When one body attracts another one, the electromagnetic energy store of gravitation is according to Wien diminished by the amount (where is the attracted mass, the gravitational constant, the distance): Henri Poincaré in 1906 argued that when mass is in fact the product of the electromagnetic field in the aether – implying that no "real" mass exists – and because matter is inseparably connected with mass, then also matter doesn't exist at all and electrons are only concavities in the aether. Mass and speed Thomson and Searle Thomson (1893) noticed that electromagnetic momentum and energy of charged bodies, and therefore their masses, depend on the speed of the bodies as well. He wrote: In 1897, Searle gave a more precise formula for the electromagnetic energy of charged sphere in motion: and like Thomson he concluded: Longitudinal and transverse mass From Searle's formula, Walter Kaufmann (1901) and Max Abraham (1902) derived the formula for the electromagnetic mass of moving bodies: However, it was shown by Abraham (1902), that this value is only valid in the longitudinal direction ("longitudinal mass"), i.e., that the electromagnetic mass also depends on the direction of the moving bodies with respect to the aether. Thus Abraham also derived the "transverse mass": On the other hand, already in 1899 Lorentz assumed that the electrons undergo length contraction in the line of motion, which leads to results for the acceleration of moving electrons that differ from those given by Abraham. Lorentz obtained factors of parallel to the direction of motion and perpendicular to the direction of motion, where and is an undetermined factor. Lorentz expanded his 1899 ideas in his famous 1904 paper, where he set the factor to unity, thus: , So, eventually Lorentz arrived at the same conclusion as Thomson in 1893: no body can reach the speed of light because the mass becomes infinitely large at this velocity. Additionally, a third electron model was developed by Alfred Bucherer and Paul Langevin, in which the electron contracts in the line of motion, and expands perpendicular to it, so that the volume remains constant. This gives: Kaufmann's experiments The predictions of the theories of Abraham and Lorentz were supported by the experiments of Walter Kaufmann (1901), but the experiments were not precise enough to distinguish between them. In 1905 Kaufmann conducted another series of experiments (Kaufmann–Bucherer–Neumann experiments) which confirmed Abraham's and Bucherer's predictions, but contradicted Lorentz's theory and