By combining his two postulates Einstein deduced the obvious nonsense that the speed of light relative to the observer is independent of the motion of the observer (any reasonable interpretation of the Doppler effect shows that the speed of light is different for differently moving observers). Einstein "explained" the nonsense in terms of spacetime - a grotesque centaur that killed physics afterwards:
http://www.aip.org/history/exhibits/einstein/essay-einstein-relativity.htm
John Stachel: "But here he ran into the most blatant-seeming contradiction, which I mentioned earlier when first discussing the two principles. As noted then, the Maxwell-Lorentz equations imply that there exists (at least) one inertial frame in which the speed of light is a constant regardless of the motion of the light source. Einstein's version of the relativity principle (minus the ether) requires that, if this is true for one inertial frame, it must be true for all inertial frames. But this seems to be nonsense. How can it happen that the speed of light relative to an observer cannot be increased or decreased if that observer moves towards or away from a light beam? Einstein states that he wrestled with this problem over a lengthy period of time, to the point of despair. We have no details of this struggle, unfortunately. Finally, after a day spent wrestling once more with the problem in the company of his friend and patent office colleague Michele Besso, the only person thanked in the 1905 SRT paper, there came a moment of crucial insight. In all of his struggles with the emission theory as well as with Lorentz's theory, he had been assuming that the ordinary Newtonian law of addition of velocities was unproblematic. It is this law of addition of velocities that allows one to "prove" that, if the velocity of light is constant with respect to one inertial frame, it cannot be constant with respect to any other inertial frame moving with respect to the first. It suddenly dawned on Einstein that this "obvious" law was based on certain assumptions about the nature of time always tacitly made."
https://www.aip.org/history/exhibits/einstein/essay-einsteins-time.htm
Peter Galison: "First, he stipulated that all the laws of physics - including electricity and magnetism - were the same in any constantly moving frame of reference. Then he added a seemingly simple (and modest) second assumption: Light travels at the same speed no matter how fast its source is moving. To anyone thinking of ether this was not so strange: Move your hands at any reasonable speed through a room of still air; once you clap your hands the sound waves propagate through the room at the same speed - independent of the original motion of your hands. Maybe light was like that: a lamp moving in the ether simply excited light waves that radiated out at a single speed independent of the motion of the lamp. Yet these two reasonable starting assumptions appeared to contradict one another. Suppose lamps were flying this way and that at various speeds, but that in some frame the light beams from those lamps were all traveling at 186,000 miles per second, just the speed predicted by the equations of electrodynamics. Wouldn't those same beams of light appear to be traveling at different speeds when seen from a different, moving frame of reference? If that was so, then the equations of electrodynamics would only be valid in one frame of reference, violating Einstein's first principle. It was to resolve this apparent contradiction that Einstein made his single most dramatic move: he criticized the very idea of time as it was usually understood. In particular, he relentlessly pursued the meaning of "simultaneity." Only by criticizing the foundational notions of time and space could one bring the pieces of the theory - that the laws of physics were the same in all constantly moving frames; that light traveled at the same speed regardless of its source - into harmony."
Nowadays physicists are desperately trying to get rid of the idiotic spacetime but it is too late:
https://edge.org/response-detail/25477
What scientific idea is ready for retirement? Steve Giddings: "Spacetime. Physics has always been regarded as playing out on an underlying stage of space and time. Special relativity joined these into spacetime... (...) The apparent need to retire classical spacetime as a fundamental concept is profound..."
https://www.youtube.com/watch?v=U47kyV4TMnE
Nima Arkani-Hamed (06:11): "Almost all of us believe that space-time doesn't really exist, space-time is doomed and has to be replaced by some more primitive building blocks."
http://www.amazon.com/Faster-Than-Speed-Light-Speculation/dp/0738205257
Joao Magueijo, Faster Than the Speed of Light, p. 250: "Lee [Smolin] and I discussed these paradoxes at great length for many months, starting in January 2001. We would meet in cafés in South Kensington or Holland Park to mull over the problem. THE ROOT OF ALL THE EVIL WAS CLEARLY SPECIAL RELATIVITY. All these paradoxes resulted from well known effects such as length contraction, time dilation, or E=mc^2, all basic predictions of special relativity. And all denied the possibility of establishing a well-defined border, common to all observers, capable of containing new quantum gravitational effects."
http://www.newscientist.com/article/mg22029410.900
New Scientist: "Saving time: Physics killed it. Do we need it back? (...) Einstein landed the fatal blow at the turn of the 20th century."
http://www.guardian.co.uk/books/2013/jun/10/time-reborn-farewell-reality-review
"And by making the clock's tick relative - what happens simultaneously for one observer might seem sequential to another - Einstein's theory of special relativity not only destroyed any notion of absolute time but made time equivalent to a dimension in space: the future is already out there waiting for us; we just can't see it until we get there. This view is a logical and metaphysical dead end, says Smolin."
http://www.bookdepository.com/Time-Reborn-Professor-Physics-Lee-Smolin/9780547511726
"Was Einstein wrong? At least in his understanding of time, Smolin argues, the great theorist of relativity was dead wrong. What is worse, by firmly enshrining his error in scientific orthodoxy, Einstein trapped his successors in insoluble dilemmas..."
https://www.newscientist.com/article/mg22730370-600-why-do-we-move-forwards-in-time/
"[George] Ellis is up against one of the most successful theories in physics: special relativity. It revealed that there's no such thing as objective simultaneity. Although you might have seen three things happen in a particular order –
A, then B, then C – someone moving
at a different velocity could have seen
it a different way – C, then B, then A.
In other words, without simultaneity there is no way of specifying what things happened "now". And if not "now", what is moving through time? Rescuing an objective "now" is a daunting task."
http://www.newscientist.com/article/mg20727721.200-rethinking-einstein-the-end-of-spacetime.html
"Rethinking Einstein: The end of space-time (...) The stumbling block lies with their conflicting views of space and time. As seen by quantum theory, space and time are a static backdrop against which particles move. In Einstein's theories, by contrast, not only are space and time inextricably linked, but the resulting space-time is moulded by the bodies within it. (...) Something has to give in this tussle between general relativity and quantum mechanics, and the smart money says that it's relativity that will be the loser."
Pentcho Valev