Earth Slowing Down In Its Rotation

Press, Volume XCVII, Issue 28481, 10 January 1958, Page 11

Earth Slowing Down In Its Rotation

(Special Correspondent N.Z.P.A.) (Rec. 8 p.m.) LONDON, January 9.

The earth appears to be slowing down in its rotation about its axis, according to a series of careful measurements of time carried out at the National Physical Laboratory, says the “Manchester Guardian” scientific correspondent.

The most probable interpretation of these observations is that the earth is slowing down at a rate which has increased the length of day by about onethousandth of a second in the last two years, says the correspondent The work has been possible“because of • new ‘'atomicclock"

installed at the laboratory three years ago. This clock is one in which the “pendulum” action is provided by the atomic vibrations of atoms of the element caesium. These vibrations are used to control the frequency of the vibration of radar waves which, in turn, transmit the record of vibration of caesium atoms to electronic counters

, Evidence of the earth's latest vagary as a timekeeper has emerged by comparison of the timekeeping of the caesium clock with earlier qbartz crystal clocks used as time standards some years ago. Comparisons have also been made with the astronomical observations from which the length of the day was defined.,

The observed irregularity in the rotation of the earth mounts to one part in a hundred, million which is 100 times as great as the expected error of the caesium clock.

There is no obvious explanation, however, of the progressive slowing down which has now been accurately measured. It is most probable that some progressive change in the structure of the earth’s interior is the cause.

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