2020-04-14 09:23:19 UTC
"One of the three classical tests for general relativity is the
gravitational redshift of light or other forms of electromagnetic
radiation. However, in contrast to the other two tests - the
gravitational deflection of light and the relativistic perihelion
shift - you do not need general relativity to derive the correct
prediction for the gravitational redshift. A combination of Newtonian
gravity, a particle theory of light, and the weak equivalence
principle (gravitating mass equals inertial mass) suffices. It is,
therefore, perhaps best regarded as a test of that principle rather
than as a test of general relativity."
That last sentence must surely be a non-contentious way of saying
that the gravitational red shift is not a definitive test of general
The writer has apparently not considered that the same combination of
factors applies also to the gravitational deflection of light, which
implies that it too is not a definitive test of general relativity.
With two of the three classical tests of GR thus seen as inconclusive,
the question arises as to whether a similar combination could provide
the correct prediction for the relativistic perihelion shift. At first
glance, the idea would seem preposterous: a particle theory of light
must surely eschew Lorentz transforms and Einstein's second postulate,
and in that case an alternative way to the relationships implied by
the gamma() factor must be found. But as it happens, there is one:
postulating that gravity propagates through a field the energy of
which varies as the gamma() factor gives us F = G M m / d² * gamma(v),
which does indeed correctly predict the relativistic perihelion shift.
And yes, the above *is* speculative, but if the math produces the
correct prediction, can it be regarded as fanciful, or in some way
illegitimate? Shouldn't we keep such alternatives in mind when theory
is being tested?