Question

Is there a static condition against which the speed of light is measured ?​

Answer 1

Answer:

The special theory of relativity implies that only particles with zero rest mass may travel at the speed of light. Tachyons, particles whose speed exceeds that of light, have been hypothesized, but their existence would violate causality, and the consensus of physicists is that they don't exist.

Answer 2

The speed of light could then be found by dividing the diameter of the Earth's orbit by the time difference. The Dutch scientist Christiaan Huygens, who first did the arithmetic, found a value for the speed of light equivalent to 131,000 miles per second. The correct value is 186,000 miles per second.