Re the above: I may need putting straight here, but I think it's the same kind of thing with the radioactivity half-life of an isotope. It's not possible the predict when a particular atom will decay, but it is possible to predict the rate of gross decay. I suppose someone might post something more about probabilties, 'sum over histories', or some such thing (I hope). I've only looked at these things from a very great height, so I don't need to be reminded that I'm ignorant about the details.


"Time is what prevents everything from happening at once" - John Wheeler