Spotlight

A Brief History of Time

The recent addition of a leap-second into our time system has sparked interest in the Time Service, guardian of our temporal reality.

The service began its life serving Wellington Province in 1864 and was responsible for calculating and disseminating Wellington Mean Time, (which became New Zealand Mean Time in 1868).

The official Gazette announced on 7 March 1864 that a Time Ball erected above the Custom House would begin operation, marking midday, primarily for the benefit of calibrating the clocks of the ships that were in port.

In 1869 clock and other instruments used to control the Time Ball were bought from Wellington Province by the General Government for 300. In the same year an Observatory was constructed opposite Bolton Street for the sum of 150 to take the transit telescope readings necessary to establish correct time.

The clock remained in use for over a century. It was remarked that at the end of its life in the 1960s it was worth much more than this as an antique, and that the General Government had secured quite a bargain.

The Observatory stayed in its position until the death of Richard Seddon in 1906, whereupon it was decided the spot was ideal for his burial site and the Observatory was peremptorily ordered to move. A reprieve was asked for but refused and the Observatory was finally dismantled on the very day of Seddon's burial. It moved to a new building at Kelburn and this building still stands.

In 1926 the DSIR was formed. The time service was maintained under its umbrella, but no effort was initially made to upgrade the equipment or improve the accuracy. Until the 1950s the accuracy claimed for outgoing signals was a quarter of a second, but during the night and at weekends errors exceeding a second were not unknown.

Because of prevailing opinion in the Public Service circles that science was humbug, and all scientists were suspect, especially physicists, founding secretary of DSIR Ernest Marsden made use of the Observatory as a convenient "front" for all kinds of physical science activities.

The Dominion Observatory's responsibilities for earthquake observations and the maintenance of standard time were functions easily understood by a clerical administration. Marsden quietly added three physicists and an instrument maker to the group -- soon establishing a nucleus of trained physicists, using the cellar workshop to study everything from cosmic rays, thermal conductivity of pumice concrete to facial eczema in sheep.

With the war it became clear a physics laboratory was needed and the workshop moved to a derelict garage in Molesworth Street to become the Physical Testing Laboratory. After the move the Observatory was left with "a bench vice that had seized up, a blunt file, a broken screwdriver and a hand drill with no bits".

The old clocks were by now incapable of maintaining accuracy for more than 24 hours. Replacements were now impossible due to the war and an alternative was cobbled together out of remains of other clocks to serve as the standard clock for more than a decade. The accuracy of time signal comparison was somewhat improved after the war with the introduction of an arrangement devised from a war-surplus oscilloscope, cotton reels and string.

Eventually the Dominion Physical Laboratory, descendant of the Observatory workshop attempted to make a quartz-crystal clock to improve the accuracy of the standard clock. The result was a spectacular failure. The crystal, intended for amateur radio use, was of lower accuracy than the free pendulum it replaced, and the divider circuits refused to remain locked for more than a day or two at a time. Criticism was ignored and three more clocks embodying the same faults in design were eventually produced.

Major improvements were finally made in 1966. Modern quartz clocks with stabilities of one part in 10¹¹ were obtained. Clock errors were corrected by comparison with radio signals transmitted from observatories cooperating with the Bureau International de l'Heure, and derived signals began to be transmitted daily over national radio -- principally to coordinate the monitoring equipment of the seismological network.

These days extremely accurate and stable atomic clocks are used to maintain New Zealand Standard Time, accurate to five parts in 10¹².

Leaping Seconds

Manager of New Zealand Standard Time, Dr Tim Armstrong of Industrial Research Limited, programmes a sixty-first second into the standard time clock for midday Thursday 1 July.

The "leap second" was decreed by the Bureau International des Poids et Mesures, an international organisation that controls weights and measures, to ensure that artificial time-keepers remain in step with nature.

"It's because the earth is slowing down, and if we did not have these leap seconds at periodic intervals, eventually lunchtime would happen in the middle of the night", says Armstrong.

The leap second was programmed into the three atomic clocks that control New Zealand's time from IRL's Measurement Standards Laboratory in Lower Hutt. They lose only one second in 30,000 years, which makes them much more stable time keepers than the Earth itself.