What is atomic clock (NIST-F1)? - Definition from WhatIs.com pneumatics An atomic clock is the most accurate type of timepiece in the world, designed to measure time according to vibrations within atom s. NIST-F1, the United States' standard atomic clock, is said to be so accurate that it would neither gain nor lose a second in over 30 million years. Atomic clocks are used to coordinate systems that require extreme precision, such as Global Positioning System ( GPS ) navigation and the Internet. A group of atomic clocks located in a number of places throughout the world are used in conjunction to establish Coordinated Universal Time ( UTC ). Like a regular clock, an atomic clock keeps time according to oscillation , which is a periodic variation or movement between two entities or between two states of a single entity, created by changes in energy. In a pendulum-driven clock, for example, the oscillation is the back and forth movement of the pendulum (the oscillator ). Such a clock keeps time according to the frequency of the pendulum's swing, which will be more or less accurate, depending on a number of variables.

The precision of an atomic clock, on the other hand, depends upon the fact that an atom, caused to oscillate, will always vibrate at the same frequency. In 1945, Isidor Rabi, a physics professor at Columbia University, proposed that atomic vibrations could be used to keep time, based on something he'd developed called atomic beam magnetic resonance . Four years later, the National Bureau of Standards (now the National Institute of Standards and Technology ) had developed an atomic clock that used the vibrations of ammonia molecules. NIST-F1, the United States' current standard, uses cesium atoms; it and a similar atomic clock standard in Paris are the most accurate timepieces ever made. The first commercial cesium-based atomic clocks were manufactured by the National Company, a Massachusetts-based firm; Frequency Electronics, FTS, and Hewlett Packard ( HP ) are among the companies producing them today. Atomic clocks have never been widely used in consumer products because they are typically large and use too much power. Recently, however, NIST developed an atomic clockwork that overcomes these problems.

About the size of a grain of rice and accurate to within one second in 126 years, the new mechanism could soon be manufactured on computer chips and used in consumer market handheld devices, such as radios, GPS systems, and cellular telephones. This was last updated in March 2011 Continue Reading About atomic clock (NIST-F1) How Does an Atomic Clock Work? How Does an Atomic Clock Work? By Adam Hadhazy | June 21, 2010 02:47pm ET MORE NIST-F1, the nation's primary time and frequency standard, is among the most accurate clocks in the world. Credit: NIST Timekeeping can be as simple as counting "one Mississippi, two Mississippi . . ." prior to blitzing in backyard football, or tracking the back-and-forth swings of a pendulum in a grandfather clock. In both cases, the trick is counting the intervals of something that occurs repeatedly with as little variation as possible. A pendulum swing, say, or a 'Mississippi' just about equates to a second, the unit of timekeeping that as we know comprises minutes and hours. But even the best mechanical pendulums and quartz crystal-based clocks develop discrepancies.

Far better for timekeeping is the natural and exact "vibration" in an energized atom. When exposed to certain frequencies of radiation, such as radio waves, the subatomic particles called electrons that orbit an atom's nucleus will "jump" back and forth between energy states. Clocks based on this jumping within atoms can therefore provide an extremely precise way to count seconds. It is no surprise then that the international standard for the length of one second is based on atoms. Since 1967, the official definition of a second is 9,192,631,770 cycles of the radiation that gets an atom of the element called cesium to vibrate between two energy states. Inside a cesium atomic clock, cesium atoms are funneled down a tube where they pass through radio waves . If this frequency is just right 9,192,631,770 cycles per second then the cesium atoms "resonate" and change their energy state. A detector at the end of the tube keeps track of the number of cesium atoms reaching it that have changed their energy states.

The more finely tuned the radio wave frequency is to 9,192,631,770 cycles per second, the more cesium atoms reach the detector. The detector feeds information back into the radio wave generator. It synchronizes the frequency of the radio waves with the peak number of cesium atoms striking it. Other electronics in the atomic clock count this frequency. As with a single swing of the pendulum, a second is ticked off when the frequency count is met. The first quality atomic clocks made in the 1950s were based on cesium, and such clocks honed to greater precisions over the decades remain the basis used to keep official time throughout the world. In the United States, the top clocks are maintained by the National Institutes of Standards and Technology (NIST) in Boulder, Colo., and the United States Naval Observatory (USNO) in Washington, D.C. The NIST-F1 cesium atomic clock can produce a frequency so precise that its time error per day is about 0.03 nanoseconds, which means that the clock would lose one second in 100 million years.

Super-accurate timekeeping is integral to many elements of modern life, such as high-speed electronic communications, electrical grids and the Global Positioning System (GPS) and of course knowing when your favorite television show comes on. Got a question? Email it to Life's Little Mysteries and we'll try to answer it. Due to the volume of questions, we unfortunately can't reply individually, but we will publish answers to the most intriguing questions, so check back soon. Author Bio Adam Hadhazy, Adam Hadhazy is a contributing writer for Live Science and Space.com. He often writes about physics, psychology, animal behavior and story topics in general that explore the blurring line between today's science fiction and tomorrow's science fact. Adam has a Master of Arts degree from the Arthur L. Carter Journalism Institute at New York University and a Bachelor of Arts degree from Boston College. When not squeezing in reruns of Star Trek, Adam likes hurling a Frisbee or dining on spicy food.

You can check out more of his work at Science Newsletter: Subscribe Atomic clock | Article about atomic clock by The Free Dictionary Atomic clock | Article about atomic clock by The Free Dictionary Related to atomic clock: Doomsday Clock atomic clock, electric or electronic timekeeping device that is controlled by atomic or molecular oscillations. A timekeeping device must contain or be connected to some apparatus that oscillates at a uniform rate to control the rate of movement of its hands or the rate of change of its digits. Mechanical clocks and watches use oscillating balance wheels, pendulums, and tuning forks. Much greater accuracy can be attained by using the oscillations of atoms or molecules. Because the frequency of such oscillations is so high, it is not possible to use them as a direct means of controlling a clock. Instead, the clock is controlled by a highly stable crystal oscillator whose output is automatically multiplied and compared with the frequency of the atomic system. Errors in the oscillator frequency are then automatically corrected. Time is usually displayed by an atomic clock with digital or other sophisticated readout devices. The first atomic clock, invented in 1948, utilized the vibrations of ammonia molecules.

