Monday, December 22, 2014

Relativity depended on the crucial experiment

I posted a defense of the integrity of physics based on the scientific method. It should not be necessary, but the method is under attack from theoretical physics promoting untestable theories, and philosophers denying that science discovers truth.

To attack the importance of the experimentum crucis (crucial experiment), some scholars (strangely and wrongly) cite the history of relativity. For an example, here is Pentcho Valev commenting on the Nature article:
Don't rely too much on the experiment. Experimental results can be interpreted so as to "confirm" the opposite of what was actually confirmed. For instance, in 1887 (prior to FitzGerald and Lorenz advancing the ad hoc length contraction hypothesis) the Michelson-Morley experiment unequivocally confirmed the variable speed of light predicted by Newton's emission theory of light and refuted the constant (independent of the speed of the source) speed predicted by the ether theory and adopted by Einstein in 1905 (nowadays the opposite is taught):
These efforts were long misled by an exaggeration of the importance of one experiment, the Michelson-Morley experiment, even though Einstein later had trouble recalling if he even knew of the experiment prior to his 1905 paper. This one experiment, in isolation, has little force. Its null result happened to be fully compatible with Newton's own emission theory of light. Located in the context of late 19th century electrodynamics when ether-based, wave theories of light predominated, however, it presented a serious problem that exercised the greatest theoretician of the day. Norton
It is true that the 1887 Michelson-Morley experiment could be interpreted to be consistent with an emitter theory or an aether drift theory, but the experts of the day had rejected those theories on other grounds.

But it is just wrong to say that Michelson-Morley had little force. The experiment was done following suggestions by Maxwell and Lorentz that it would be crucial. The length contraction was first suggested by FitzGerald in 1889 as a logical consequence of the experiment. Lorentz's relativity theories of 1892 and 1895 were explicitly created to explain the experiment. Poincare's criticisms of 1900 and Lorentz's improvement of 1904 were based on the accuracy of the experiment.

The most popular early relativity paper was Minkowski's 1908 paper saying:
But all efforts directed towards this goal [of optically detecting the Earth's motion], and even the celebrated interference-experiment of Michelson have given negative results. In order to supply an explanation for this result, H. A. Lorentz formed a hypothesis ... According to Lorentz every body in motion, shall suffer a contraction in the direction of its motion, ...

This hypothesis sounds rather fantastical. For the contraction is not to be thought of as a consequence of resistances in the ether, but purely as a gift from above, as a condition accompanying the state of motion.

I shall show in our figure, that Lorentz's hypothesis is fully equivalent to the new conceptions about time and space, by which it becomes more intelligible.
It is a historical fact that relativity was developed with Michelson-Morley as the crucial experiment.

Einstein's 1905 paper gives an exposition in terms of two postulates that everyone agrees he got from Lorentz and Poincare. Maybe Einstein understood how those postulates depended on Michelson-Morley in 1905 and maybe he did not. Statements by Einstein and by historians are confusing on the matter. He did seem to understand later, as he said so in his 1909 paper. But it does matter when Einstein learned the significance of Michelson-Morley, because he was not the one who discovered the length contraction, local time, time dilation, constant speed of light, relativity principle, covariance of Maxwell's equations, spacetime geometry, and all the other crucial aspects of relativity. Those who discovered those things relied on Michelson-Morley, and that is a historical fact.

Modern philosophers reject the positivism of most scientists, and their foolish views depend largely on a misunderstanding of how relativity depended on experiment.

1 comment:

  1. In a sense Einstein outdid Poincaré and Lorentz by converting the "local time" into "time":
    "...the egregious merit of Einstein was (...) the conceptual breakthrough that the rescaled "local time" variable t' of Lorentz was "purely and simply, the time", as experienced by a moving observer."

    That was an illegitimate step. It follows from Einstein's 1905 two postulates that time dilation is symmetrical - either observer sees the other's clock running slow. Yet Einstein found it profitable to inform the world that, although time dilation is symmetrical, it is still asymmetrical - the stationary clock runs faster than the travelling one:
    ON THE ELECTRODYNAMICS OF MOVING BODIES, by A. Einstein, June 30, 1905: "From this there ensues the following peculiar consequence. If at the points A and B of K there are stationary clocks which, viewed in the stationary system, are synchronous; and if the clock at A is moved with the velocity v along the line AB to B, then on its arrival at B the two clocks no longer synchronize, but the clock moved from A to B lags behind the other which has remained at B by tv^2/2c^2 (up to magnitudes of fourth and higher order), t being the time occupied in the journey from A to B."

    This is tantamount to saying that, although elephants are unable to fly, they can still do so by just flapping their ears. Yet the breathtaking impliciations of Einstein's blatant hoax (time travel into the future etc) enchanted the gullible world:
    John Barrow FRS, professor of mathematical sciences at the University of Cambridge: "Einstein restored faith in the unintelligibility of science. Everyone knew that Einstein had done something important in 1905 (and again in 1915) but almost nobody could tell you exactly what it was. When Einstein was interviewed for a Dutch newspaper in 1921, he attributed his mass appeal to the mystery of his work for the ordinary person: "Does it make a silly impression on me, here and yonder, about my theories of which they cannot understand a word? I think it is funny and also interesting to observe. I am sure that it is the mystery of non-understanding that appeals to impresses them, it has the colour and the appeal of the mysterious." Relativity was a fashionable notion. It promised to sweep away old absolutist notions and refurbish science with modern ideas. In art and literature too, revolutionary changes were doing away with old conventions and standards. All things were being made new. Einstein's relativity suited the mood. Nobody got very excited about Einstein's brownian motion or his photoelectric effect but relativity promised to turn the world inside out."

    Pentcho Valev