Marking time

Press, 2 May 1984, Page 14

Marking time

In February this year Soviet scientists started a new generation standard clock. The atomic chronometer will be only one second out in 700,000 years. The Soviet Union was among the first countries to pass from the astronomical second, based on the Earth’s daily revolution around its axis, to the “man-made” atomic second.

The new atomic clock embodies all the latest achievements of physics, instrument-making, and special technology. It can be called a clock only for the sake of tradition. The key instrument is the caesium frequency mark. The role of the pendulum.is played in it by an oscillating atom. In one second the atom of the caesium-133 metal makes 9,192,631,770 oscillations. Scientists are now working on the next generation system, with built-in lasers. These are Jietter known oscillation gfnera-

tors in their frequency stability. Thus a chronometer with a laser “pendulum” promises to be even more accurate than the atomic one.

Lasers can also be used for accurate linear measuring. An international forum in 1983 adopted a new definition of the metre, which involves linear and time units. The metre is defined as the distance which laser-emanated light covers in 1/299,791,458th of a second. The idea — formerly considered fantastic — of uniting the standards of the two physical variables of time and distance into one universal meter is coming true. The time, frequency and distance meters, all in one, will make it possible to increase the accuracy of linear measurements. That is necessary for astronomy, biology, physics, chemistry, precision engineering, and microelectronics. Novosti News Service. H