Liquid helium of liquid water. Helium was first liquefied on July 10, 1908, by the Dutch physicist Heike Kamerlingh Onnes at the University of Leiden in the Netherlands. At that time, helium-3 was unknown because the mass spectrometer had not yet been invented. In more recent decades, liquid helium has been used as a cryogenic refrigerant, and liquid helium is produced commercially for use in superconducting magnets such as those used in magnetic resonance imaging (MRI), nuclear magnetic resonance (NMR), Magnetoencephalography (MEG), and experiments in physics, such as low temperature Mössbauer spectroscopy. The temperature required to produce liquid helium is low because
Einstein's Sink Einstein's Sink Einstein's Sink is an antique sink that has been in use by the physics faculty of Leiden University since 1920. Originally the sink stood in the large lecture room of the old Kamerlingh Onnes Laboratory. It was taken to the new building when the physicists moved to the Leiden Bioscience park in 1977. Here it still stands in the current large lecture room (The De Sitterzaal of the J.H. Oortgebouw), continuing the tradition of washing the hands of visiting famous scientists. A short list of 'sink users' consists out of Paul Ehrenfest, Heike Kamerlingh Onnes, Hendrik Antoon Lorentz