Atomic Clock

Atomic ClockThe accuracy of time measurement is one of the major problems throughout the whole history of mankind. As the technology developed, the requirements for clock accuracy grew. Clocks have passed a long way of evolution: sundial, water, sand, mechanical, quartz, and finally, atomic. Atomic, or as it is sometimes called molecular or quantum, clock is a device for measuring time, which uses the natural oscillations of atoms or molecules as a batch process. Atomic clocks have the greatest importance for navigation. Determining positions of spacecrafts, satellites, ballistic missiles, aircrafts, submarines, and vehicular traffic in an automatic mode using satellite communication (GPS, GLONASS) are unthinkable without the atomic clock. Since 1967, the international system of units defines one second as a certain number of periods of the electromagnetic radiation generated during the transition of cesium-133 atom between two levels of the ground state. According to this definition, an atom of cesium-133 is a standard to measure time and frequency. The accuracy of determining the second determines the accuracy of all other major units, such as, for example, a volt or a meter, which contain "second" in their definition. Cesium clocks have been considered the most accurate for the last 50 years. A cesium clock will face 1 second error no earlier than in 70-80 million years. But scientists continue to work on improving atomic clocks. The latest achievement belongs to the physicists of the U.S. National Institute of Standards and Technology. They have used aluminum ions in an atomic clock. These ions have a 3-degree higher transition frequency than that of cesium atoms. These devices will accumulate one second error in 3,7 billion years.