From the dawn of history, man has been engaged in a continuous search for more precise methods of measuring time. Wise men of all ages have relied on the motions of the heavenly bodies in calculations recording the passage of time. In 1903 an Oxford don experimented with the possibility of photographing the moon in a moving time exposure against a background of stars. This celestial clock has proved to be the most accurate method of time measurement ever devised. During the recently ended International Geophysical Year, 20 Markowitz moon cameras were located at strategic centres around the world to gain important information for time services and -- by correlating findings of the various cameras -- valuable data concerning the size and shape of the earth will also be revealed. Canada's Dominion Observatory in Ottawa is the site of one of the 20 IGY moon-cameras; astronomer M. M. Thomson is shown above inserting a photographic plate into the powerful camera. Studies so far have established that earth clocks have lost 30 precious seconds since the beginning of this century -- a scientific finding of incalculable import in a space-conscious age where man's efforts to land on the moon must be infinitesimally geared to split-second tuning.