The error between a pair of such clocks, i.e., the difference in indicated time if both were started at the same instant and later compared, was typically about one second in three thousand years. In 1955 the first cesium-beam clock (a device that uses as a reference the exact frequency of the microwave spectral line emitted by cesium atoms) was placed in operation at the National Physical Laboratory at Teddington, England. It is estimated that such a clock would gain or lose less than a second in three million years. The U.S. standard consists of two clocks, NIST-F1 and NIST-F2, which went into service in 1999 and 2014 respectively. They are accurate to 1 second in 100 million years (NIST-F1) and in 300 million years (NIST-F2). Fountain atomic clocks, they consist of a 3-foot vertical tube inside a taller structure, and use lasers to cool cesium atoms, forming a ball of atoms that lasers then toss into the air, much like one would toss a tennis ball, creating a fountain effect. This allows the atoms to be observed for much longer than could be done with any previous clock.

NIST-F2's greater accuracy is achieved by operating at −193&degC; (−315.4&degF;) instead of at 27&degC; (80.6&degF;). Many of the world's nations maintain atomic clocks at standards laboratories, the time kept by these clocks being averaged to produce a standard called international atomic time (TAI). Highly accurate time signals from these standards laboratories are broadcast around the globe by shortwave-radio broadcast stations or by artificial satellites, the signals being used for such things as tracking space vehicles, electronic navigation systems, and studying the motions of the earth's crust. The accuracy of these clocks made possible an experiment confirming an important prediction of Einstein's theory of relativity. Prototypes of atomic clocks using atoms such as hydrogen or beryllium could be still thousands of times more accurate. For example, researchers at the U.S. National Institute of Standards and Technology have demonstrated an atomic clock based on an energy transition in a single trapped mercury ion (a mercury atom that is missing one electron) that has the potential to be up to 1,000 times more accurate than current atomic clocks. Bibliography See F. G.

Major, The Quantum Beat: The Physical Principles of Atomic Clocks (1999). Atomic clock A device that uses an internal resonance frequency of atoms (or molecules) to measure the passage of time. The terms atomic clock and atomic frequency standard are often used interchangeably. A frequency standard generates pulses at regular intervals. It can be made into a clock by the addition of an electronic counter, which records the number of pulses. Most methods of timekeeping rely on counting some periodic event, such as the rotation of the Earth, the motion of a pendulum in a grandfather clock, or the vibrations of a quartz crystal in a watch. An atomic clock relies on counting periodic events determined by the difference of two different energy states of an atom. A transition between two energy states with energies E1 and E2 may be accompanied by the absorption or emission of a photon (particle of electromagnetic radiation). The frequency ν of this radiation is given by the equation where h is Planck's constant. A basic advantage of atomic clocks is that the frequency-determining elements, atoms of a particular isotope, are the same everywhere. Thus, atomic clocks constructed and operated independently will measure the same time interval.

See Atomic structure and spectra , Energy level (quantum mechanics) , Quantum mechanics An atomic frequency standard can be either active or passive. An active standard uses as a reference the electromagnetic radiation emitted by atoms as they decay from a higher energy state to a lower energy state. A passive standard attempts to match the frequency of an electronic oscillator or laser to the resonant frequency of the atoms by means of a feedback circuit. Either kind of standard requires some kind of frequency synthesis to produce an output near a convenient frequency that is proportional to the atomic resonance frequency. See Laser , Maser Two different gages of the quality of a clock are accuracy and stability. The accuracy of a frequency standard is defined in terms of the deviation of its frequency from an ideal standard. The stability of frequency standard is defined in terms of the constancy of its average frequency from one interval of time to the next. The three most commonly used types of atomic clock are the cesium atomic beam, the hydrogen maser, and the rubidium gas cell. The cesium clock has high accuracy and good long-term stability. The hydrogen maser has the best stability for periods of up to a few hours. The rubidium cell is the least expensive and most compact and also has good short-term stability.

The cesium atomic-beam clock uses a 9193-MHz transition between two hyperfine energy states of the cesium-133 atom. Both the atomic nucleus and the outermost electron have magnetic moments; that is, they are like small magnets, with a north and a south pole. The two hyperfine energy states differ in the relative orientations of these magnetic moments. The cesium atoms travel in a collimated beam through a series of evacuated regions, where they are exposed to microwave radiation near their resonance frequency and are deflected into different trajectories by nonuniform magnetic fields. See Electron spin , Hyperfine structure , Molecular beams , Nuclear moments Cesium has become the basis of the international definition of the second; the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine states of the ground state of the cesium-133 atom. The cesium clock is especially well suited for applications such as timekeeping, where absolute accuracy without recalibration is necessary.

Measurements from many cesium clocks throughout the world are averaged together to define an international time scale that is uniform to parts in 1014, or about 1 microsecond in a year. See Physical measurement The hydrogen maser is based on the hyperfine transition of atomic hydrogen, which has a frequency of 1420 MHz. Atoms in the higher hyperfine energy state enter an evacuated storage bulb inside a microwave cavity, and are induced to make a transition to the lower hyperfine state by a process called stimulated emission. The rubidium gas cell is based on the 6835-MHz hyperfine transition of rubidium-87. The rubidium atoms are contained in a glass cell together with a buffer gas, where they are subjected to optical pumping and microwave radiation at the hyperfine transition frequency; this results in a detectable decrease in the light transmitted through the cell. Many other kinds of atomic clocks, such as thallium atomic beams and ammonia and rubidium masers, have been demonstrated in the laboratory. The first atomic clock, constructed at the National Bureau of Standards in 1949, was based on a 24-GHz transition in the ammonia molecule.

Some laboratories have tried to improve the cesium atomic-beam clock by replacing the magnetic state selection with laser optical pumping and fluorescence detection. One such standard, called NIST-7, is in operation at the U.S. National Institute of Standards and Technology and is the primary frequency standard for the United States. Atomic frequency standards can also be based on optical transitions. One of the best-developed optical frequency standards is the 3.39-micrometer (88-THz) helium-neon laser, stabilized to a transition in the methane molecule. Frequency synthesis chains have been built to link the optical frequency to radio frequencies. Atomic clocks are used in applications for which less expensive alternatives, such as quartz oscillators, do not provide adequate performance. In addition to maintaining a uniform international time scale, atomic clocks are used to keep time in the Global Positioning System, various digital communications systems, radio astronomy, and navigation of space probes. atomic clock The most accurate type of clock to date, in which the periodic process used as the timing mechanism is an atomic or molecular event with which is associated a constant and very accurately known frequency .

