That’s the stupidest argument I’ve ever heard from someone attempting to be a physicist.
The gear experiment is the simplest answer. With a gear whose diameter spans the distance between the light source and receiver, and where the speed of rotation is controlled by an atomic clock, the gear could have a small hole through it. If light sent from one side to the other while the gear is spinning is too slow, it will not make it through the gear.
The size of the bike through the gear will dictate the speed, because the gear itself measures duration and distance in a single direction.
The gear experiment is the simplest answer. With a gear whose diameter spans the distance between the light source and receiver, and where the speed of rotation is controlled by an atomic clock, the gear could have a small hole through it. If light sent from one side to the other while the gear is spinning is too slow, it will not make it through the gear.
The size of the bike through the gear will dictate the speed, because the gear itself measures duration and distance in a single direction.