Kenneth Nordtvedt

Kenneth Leon Nordtvedt (born 1939) is an American senior researcher specializing in relativistic theories of gravity. He was born on April 16, 1939, in Chicago, Illinois. Nordtvedt graduated from the Massachusetts Institute of Technology (1960) and Stanford University (Ph.D., 1964) and was a junior fellow in the Harvard Society of Fellows (1963-1965). Soon after witnessing the Sputnik spacecraft cross the Boston sky in fall of 1957, he became a part-time student employee for the Mars Probe project at the MIT Instrumentation Lab, and in early 1960s was staff physicist at the same Laboratory's project to develop the Apollo Mission's navigation and guidance system.

In the mid-1960s he showed how lunar laser ranging could be used to test a cornerstone of general relativity known as the equivalence principle, especially as extended to gravitationally compact bodies. He was a board member and scientific advisor overseeing the joint NASA-ESA Space Test of Equivalence Principle mission. In 1986 he was appointed by then President Ronald Reagan to the National Science Board.He was elected to three terms in the Montana state legislature for a six-year period 1979-1984, and there he wrote one of the first inflation indexing reforms of income tax law in the nation. He served briefly in 1989 as Director of the Montana Department of Revenue. He had support from NASA and NSF for much of his research, as well as being a Sloan Fellow. His research was the subject of a Wall Street Journal article featured on the front page.

He showed in 1988 that General Relativity's gravitomagnetism between Earth and Moon, as those bodies orbited the Sun, was essential to fitting the synodic month and half synodic month range signals from lunar laser ranging.

He is also an active genetic genealogist by interests. He has done his own research into genetic haplogroups, particularly the Y DNA group I, to which he belongs.

• Nordtvedt effect