Various atoms and molecules have been employed in atomic clocks, the frequency involved in the timing mechanism being a microwave frequency; such frequencies can be produced and manipulated by sophisticated electronic techniques. The accuracy is at present better than one part in one thousand million million. See also atomic time . atomic clock [ə′täm·ik ′kläk] (horology) An electronic clock whose frequency is supplied or governed by the natural resonance frequencies of atoms or molecules of suitable substances. Atomic oscillator | Article about Atomic oscillator by The Free Dictionary Atomic oscillator | Article about Atomic oscillator by The Free Dictionary Also found in: Dictionary , Thesaurus , Wikipedia . atomic clock, electric or electronic timekeeping device that is controlled by atomic or molecular oscillations. A timekeeping device must contain or be connected to some apparatus that oscillates at a uniform rate to control the rate of movement of its hands or the rate of change of its digits. Mechanical clocks and watches use oscillating balance wheels, pendulums, and tuning forks. Much greater accuracy can be attained by using the oscillations of atoms or molecules. Because the frequency of such oscillations is so high, it is not possible to use them as a direct means of controlling a clock.

Instead, the clock is controlled by a highly stable crystal oscillator whose output is automatically multiplied and compared with the frequency of the atomic system. Errors in the oscillator frequency are then automatically corrected. Time is usually displayed by an atomic clock with digital or other sophisticated readout devices. The first atomic clock, invented in 1948, utilized the vibrations of ammonia molecules. The error between a pair of such clocks, i.e., the difference in indicated time if both were started at the same instant and later compared, was typically about one second in three thousand years. In 1955 the first cesium-beam clock (a device that uses as a reference the exact frequency of the microwave spectral line emitted by cesium atoms) was placed in operation at the National Physical Laboratory at Teddington, England. It is estimated that such a clock would gain or lose less than a second in three million years. The U.S. standard consists of two clocks, NIST-F1 and NIST-F2, which went into service in 1999 and 2014 respectively. They are accurate to 1 second in 100 million years (NIST-F1) and in 300 million years (NIST-F2).

Fountain atomic clocks, they consist of a 3-foot vertical tube inside a taller structure, and use lasers to cool cesium atoms, forming a ball of atoms that lasers then toss into the air, much like one would toss a tennis ball, creating a fountain effect. This allows the atoms to be observed for much longer than could be done with any previous clock. NIST-F2's greater accuracy is achieved by operating at −193&degC; (−315.4&degF;) instead of at 27&degC; (80.6&degF;). Many of the world's nations maintain atomic clocks at standards laboratories, the time kept by these clocks being averaged to produce a standard called international atomic time (TAI). Highly accurate time signals from these standards laboratories are broadcast around the globe by shortwave-radio broadcast stations or by artificial satellites, the signals being used for such things as tracking space vehicles, electronic navigation systems, and studying the motions of the earth's crust. The accuracy of these clocks made possible an experiment confirming an important prediction of Einstein's theory of relativity. Prototypes of atomic clocks using atoms such as hydrogen or beryllium could be still thousands of times more accurate.

For example, researchers at the U.S. National Institute of Standards and Technology have demonstrated an atomic clock based on an energy transition in a single trapped mercury ion (a mercury atom that is missing one electron) that has the potential to be up to 1,000 times more accurate than current atomic clocks. Bibliography See F. G. Major, The Quantum Beat: The Physical Principles of Atomic Clocks (1999). Atomic clock A device that uses an internal resonance frequency of atoms (or molecules) to measure the passage of time. The terms atomic clock and atomic frequency standard are often used interchangeably. A frequency standard generates pulses at regular intervals. It can be made into a clock by the addition of an electronic counter, which records the number of pulses. Most methods of timekeeping rely on counting some periodic event, such as the rotation of the Earth, the motion of a pendulum in a grandfather clock, or the vibrations of a quartz crystal in a watch. An atomic clock relies on counting periodic events determined by the difference of two different energy states of an atom. A transition between two energy states with energies E1 and E2 may be accompanied by the absorption or emission of a photon (particle of electromagnetic radiation).

The frequency ν of this radiation is given by the equation where h is Planck's constant. A basic advantage of atomic clocks is that the frequency-determining elements, atoms of a particular isotope, are the same everywhere. Thus, atomic clocks constructed and operated independently will measure the same time interval. See Atomic structure and spectra , Energy level (quantum mechanics) , Quantum mechanics An atomic frequency standard can be either active or passive. An active standard uses as a reference the electromagnetic radiation emitted by atoms as they decay from a higher energy state to a lower energy state. A passive standard attempts to match the frequency of an electronic oscillator or laser to the resonant frequency of the atoms by means of a feedback circuit. Either kind of standard requires some kind of frequency synthesis to produce an output near a convenient frequency that is proportional to the atomic resonance frequency. See Laser , Maser Two different gages of the quality of a clock are accuracy and stability. The accuracy of a frequency standard is defined in terms of the deviation of its frequency from an ideal standard. The stability of frequency standard is defined in terms of the constancy of its average frequency from one interval of time to the next.

The three most commonly used types of atomic clock are the cesium atomic beam, the hydrogen maser, and the rubidium gas cell. The cesium clock has high accuracy and good long-term stability. The hydrogen maser has the best stability for periods of up to a few hours. The rubidium cell is the least expensive and most compact and also has good short-term stability. The cesium atomic-beam clock uses a 9193-MHz transition between two hyperfine energy states of the cesium-133 atom. Both the atomic nucleus and the outermost electron have magnetic moments; that is, they are like small magnets, with a north and a south pole. The two hyperfine energy states differ in the relative orientations of these magnetic moments. The cesium atoms travel in a collimated beam through a series of evacuated regions, where they are exposed to microwave radiation near their resonance frequency and are deflected into different trajectories by nonuniform magnetic fields.

See Electron spin , Hyperfine structure , Molecular beams , Nuclear moments Cesium has become the basis of the international definition of the second; the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine states of the ground state of the cesium-133 atom. The cesium clock is especially well suited for applications such as timekeeping, where absolute accuracy without recalibration is necessary. Measurements from many cesium clocks throughout the world are averaged together to define an international time scale that is uniform to parts in 1014, or about 1 microsecond in a year. See Physical measurement The hydrogen maser is based on the hyperfine transition of atomic hydrogen, which has a frequency of 1420 MHz. Atoms in the higher hyperfine energy state enter an evacuated storage bulb inside a microwave cavity, and are induced to make a transition to the lower hyperfine state by a process called stimulated emission. The rubidium gas cell is based on the 6835-MHz hyperfine transition of rubidium-87.

