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
What Kate Did 'Dad?' Hurley comments that he did not expect Rose's husband to be white, before Jack quickly changes the subject. The producers felt it was important to address that they are an interracial couple, and that Hurley was saying what the audience would be thinking. Caldwell agreed with them and thought it would be odd if the issue was not addressed. Anderson also was glad that Hurley brought up the issue, and liked that Jack did not pay any attention. The episode gained 21.54 million American viewers in its first airing. What Kate Did "What Kate Did" is the 34th episode