University of Minnesota
School of Physics & Astronomy

Physics and Astronomy Calendar

Wednesday, February 18th 2015
3:35 pm:
Speaker: Michel Janssen, University of Minnesota
Subject: The centenary of general relativity: How did Einstein find his gravitational field equations?
Refreshments served in Room 216 Physics after colloquium

In his search for gravitational field equations from late 1912 to late 1915, Einstein vacillated between two different strategies. Following a "mathematical strategy," he extracted candidate field equations from the Riemann curvature tensor and checked whether these equations were compatible with energy-momentum conservation and reproduced Newton’s theory of gravity in the appropriate limit. Following a "physical strategy," he constructed field equations for the gravitational field in close analogy with those for the electromagnetic field. In his later years, Einstein routinely claimed that he brought his search for gravitational field equations to a successful conclusion in November 1915 by switching to the mathematical strategy at the eleventh hour. Most commentators have accepted this later assessment but we have argued that Einstein achieved his breakthrough of November 1915 by doggedly pursuing the physical strategy. In a lecture in Vienna in September 1913, Einstein clearly laid out this physical strategy. As long as one took the older Einstein’s word for it that the mathematical strategy was responsible for the success of November 1915, one could quickly pass over the Vienna lecture. But if it was really the physical strategy that was responsible for this success, as we believe, the Vienna lecture deserves a much more prominent place in the account of the genesis of general relativity than it has been given so far.

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