Albert Einstein received the Nobel Prize for explaining the photoelectric effect: in its most intuitive form, a single atom is irradiated with light. According to Einstein, light consists of particles (photons) that transfer only quantized energy to the electron of the atom. If the photon’s energy is sufficient, it knocks the electrons out of the atom. But what happens to the photon’s momentum in this process? Physicists at Goethe University are now able to answer this question. To do so, they developed and constructed and new spectrometer with previously unattainable resolution. Doctoral student Alexander Hartung became a father twice during...