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NIST General

NIST General

Science Facts Written by NIST General

Engineering

How We Use Crystals To Tell Time

Quartz clock operation is based on the piezoelectric property of quartz crystals. If you apply an electric field to the crystal, it changes its shape, and if you squeeze it or bend it, it generates an ... Continue reading

Quartz crystal mechanisms, common since the 1930s and 1940s, can keep a watch accurate to within a couple of seconds a month, or one part in a million.
Mathematics

Origins Of The Meter

The origins of the meter go back to at least the 18th century. At that time, there were two competing approaches to the definition of a standard unit of length. Some suggested defining the meter as ... Continue reading

The engraving shows the casting of the platinum-iridium alloy called the '1874 Alloy.'
Mathematics

Leaps and Bounds

Leap years are years with 366 days, instead of the usual 365. Leap years are necessary because the actual length of a year is 365.242 days, not 365 days, as commonly stated. Basically, leap years ... Continue reading

Mathematics

Unit Of Luminous Intensity (candela)

Originally, each country had its own, and rather poorly reproducible, unit of luminous intensity; it was necessary to wait until 1909 to see a beginning of unification on the international level, when ... Continue reading

Engineering

Dress Sizes The Scientific Way

In pre-industrial America, most clothing was crafted at home or by professional tailors or dressmakers from individual measurements taken of each customer. In the early Twentieth Century, the growing ... Continue reading