Length contraction occurs as objects approach this constant.
The Einstein tensor contains this quantity to the fourth power in its denominator. Maxwell discovered that this quantity is equal to one over the square root of the product of the vacuum permittivity and permeability. Cherenkov radiation occurs when this quantity is (*) exceeded in its local frame. Length contraction occurs as objects approach this constant. The equivalence of mass to energy depends on this constant squared, according to Einstein's famous equation. For 10 points, name this constant, the rate at which a photon travels in a vacuum, denoted by the letter "c."
The Einstein tensor contains this quantity to the fourth power in its denominator.
speed of light [prompt on “c”] &lt;SY Physics&gt;