George Gale

Philosophical midwifery and the birthpangs of modern cosmology

Philosophical considerations sometimes direct developments in physics. Such influence most frequently operates during the genesis of new fields. The birth of modern cosmology provides clear evidence of the interaction between philosophical issues and the shape and direction of a new physical discipline. Philosophical controversy between E. A. Milne and other astrophysicists, including A. S. Eddington, James Jeans, and H. P. Robertson, directly affected the models, methods, and very nature of cosmological science for future generations. Today’s standard space‐time metric, for example, resulted from responses by Robertson and A. G. Walker to philosophical challenges presented in Milne’s proposals to scrap the very idea of expanding ‘‘space.’’ Analysis of published works, unpublished manuscripts and correspondence, and personal interviews illustrates the role philosophical considerations played in development of this new field in physics.

Dingle and de Sitter Against the Metaphysicians, or Two Ways to Keep Modern Cosmology Physical

It would be hard to find two more radically different personalities than the irascible Herbert Dingle and the courtly Willem de Sitter. Yet, when it came to their philosophy of science, these two otherwise-so-different men were united against a common enemy, those they both called the “metaphysicians.” Right from 1917, de Sitter attempted always to keep cosmology tightly bound to real observations made upon a real world. In Kosmos, written near the end of his life, he re-affirms most strongly his principle that “there is nothing an orthodox physicist abhors more than metaphysics.” Dingle, for his part, accepts early on the positivist use of the verifiability principle to eliminate metaphysics from science, and continuously wields the principle as a weapon against those errant cosmologists who would sacrifice science for a sort of mysticism. Both men reject the strict and literal use of the term “universe,” and for the same reasons: there is no observation, no verification, of statements containing that term. Both men reject the “cosmological principle” as Milne and others use it, on the grounds, as de Sitter puts it, that “we have . . . no means of communicating with other observers, situated on faraway stars.” Eddington, although always closely associated with de Sitter personally, comes in for his own fine share of criticism. After de Sitter’s death, Dingle carried on the battle alone, always on the bases that he and de Sitter had earlier established. The two peaks in Dingle’s long struggle were the notorious 1937 controversy in the pages of Nature, a nasty dogfight which managed to involve almost every single important physicist in Britain; thirteen years later, the long war with the metaphysicians ended with the pyrrhic victory of Dingle’s Royal Astronomical Society Presidential Address’ invective against the latest and greatest metaphysical creation, Bondi’s steady state universe theory. In the end, however, it would be a mistake to believe that the campaign of de Sitter and Dingle accomplished nothing. On the contrary, it is clear that their critique succeeded magnificently in keeping the metaphysicians at least somewhat in check, and, more importantly, maintaining cosmology’s connection to the real and observable world. As I will show, the common philosophical spirit of the two men grows out of precisely the same terrain: both men are exquisitely, excruciatingly, anchored in the rich empirical detail of observational astronomy. Unlike most of the other cosmologists, both men knew exactly what it took to construct data out of astronomical observations, both men knew exactly how hard is the subsequent task of interacting their hard-won data with theory, and it was this direct experience of real, genuine empirical science that they brought into the fray with the cosmological metaphysicians. And cosmology was the better for it.

An extension of special relativity to accelerating frames and some of its philosophical implications

A rigorous extension of the full Lorentz group is found which is parameterized by interframe velocities v(t) and which reduces to Special Relativity for acceleration-free cases and to Galilean relativity for low velocity cases. Full group properties are exhibited. Four-momentum is defined and particle masses are shown to be invariants. Four-force is introduced and pseudoforces are shown to enter the equations of particle dynamics. Maxwells equations are shown to take on pseudocurrent terms in accelerating frames. A four-vector Green function solution to the modified Maxwell equations is presented. Finally, a discussion is offered concerning philosophical questions such as the operational definition of time.