Saturday, November 07, 2020

Detecting Anisotropic Speed of Light by measuring ballistic trajectory of photons in Vacuum

Derek Muller of Veritasium posits that it is not possible to measure the speed of light in one direction only. I believe it is possible, but just barely.

Here's a thought experiment/grant proposal that I think might settle the question.

Assume a laser and a mirror in perfect alignment in vacuum, 20 Kilometers apart.

Travel to the center of the experiment, examine the relative position of the two beams, they should be co-linear. If the speed of light is anisotropic, the time of flight would be different from the left or right portion of the beam If the time of flight is different, the ballistic drop is different. The drop of a photon on the surface of the earth in 10Km is about 5 nanometers, so detecting a 10% shift in the speed of light would require finding an offset of 0.5 nanometers. It's possible... but outside my budget.

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