In his book The Physics of Einstein, scientist Jason Lisle describes the theories and implications of Special and, to a lesser extent, General Relativity. Towards the end of his book, he wrote about the issue of measuring the one-way speed of light, stating correctly that all measurements of the speed of light so far has been the two-way speed of light. The model Lisle is promoting is the anisotropic synchrony convention (ASC) whereby the speed of light is different in one direction than it is in its return trip. Specifically, light could be infinite in speed in one direction, while having half c when it returns. Besides changing the reference plane, the choice between the conventional view and Lisle's ASC cannot be decided based upon current empirical evidence. So which one of them is correct?
While versions of ASC exists that might be plausible, I think that Lisle's version with an infinite one-way speed is problematic. Let us start with the first problem with such a view of light:
c = fλ
where c is speed of light, f is frequency, and λ is wavelength
Now, the different waves of the electromagnetic spectrum follow this equation, as they travel at the speed of light. The different types of waves are distinguished by their wavelengths, where radio waves have long wavelengths while X-rays have very short wavelengths. The question for an infinite speed of light is simple: If light has infinite speed, how can the different types of radiation function? For speed to be infinite implies an infinite frequency, but if both speed and frequency are infinite, then the wavelength does not make any sense, does it?
The second problem with Lisle's ASC comes from this:
E = hf
where E is energy, h is Planck's constant, and f is frequency
If light has infinite speed, then it must have infinite frequency. But if light has infinite frequency, then does it not have infinite energy? Given that in Lisle's model, the one-way speed of light from the stars to earth imply that everything we see in the night sky is actually happening now (since light speed is infinite one way), then shouldn't the light from these stars have infinite energy and destroy Earth by now? Now, Lisle could rescue his scenario by making Planck's constant variable (not a constant), or assert that the energy of a photon depends on the two-way speed despite its one-way speed, an assertion that makes no sense since the photon that reaches earth from the stars do not return to those stars but are absorbed (and maybe partially reflected) by the Earth.
Lastly, the question of direction is to be raised. What makes light move at innfinite speed in a certain direction? The reason why the speed of light is seen be to equal in both directons is that we have no reason to think otherise. Expansion of space does not help because that means that the one-way speed of light varies according to direction, whereas light coming to earth is from many different directions.
Due to these problems, I do not think Lisle's version of ASC is acceptable. Since the speed of light is fundamental to many different equations and the nature of reality, I think it takes more to postulate ASC than it is to hold to the conventional view. While ASC is not necesssarily wrong, the burden of proof is on those who hold to such theories to justify them as superior to the conventional view, not just as a possible alternate view.
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