Speed of light zero, "γ" is equal to one, giving rise to the famous formula for mass–energy equivalence. The "γ" factor approaches infinity as "v" approaches "c", and it would take an infinite amount of energy to accelerate an object with mass to the speed of light. The speed of light is the upper limit for the speeds of objects with positive rest mass, and individual photons cannot travel faster than the speed of light. This is experimentally established in many tests of relativistic energy and momentum. More generally, it is normally impossible for information or energy to travel faster than "c". One
One-way speed of light the time of flight of light signals through a fibre optic link between two hydrogen maser clocks. In 1992 the experimental results were analysed by Clifford Will who concluded that the experiment did actually measure the one-way speed of light. In 1997 the experiment was re-analysed by Zhang who showed that, in fact, only the two-way speed had been measured. The first experimental determination of the speed of light was made by Ole Christensen Rømer. It may seem that this experiment measures the time for light to traverse part of the Earth's orbit and thus determines its one-way speed, however,