we only measure the two directional speed of light (bounce timing). The Einstein convention assumes that speed is the same in all directions. i'm not saying it'

we only measure the two directional speed of light (bounce timing). The Einstein convention assumes that speed is the same in all directions. i'm not saying it's not. Just that it's impossible to tell otherwise. Einstein mentioned this in his paper. https://en.wikipedia.org/wiki/One-way_speed_of_light https://en.wikipedia.org/wiki/One-way_speed_of_light