Muonic Chamber (IMAGE) Max-Planck-Gesellschaft Caption In a measuring chamber for protons: the muon beam moves through the ring-shaped electrodes from the left. In the space between the two grey-metallic bars under the pane of glass the muons impact on gaseous hydrogen -- and displace the electrons from some of the atoms. The apparatus registers this process and fires a laser through the hole in the bottom bar onto the muonic hydrogen in order to reveal details of the atomic structure and thus ultimately the radius of the proton. Credit Image: Randolf Pohl / MPI of Quantum Optics Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.