The most precise scientific standard of time is based on
A) a specified fraction of the mean solar day.
B) the time taken for a specific "seconds" pendulum kept at special conditions to complete one oscillation.
C) a property of a particular kind of atom.
D) the speed of light.
E) the travel time of light from the nearest star.

Question

Quizplus · Accepted Answer

The most precise scientific standard of time is based on the property of a particular kind of atom, specifically the vibrations of cesium atoms. This method defines a second as the duration of 9,192,631,770 periods of radiation corresponding to the transition between two energy levels of the cesium-133 atom.

The Most Precise Scientific Standard of Time Is Based on