerides are used for astronomy and astrology...

 dial, showing the year according to our current Gregorian calendar
Gregorian calendar
The Gregorian calendar, also known as the Western calendar, or Christian calendar, is the internationally accepted civil calendar. It was introduced by Pope Gregory XIII, after whom the calendar was named, by a decree signed on 24 February 1582, a papal bull known by its opening words Inter...

 system. This will be a five-digit display, indicating the current year in a format like "02000" instead of the more usual "2000" (to avoid a Y10K problem
Year 10,000 problem
The Year 10,000 problem is the class of all potential software bugs that would emerge when the need to express years with five digits arises...

). Hillis and Brand plan, if they can, to add a mechanism whereby the power source generates only enough energy to keep track of time; if visitors want to see the time displayed, they would have to manually supply some energy themselves.

Time calculations

Options considered for the part of the clock that converts time source (for example, a pendulum) to display units (for example, clock hands) include electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...

, hydraulics
Hydraulics is a topic in applied science and engineering dealing with the mechanical properties of liquids. Fluid mechanics provides the theoretical foundation for hydraulics, which focuses on the engineering uses of fluid properties. In fluid power, hydraulics is used for the generation, control,...

, fluidics
Fluidics or Fluidic logic is the use of a fluid to perform analog or digital operations similar to those performed with electronics.The physical basis of fluidics is pneumatics and hydraulics, based on the theoretical foundation of fluid dynamics...

, and mechanics
Mechanics is the branch of physics concerned with the behavior of physical bodies when subjected to forces or displacements, and the subsequent effects of the bodies on their environment....


A problem with using a conventional 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...

 (which has been the standard mechanism for the past millennium) is that gears necessarily require a ratio relationship between the timing source and the display. The required accuracy of the ratio increases with the amount of time to be measured. (For instance, for a short period of time the count of 29.5 days per lunar month
Lunar month
In lunar calendars, a lunar month is the time between two identical syzygies . There are many variations. In Middle-Eastern and European traditions, the month starts when the young crescent moon becomes first visible at evening after conjunction with the Sun one or two days before that evening...

 may suffice, but over 10,000 years the number 29.5305882 is a much more accurate choice.)

Achieving such precise ratios with gears is possible, but awkward; similarly, gears degrade over time in accuracy and efficiency due to the deleterious effects of friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...

 (which is to say, they get smaller, and thus move faster, becoming cumulatively less accurate). Instead, the clock uses binary digital logic, implemented mechanically in a sequence of stacked binary adders (or as their inventor, Hillis, calls them, serial bit-adders). In effect, the conversion logic is a simple digital computer (more specifically, a digital differential analyser
Differential analyser
The differential analyser is a mechanical analogue computer designed to solve differential equations by integration, using wheel-and-disc mechanisms to perform the integration...

), implemented with mechanical wheels and levers instead of typical electronics. The computer has 32 bits of accuracy, with each bit represented by a mechanical lever or pin that can be in one of two positions. This binary logic can only keep track of elapsed time, like a stopwatch; to convert from elapsed to local solar time (that is, time of day), a cam
A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion or vice-versa. It is often a part of a rotating wheel or shaft that strikes a lever at one or more points on its circular path...

 subtracts from (or adds to) the cam slider, which the adders move.

Another advantage of the digital computer over the gear train is that it is more evolvable. For instance, the ratio of day to years depends on Earth's rotation, which is slowing at a noticeable but not very predictable rate. This could be enough to, for example, throw the phase of the Moon off by a few days over 10,000 years. The digital scheme allows that conversion ratio to be adjusted, without stopping the clock, if the length of the day changes in an unexpected way.


The Long Now Foundation has purchased the top of Mount Washington
Mount Washington (Nevada)
Mount Washington is a mountain in White Pine County in the state of Nevada. The mountain climbs to an elevation of and is in Great Basin National Park....

 near Ely, Nevada
Ely, Nevada
Ely is the largest city and county seat of White Pine County, Nevada, United States. Ely was founded as a stagecoach station along the Pony Express and Central Overland Route. Ely's mining boom came later than the other towns along US 50, with the discovery of copper in 1906...

 which is surrounded by Great Basin National Park
Great Basin National Park
Great Basin National Park is a United States National Park established in 1986, located in east-central Nevada near the Utah border. The park derives its name from the Great Basin, the dry and mountainous region between the Sierra Nevada and the Wasatch Mountains. Topographically, this area is...

