Dark matter detector. Optical bench of the PVLAS (Polarizzazione del Vuoto con Laser) optical apparatus. The PVLAS is used to search for the presence of dark matter by detecting the small flattening acquired by a linearly polarised laser beam after it passes through a vacuum space where an intense magnetic field has been applied. This view shows the light passing up into the apparatus' magnet. Photographed at the Legarno National Laboratory, National Institute of Nuclear Physics, Padova, Italy.