Planck Length

Planck Length

In physics, the Planck Length, (denoted `l_P`), is a fundamental unit of length.  It is a base unit in the system of Planck units, developed by physicist Max Planck. The Planck Length can be defined from three fundamental physical constants: the speed of light in a vacuum, Planck's constant, and the gravitational constant.  This constant is expressed in units of meters.  

This unit of length is so small it is not feasible to consider measuring it directly but the Planck Length relates to planck's constant which is being used in the determination of the standard kilogram.

The Math

The Planck length can be defined from three fundamental physical constants: the speed of light in a vacuum, the Planck constant, and the gravitational constant/

`l_P = sqrt((h * G)/c^3)` where h is Planck's Constant, G is the gravitational constant, and c is the speed of light

Notes

This constant, the Planck Length, is specified with a standard uncertainty (standard deviation) of 0.000 097 x `10^(-35)` m

See Uncertainty of Measurement Results, a discussion provided by NIST of the application of uncertainty to the documented constants.