We Don’t Really Know the Speed of Light
And we have no way to figure it out
The speed of light is an assumption, not a certainty. It’s an assumption in that we have never experimentally measured the one-way speed of light. The best we have been able to do, even with our most sophisticated modern technology, is measure the roundtrip speed of light and assume that the speed is the same in both directions. This is what’s known as being isotropic — a value is uniform no matter the direction. To be anisotropic, then, means that a value varies depending on the direction. Einstein’s theory of special relativity assumes that the one-way speed of light is constant and isotropic. So what happens if the one-way speed of light is anisotropic? What does it mean for our universe if one of our most successful theories of physics is based on an assumption that turns out to be false?
The current accepted value for the speed of light in a vacuum is 186,282 miles per second (299,792 kilometers per second). Light is able to travel at this incredible speed not because of what it is, but because of what it isn’t.
Fundamental particles of light — photons — are not very massive at all. In fact, they have no mass whatsoever. A particle’s mass comes from the emergence of the Higgs field. The Higgs field is a property of spacetime, one that arose as the universe…
