In the summer of 1905, Minkowski and Hilbert led an advanced seminar on mathematical physics, on electrodynamical theory. Minkowski told Born later that it came to him as a great shock when Einstein published his paper in which the equivalence of the different local times of observers moving relative to each other was pronounced; for he had reached the same conclusions independently. He never made a priority claim and always gave Einstein his full share in the great discovery. In his famous talk, "Space and Time" Minkowski wrote that the credit of first recognizing sharply that t and t' are to be treated the same, is of A. Einstein.In Space and Time, Minkowski does credit Einstein for observing that local time is the local time of an electron. It is the only part of relativity that Minkowski credits to Einstein. Minkowski's wrote:
Lorentz denoted the combination t' of (t and x) as the local time (Ortszeit) of the uniformly moving electron, and used a physical construction of this idea for a better comprehension of the contraction-hypothesis. But to perceive clearly that the time of an electron is as good as the time of any other electron, i.e., that t and t' are to be treated equivalently, has been the service of A. Einstein.This is quite similar to what Einstein had just written in his 1907 review paper:
It required only the recognition that the auxiliary quantity introduced by H. A. Lorentz, and called by him "local time", can be defined as simply "time."Einstein seems to be taking credit for this idea, but Poincare clearly had this idea before Einstein and Minkowski. Lorentz may have had it also, as Poincare attributed it to Lorentz. Poincare even nominated Lorentz for a Nobel Prize in 1902 to recognize his idea of local time. Minkowski studied Poincare's papers in his seminar, and should have known that Poincare had the idea before Einstein. As Weinstein explains:
Scott Walter writes, "This story of Minkowski’s recollection of his encounter with Einstein’s paper on relativity is curious, in that the idea of the observable equivalence of clocks in uniform motion had been broached by Poincaré in one of the papers studied during the first session of the electron-theory seminar. It is possible, of course, that Poincaré’s operational definition of local time escaped Minkowski’s attention, or that Minkowski was thinking of an exact equivalence of timekeepers".25 Before 1905 Poincaré stressed the importance of the method of clocks and their synchronization by light signals. He gave a physical interpretation of Lorentz's local time in terms of clock synchronization by light signals, and formulated a principle of relativity. John Stachel explains: "Poincaré had interpreted the local time as that given by clocks at rest in a frame moving through the ether when synchronized as if – contrary to the basic assumptions of Newtonian kinematics – the speed of light were the same in all inertial frames. Einstein dropped the ether and the 'as if': one simply synchronized clocks by the Poincaré convention in each inertial frame and accepted that the speed of light really is the same in all inertial frames when measured with clocks so synchronized".26Stachel has made a career out of editing Einstein's papers and finding ways to credit Einstein, and is correct about Poincare having the operational definition of local time that Minkowski credited to Einstein.
The only thing left for Stachel to credit Einstein is Poincare's aether and "as if". But Poincare's explanation did not involve the aether or an "as if". Stachel is quoting himself, not Poincare.
I did not know that Minkowski told Born that he reached some relativity conclusions independently of Einstein. But Minkowski appears to have gotten those conclusions from Poincare. His famous Space And Time paper does not mention Poincare, but his previous paper cites Poincare and directly follows him with the Lorentz group, four-dimensional spacetime, and electromagnetic covariance. So yes, Minkowski probably did come to all those conclusions independently of Einstein because he got them from Poincare.
At any rate, it was Minkowski's 1908 Space And Time article that got everyone excited about relativity and popularized the new geometrical interpretation of spacetime. Einstein's 1905 paper was considered an elaboration of Lorentz's ideas. As Weinstein documents, Minkowski wrote to Einstein in late 1907 asking for a reprint of his 1905 paper, just a couple of months before Minkowski presented his own results. So Minkowski's seminar and work were based almost entirely on Lorentz and Poincare. The supposedly original idea of the operational identification of local time had been published years earlier by Poincare.Brother HL-2270DW Laser Printer (Google Affiliate Ad)