X-Message-Number: 11578 From: Thomas Donaldson <> Subject: For Damien Broderick: experimental proof remains VERY scanty Date: Mon, 19 Apr 1999 23:51:25 +1000 (EST) To Damien Broderick: I too have noticed the theoretical work (and workers) who aim to form a theory containing both quantum mechanics and general relativity. I've even written about such things in ANALOG, though that was several years ago and I'm sure that Witten and others have come up with new and better ideas. HOWEVER one unhappy characteristic of such theories is that so far they are almost impossible to actually prove or disprove. I say "almost" here quite consciously: several workers have quite recently worked out one parameter (predicted by such theories) which they can actually test. You may wish to look at G. Amelino-Carnelia, in NATURE (398(1999) 216-218) or KC Littrel et al in PHYSICAL REVIEW A (56(1997) 1767ff). The issue of NATURE containing Amelino-Carnelia's paper gives some other places to look. (I discuss this in a sidebar in the 1 March 1999 issue of my newsletter PERIASTRON --- which is mostly about scientific matters relating to cryonics). It is interesting that even now such experiments exclude some possible theories. Our tools remain too gross to test others, but even so there has begun to be an EXPERIMENTAL handle on quantum gravity. This is very pleasing and important, though I doubt that it will prolong our lives. I point this out for the simple reason that we can't really claim to understand how quantum theory and general relativity combine until we have actual experimental evidence for our ideas. No amount of purely theoretical mumbo-jumbo can bring us even a nanometer closer to a theory which contains both of them. Best and long long life, Thomas Donaldson Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=11578