Richard Feynman: "Another consequence of the [Maxwell's] equations is that if the source of the disturbance is moving, the light emitted goes through space at the same speed c. This is analogous to the case of sound, the speed of sound waves beinglikewise independent of the motion of the source. This independence of the motion of the source, in the case of light, brings up an interesting problem: Suppose we are riding in a car that is going at a speed u, and light from the rear is going past the
The light-from-rear-going-past-car experiment and the Michelson-Morley experiment are by no means analogous. In the former, the light source is OUTSIDE the moving system. In the latter, the light source is INSIDE the moving system. So applying theprinciple of relativity to the light-from-rear-going-past-car experiment is incorrect and the result c'=c-u is true, as demonstrated here:
"When an observer moves away from a stationary source...the velocity of the wave relative to the observer is slower than that when it is still." http://www.youtube.com/watch?v=SC0Q6-xt-Xsalways return simultaneously. This implies, however, that relative to a stationary observer OUTSIDE the moving system, the speed of light will be c'=c±v, as posited by Newton's theory (it is THIS scenario that is analogous to the light-from-rear-going-
Applying the principle of relativity to the Michelson-Morley experiment is correct because both source and observer are INSIDE the moving system. The measured speed of light will always be constant, c'=c, and the two perpendicular beams of light will
"The null result of the Michelson-Morley experiment was unhelpful and possibly counter-productive in Einstein's investigations of an emission theory of light, for the null result is predicted by an emission theory." http://philsci-archive.pitt.edu/12289/1/Einstein_Discover.pdf
"Emission theory, also called emitter theory or ballistic theory of light, was a competing theory for the special theory of relativity, explaining the results of the Michelson–Morley experiment of 1887...The name most often associated with emissiontheory is Isaac Newton. In his corpuscular theory Newton visualized light "corpuscles" being thrown off from hot bodies at a nominal speed of c with respect to the emitting object, and obeying the usual laws of Newtonian mechanics, and we then expect
Banesh Hoffmann, Einstein's co-author, admits that, originally ("without recourse to contracting lengths, local time, or Lorentz transformations"), the Michelson-Morley experiment was compatible with Newton's variable speed of light, c'=c±v, andincompatible with the constant speed of light, c'=c:
"Moreover, if light consists of particles, as Einstein had suggested in his paper submitted just thirteen weeks before this one, the second principle seems absurd: A stone thrown from a speeding train can do far more damage than one thrown from a trainat rest; the speed of the particle is not independent of the motion of the object emitting it. And if we take light to consist of particles and assume that these particles obey Newton's laws, they will conform to Newtonian relativity and thus
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