Time measurement systems

Category:Time measurement systems - Wikipedia

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Decimal time Solar time Sidereal time Coordinated Universal Time

The second has been defined by caesium-133 since 1967: counting 9192631770 oscillations replaced the rotating Earth Sealing a capsule with stainless steel and silica gel under inert gas How much does a country spend to keep one agreed second? What is a jiffy and why does its length depend on who is asking? Why do navigators still count time in degrees minutes and seconds? The sidereal day is 4 minutes shorter and that is why stars rise earlier each night Why does the SI second get redefined every few decades? Why physics needed a second that does not depend on the rotation of the Earth How did a sixty-day cycle end up organising Chinese year counting? Why do we still split hours into 60 minutes instead of 100? Why do metrology labs quote timing uncertainty in parts per billion instead of seconds? Why do stock exchanges keep their own reference clock instead of trusting the wall clock? Why the international date line bends around island groups instead of running straight Why is the correct time something somebody has to run and pay for? Why does averaging repeated timings not always improve the answer?

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