Pair to build new laser in caverns to measure day length

17:00, Sep 23 2010
Robert Hurst and Jon-Paul Wells
LIGHT WORK: Robert Hurst, left, and Jon-Paul Wells, of the University of Canterbury's department of physics and astronomy, are to build a laser gyroscope in the Cashmere Hills.

Giant lasers under Christchurch's Port Hills will help pinpoint the length of a day.

Dr Jon-Paul Wells and Dr Robert Hurst, of Canterbury University's physics and astronomy department, have been granted $870,000 from the Marsden Fund to build a new ring-laser gyroscope in the Cashmere Cavern.

The department has been building large-scale lasers in the cavern for almost 20 years.

Wells said the new laser would, hopefully, be used to detect small changes in a day's length that occurred because of exchanges of momentum between the solid Earth and the atmosphere of the oceans.

While the differences would only be in the thousandths of a second, the information would be important for many applications, such as GPS.

"The length of a day is certainly of interest ... it's fundamental for everything we do," he said.


"This will be of great interest, if we achieve that ... I think if we're successful in this you can honestly say it will be a very copied device."

The pair assured Canterbury residents they were not building anything as controversial as the Large Hadron Collider in Switzerland, a particle accelerator.

"It's absolutely non-lethal; it's 1000 times too weak to damage the eye," Hurst said.

Another aim was to measure effects predicted by Einstein's theory of relativity, he said.

The laser technology bounces two lasers in opposite directions around a pipe off "supermirrors" that reflect 99.99 per cent of the beam. Interference between the two beams provides a sensitive measure of the rotation of the Earth.

The daily wobble of the Earth on its axis as well as slow rotations caused by the pull of the Moon and fast rotations caused by earthquakes can be measured.

The Press