Philipp Frank (March 20, 1884, Vienna, Austria-Hungary – July 21, 1966, Cambridge, Massachusetts, USA) was a physicist, mathematician and also an influential philosopher during the first half of the 20th century. He was a logical-positivist, and a member of the Vienna Circle.
He studied physics at the University of Vienna and graduated in 1907 with a thesis in theoretical physics under the supervision of Ludwig Boltzmann. Albert Einstein recommended him as his successor for a professorship at the German Charles-Ferdinand University of Prague, a position which he held from 1912 until 1938. He then emigrated to the United States, where he became a lecturer of physics and mathematics at Harvard University.
Astronomer Halton Arp described Frank's Philosophy of Science class at Harvard as being his favorite elective.
He was a colleague and admirer of both Mach and Einstein. In lectures given during World War II at Harvard, Frank attributed to Mach himself the following graphic expression of "Mach's Principle":
"When the subway jerks, it's the fixed stars that throw you down."
In commenting on this formulation of the principle, Frank pointed out that Mach chose the subway for his example because it shows that inertial effects are not shielded (by the mass of the earth): The action of distant masses on the subway-rider's mass is direct and instantaneous. It is apparent why Mach's Principle, stated in this fashion, does not fit with Einstein's conception of the retardation of all distant action.
His books include:
- Philosophy of Science, Prentice Hall (1957)
- Einstein: His Life and Times (1947)
- Foundations of Physics