The rubidium atoms are contained in a glass cell together with a buffer gas, where they are subjected to optical pumping and microwave radiation at the hyperfine transition frequency; this results in a detectable decrease in the light transmitted through the cell. Many other kinds of atomic clocks, such as thallium atomic beams and ammonia and rubidium masers, have been demonstrated in the laboratory. The first atomic clock, constructed at the National Bureau of Standards in 1949, was based on a 24-GHz transition in the ammonia molecule. Some laboratories have tried to improve the cesium atomic-beam clock by replacing the magnetic state selection with laser optical pumping and fluorescence detection. One such standard, called NIST-7, is in operation at the U.S. National Institute of Standards and Technology and is the primary frequency standard for the United States. Atomic frequency standards can also be based on optical transitions. One of the best-developed optical frequency standards is the 3.39-micrometer (88-THz) helium-neon laser, stabilized to a transition in the methane molecule. Frequency synthesis chains have been built to link the optical frequency to radio frequencies.

Atomic clocks are used in applications for which less expensive alternatives, such as quartz oscillators, do not provide adequate performance. In addition to maintaining a uniform international time scale, atomic clocks are used to keep time in the Global Positioning System, various digital communications systems, radio astronomy, and navigation of space probes. atomic clock The most accurate type of clock to date, in which the periodic process used as the timing mechanism is an atomic or molecular event with which is associated a constant and very accurately known frequency . Various atoms and molecules have been employed in atomic clocks, the frequency involved in the timing mechanism being a microwave frequency; such frequencies can be produced and manipulated by sophisticated electronic techniques. The accuracy is at present better than one part in one thousand million million. See also atomic time . atomic clock [ə′täm·ik ′kläk] (horology) An electronic clock whose frequency is supplied or governed by the natural resonance frequencies of atoms or molecules of suitable substances. Announcing: Companion book to EngineerGuy Series #4 About the book This book reveals some of the stories behind how engineers use specific elements to create the material world around us.

In eight chapters, the EngineerGuy team exposes the magnificence of the innovation and engineering of digital camera imagers, tiny accelerometers, atomic clocks, enriching fissile material, batteries, anodizing metals, microwave ovens, and lasers. To help readers of all backgrounds, the book also includes introductions to the scientific principles necessary for a deeper understanding of the material presented in the chapters. The reader will be delighted by primers on waves, nuclear structure, and electronic transitions. It also features “In depth” sections on entropy, semiconductors, and the mathematics of capacitors. Watch the companion video series! This book forms the basis of the fourth series of EngineerGuy videos. The eight videos in the series serve as great introductions to the book. In typical EngineerGuy style they present a "snackable" distillation of the essential engineering underlying an object. The videos feature the hallmarks of an EngineerGuy video: Clear visuals, illustrative close-ups, and demonstrations - not a surprise because the same team created the succesful EngineerGuy videos that revealed how an LCD monitor worked, exposed the basics of a hard drive , and explained fiber optics .

What's inside the book Digital Cameras: How a CCD Works This chapter discusses how silicon-based pixels use the photoelectric effect to measure light intensity. It covers these topics: How the first x-y imagers from the 1960s failed because of capacitive coupling, and how the CCD (charge coupled device) solves the problem by eliminating wires. How semiconductors are used to create a trap for the electrons generated as light falls on the CCD. The timing of the “clock cycle” that moves these trapped electrons to the camera’s electronics. The Color Filter Array used so a single CCD can create a color image. A brief section on active pixel sensors (APS) used in modern mobile phones. A section on “The CCD and the Nobel Prize," noting that the engineer who perfected the CCD as an imager did not win. How a Smartphone Knows Up from Down Accelerometers inside many electronic devices - tablets and phones - re-orient the screen as a user moves the device. This chapter opens by using a simple ball and spring device to explain the general principle of an accelerometer. It then describes: The typical accelerometer used in digital devices, focusing on how they use a differential capacitor to measure changes in gravitational pull.

Two simple examples of etching in silicon - creating a pyramidal hole and then a cantilever beam - show the principles underlying how silicon-based accelerometers are made. An “In Depth” section on the mathematics of capacitors, which explains why a differential capacitor is linear, while a simple two-plate capacitor is non-linear. How an Atomic Clock Works This chapter lays out the essential principles and operation of an atomic clock. Specifically, it includes: A discussion of the basics of timekeeping using resonance, focusing on the pendulum of a grandfather clock at first and then the vibrations of a quartz crystal oscillator, explaining briefly the piezoelectric effect in quartz. A clear description of how the “atomic” part of an atomic clock functions as a feedback loop for a quartz oscillator. It goes in detail on the workings of the first cesium-based atomic clock. A short discussion of the uses of accurate time. The basic details and elementary mathematics underlying the GPS (Global Positioning System). Primer: Nuclear Structure This chapter gives a brief overview of nuclear structure. It describes: How protons and neutrons make up an atom and the definition of an isotope. Introduces, briefly, the nuclear strong force.

Describes fission, focusing on uranium. Briefly describes nuclear explosions and chain reactions. The Hardest Step in Making a Nuclear Bomb The hardest step is obtaining isotope uranium-235, which must be separated from uranium-238. The chapter includes: The reaction of Werner Heisenberg and other German scientists who worked for the Nazi’s on their attempts to separate uranium to the U.S. built bomb that destroyed Hiroshima. A description of how the close chemical and physical identity of these isotopes makes separation extremely difficult. How the uranium used in the first nuclear bomb was prepared, including a description of the immense diffusion plants used. Modern methods of separating uranium isotopes using centrifuges, including pinpointing why these devices must be engineered carefully so they don’t destroy themselves as they spin. A description of the “flexural critical speeds” that occur when a centrifuge operates and the magnetic bearings used to reduce the importance of these critical speeds. An outline of cutting edge methods for separating uranium isotopes: Atomic vapor laser isotope separation and molecular laser isotope separation.

The Lead-Acid Battery: A Nineteenth Century Invention for the Twenty-first Century The lead-acid battery lies at the center of our technological world: The single largest use of batteries is for starting engines of cars and trucks. This chapter includes: A description of the basis of all batteries: The transfer of electrons. The essential engineering of a battery: Electrodes, electrolytes, and separators. It reveals why an automotive lead-acid battery is a shallow charge battery and why solar energy installations need a deep discharge battery. A description of a device built in Persia 2,000 years ago that might be the first battery ever built. What makes the lead-acid battery unique so that it still thrives even though it is heavy and filled with environmentally unfriendly lead. A description of the internal mechanism of a lithium-ion battery. Why lithium ion batteries explode. An “In Depth” section on entropy. It helps readers to understand and visualize the thermodynamic concept of entropy. Anodizing, or the Beauty of Corrosion Apple’s ipod and laptops use gorgeous anodized aluminum. although it looks like a painted coating it is actually an integral layer grown into the aluminum. This chapter reveals how this process works.

