Criticism of the theory of relativity

Criticism of the theory of relativity of Albert Einstein was mainly expressed in the early years after its publication in the early twentieth century, on scientific, pseudoscientific, philosophical, or ideological bases. Though some of these criticisms had the support of reputable scientists, Einstein's theory of relativity is now accepted by the scientific community. Criticism of the theory of relativity of Albert Einstein was mainly expressed in the early years after its publication in the early twentieth century, on scientific, pseudoscientific, philosophical, or ideological bases. Though some of these criticisms had the support of reputable scientists, Einstein's theory of relativity is now accepted by the scientific community. Reasons for criticism of the theory of relativity have included alternative theories, rejection of the abstract-mathematical method, and alleged errors of the theory. According to some authors, antisemitic objections to Einstein's Jewish heritage also occasionally played a role in these objections. There are still some critics of relativity today, but their opinions are not shared by the majority in the scientific community. Around the end of the 19th century, the view was widespread that all forces in nature are of electromagnetic origin (the 'electromagnetic worldview'), especially in the works of Joseph Larmor (1897) and Wilhelm Wien (1900). This was apparently confirmed by the experiments of Walter Kaufmann (1901–1903), who measured an increase of the mass of a body with velocity which was consistent with the hypothesis that the mass was generated by its electromagnetic field. Max Abraham (1902) subsequently sketched a theoretical explanation of Kaufmann's result in which the electron was considered as rigid and spherical. However, it was found that this model was incompatible with the results of many experiments (including the Michelson–Morley experiment, the Experiments of Rayleigh and Brace, and the Trouton–Noble experiment), according to which no motion of an observer with respect to the luminiferous aether ('aether drift') had been observed despite numerous attempts to do so. Henri Poincaré (1902) conjectured that this failure arose from a general law of nature, which he called 'the principle of relativity'. Hendrik Antoon Lorentz (1904) created a detailed theory of electrodynamics (Lorentz ether theory) that was premised on the existence of an immobile aether and employed a set of space and time coordinate transformations that Poincaré called the Lorentz transformations, including the effects of length contraction and local time. However, Lorentz's theory only partially satisfied the relativity principle, because his transformation formulas for velocity and charge density were incorrect. This was corrected by Poincaré (1905) who obtained full Lorentz covariance of the electrodynamic equations. Criticizing Lorentz's 1904 theory, Abraham (1904) held that the Lorentz contraction of electrons requires a non-electromagnetic force to ensure the electron's stability. This was unacceptable to him as a proponent of the electromagnetic worldview. He continued that as long as a consistent explanation is missing as to how those forces and potentials act together on the electron, Lorentz's system of hypotheses is incomplete and doesn't satisfy the relativity principle. Poincaré (1905) removed this objection by showing that the non-electromagnetic potential ('Poincaré stress') holding the electron together can be formulated in a Lorentz covariant way, and showed that in principle it is possible to create a Lorentz covariant model for gravitation which he considered non-electromagnetic in nature as well. Thus the consistency of Lorentz's theory was proven, but the electromagnetic worldview had to be given up. Eventually, Albert Einstein published in September 1905 what is now called special relativity, which was based on a radical new application of the relativity principle in connection with the constancy of the speed of light. In special relativity, the space and time coordinates depend on the inertial observer's frame of reference, and the luminiferous aether plays no role in the physics. Although this theory was founded on a very different kinematical model, it was experimentally indistinguishable from the aether theory of Lorentz and Poincaré, since both theories satisfy the relativity principle of Poincaré and Einstein, and both employ the Lorentz transformations. After Minkowski's introduction in 1908 of the geometric spacetime model for Einstein's version of relativity, most physicists eventually decided in favor of the Einstein-Minkowski version of relativity with its radical new views of space and time, in which there was no useful role for the aether. Kaufmann–Bucherer–Neumann experiments: To conclusively decide between the theories of Abraham and Lorentz, Kaufmann repeated his experiments in 1905 with improved accuracy. However, in the meantime the theoretical