Speed of light fibre optic signals which travel 30–40% slower at the speed of light through glass. There are different ways to determine the value of "c". One way is to measure the actual speed at which light waves propagate, which can be done in various astronomical and earth-based setups. However, it is also possible to determine "c" from other physical laws where it appears, for example, by determining the values of the electromagnetic constants "ε" and "μ" and using their relation to "c". Historically, the most accurate results have been obtained by separately determining the frequency and wavelength of a light beam,
Max Planck Institute for the Science of Light Planck Society. In June 2008, after an evaluation, the senate of the Max Planck Society decided to convert this group to a Max Planck institute and thereupon founded the "Max Planck Institute for the Science of Light" (German "Max-Planck-Institut für die Physik des Lichts"). with effect from January 1, 2009. In 2016, the new building was opened. The project was made by the Munich architecture bureau "Fritsch + Tschaidse Architekten GmbH". Max Planck Institute for the Science of Light The Max Planck Institute for the Science of Light (MPL) performs basic research in optical metrology, optical communication, new optical materials,