In physics, the Planck mass, denoted by mP, is the unit of mass in the system of natural units known as Planck units. It is defined so that
- ≈ 1.2209×1019 GeV/c2 = 2.17651(13)×10−8 kg, (or 21.7651 µg),
where c is the speed of light in a vacuum, G is the gravitational constant, and ħ is the reduced Planck constant.
Particle physicists and cosmologists often use the reduced Planck mass, which is
- ≈ 4.341×10−9 kg = 2.435 × 1018 GeV/c2.
The added factor of 1/ simplifies a number of equations in general relativity.
The name honors Max Planck because the unit measures the approximate scale at which quantum effects, here in the case of gravity, become important. Quantum effects are typified by the magnitude of Planck's constant, .
Read more about Planck Mass: Significance
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