The Cosmological Constant

Contrary to popular mythology, Einstein did not invent the cosmological constant just in order construct his model universe. He discussed it earlier in “The Foundations of General Relativity”in connection with the proper structure of the source-free field equations. There he dismissed it as arbitrary and unnecessary. It was later that he found its inclusion to be essential to the construction of his model. Contrary to virtually universal belief, the cosmological constant was not invented by Einstein [1] for use in his cosmological Considerations Concerning General Relativity [2]. The fact is, he discussed it explicitly about a year earlier in Sect. (14) of The Foundations of General Relativity [3] where he introduced the source-free field equations. ∂Γμν ∂xα + ΓμβΓ β να = 0 (1a) √ −g = 1 . (1b) (The second equation is a “coordinate condition”which permits writing the field equations elegantly if severely truncated. In this form, the field equations have never been applied to any problem.) There he comments, “It must be pointed out that there is only a minimum of arbitrariness in the choice of these equations. For besides Gμν there is no tensor of second rank which is formed from the gμν and its derivatives, contains no derivatives higher than the second and is linear [4] in these derivatives.” Then he adds a footnote,