impossible. This result was found to be flawed by Grete Hermann three years later, though this went unnoticed by the physics community for over fifty years. In 1952, David Bohm, dissatisfied with the prevailing orthodoxy, rediscovered de Broglie's pilot wave theory. Bohm developed pilot wave theory into what is now called the de Broglie–Bohm theory. The de Broglie–Bohm theory itself might have gone unnoticed by most physicists, if it had not been championed by John Bell, who also countered the objections to it. In 1987, John Bell rediscovered Grete Hermann's work, and thus showed the physics community that Pauli's and von Neumann's objections "only" showed that the pilot wave theory did not have locality. Yves Couder and co-workers in 2010 reported a macroscopic pilot wave system in the form of walking droplets. This system was said to exhibit behavior of a pilot wave, heretofore considered to be reserved to microscopic phenomena. However, more careful fluid dynamics experiments have been carried out since 2015 by two American groups and one Danish team led by Tomas Bohr (grandson of Niels Bohr). These new experiments have not replicated the results of the 2010 experiment as of 2018. The pilot wave theory Principles The pilot wave theory is a hidden-variable theory. Consequently: the theory has realism (meaning that its concepts exist independently of the observer); the theory has determinism. The positions of the particles are considered to be the hidden variables. The observer doesn't know the precise values of these variables; they cannot know them precisely because any measurement disturbs them. On the other hand, the observer is defined not by the wave function of their own atoms but by the atoms' positions. So what one sees around oneself are also the positions of nearby things, not their wave functions. A collection of particles has an associated matter wave which evolves according to the Schrödinger equation. Each particle follows a deterministic trajectory, which is guided by the wave function; collectively, the density of the particles conforms to the magnitude of the wave function. The wave function is not influenced by the particle and can exist also as an empty wave function. The theory brings to light nonlocality that is implicit in the non-relativistic formulation of quantum mechanics and uses it to satisfy Bell's theorem. These nonlocal effects can be shown to be compatible with the no-communication theorem, which prevents use of them for faster-than-light