Which of the SI standard units is NOT based on a constant of nature?
A)The meter, because the speed of light can vary from place to place.
B)The second, because cesium cannot be found everywhere.
C)The kilogram, because it is based on an arbitrary piece of metal.
D)The kilogram, because the gram is the standard unit.
E)The meter, because it is defined in terms of the speed of light in vacuum, and there is no perfect vacuum anywhere.

Question

Quizplus · Accepted Answer

The kilogram is currently defined by a physical artifact, the International Prototype of the Kilogram, which is an arbitrary piece of metal kept at the International Bureau of Weights and Measures (BIPM) in France. It is not based on a constant of nature. However, it is important to note that in May 2019, the kilogram was redefined in terms of Planck's constant (a constant of nature) and the definition of the kilogram is now based on this constant.

Which of the SI Standard Units Is NOT Based on a Constant