Transcript: Pulsars make excellent clocks. The collapse of the star by a factor of a million increases the spin rate by the same factor so that the star spins a number of times per second. A typical pulsar might have a frequency of ten Hertz in its spin rate, and its rotation period will typically slow by about a thirty-millionth of a second per year. Pulsars are the most accurate time keeping devices known. Even so, the spin rate is slowing down which corresponds to release of energy in the form of gravity waves. Not all pulsars keep excellent continuous time. Some pulsars show abrupt small changes in their spin rate called glitches. These are due to seismic variations in the neutron star crust itself. The corresponding changes in the magnetic field affect the rotation rate.