Time is now precisely measured with primary standard clocks that are based on
A) very precise pendulum motion.
B) the pulsed vibrations of quartz crystals.
C) the vibration of cesium atoms.
D) the pulse rate of pulsar stars.

Question

Quizplus · Accepted Answer

Primary standard clocks now use the vibration of cesium atoms to precisely measure time. This is known as an atomic clock and is the most accurate way to measure time.

Time Is Now Precisely Measured with Primary Standard Clocks That