It includes: A description of a 5th century pillar in India that has survived intact because of natural anodizing. An explanation of why metals corrode. A description of oxidation-reduction reactions, which are essential in anodizing. How engineers control corrosion with coatings, cathodic protection and anodizing. Why stainless steel doesn’t rust. How aluminium is anodized. Why aluminum can be colored permanently with dye. How anodizing titanium creates colors. Primer: Waves Many of the objects and processes described in the book depend on the movement of waves. This chapter covers a few basic definitions and principles of waves, including: Pictorial definitions of wavelength, frequency, and their relationship to a wave's velocity. The interactions of waves: How they can superimpose (combine) and how standing waves arise. A brief description of electromagnetic waves, including a chart that shows the complete spectrum and how specific frequencies of waves are used technologically. How a Microwave Oven Works Microwave ovens exist in nearly every American home, yet few realize that this modern device depends on an older technology: The vacuum tube. This chapter describes the operation of an oven, focusing on how its inner workings create microwave radiation.

The chapter includes: A definition and description of a vacuum tube. How a microwave oven heats food, including whether it heats from the inside out. A clear description of a magnetron, which is the vacuum tube that creates microwave radiation. The description starts with the basics from Faraday and Ampere and works its way step-by-step to the operation of the cavity magnetron. A description of how tungsten produces the electrons needed for the magnetron to generate radiation. Why we heat food with 2,450 megahertz frequency radiation. Primer: Electrons, Energy Levels, and Light Emission The final chapter discusses the operation of a laser. This chapter gives the essential details needed to understand its operation. It includes: A description of an electron cloud in a molecule or solid, including the definition of an excited state. Energy levels and quantization of electron energy states in solids. Why electrons give off light or heat when they fall (decay) from an excited state. How a Laser Works This chapter reveals the essential engineering details in making a laser. It includes: A description of an amazing experiment where scientists bounced laser light off the moon.

A description of the key characteristics of a laser beam A discussion of why anything gives of light - from tungsten light bulbs to glow in the dark toys to lasers. A discussion of stimulated emission, the process that lies at the heart of creating laser light. An answer to why stimulated emission occurs. A description of the first laser: Ted Maiman’s ruby laser. A description of a helium-neon laser, including an explanation of why it uses two gases. A discussion of who really invented the laser: An outline of the legal cases of Gordon Gould. How the resonator cavity of a laser makes collimated light, and light of nearly a single wavelength. How a semiconductor laser works. How the erbium amplifier used in fiber optic cables works. An “In Depth” section on semiconductors, electrons and holes. This is a brief introduction to the principles of semiconductor diodes. ebook, paperbound or hardcover The book can be purchased in either paperbound, hardbound or ebook versions. We've made sure it's available on all major platforms.

atomic charge definition | English definition dictionary | Reverso 2 of, related to, or comprising atoms atomic hydrogen 3 extremely small; minute 4 (Logic) (of a sentence, formula, etc.) having no internal structure at the appropriate level of analysis. In predicate calculus, Fa is an atomic sentence and Fx an atomic predicate ♦ atomically adv atomic age n the. the current historical period, initiated by the development of the first atomic bomb towards the end of World War II and now marked by a balance of power between nations possessing the hydrogen bomb and the use of nuclear power as a source of energy atomic bomb , atom bomb n a type of bomb in which the energy is provided by nuclear fission.

Uranium-235 and plutonium-239 are the isotopes most commonly used in atomic bombs, (Also called) A-bomb, fission bomb Compare → fusion bomb atomic clock n an extremely accurate clock in which an electrical oscillator is controlled by the natural vibrations of an atomic or molecular system such as caesium or ammonia atomic cocktail n an aqueous solution of radioactive substance, such as sodium iodide, administered orally as part of the treatment for cancer atomic energy n another name for → nuclear energy Atomic Energy Authority n (in Britain) a government body established in 1954 to control research and development in atomic energy, (Abbrev.) AEA Atomic Energy Commission n (in the U.S.) a federal board established in 1946 to administer and develop domestic atomic energy programmes, (Abbrev.) AEC atomic heat n the product of an element's atomic weight and its specific heat (capacity) atomic mass 1 the mass of an isotope of an element in atomic mass units 2 short for relative atomic mass; see atomic weight atomic mass unit n a unit of mass used to express atomic and molecular weights that is equal to one twelfth of the mass of an atom of carbon-12.

It is equivalent to 1.66x10--27 kg, (Abbrev.) amu (Also called) unified atomic mass unit, dalton atomic number n the number of protons in the nucleus of an atom of an element., (Abbrev.) at. no. (Symbol) Z (Also called) proton number atomic pile n the original name for a → nuclear reactor atomic power n another name for → nuclear power atomic structure n the concept of an atom as a central positively charged nucleus consisting of protons and neutrons surrounded by a number of electrons. The number of electrons is equal to the number of protons: the whole entity is thus electrically neutral atomic theory n 1 any theory in which matter is regarded as consisting of atoms, esp. that proposed by John Dalton postulating that elements are composed of atoms that can combine in definite proportions to form compounds 2 the current concept of the atom as an entity with a definite structure See → atomic structure n the atomic weight (relative atomic mass) of an element divided by its density atomic weight n the former name for → relative atomic mass (Abbrev.) at.

wt Dalton's atomic theory n (Chem) the theory that matter consists of indivisible particles called atoms and that atoms of a given element are all identical and can neither be created nor destroyed. Compounds are formed by combination of atoms in simple ratios to give compound atoms (molecules). The theory was the basis of modern chemistry (C19: named after J. Dalton) International Atomic Time n the scientific standard of time based on the SI unit, the second, used by means of atomic clocks and satellites to synchronize the time standards of the major nations, (Abbrev.) TAI intra-atomic adj existing or occurring within an atom or atoms Compare → interatomic relative atomic mass n the ratio of the average mass per atom of the naturally occurring form of an element to one-twelfth the mass of an atom of carbon-12., (Symbol) Ar (Abbrev) r.a.m (Former name) atomic weight unified atomic mass unit NIST-F1 Cesium Fountain Clock | NIST NIST-F1 Cesium Fountain Clock Facebook Google Plus Twitter There's nothing like the joy of receiving a precision timepiece as a holiday gift.

