The frequency of light is measurable Measuring the frequency of visible light (pptx), pdf
Measurements do not confirm always the same speed of light in a vacuum. Anyway, it seems impossible for physical science to be wrong.
This record is based on the measurement that shows how the speed of a comet affects the speed of light from it. The measurement can be repeated by many astronomical laboratories.
Light shows us the universe. The fallacy of the speed of light leads us to the misconception of the universe. It creates us illusions. Instead of eliminating the cause of these illusions and measuring the speed of light, we try to patch them up with magical dark matter and dark energy. more