On Tue, Jan 7, 2014 at 1:50 PM, LizR <lizj...@gmail.com> wrote: > On 8 January 2014 05:51, John Clark <johnkcl...@gmail.com> wrote: > >> On Mon, Jan 6, 2014 , LizR <lizj...@gmail.com> wrote: >> >>> >>> >>> Bell's theorem holds only under a certain set of assumptions, >>>>>>> >>>>>> >>>>>> >>>>True. As I've said many times Bell made exactly 3 assumptions: >>>>>> 1) High School algebra and trigonometry works. >>>>>> 2) Things are local. >>>>>> 3) Things are realistic. >>>>>> >>>>> >>>>> >>> In fact Bell made a fourth assumption, although he didn't realise >>>>> he was making it until later. Namely, he assumed that time is asymmetric. >>>>> >>>> >>>> >>I won't bother to argue if Bell made this assumption or not because >>>> it doesn't matter, time is asymmetric. >>>> >>> >>> > Not in a manner that affects EPR experiments. Show me an EPR >>> experiment that involves neutral kaon decay and you will have a point, >>> otherwise this is simply not true. >>> >> >> I don't understand your point, are you arguing that time is asymmetric >> or that it is not? The existence of neutral kaon decay strengthens the >> already very strong argument that time is asymmetric, but only very >> slightly. Yes a movie of neutral kaon decay would look slightly different >> if run forward rather than backward, but not if you looked at the reversed >> film in a mirror and you assumed the electrical charges were reversed. CPT >> (Charge Parity Time) symmetry still holds true. >> > > I'm arguing that time is symmetric, and that hence Bell's (implicit) 4th > assumption is violated. Bell agreed that this was true, but said the > assumption was valid - he thought time was asymmetric at all levels. > Physics indicates he was wrong (wrong when it counts in EPR experiments, > that is). > > I don't know why there is so much fuss over Bell's inequality, and so much > mystical mumbo jumbo about non locality and spooky action and so on, when > it was actually discovered before Bell died that there's a perfectly > reasonable explanation for how his inequality can be violated that retains > locality and realism. It's like physics being sime symmetric is so "far > out" that no one can believe it, yet it requires no new physics and fixes > up all those problems! > >
Well, most physicists already agrees physics is time-symmetric (well, CPT-symmetric, but the implications are the same for Bell's inequality and thermodynamics), but I don't see how this alone can explain violations of the Bell inequality. To explain Bell inequality violations using a time-symmetric theory like the one sketched out by Huw Price, you need to assume hidden variables (the particles have predetermined spin states along all axes the experimenters might choose to measure), *and* you must further assume that the particle emitter that creates the particles can "predict" what axes the experimenters will choose to measure on each trial, so that the statistics of what combinations of hidden variables get created will depend on the experimenters' later choices. For examples on trials where they are both going to measure along the x-axis the emitter will always create particles that have opposite spins along the x-axis, whereas on trials where the experimenters both measure on some other axis, or where they each choose different axes to measure, the emitter can create particle pairs that don't have opposite spins on the x-axis. Is this the type of solution you're thinking of? If so, it seems like this goes well beyond time-symmetry, since time-symmetry doesn't normally allow for systems to contain localized "records" of events in the future the way that they can for events in the past (which presumably could be explained in terms of the thermodynamic arrow of time caused by the universe having a low-entropy past boundary condition but not a low-entropy future boundary condition). With time-symmetric deterministic laws, it's true that complete knowledge of everything in the past light cone of an event A at some earlier time can allow you to determine the outcome at A, but if A is an event that exhibits sensitive dependence on initial conditions (as the experimenter's choices could plausibly be), then anything short of complete knowledge of everything in the past light cone probably wouldn't be enough to determine A. You wouldn't expect to have a situation where knowing the state of some localized system in the past light cone of A (like the hidden variables of the particle that have just been created by the emitter) gives you sufficient information to determine A, at least not in an "ordinary" time-symmetric theory where entropy is increasing. Try to get violations of Bell's inequality in a computer simulation with time-reversible laws, like a reversible cellular automaton ( https://en.wikipedia.org/wiki/Reversible_cellular_automaton)--I don't think anyone who points to the "information flowing back in time" loophole has actually come up with such a simulated example. Jesse -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to email@example.com. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/groups/opt_out.