Aside

Robert Dicke and the Naissance of Experimental Gravity Physics

The photograph in the upper left shows Eotvos and colleagues, likely measuring gravitational field gradients. On the right is an illustration of features common to the two repetitions of the Eotvos experiment in Dicke’s group: the balance placed in a vacuum, the torque detected remotely, and the instrument buried. On the lower left is a sketch of the torsion balance used in the static version (in an early design)

The photograph in the upper left shows Eotvos and colleagues, likely measuring
gravitational field gradients. On the right is an illustration of features common to the two repetitions of the Eotvos experiment in Dicke’s group: the balance placed in a vacuum, the torque detected remotely, and the instrument buried. On the lower left is a sketch of the torsion balance used in the static version (in an early design)

P. J. E. Peebles
The experimental study of gravity became much more active in the late 1950s, a change pronounced enough be termed the naissance of empirical gravity physics. A review of the developments since 1915, and up to the transition to what might be termed a normal and accepted part of physical science in the late 1960s, shows the importance of advances in technologies, here as in all branches of science. The role of contingency is illustrated by Robert Dicke’s decision to change directions in mid-career, to lead a research group dedicated to the experimental study of gravity. One sees the power of nonempirical evidence, which led some in the 1950s to feel that general relativity theory is so logically sound as to be scarcely worth the testing, while Dicke and others argued that a poorly tested theory is only that, and that other nonempirical arguments, based on Mach’s Principle and Dirac’s Large Numbers, suggested it was worth looking for a better theory of gravity. I conclude by offering lessons from this history, some peculiar to the study of gravity physics during the naissance, some of more general relevance. The central lesson, which is familiar but not always well advertised, is that physical theories can be empirically established, sometimes with surprising results.
… Read more at arxiv.org

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