If tachyons exist, they travel faster than this speed.
This quantity's square is in the denominator of the "B nu" formulation of the Rayleigh-Jeans law. In a medium, this quantity is scaled by the square root of the product of the relative permeability and permittivity. In Planck units, this electromagnetic quantity is normalized to one. This physical constant is used to define the meter. This quantity is the only one of its type to be constant in all inertial reference frames. The Michelson-Morley experiment demonstrated its constancy by showing that luminiferous ether did not exist. If tachyons exist, they travel faster than this speed. For 10 points, what is the maximum speed at which anything can travel, often denoted "c"?
This quantity's square is in the denominator of the "B nu" formulation of the Rayleigh-Jeans law.
the speed of light (in vacuum) [accept c until it is read]