Thanks to the Commerce Department's National Institute of Standards and Technology, the whole world can share that feeling because the agency today placed into operation a new atomic clock that will neither gain nor lose a second in nearly 20 million years. Termed NIST-F1, the new cesium atomic clock at NIST's Boulder, Colo., laboratories, began its role as the nation's primary frequency standard by contributing to an international pool of the world's atomic clocks that is used to define Coordinated Universal Time (known as UTC), the official world time. Because NIST-F1 shares the distinction of being the most accurate clock in the world (with a similar device in Paris), it is making UTC more accurate than ever before. NIST-F1 recently passed the evaluation tests that demonstrated it is approximately three times more accurate than the atomic clock it replaces, NIST-7, also located at the Boulder facility. NIST-7 has been the primary atomic time standard for the United States since 1993 and is among the best time standards in the world. NIST-F1 is referred to as a fountain clock because it uses a fountain-like movement of atoms to obtain its improved reckoning of time.

First, a gas of cesium atoms is introduced into the clock's vacuum chamber. Six infrared laser beams then are directed at right angles to each other at the center of the chamber. The lasers gently push the cesium atoms together into a ball. In the process of creating this ball, the lasers slow down the movement of the atoms and cool them to near absolute zero. Two vertical lasers are used to gently toss the ball upward (the "fountain" action), and then all of the lasers are turned off. This little push is just enough to loft the ball about a meter high through a microwave-filled cavity. Under the influence of gravity, the ball then falls back down through the cavity. As the atoms interact with the microwave signal—depending on the frequency of that signal—their atomic states might or might not be altered. The entire round trip for the ball of atoms takes about a second. At the finish point, another laser is directed at the cesium atoms. Only those whose atomic states are altered by the microwave cavity are induced to emit light (known as fluorescence). The photons (tiny packets of light) emitted in fluorescence are measured by a detector. This procedure is repeated many times while the microwave energy in the cavity is tuned to different frequencies.

Eventually, a microwave frequency is achieved that alters the states of most of the cesium atoms and maximizes their fluorescence. This frequency is the natural resonance frequency for the cesium atom—the characteristic that defines the second and, in turn, makes ultraprecise timekeeping possible. The NIST-F1 clock's method of resolving time differs greatly from that of its predecessor, NIST-7. That device—and the versions before it—fired heated cesium atoms horizontally through a microwave cavity at high speed. NIST-F1's cooler and slower atoms allow more time for the microwaves to "interrogate" the atoms and determine their characteristic frequency, thus providing a more sharply defined signal. NIST-F1 was developed by Steve Jefferts and Dawn Meekhof of the Time and Frequency Division of NIST's Physics Laboratory in Boulder, Colo. It was constructed and tested in less than four years. This new standard is more accurate by a wide margin than any other clock in the United States and assures the nation's industry, science and business sectors continued access to the extremely accurate timekeeping necessary for modern technology-based operations. Together with the U.S. Naval Observatory in Washington, D.C., NIST provides official time to the nation.

How the NIST-F1 Cesium Fountain Clock Works For hi-res .jpg versions, Shift Left Mouse click on images. FIGURE 1: A gas of cesium atoms enters the clock's vacuum chamber. Six lasers slow the movement of the atoms, cooling them to near absolute zero and force them into a spherical cloud at the intersection of the laser beams. FIGURE 2: The ball is tossed upward by two lasers through a cavity filled with microwaves. All of the lasers are then turned off. FIGURE 3: Gravity pulls the ball of cesium atoms back through the microwave cavity. The microwaves partially alter the atomic states of the cesium atoms. FIGURE 4: Cesium atoms that were altered in the microwave cavity emit light when hit with a laser beam. This fluorescence is measured by a detector (right). The entire process is repeated until the maximum fluorescence of the cesium atoms is determined. This point defines the natural resonance frequency of cesium, which is used to define the second. As a non-regulatory agency of the U.S. Department of Commerce's Technology Administration, NIST strengthens the U.S.

economy and improves the quality of life by working with industry to develop and apply technology, measurements and standards through four partnerships: the Measurement and Standards Laboratories, the Advanced Technology Program, the Manufacturing Extension Partnership and the Baldrige National Quality Program . A Brief History of Atomic Clocks 1945 -- Isidor Rabi, a physics professor at Columbia University, suggests a clock could be made from a technique he developed in the 1930's called atomic beam magnetic resonance. 1949 -- Using Rabi's technique, NIST (then the National Bureau of Standards) announces the world's first atomic clock using the ammonia molecule as the source of vibrations. 1952 -- NIST announces the first atomic clock using cesium atoms as the vibration source. This clock is named NBS-1. 1954 -- NBS-1 is moved to NIST's new laboratories in Boulder, Colo. 1955 --The National Physical Laboratory in England builds the first cesium-beam clock used as a calibration source. 1958 -- Commercial cesium clocks become available, costing $20,000 each.

1960 -- NBS-2 is inaugurated in Boulder; it can run for long periods unattended and is used to calibrate secondary standards. 1963 -- The search for a clock with improved accuracy and stability results in NBS-3. 1967 -- The 13th General Conference on Weights and Measures defines the second on the basis of vibrations of the cesium atom; the world's timekeeping system no longer has an astronomical basis. 1968 -- NBS-4, the world's most stable cesium clock, is completed. This clock was used into the 1990s as part of the NIST time system. 1972 -- NBS-5, an advanced cesium beam device, is completed and serves as the primary standard. 1975 -- NBS-6 begins operation; an outgrowth of NBS-5, it is one of the world's most accurate atomic clocks, neither gaining nor losing one second in 300,000 years.

1989 -- The Nobel Prize in Physics is awarded to three researchers -- Norman Ramsey of Harvard University, Hans Dehmelt of the University of Washington and Wolfgang Paul of the University of Bonn -- for their work in the development of atomic clocks. NIST's work is cited as advancing their earlier research. 1993 -- NIST-7 comes on line; eventually, it achieves an uncertainty of 5 parts in 10 to the 15th power, or 20 times more accurate than NBS-6. 1999 -- NIST-F1 begins operation with an uncertainty of 1.7 parts in 10 to the 15th power, or accuracy to about one second in 20 million years, making it the most accurate clock ever made (a distinction shared with a similar standard in Paris). High-Accuracy Timekeeping Who Needs High-Accuracy Timekeeping and Why? High-accuracy timekeeping is critical to a number of important systems, including telecommunications systems that require synchronization to better than 100 billionths of a second and satellite navigation systems such as the Defense Department's Global Positioning System where billionths of a second are significant.

