Julian Barbour
British physicist, known for his persistent study of the Machian mechanics (classical and relativistic). It is well known that Mach criticized the Newtonian notion of absolute space and time, and that Mach tried to interpret the law of inertia in terms of the interaction of a test particle and the rest of the universe. Combining this idea with Poincare's formulation of the initial value problem, Barbour formulates the conditions for a Machian mechanics:
(1) the dynamical evolution of the universe as a whole should be predicted uniquely on the basis of purely relative initial data, and
(2) time independent from dynamics should not be assumed, so that intial data should depend only on the conditions specifiable without assuming such time.
Barbour's first result was published in the 70's, but his long research (with several collaborators) culminated in a number of papers published in the 90's. The classical (Newtonian) mechanics can be reconstructed as a Machian mechanics, and similar results can be extended to general relativity. Thus, although many philosophers of space and time now insist that the general relativity satisfies neither the "Machian requirement" (variously interpreted), nor the relational ideal (such as Leibniz's) , Barbour argues that there is a good sense in which the general relativity is a perfect Machian theory of dynamics. Whether or not you agree with this claim, Barbour's research is quite important for any students of space and time.
Visit his site Platonia; also see my review, Newslet. 42
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