Planck mass

Planck mass

The Planck mass is the unit of mass, denoted by "m"P, in the system of natural units known as Planck units. Named after Max Planck, it is the mass for which the Schwarzschild radius is equal to the Compton length divided by π.:m_P = sqrtfrac{hbar c}{G} ≈ 1.2209 × 1019 GeV/c2 = 2.176 × 10-8 kgThe 2002 CODATA-recommended value for the Planck mass is 2.17645(16) × 10-8 kg, where the part in parentheses indicates the uncertainty in the last digits shown — that is, a value of 2.17645 × 10-8 kg ± 0.00016 × 10-8 kg.

Particle physicists and cosmologists often use the reduced Planck mass, which is:sqrtfrac{hbar{}c}{8pi G} ≈ 4.340 µg = 2.43 × 1018 GeV/c2.Adding the 8π simplifies several equations in gravity.

Unlike most of the other Planck units, the Planck mass is on a scale more or less conceivable to humans, as the body mass of a flea is roughly 4000 to 5000 "m"P.

ignificance

The Planck mass is an idealized mass that is thought to have special significance for quantum gravity when General Relativity and the fundamentals of quantum physics become mutually important to describe mechanics.

See also

* Planck unit
* Planck length
* Planck particle
* Orders of magnitude (mass)

External links

* [http://physics.nist.gov/cuu/Constants/index.html The NIST Reference on Constants, Units, and Uncertainty]


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