Contents, clocks and solar time edit, a mechanical clock, one which does not depend on measuring the relative rotational position of the earth, keeps uniform time called mean time, within whatever accuracy is intrinsic.Retrieved December 22, 2013.So a clock with 60 divisions would have a mark for thirds, fourths, fifths, sixths and twelfths (the hours whatever units the clock would likely keep time in, would have marks.

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cloth wrinkled up in the intense heat. Our teaching team works closely together to provide a rich learning environment for every student. Image caption The Italian government's spending plans

The tropical year in the definition was not measured but calculated from a formula describing a mean tropical year that decreased linearly over time.The second is also part of several other units of measurement like velocity, acceleration, and frequency.

TAI "ticks" atomic seconds.The second became accurately measurable with the development of mechanical clocks keeping mean time, as opposed to the apparent time displayed by sundials.