Planck units

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A system of units, used principally in discussions of quantum theories of gravity, in which length, mass, and time are expressed as multiples of the Planck length, mass, and time respectively. This is equivalent to setting the gravitational constant, the speed of light, and the reduced Planck constant all equal to unity. All quantities that ordinarily have dimensions involving length, mass, and time become dimensionless in Planck units. Since, in the subject area where Planck units are used, it is normal to employ Gaussian units or Heaviside–Lorentz units for electromagnetic quantities, these then become dimensionless. See also geometrized units; natural units.

Subjects: Physics.

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