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Planck Mass

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The '''Planck mass''' is the Natural units natural unit of mass, denoted by ''m''_P. It is the mass for which the Schwarzschild radius is equal to the Compton length divided by π. :

m_P = \sqrt{\frac{\hbar c}{G}}

â‰ˆ 1.2209 Ã— 10¹⁹ GeV/c² = 21.76 micro Âµ gram g The 2002 CODATA-recommended value for the Planck mass is 2.176 45(16) Ã— 10^-8 kg, where the part in parentheses indicates the uncertainty in the last digits shown — that is, a value of 21.7645 Âµg Â± 0.0016 Âµg. Particle physics Particle physicists and physical cosmology cosmologists often use the '''reduced Planck mass''', which is :

\sqrt{\frac{\hbar{}c}{8\pi G}}

â‰ˆ 4.340 Âµg. 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 it is roughly the mass of some fleas.

Significance
The Planck mass is the mass of a black hole whose Schwarzschild radius multiplied by π equals its Compton wavelength. The radius of such a black hole is roughly the Planck length, which is believed to be the length scale at which both general relativity and quantum mechanics simultaneously become important.

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

External links

- The NIST Reference on Constants, Units, and Uncertainty {{Planckunits}} {{physics-stub}} Category:Physical constants Category:Natural units Mass Category:Units of mass fr:Masse de Planck ja:ãƒ—ãƒ©ãƒ³ã‚¯è³ªé‡? la:Massa planckiana ko:í”Œëž‘í?¬ ì§ˆëŸ‰ pl:Masa Plancka vi:Khá»‘i lÆ°á»£ng Planck zh:è’²æœ—å…‹è³ªé‡? see Planck mass