Protons - smaller than we thought

The proton - one of the smallest building blocks of all matter - is even smaller than previously assumed. As a consequence of this discovery, a correction will have to be made to either the quantum theory of how light and matter interact or to the value of the Rydberg Constant - i.e. an important change is needed to either the most precise theory in physics or the most precisely determined physical constant. The question of which correction will be necessary now presents an enormous challenge to physicists. Protons are among the basic building blocks of matter - in conjunction with neutrons they form the nuclei of the atoms. Normally, nuclei are surrounded by orbiting electrons and the electrons and nuclei form the atoms of the various chemical elements. Practically everything that surrounds us is made up of these three types of particle. The hydrogen atom is the simplest of all atoms, with a nucleus consisting of a single proton which is paired up with a single electron, forming one of the simplest systems describable in quantum physics.