Electrical power companies use synchronized systems to accurately determine the location of faults (for example, lightning damage) when they occur and to control the stability of their distribution systems. In the domain of space exploration, radio observations of distant objects in the universe, made by widely separated receivers in a process called long-baseline interferometry, require exceedingly good atomic reference clocks. And navigation of probes within our solar system depends critically on well-synchronized control stations on earth. Time is also important in the ordering of many human activities including the activities of financial markets. Time/date stamps are used to identify transactions so that these can be placed in order, a process that is becoming increasingly important as commerce moves electronically at faster and faster speeds. The need for good timing in this area is emphasized by a recent Securities and Exchange Commission-approved rule of the National Association of Securities Dealers that requires all member brokers synchronize their time stamps to NIST. The time-related quantity called frequency, basically the rate at which a clock runs, is needed by the radio and television broadcast industry to maintain proper control of transmissions and thus avoid interference between stations.

Frequency is also the basis for many electronic systems such as event counters, and many physical quantities such as length, voltage, pressure, and so on are often transformed to frequency, since frequency is a quantity that can be measured with very high precision. How Does NIST Support These High-Technology Requirements? The most fundamental way in which NIST supports such commercial activities is through its traditional role in providing the very accurate measurements needed to assure that specifications of high-technology equipment can be trusted. In fact, most countries would not accept United States high-technology exports without a guarantee that the specifications for this equipment are based on measurements that are traceable to NIST, which must then be sure that these measurements are compatible with those of the rest of the world. So, one key use of this new standard is to serve as a reference for supporting specifications for equipment manufactured in this country. Beyond this fundamental mission role, NIST works to distribute timing signals to a wide range of users through the Internet, by telephone, through radio broadcast signals, and by means of very precise signals distributed by satellite. The usage of NIST's Internet Time Service, now receiving more than 500 million calls per year, is growing extremely rapidly.

Radio time broadcasts from stations WWV and WWVB are used to set a large number of clocks; in fact, there is a growing list of consumer products (desk clocks, wristwatches, etc.) that use these radio broadcasts to maintain accurate time and even handle daylight saving time changes automatically. At the highest level of accuracy, NIST supports scientific studies, the space program and the development of advanced timing equipment by delivering timing signals using satellite transfer methods. How Does NIST Disseminate its time and frequency information? The oldest service is radio station WWV, near Fort Collins, Colo. It can be received all over the world and broadcasts at 2.5, 5, 10, 15 and 20 megahertz on the short wave band. A sister station, WWVH, broadcasts to the Pacific basin from Kauai, Hawaii, on everything but the 20 megahertz frequency. The broadcasts include standard frequencies and time intervals, the time (both voice and digital code), astronomical time corrections, and public service announcements such as marine weather, geophysical alerts and radio propagation information. The accuracy of these broadcasts, as received, is between one and 100 milliseconds, depending on the distance to the receiver.

A telephone time service, which carries the WWV broadcast, is available by dialing (303) 499-7111 (a toll call outside the Denver Metro area). WWV has been broadcasting since 1923. Another NIST radio station, WWVB, broadcasts a digital time code at the standard frequency of 60 kilohertz. Also located near Fort Collins, this low frequency station, which covers the continental U.S., has an accuracy for time comparison of between 0.1 and one millisecond. Its 60 kilohertz carrier frequency can be used for frequency calibrations with an accuracy of better than 1 part in 100 billion. The Automated Computer Time Service (ACTS) provides millisecond accuracy for computer clocks and other digital systems using dial-up telephone lines. This service includes automatic compensation for telephone-line delay and advance notices of changes to and from daylight savings time as well as leap seconds. NIST's time signals also are available on the Internet. A visual display of the correct time can be seen at , a service provided jointly with the U.S. Naval Observatory.

NIST time can also be obtained via the Internet to set the internal clocks of computers automatically, using free software available at . NIST also disseminates time code information via satellite, utilizing two of the National Oceanic and Atmospheric Administration's GOES weather satellites. The coverage includes North and South America plus portions of the Atlantic and Pacific oceans. This digital time code is accurate to within 100 microseconds, depending on knowledge of the position of the satellite. Atomic clock breakthrough: It could be time to test Einstein theories - NBC News Aug 22 2013, 9:11 pm ET Atomic clock breakthrough: It could be time to test Einstein theories by Tia Ghose advertisement Scientists have designed a new atomic clock, using laser light and ytterbium atoms, that is 10 times more stable than previously reported clocks. Ytterbium atoms are generated in an oven (large metal cylinder on the left) and sent to a vacuum chamber in the center of the photo to be manipulated and probed by lasers. Laser light is transported to the clock by five fibers. Atomic clocks are set to become even more precise than they currently are.

A new technique can ensure that the "ticking" of individual atoms — which is the basis of atomic clocks — is extremely constant, with the interval between ticks varying by less than two parts in 1 quintillion (1 followed by 18 zeros). That would lead to atomic clocks that are about 10 times more stable than the previously described clocks. The new breakthrough, described Thursday in the journal Science, may not help people make their 9 o'clock meetings, but it could pave the way for atomic clocks so precise that physicists could test Einstein's theory of general relativity or probe the mysteries of the fundamental constants. [ The 9 Biggest Unsolved Mysteries in Physics ] Atomic clocks The current U.S. time standard is set by cesium clocks, in which cesium atoms are pulsed with microwaves. The microwaves cause the cesium atoms' outer electrons to jump to a higher energy level, and the resulting vibration rate sets the clock's tick rate. But newer atomic clocks have the potential to become even more accurate. Instead of using microwaves, these clocks trap bunches of atoms within standing waves of a powerful laser and excite these atoms with a second laser.

The lasers can cause the atoms to vibrate, or "tick," at a higher frequency than the old microwave method could. "The higher the ticking rate, the more finely you can divide time up," said study co-author Andrew Ludlow, a physicist at the National Institute of Standards and Technology in Boulder, Colo. Quantum mechanics prohibits scientists from knowing what any particular atom does, precisely, but researchers can average the energy jumps of thousands of atoms to calculate an incredibly precise measure, Ludlow added. Ultrastable clock In the current study, Ludlow and his colleagues cooled 10,000 ytterbium atoms to 10 Microkelvin, just a hair's breadth away from absolute zero. Next, they trapped the atoms in tiny wells formed by the laser's standing wave. A second laser, which oscillates 518 trillion times a second, excited the atoms. The team achieved incredibly stable ticks by developing lasers that produce very little noise, or instability in the light wave. At the same time, they accounted for or eliminated many factors that jostle atoms around and would have led to greater unpredictability in their behavior.

