This quantity is raised to the negative fourth power in the definition of Einstein’s gravitational constant. The slope of a 45 degree line on a Minkowski diagram (10[1])equals this quantity (10[2])because Minkowski time (10[1])is scaled by this quantity. The ratio of velocity to this quantity is denoted by beta. By comparing (10[1])interference patterns, this quantity was found not to depend on the direction of measurement (-5[1])in the Michelson-Morley experiment. The mass-energy equivalence states (read slowly) (10[1])rest energy equals mass times this (10[2])quantity squared. For 10 points, name this universal speed limit equal to about three times ten to the eight meters per (10[1])second. ■END■