, for the permanent storage of the full sized clock, once it is constructed. It will be housed in a series of rooms (the slowest mechanisms visible first) in the white limestone cliffs, approximately 10,000 feet up the Snake Range. The site's dryness, remoteness, and lack of economic value should protect the clock from corrosion, vandalism, and development. Hillis chose this area of Nevada in part because it is home to a number of dwarf bristlecone pines
Great Basin Bristlecone Pine
Pinus longaeva, the Great Basin Bristlecone Pine, is a long-living species of tree found in the higher mountains of the southwest United States. The species is one of three closely related trees known as bristlecone pines and is sometimes known as the Intermountain or Western bristlecone pine...

, which the Foundation notes are nearly 5,000 years old. The clock will be almost entirely underground, and only accessed by foot traffic from the East once complete.

Before building the public clock in Nevada, the foundation is building a full-scale clock of similar design in a mountain in near Van Horn, Texas
Van Horn, Texas
Van Horn is a town in and the county seat of Culberson County, Texas, United States. The population was 2,435 at the 2000 census.-Geography:Van Horn is located at ....

. The test drilling for the underground construction at this site was started in 2009. The site is on property owned by founder Jeff Bezos
Jeff Bezos
Jeffrey Preston "Jeff" Bezos is the founder, president, chief executive officer , and chairman of the board of life and background:...

, who is also funding its construction. The lessons learned in the construction of this first full-scale 10,000-year clock will inform the final design of the clock in Nevada.

Inspiration and support

The project is supported by the Long Now Foundation
Long Now Foundation
The Long Now Foundation, established in 1996, is a private organization that seeks to become the seed of a very long-term cultural institution. It aims to provide a counterpoint to what it views as today's "faster/cheaper" mindset and to promote "slower/better" thinking...

, which also supports a number of other very-long-term projects, including the Rosetta Project
Rosetta Project
The Rosetta Project is a global collaboration of language specialists and native speakers working to develop a contemporary version of the historic Rosetta Stone to last from 2000 to 12,000 AD; it is run by the Long Now Foundation. Its goal is a meaningful survey and near permanent archive of 1,500...

 (to preserve the world's languages) and the Long Bet Project.

Neal Stephenson
Neal Stephenson
Neal Town Stephenson is an American writer known for his works of speculative fiction.Difficult to categorize, his novels have been variously referred to as science fiction, historical fiction, cyberpunk, and postcyberpunk...

's novel Anathem
Anathem is a speculative fiction novel by Neal Stephenson, published in 2008. Major themes include the many-worlds interpretation of quantum mechanics and the philosophical debate between Platonic realism and formalism.-Plot summary:...

was partly inspired by his involvement with the project, to which he contributed three pages of sketches and notes. The Long Now Foundation sells a soundtrack for the novel with profits going to the project.

Musician Brian Eno
Brian Eno
Brian Peter George St. John le Baptiste de la Salle Eno , commonly known as Brian Eno or simply as Eno , is an English musician, composer, record producer, singer and visual artist, known as one of the principal innovators of ambient music.Eno studied at Colchester Institute art school in Essex,...

 gave the Clock of the Long Now its name (and coined the term "Long Now") in an essay; he has collaborated with Hillis on the writing of music for the chimes for a future prototype.

See also

  • As Slow As Possible
    As Slow As Possible
    Organ²/ASLSP is a musical piece composed by John Cage and is the subject of one of the longest-lasting musical performances yet undertaken. It was originally written in 1987 for organ and is adapted from the earlier work ASLSP 1985; a typical performance of the piano piece lasts for about 20 to 70...

  • Deep time
    Deep time
    Deep time is the concept that the Geologic time scale is vast because the Earth is very old. The modern philosophical concept was developed in the 18th century by Scottish geologist James Hutton...

  • Jens Olsen's World Clock
    Jens Olsen's World Clock
    Jens Olsen's World Clock or Verdensur is an advanced astronomical clock which is displayed in Copenhagen City Hall.The clock was designed and calculated by Jens Olsen who was a skilled locksmith, but later learned the trade of clockmaking...

  • Time capsule
    Time capsule
    A time capsule is an historic cache of goods or information, usually intended as a method of communication with future people and to help future archaeologists, anthropologists, or historians...

  • Longplayer
    "Longplayer" is a piece of music that is designed to last for one thousand years. It started to play on 1 January 2000, and if all goes as planned, will continue without repetition until 31 December 2999, at which point it will restart....

  • Orders of magnitude (time)
    Orders of magnitude (time)
    -Seconds:- See also :* Heat Death* Second law of thermodynamics* Big Rip* Big Crunch* Big Bounce* Big Bang* Cyclic model* Dyson's eternal intelligence* Final anthropic principle* Ultimate fate of the Universe* Timeline of the Big Bang...

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.