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
Pieter Rijke 1836. The title of his Ph.D. thesis was "De origine electricitatis voltaicae". In 1835 he was appointed professor of physics at the Royal Athenaeum in Maastricht. In 1845 he became extraordinary professor and in 1854 he was promoted to full professor of physics at the University of Leiden. There he started a physics laboratory with a large collection of scientific instruments. His most important students were H.A. Lorentz and J.D. van der Waals. He retired in 1882, and was succeeded by Heike Kamerlingh Onnes as professor of experimental physics at the University of Leiden. Rijke became a member of the