Sunday, November 30, 2014

Special Relativity and Gravity


As Einstein was seeking a relativistic theory of gravity, he thought that special relativity should be upgraded to general relativity thus promoting the Minkowski space to curved pseudo-Riemannian (Lorentzian) one. Does this mean that special relativity as a theory never discussed gravity from any perspective?



Answer




Does this mean that special relativity as a theory never discussed gravity from any perspective?



It all hinges on the luminiferous aether which was prevalent in the 19th century theories:


The Michelson Morley experiment was crucial in discovering that there does not exist a luminiferous aether.




The Michelson–Morley experiment was performed over the spring and summer of 1887 by Albert A. Michelson and Edward W. Morley at what is now Case Western Reserve University in Cleveland, Ohio, and published in November of the same year. It compared the speed of light in perpendicular directions, in an attempt to detect the relative motion of matter through the stationary luminiferous aether ("aether wind"). The negative results are generally considered to be the first strong evidence against the then-prevalent aether theory, and initiated a line of research that eventually led to special relativity



To start with the Lorenz transformations were discovered/invented to make consistent Maxwells equations with the existence of a luminiferous ether, i.e. an inertial framework against which everything else would be moving with classical mechanics equations of motion.


Here is the history of Lorenz transformations, the lynch pin of special relativity.



Lorentz (1892–1904) and Larmor (1897–1900), who believed the luminiferous ether hypothesis, were also seeking the transformation under which Maxwell's equations are invariant when transformed from the ether to a moving frame. They extended the FitzGerald–Lorentz contraction hypothesis and found out that the time coordinate has to be modified as well ("local time"). Henri PoincarĂ© gave a physical interpretation to local time (to first order in v/c) as the consequence of clock synchronization, under the assumption that the speed of light is constant in moving frames. Larmor is credited to have been the first to understand the crucial time dilation property inherent in his equations.


In 1905, Poincaré was the first to recognize that the transformation has the properties of a mathematical group, and named it after Lorentz.


Later in the same year Albert Einstein published what is now called special relativity, by deriving the Lorentz transformation under the assumptions of the principle of relativity and the constancy of the speed of light in any inertial reference frame, and by abandoning the mechanical aether.



The "out of the box" thinking of Einstein comes when he applied the Lorenz transformations to particles, not light. It took some time to confirm it , and the real validation comes from nuclear physics and the huge number of particle physics experiments which can only be interpreted by assuming a four dimensional space time.



As you see from the above precis gravity does not enter into the special relativity validation.,


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