On 14 Jan 2014, at 22:04, LizR wrote:
Sorry, I realise that last sentence could be misconstrued by someone
who's being very nitpicky and looking for irrelevant loopholes to
argue about, so let's try again.
Now how about discussing what I've actually claimed, that the time
symmetry of fundamental physics could account for the results
obtained in EPR experiments?
Logically, yes.
But you need "hyper-determinism", that is you need to select very
special boundary conditions, which makes Cramer's transaction theory
close to Bohm's theory.
Those are still many-world theories, + some "ugly" selection principle
to get one branch. It is very not "natural", as you have quasi
microsuperposition (appearance of many branches), but the macro-one
are eliminated by ad hoc boundary conditions, which will differ
depending on where you will decide to introduce the Heisenberg cut.
Also, QM will prevent us to know or measure those boundary conditions,
which makes them into (local, perhaps, in *some* sense) hidden
variable theory.
Many worlds is far less ad-hoc, imo. There is no Heisenberg cut, and
the boundary conditions does not play any special role, and indeed
they are all realized in the universal wave (and in arithmetic).
Bruno
On 15 January 2014 10:01, LizR <lizj...@gmail.com> wrote:
On 15 January 2014 06:11, John Clark <johnkcl...@gmail.com> wrote:
On Sun, Jan 12, 2014 at 6:41 PM, LizR <lizj...@gmail.com> wrote:
>>> "Retro-causality" (time symmetry is a better term) only exists
at the quantum level.
>> Why? Where is the dividing line? And with a Schrodinger's Cat
type device a quantum event can easily be magnified to a macro-event
as large as desired, you could connect it up to an H-bomb.
> The dividing line appears to be roughly where decoherence occurs.
Basically anything above a single quantum entity engaged in a
carefully controlled interaction is liable to get its time symmetric
properties washed out by interactions with other particles
The nucleus of an atom is tiny even by atomic standards so it is
certainly at the quantum level, and in its natural state of existing
inside a huge chunk of irregular gyrating matter this tiny thing is
constantly subject to the slings and arrows of outrageous fortune
from an astronomical number of other clumsy atoms; and yet the half
life of Bismuth 209 is 1.9 * 10^19 years. Why?
Because that's how long it takes for the relevant particles to get
over the potential barrier. But this is irrelevant. Atomic nuclei
are (probably) already on the wrong side of the "entropy fence" in
any case. They're bound states which can only occur under certain
special cirumstances, namely when the universe expands and cools
enough to allow them to form. And atomic nuclei haven't been used to
violate Bell's inequality as far as I know.
>> It's just a fact, if time were symmetrical then you'd be just as
good at predicting the future as you are at remembering the past, so
you'd know the outcome of an experiment before you performed it just
as well as you remember setting up the apparatus. But this is not
the way things are because the second law exists. And the second law
exists because of low entropy initial conditions. And I don't know
why there were low entropy initial conditions.
> OK. So the above statement of yours about predicting the future is
still false,
Yes it's false, I don't think this will come as a great news flash
but the truth is we're not as good at predicting the future as we
are at remembering the past. And the reason we're not is that time
is not symmetrical.
Except below the level of coarse graining at which entropy operates,
that is correct. And I never claimed otherwise. As I keep saying,
I'm only claiming this is relevant in special circumstances like EPR
experiments.
> To recap briefly -- the laws of physics are time symmetrical,
Yes, the fundamental laws of physics, the ones we know anyway, seem
to be time symmetrical. But that doesn't mean that time is
symmetrical.
...is just words. Stop nitpicking. If the laws of physics are time
symmetrical, that has a potential influence on EPR experiments.
> and most particle interactions are constrained by boundary
conditions.
Yes, and that is why time is NOT symmetrical.
Stop playing with words. The time symmetry of fundamental physics is
there, so it's perfectly valid to say time is symmetrical below the
level of coarse graining needed to derive the 2nd law, and
asymmetrical above it. (That's virtually a simple restatement of
Boltzmann's H-theorem "for dummies".) The point is that symmetrical
time may become apparent in EPR setups. You haven't yet given even a
suggestion of a reason why it wouldn't, just a load of hand waving
about stuff that is IRRELEVANT to EPR experiments, which are
carefully prepared to avoid all the influences you've mentioned.
Now how about discussing what I've actually claimed, that time
symmetry of physics could account for the special situation which
has to be created to obtain EPR results?
--
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 everything-list@googlegroups.com.
Visit this group at http://groups.google.com/group/everything-list.
For more options, visit https://groups.google.com/groups/opt_out.
http://iridia.ulb.ac.be/~marchal/
--
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 everything-list@googlegroups.com.
Visit this group at http://groups.google.com/group/everything-list.
For more options, visit https://groups.google.com/groups/opt_out.
