John Linsley

John D. Linsley
John Linsley's 1963 passport photograph
Born	John David Linsley (1925-03-12)12 March 1925 Minneapolis, Minnesota, USA
Died	25 September 2002(2002-09-25) (aged 77) Albuquerque, New Mexico, USA
Nationality	United States
Fields	Physics
Institutions	University of Minnesota Massachusetts Institute of Technology University of New Mexico University of Palermo
Alma mater	University of Minnesota
Doctoral advisor	Edward P. Ney
Known for	Seminal contributions to study of cosmic rays
Notable awards	Nominated for the Nobel Prize in Physics (1980)

John David Linsley (12 March 1925 – 25 September 2002) was an American physicist who performed pioneering research on cosmic rays, particularly ultra-high-energy cosmic rays. He did his most significant work from 1959 to 1978 using a ground-based array of detectors at Volcano Ranch in New Mexico. He is best known for being the first to detect an air shower created by a primary particle with an energy of 10²⁰ eV. This was the highest energy cosmic ray observed up to that point. Linsley's observations suggested that not all cosmic rays are confined within the galaxy and showed the first evidence of a flattening of the cosmic ray spectrum at energies above 10¹⁸ eV.

John David Linsley was born on March 12, 1925 in Minneapolis, Minnesota. His father, James Adolphus Linsley, was born in Morris, Minnesota and worked for the Minneapolis Transit Company as a streetcar conductor. His mother, Martha Carolina Linsley, was born in Follinge, Sweden and was a graduate of the University of Minnesota. He had one sister, Ruth Anne Linsley Forman.

Linsley was homeschooled by his mother for much of his childhood and graduated from Roosevelt High School in Minneapolis in 1941. He attended the University of Minnesota, graduating in 1946. While working on his bachelor's degree, Linsley also served in the U.S. Army from 1944 to 1946.

After completing his undergraduate education, Linsley remained at the University of Minnesota to work on his Ph.D. under the direction of Edward P. Ney. He completed his Ph.D. in 1952, after which he worked as a research fellow at the University of Minnesota from 1952 to 1954. In 1954, Linsley took a job as a Research Associate at the Massachusetts Institute of Technology (MIT). He held this position from 1954 to 1955 and from 1958 to 1972. While at MIT, Linsley was a member of a team led by Bruno Rossi. This team used an air shower array at Harvard University's Agassiz Astronomical Station to observe air showers created by cosmic rays using ground-based liquid scintillator detectors. The analysis techniques Rossi's group developed laid the groundwork for the analysis of data from future arrays.