Dennis Sciama's essay is a lucid account of time in Einstein's two great theories of space and time, special and general relativity. Michael Shallis writes about tachyons, hypothetical particles that travel faster than light and slow down as they acquire energy. Peter Atkins, explaining entropy and the law of entropy growth, argues that "the deep structure of change is decay." Paul Davies discusses issues raised by Niels Bohr and John Wheeler concerning the role of the observer in the physicist's description of "the external world." Short essays by W.H. Newton-Smith and J.R. Lucas seek to relate aspects of physical theories of time to philosophical questions.
The longest and most interesting contributions are physicist Roger Penrose's "Big Bangs, Black Holes and 'Time's Arrow' "and philosopher Michael Dummett's "Causal Loops."
The phrase time's arrow refers to the lack of symmetry in ordinary experience and in laws that govern such phenomena as the ...
