Superconductivity and carbon nanotubes, are Type I, while almost all impure and compound superconductors are Type II. Conversely, a spinning superconductor generates a magnetic field, precisely aligned with the spin axis. The effect, the London moment, was put to good use in Gravity Probe B. This experiment measured the magnetic fields of four superconducting gyroscopes to determine their spin axes. This was critical to the experiment since it is one of the few ways to accurately determine the spin axis of an otherwise featureless sphere. Superconductivity was discovered on April 8, 1911 by Heike Kamerlingh Onnes, who was studying the resistance
Johannes Kuenen experiments with x-rays with the physiologist Edward Waymouth Reid. In 1907 he was appointed professor of physics at Leiden University. Heike Kamerlingh Onnes and Kuenen led the Kamerlingh Onnes physics Laboratory. On the basis of his scientific work he was elected in 1911 as a member of the Royal Netherlands Academy of Arts and Sciences (KNAW), and became a member of the Hollandsche Maatschappij der Wetenschappen in 1915. He discovered retrograde condensation and published his findings in 1892 in the Ph.D. thesis with the title "Metingen betreffende het oppervlak van Van der Waals voor mengsels van koolzuur en chloormethyl". (Measurements