Wow My thought experiment has gotten you all fired up it seems In the case of the Trouton Noble experiment all the interactions involved are electromagnetic interactions So once a theoretician has granted that in the physics of electromagnetism the Lorentz transformations apply things can be taken from there Now of course Lorentz had to assume that a planet that is moving through the lorentzian ether is flattened in the direction of motion just as everything else That is a modification of how the force of gravity is transmitted Coulomb force couples to electric charge what does gravity couple to But does the force of gravity couple to the rest mass or to the total mass If gravity couples only to the rest mass then the ether theory stands a chance of reproducing the prediction of the Einstein interpretation as the rest mass is invariant under Lorentz transformation But as far as we know gravitation involves the total mass This is an illustration of the fact that in relativistic physics gravitation just bursts out of the confines of special relativity Something has to give This theme is similar I think to the theme in John Nortons paper about Nordstr m s Lorentz invariant scalar theory of gravitation gravitation just bursts out of special relativity and a successor to special relativity is needed And was provided by Einstein Poincar s 1905 Palermo paper facsimile reproduction non digital 3 MB file has a considerable section about gravitation I m not sure but I don t think that Poincar demands gravitational inertial mass equivalence as a constraint on the theory I think that if Poincar had anticipated that light is deflected by gravitation he would have written so I think it was well after 1905 that recognition came that light does not only carry momentum it also carries inertial mass When light propagates from an emitter to a receiver it not only transmits momentum it also transmits inertial mass The inertial mass of the emitter decreases on emission of the light and the inertial mass of the receiver increases on absorption Of course light has zero rest mass Since light has zero rest mass the natural assumption is that light is not affected by gravity Possibly considerations of this nature made Poincar very very cautious towards attributing inertial mass to energy In his 1909 G ttingen lecture Poincar went very far in attributing the increased inertia of a fast moving electron to increased energy of the ether surrounding the electron in response to the high velocity of the electrons Can that still work for muons and tauon s My understanding is that electrons and muons are identical as far as electric charge and spin are concerned but that they are different in rest mass Should electrons and muons become more and more alike at higher velocities To my knowledge at all velocities the energy of muons is the muon s rest mass multiplied with the relativistic factor I am indeed very curious how Lorentz dealt with these issues As you indicate historians of science describe that Lorentz retained a preference for using a lorentzian interpretation but from the lectures Lorentz gave in the 1920ties it can be seen that Lorentz had full mathematical mastery of special and general relativity Talk