1. The discussion of relativity which follows owes much to Marijke van Gans’ in the Science and Maths forum on CompuServe. Since I first wrote this essay she has put her explanations on the web, here. Taylor & Wheeler is also a good source.

2. Note that the space-time interval is often given with the signs reversed; this makes no difference to the discussion here. I use the signs this way round to stress the continuity of the idea of a spacetime interval with that of distance.

3. Note that it was once thought that only particles which have interacted in the past can be entangled, but this turns out to have been due to a miscalculation - in fact, particles which have never been anywhere near each other appear to be entangled in much the same way, so that the universe is actually full of entanglement - it is the rule, rather than the exception.. See John Gribbin (1996).

4. A. Einstein, B. Podolsky and N. Rosen (1935).

5. J. von Neumann (1932).

6. See Bell (1966) in Speakable & Unspeakable in Quantum Mechanics.

7. Hermann (1935).

8. Bell (1982)

9. Bell (1966)

10. See especially A. Aspect (1982).  Note, however, that even with the still better tests which have now been performed there remains some room for doubt on an experimental level. Aspect's conclusions assume that the particles which are measured in the experiments are a representative sample of those created – a reasonable enough assumption, but one which could still turn out to be wrong if for some obscure reason we are more likely to detect particles whose properties fit with the predictions of quantum mechanics.

11. Bell (1964), in Bell (1987, p. 20).

12. John Earman and Paul Horwich both discuss the possibility of different sorts of time travel or backwards causation in Savitt (1995).  The former, whose account is more technical and thorough, concludes that we cannot rule out any sort of time travel but rather we need new global consistency constraints to make such time travel, if possible, coherent.  Horwich feels that certain sorts of backwards causation, such as perfect precognition, are impossible because they lead to contradictions.

13. As discussed, for instance, in Cramer (1988).

14. See eg. Maudlin (1994), chapter 7. Maudlin maintains that the supposed explanatory power of Cramer's theory is illusory, relying on the fiction of 'pseudo-time' to make it even appear to work.

15.   See Brody (1993, 205-238); his arguments were originally published in 1985 and 1989.

16.  eg. de Muynck (1986, 1996).

17.  See Buchanan (1999) in New Scientist.

18.  Healey (1997)

19.  See Chown (1998, 1999) in New Scientist, and Mark Hadley’s article in a forthcoming issue of the International Journal of Theoretical Physics; also his web page.