From Julian Barbour
Amanda Gefter writes, almost correctly, that I proposed that “time must not exist in a quantum theory of the universe” (19 January, p 26). Replace “must not” with “probably does not” and I agree. I think Peter Fyfe is right to alert would-be time travellers to this possibility (15 March, p 23), but I do not deny the existence of “any time but the present”.
In my view, all possible instants – the present one and umpteen others – exist on an equal footing, in much the same way that mathematicians say the integers do. Moreover, if quantum mechanics really is universal, I think the belief that you did actually experience what you call past instants commits you to a form of many-worlds interpretation. I call it the many-instants interpretation.
South Newington, Oxfordshire, UK