situation had changed. Alfred Bucherer and Paul Langevin (1904) developed another model, in which the electron is contracted in the line of motion, and dilated in the transverse direction, so that the volume remains constant. While Kaufmann was still evaluating his experiments, Einstein published his theory of special relativity. Eventually, Kaufmann published his results in December 1905 and argued that they are in agreement with Abraham's theory and require rejection of the 'basic assumption of Lorentz and Einstein' (the relativity principle). Lorentz reacted with the phrase 'I am at the end of my Latin', while Einstein did not mention those experiments before 1908. Yet, others started to criticize the experiments. Max Planck (1906) alluded to inconsistencies in the theoretical interpretation of the data, and Adolf Bestelmeyer (1906) introduced new techniques, which (especially in the area of low velocities) gave different results and which cast doubts on Kaufmann's methods. Therefore, Bucherer (1908) conducted new experiments and arrived at the conclusion that they confirm the mass formula of relativity and thus the 'relativity principle of Lorentz and Einstein'. Yet Bucherer's experiments were criticized by Bestelmeyer leading to a sharp dispute between the two experimentalists. On the other hand, additional experiments of Hupka (1910), Neumann (1914) and others seemed to confirm Bucherer's result. The doubts lasted until 1940, when in similar experiments Abraham's theory was conclusively disproved. (It must be remarked that besides those experiments, the relativistic mass formula had already been confirmed by 1917 in the course of investigations on the theory of spectra. In modern particle accelerators, the relativistic mass formula is routinely confirmed.) In 1902–1906, Dayton Miller repeated the Michelson–Morley experiment together with Edward W. Morley. They confirmed the null result of the initial experiment. However, in 1921–1926, Miller conducted new experiments which apparently gave positive results. Those experiments initially attracted some attention in the media and in the scientific community but have been considered refuted for the following reasons: Einstein, Max Born, and Robert S. Shankland pointed out that Miller hadn't appropriately considered the influence of temperature. A modern analysis by Roberts shows that Miller's experiment gives a null result, when the technical shortcomings of the apparatus and the error bars are properly considered. Additionally, Miller's result is in disagreement with all other experiments, which were conducted before and after. For example, Georg Joos (1930) used an apparatus of similar dimensions to Miller's, but he obtained null results. In recent experiments of Michelson–Morley type where the coherence length is increased considerably by using lasers and masers the results are still negative. In the 2011 Faster-than-light neutrino anomaly, the OPERA collaboration published results which appeared to show that the speed of neutrinos is slightly faster than the speed of light. However, sources of errors were found and confirmed in 2012 by the OPERA collaboration, which fully explained the initial results. In their final publication, a neutrino speed consistent with the speed of light was stated. Also subsequent experiments found agreement with the speed of light, see measurements of neutrino speed. It was also claimed that special relativity cannot handle acceleration, which would lead to contradictions in some situations. However, this assessment is not correct, since acceleration actually can be described in the framework of special relativity (see Acceleration (special relativity), Proper reference frame (flat spacetime), Hyperbolic motion, Rindler coordinates, Born coordinates). Paradoxes relying on insufficient understanding of these facts were discovered in the early years of relativity. For example, Max Born (1909) tried to combine the concept of rigid bodies with special relativity. That this model was insufficient was shown by Paul Ehrenfest (1909), who demonstrated that a rotating rigid body would, according to Born's definition, undergo a contraction of the circumference without contraction of the radius, which is impossible (Ehrenfest paradox). Max von Laue (1911) showed that rigid bodies cannot exist in special relativity, since the propagation of signals cannot exceed the speed of light, so an accelerating and rotating body will undergo deformations. Paul Langevin and von Laue showed that the twin paradox can be completely resolved by consideration of acceleration in special relativity. If two twins move away from each other, and one of them is accelerating and coming back to the other, then the accelerated twin is younger than the other one, since he was located in at least two inertial frames of reference, and therefore his assessment of which events are simultaneous changed during the acceleration. For the other twin nothing changes since he remained in a single frame.