ANDREW BROOKES, NATIONAL PHYSICAL LABORATORY / SCIENCE PHOTO LIBRARY ANDREW BROOKES, NATIONAL PHYSICAL LABORATORY / SCIENCE PHOTO LIBRARY
Ytterbium optical clock. This apparatus is also known as a frequency standard. Inside it is an ion trap, where ytterbium ions oscillate between two energy levels in response to the light of a laser beam. Counting these oscillations is the basis for the standard second. The current basis for the international definition of time is the caesium atomic clock, where one second is about 9193 million oscillations of caesium-133 atoms. Optical clocks are more precise than the caesium clock as higher numbers of oscillations in a given time provide a more accurate measurement. Photographed in 2014, at the National Physical Laboratory, Teddington, UK.
Model release not required. Property release not required.