In 1957, Robert Dicke proposed that this quantity has a small correction term inversely proportional to the distance to a star, which is consistent with Mach’s principle. A 2012 freeware developed by MIT depicts a world in which this quantity decreases as the ghost of a young child collects more magic orbs. A toothed rotating cogwheel is used to measure (15[1])this quantity in the (*) Fizeau experiment. This quantity is equal to (10[1])one over the square root of the product of permittivity and permeability of (10[1])free space. The ratio of this quantity to the phase velocity of the medium gives the refractive index. This quantity is shown to be constant when luminiferous ether was not found in the Michaelson-Morley experiment. For 10 points, identify this constant equal to 3 times 10 to the 8th meters per second. ■END■