This however did not prove to be a suitable environment as the experiment was affected by factors such as the building swaying and vibrations from traffic. The discovery of the Cracroft Caverns with its stable environment over 100 ft below the ground was the ideal solution to the University's problems and a tailor made home for the ring laser experiment. The beams of light form separate lasers. There is a fixed number of wavelengths in any round trip and the light speed is fixed by relativity. When the whole device rotates, say with the earth, the beam which is travelling the same way as the rotation has to travel further to get back to any one mirror.
Rotation then makes the colours of the beam very slightly different.
The colour difference can be detected with more accuracy than any other laser because of the supermirror quality and the overall size of the ring laser, making C-I the most precise laser in the world for colour resolution. C-II is to be housed in the Cracroft Caverns on its arrival in New Zealand. This means altogether better engineering and better control of gas purity. All this should improve accuracy and produce better results. In the future it is hoped among other things that C-II will be able to measure rotational movements in earthquakes and lunar and solar tides in the solid earth.