A distinguished American physicist and teacher delivers a landmark study thatdevelops three essential scientific themes on each subject.

Following a line of research that I have developed for several years, I argue that the best strategy for understanding quantum gravity is to build a picture of the physical world where the notion of time plays no role at all. I summarize here this point of view, explaining why I think that in a fundamental description of nature we must “forget time”, and how this can be done in the classical and in the quantum theory. The idea is to (...) develop a formalism that treats dependent and independent variables on the same footing. In short, I propose to interpret mechanics as a theory of relations between variables, rather than the theory of the evolution of variables in time. (shrink)

Relative distance and velocity magnitudes between two arbitrarily moving particles are independent of an observer's reference frame, and may be used to construct theoretically a clock whose rate is Lorentz-invariant. This result is in accord with the principle of relativity, using the interaction interpretation: Relativistic changes arise in association with momentum-energy transfer, rather than in consequence of velocity-induced changes in measuring clocks and rods.

Hardly any other problem has been discussed more than that of the status of time in modem physics. This is only natural since there are not many other more important problems in philosophy of science and in philosophy in general. There are also few other areas where controversies as well as confusion were more frequent. This is true not only of popular and semi-popular expositions of the Minkowski concept of space-time but also of a number of its philosophical interpretations. Generally (...) we do not find anything of this kind in the writings of physicists, at least as long as they confine themselves to strictly mathematical and physical expositions; but when they sometimes venture beyond a strictly mathematical approach, they often do not escape certain unconscious or semi-conscious prejudices which are contrary not only to the spirit but sometimes even to the letter of relativity. The true significance of the relativistic fusion of space and time can be understood only when we contrast it with its classical counterpart, i.e., with what may be called the Newtonian space-time. Only on such a contrasting background will the revolutionary meaning of the new concept clearly stand out. (shrink)