Testing basic physics If the new technology can be incorporated into an atomic clock , it could provide incredibly precise measurements of time. That, in turn, could shed light on some of the most mysterious problems in physics. Einstein's theory of relativity , which explains how gravity warps space-time, is incompatible with quantum mechanics, the reigning model that explains the behavior of the tiny particles that make up matter. Because gravity slows time, atomic clocks will actually tick more slowly in a gravitational field — a phenomenon known as gravitational red shift. But some theories predict that gravitational red shifting breaks down, and ultraprecise clocks could test to see whether that happens by even the tiniest amount. Other physicists have proposed that the fundamental constants, such as the ratio of electron-to-proton mass or the speed of light in a vacuum, may not be so constant after all. Incredibly precise atomic clocks could begin to test that proposition. "These clocks are weakly sensitive to the value of these constants, so you can try to ascertain whether the underlying atomic constants are changing," Ludlow told LiveScience.

Elements of Atomic Clocks Elements of Atomic Clocks By Richard Romando | Submitted On September 19, 2006 An atomic clock is a kind of clock that uses an atomic resonance frequency standard as its counter. While the time base of a conventional clock is the oscillating pendulum, the atomic clock is based on the properties of atoms transitioning between different energy states. The first person to express the concept of the atomic clock was the Columbia University Isidor Rabi in the year 1945. He suggested that a clock could be made from a technique he developed in the 1930s, called atomic beam magnetic resonance. By 1949, the National Bureau of Standards introduced the world's first atomic clock using the ammonia molecule as the source of vibrations, and the first atomic clock using cesium atoms as the vibration source was announced in 1952. Both conventional clocks and atomic clocks use oscillations to keep track of passing time. The oscillation frequencies within the atom depend on the mass of the nucleus and the gravity and electrostatic "spring" between the positive charge on the nucleus and the electron cloud around it. The most accurate atomic clocks available today use the cesium atom and normal magnetic fields and detectors.

Cesium 133 is the element most commonly chosen for atomic clocks. The operation of a cesium-beam atomic clock is based on the transition between two states in the cesium atom. Rubidium is also used in atomic clocks, and it lowers the cost; however, rubidium clocks are less stable. Hydrogen masers have short-term stability and low long-term accuracy. Mercury ions are also used in some atomic clocks. A particular isotope of Ytterbium has a particularly precise resonance frequency in one of its hyperfine transitions. Strontium has a hyperfine transition that is not precise. But strontium can be driven by solid-state lasers that can be utilized to make a very inexpensive, long-lasting, and compact clock. Cesium atomic clocks are used in laboratories like the National Institute of Standards and Technology to maintain national time scales. Atomic Clocks [ provides detailed information on Atomic Clocks, Atomic Clock Times, Atomic Alarm Clocks, Atomic Wall Clocks and more.

Atomic Clocks is affiliated with Printable Calendars [ The Mouse Ran Up The Clock The Mouse Ran Up The Clock By Allan Eastman Go back to Page 4 Modern Times The Weltzeituhr (World Time Clock), found in Berlin, is a modern-day example of time tool development in human history. The clock shows the current time in each time zone. ©iStockphoto.com/TristanH Increasingly more accurate mechanical clocks remained the main timekeeping Tool until well into the 20th century. But then things began to change rapidly due to the quantum leap in Science and Technology. The first really major change came with the development of Quartz Clocks by Bell Labs in the USA in the 1920s. They found that if an accurately shaped crystal of Silicon Dioxide could be made to vibrate with AC electricity, it would oscillate at a precisely desired and regular frequency. From this, it was an easy next step to connect it to a calibrated time display. Initially, this controlled an analog clock face but eventually the timekeeping was designated by an electric pulse and became digital, which meant no more moving parts to wear down. Already by the 1930s, Quartz clocks were becoming the timekeeping standard.

In the post WWII era, they became widely used and the first quartz powered wrist watches made their appearance in the 1960s. The basis for timekeeping Tools became electronic and they provided an accuracy that was much advanced from mechanical devices. But this process was just beginning. The next major evolution in Time Tools came with the arrival of the Atomic Age. Scientists recognized that the atoms of each element or compound emit electromagnetic radiation at its own characteristic frequency and these resonances are totally stable over Space and Time. They would be the same over millions of years or on the other side of the Universe. Various elements were tested until Cesium became the main element used in the first really accurate Atomic Clock built in 1955. It quickly became the most used scientific standard of Time measurement and became the official standard in 1967. One “Atomic Second” of Time was defined as “The duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the Cesium-133 atom.” So, now you know.

The latest versions of Atomic Clocks in the National Institute of Standards and Technology (NIST) in the US are called the Quantum Logic Clocks and are based on the oscillations in Mercury and Aluminum atoms. They are claimed to be accurate to within 1 second in 1 Billion (1, 000,000,000) years. Advertising The ultimate Tool in bringing this completely accurate Atomic timekeeping to the entire Planet was the establishment of Coordinated Universal Time – UTC – in the 1960s with its full adoption in 1967. At an Institute in Paris, time signals generated by a series of Atomic Clocks in Scientific Institutions from around the World are compared by computer and a weighted average from these signals is generated as the official World Time. The UTC time signal is sent around the planet electronically. The Network Time Protocol –NTP – was set up in 1985 and remains one of the oldest internet protocols in use. It zips the UTC through the internet accurate to milliseconds. The servers here at timeanddate.com use NTP to provide their service to all of the timepieces on your Personal World Clock. Twenty of them, in my case.

World commerce and technology has become tightly integrated with UTC and NTP for accurate time measurement. Accurate time is crucial to the accurate functioning of the GPS system above us in geosynchronous orbit. Financial transactions, aircraft navigation, the operation of manufacturing robots and most other Time related aspects of modern life have become completely dependent on the integrated GPS, UTC and NTP systems. One curious sidelight to the development of these most advanced Time Tools is that they have actually become too accurate for the astronomical phenomena they were invented to measure. The official definitions of Time as an expression of the oscillation of cesium atoms does not take into account that the Earth’s rotation is gradually slowing down due to gravitational friction so in effect, our days are becoming longer at a miniscule pace. So corrections to our timekeeping Tools have to be made periodically to keep everything in sync. This is accomplished by adding a Leap Second from time to time to keep UTC aligned with the rotation of our planet. During 1972, a second was added to UTC on both 30 June and 31 December to catch up.

Since then, another 22 seconds have periodically been added over the last 38 years, at the average rate of 1 second every 1 to 2 years. So, similar to that incredible transformation from the bone to the satellite in 2001: A Space Odyssey, our Time Tools have evolved from manmade scratches on an antler to an elaborate electronic system based on the vibration of atoms that more or less simultaneously informs the entire Human Race of what Time it really is. Do we need or will we get even more accurate Time Tools in the future? Well, Time Will Tell, of course.

Question: The vibrations of which element formed the basis of the first atomic clock?
Answer: Caesium