Myths
Absolute Space
Points of View
Twin Paradox
Einstein's Train
Andromeda Paradox
Time in Spacetime
Clocks & Time
Velocity of Light
The Velocity of Light
The idea that the velocity of light, in empty space, is the same in all frames of reference is mainstream physics. It is fundamental to Albert Einstein's Special and General Theories of Relativity. So could it really be a myth? Well, perhaps.
The reason why this might be a myth is that it is only indirectly supported by the evidence. Now it is perfectly legitimate say that the success of Einstein's theory implies that the velocity of light is constant in all frames of reference, but that is not the same as saying that it has been shown to be true. To be shown to be true, it would have to follow deductively from the evidence supporting the theory, which it does not. Indeed Einstein never claimed that it did.
The evidence from experiments like the Michelson-Morley experiment only show that the velocity of light is constant in the rest frame of the equipment used to measure it. In other words, it may be deduced that the velocity of light is constant with respect to the object that the light is approaching. That says nothing about the speed that the light is travelling at with respect to other objects in different rest frames.
So to claim that the Michelson-Morley experiment shows that the velocity of light is constant in all frames of reference would invoke a logical fallacy known as Affirming the consequent:
- If the velocity of light is constant in all frames of reference, then it is constant in a specific frame of reference: the rest frame of the target.
- The velocity of light has been shown to be constant in the rest frame of the target.
- Therefore, the velocity of light is constant in all frames of reference.
That is a logical fallacy because, even though the first two statements are true, the third statement is only true if the second statement ONLY follows from the first. I.e. It could not arise in any other circumstance. Such a relationship has not been established, therefore the conclusion is false.
But why should it matter whether the light is approaching the object or not? Well, firstly, the idea that the velocity of light is constant in all frames of reference gives rise to the Lorentz transformation, and the time dilation that describes. Secondly, there are alternatives to Einsteinian relativity in its present form. These are discussed in the Speculation section under Absolute Simultaneity, CICS and, to a lesser extent, Simultaneity-Time.
