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Is there an Aether? | |

## Web Publication by Mountain Man Graphics, Australia - Southern Winter 2004 | |

## Is there an Aether? |
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"Physical knowledge has advanced much since 1905, notably by the arrival of quantum mechanics, and the situation [about the scientific plausibility of aether] has again changed. If one examines the question in the light of present-day knowledge, one finds that the aether is no longer ruled out by relativity, and good reasons can now be advanced for postulating an aether. . . . We can now see that we may very well have an aether, subject to quantum mechanics and conformable to relativity, provided we are willing to consider a perfect vacuum as an idealized state, not attainable in practice. From the experimental point of view there does not seem to be any objection to this. We must make some profound alterations to the theoretical idea of the vacuum. . . . Thus, with the new theory of electrodynamics we are rather forced to have an aether" From the following document, further quotations relating to Dirac(bolded)and the aether: http://philsci-archive.pitt.edu/archive/00001614/01/Open_or_Closed-preprint.pdfOpen or Closed? Dirac, Heisenberg, and the relation between classical and quantum mechanics========[quoted material]=========== Among these [outstanding problems apart from renormalisation] he [Dirac] lists the following:One of the problems is . . . accounting for the number 137. Other problems are how to introduce the fundamental length to physics in some natural way, how to explain the ratios of the masses of the elementary particles and how to explain their other properties. I believe separate ideas will be needed to solve these distinct problems and that they will be solved one at a time through successive stages in the future evolution of physics. At this point I find myself in disagreement with most physicists. They are inclined to think one master idea will be discovered that will solve all these problems together.(Dirac 1963, p. 50) Clearly Heisenberg would be counted among those who believed these various problems needed to be solved all at once. One of Dirac's more surprising approaches to solving these problems involved reintroducing an aether. Once again, he took the key to solving a quantum problem to lie in the development of a more adequate classical theory. In 1951 he had developed yet another classical electrodynamics, one that required postulating a velocity field defined at all points of space-time. Dirac interpreted this velocity as the velocity of the aether relative to the Earth. He argued that such an aether could be rendered consistent with relativity theory as long as one subjected the aether velocity to the quantum uncertainty relations. In this way Dirac was able to recover the Lorentz invariance of his theory. When, in 1952, Leopold Infeld pointed out that one could accept all of the conclusions of Dirac's new electrodynamics without postulating an aether, Dirac responded as follows:"Infeld has shown how the field equations of my new electrodynamics can be written so as not to require an aether. This is not sufficient to make a complete dynamical theory. It is necessary to set up an action principle and to get a Hamiltonian formulation of the equations suitable for quantization purposes, and for this the aether velocity is required"(Dirac 1952). For Dirac, the Poisson bracket correspondence that he had discovered in 1925 provided an important link between classical and quantum mechanics. One can only take an advantage of this correspondence if one has a Hamiltonian version of the classical theory. Thus in his search for a new QED, his strategy was to develop an appropriate Hamiltonian version of classical electrodynamics, which could then be quantized. If this meant reintroducing an aether and absolute simultaneity, then he was willing to do this. This reinforces the fact that, for Dirac, even the most accepted and well- established parts of theories were open to future revision. When confronted with these same difficulties of QED, Heisenberg, by contrast,attempted to solve all of these problems at once by restricting himself to observables only -the same trick that had worked for him in 1925. This approach led Heisenberg to abandon quantum field theory in favor of the S-matrix program. For Dirac, on the otherhand, agreement with experiments was not the final test of a theory. Regarding renormalization theory he writes,"Just because the results happen to be in agreement with observation does not prove that one's theory is correct"(Dirac 1987, p. 196). ==============[end Dirac quote]============="I think it is safe to say that no one understands Quantum Mechanics.---- Richard Feynman

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