Shan Gao, University of Sydney, Australia and Chinese Academy of Sciences, China
How do electrons move in atoms? ‒ From the Bohr model to quantum mechanics

Niels Bohr proposed what is now called the Bohr model of the atom in 1913. He suggested that electrons are particles and they undergo two kinds of motion in atoms; they either move continuously around the nucleus in certain stationary orbits or discontinuously jump between these orbits. The Bohr model was latterly replaced by quantum mechanics, in which the physical state of an electron is described by a wave function. What, then, does the wave function truly represent? Exactly what are electrons? And how do they move in atoms? In this talk, I will show that a deep analysis of protective measurements and the mass and charge distributions of a single quantum system may provide the answers. It turns out that microscopic particles such as electrons are indeed particles, while their motion is not continuous but essentially discontinuous and random, displaying wave-like behavior. Moreover, the wave function represents the state of random discontinuous motion of particles, and in particular, the modulus square of the wave function gives the objective probability density of the particles being in certain locations. In some sense, this new picture of quantum reality can be regarded as a certain extension of Bohr’s discontinuous quantum jumps.