What is the Definition of Time Second in science ?
Scientific Definition of Time (Second)
Time defined to be
"One second is the time taken by 9 192 631 770 oscillations of the light (of a specified
wavelength) emitted by a cesium-133 atom."
Time has two aspects. For civil and some scientific purposes, we want to know the time of day so that we can order events in sequence. In much scientific work, we want to know how long an event lasts. Thus, any time standard must be able to answer two questions: “When did it happen?” and “What is its duration?”
Any phenomenon that repeats itself is a possible time standard. Earth’s rotation, which determines the length of the day, has been used in this way for centuries. A quartz clock, in which a quartz ring is made to vibrate continuously, can be calibrated against Earth’s rotation via astronomical observations and used to measure time intervals in the laboratory. However, the calibration cannot be carried out with the accuracy called for by modern scientific and engineering technology.
ref :Fundamentals of Physics
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