Kenneth Greisen

Kenneth Ingvard Greisen (24 January 1918 in Perth Amboy, New Jersey – 17 March 2007 in Ithaca, New York)[1] was an American physicist who worked on nuclear physics and the astrophysics of cosmic rays and gamma radiation.

[3] In 1942 Greisen earned his PhD in physics at Cornell University under Bruno Rossi with thesis Intensity of cosmic rays at low altitude and the origin of the soft component.

In 1971 he and his colleagues discovered pulsed gamma rays with energies greater than 200 MeV from the pulsar in the Crab Nebula.

Rossi and Greisen built an apparatus, centered around a Geiger-Müller counter, to distinguish the altitude dependence of hard (mesotron, i.e. muon) and soft (electron) cosmic ray secondaries.

The goal of Rossi and Greisen was to confirm that the lifetimes of the muons depended upon their energy as predicted by the theory of special relativity.

[6] "From 1943 to 1946 Greisen was a member of the group of physicists who worked on the Manhattan Project at Los Alamos.