For 10 points, name this constant often symbolized as "c," the maximum speed at which all matter in the universe can travel.
This quantity equals one over the square root of mu naught times epsilon naught. In one formulation of Planck's Law, spectral radiance is proportional to the cube of frequency divided by the square of this property. In particle physics, mass is measured as (*) electron volts divided by the square of this quantity and Cherenkov radiation is emitted when a particle's velocity exceeds this constant for a medium. In September 2011, the OPERA project erroneously claimed that they had measured tau neutrinos moving faster than this constant. For 10 points, name this constant often symbolized as "c," the maximum speed at which all matter in the universe can travel.
This quantity equals one over the square root of mu naught times epsilon naught.
speed of light [accept c before read] &lt;AP&gt;