XN000022-1972-06-28 — Page 14

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Wednesday, June 28, 1972

THE MISSING SECOND

The usual six-pip time signals from the Royal Observatory will

not be broadcast at nine o'clock this Saturday morning (July 1). But

they will be resumed 15 minutes later at 9:15 a.m.

A spokesman for the Royal Observatory said today this was to

enable a correction to be applied which would result in an apparent

delay of one second to the resumed time service signals.

The need to set the clock back by one second arises because

world-wide time standards are now based on the atomic time scale. This

provides a more precise and uniform second than that derived from the

rate of rotation of the earth measured by astronomical means.

The spokesman said the time service in Hong Kong had been maintained

by reference to the atomic scale since January 1 this year.

One day on the astronomical time scale is, on the average,

three-thousandths of a second longer than the day on the atomic time scale.

"However, it has been internationally agreed that the two times

should never differ significantly and that periodic adjustments of the

whole second would be made to the time shown by those clocks using or being

maintained by reference to the atomic time scale," he said.

By the end of June, the difference will be almost six-tenths of

a second and the first of these adjustments is to be made at 9 a.m, on

July 1, 1972.

"This correction of one second, called a leap-second, is analogous

to 29th February in a leap year, which everyone is familiar," the spokesman

added.

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