On 4/13/2022 3:22 AM, smitra wrote:
On 12-04-2022 22:59, Brent Meeker wrote:
On 4/11/2022 11:30 PM, smitra wrote:
On 11-04-2022 20:40, Brent Meeker wrote:
On 4/11/2022 12:47 AM, smitra wrote:
On 11-04-2022 09:19, Bruce Kellett wrote:
On Mon, Apr 11, 2022 at 3:58 PM smitra <smi...@zonnet.nl> wrote:
On 10-04-2022 06:15, Bruce Kellett wrote:
Not relevant, since there is no enclosing reflecting boundary.
Yes there is.
Where is it then?
One can also consider an observation inside the event
horizon of a supermassive black hole. No photons escape from there.
We are not currently inside a supermassive black hole. Besides, you
knowledge of BH physics seems somewhat faulty. Inside the horizon, all
particles move towards the singularity at r = 0 (because that is the
forward direction of time). So there is no reflection off the inside
of the horizon. That is a fanciful (and wrong) idea.
The escaping Hawking radiation is so small that it doesn't contain
much
information.
And since you are attempting to promote a FAPP argument to an in
principle argument, you also have to consider that the space
environment
is not a perfect vacuum, so photons do not travel at exactly the
speed
of light. This means that in principle one can retrieve the
escaping
photons
I don;t think the difference between c, the speed of light in a
vacuum, and the speed of light in outer space is a relevant
consideration -- you still are not going to catch and reverse those
IR
photons.
That's all FAPP, not in principle. The laws of physics are reversible,
it requires a rigorous argument from the fundamental laws of physics
to demonstrate that reversing a measurement is impossible. Arguing
from a practical situation and pointing to immense difficulties is a
FAPP argument.
You seem to think the purpose of physics is to study the consequences
of equations. If something is impossible to observe, I think the
purpose of physics is to explain why it's impossible.
In physics, when we try to figure out something new, one has to
accept that there is incomplete knowledge about it and that in
principle a large number of possibilities are in principle possible.
But not all possibilities are equally reasonable. We all know how
creationists invoke a "God of the gaps". In principle God could have
created the universe not so long ago and one can always point to
something science has not yet been able to figure out yet.
So, in practice one can always invoke a "God of the gaps" argument
against a reasonable hypothesis. This is how Bruce is arguing here in
opposition to the MWI. One may oppose the MWI on many reasonable
grounds, but Bruce has the habit of invoking gaps that do not even
exist, like that QFT is inconsistent with ordinary QM because QFT is
manifestly local and he insist that the dynamics of QM must be
non-local to account for Bell-type correlations. So, he is invoking a
gap that doesn't even exists to argue his point.
Bruce has considered the QFT version of EPR. That's the
interpretation in which all combinations of Alice and Bob meet in the
future and almost all combinations somehow are annihilated, leaving
only those that are observed.
That's not the QFT version of EPR, it's his own personal version of
EPR. If it were true that QFT were to imply what he says, then the MWI
would never had the support that it has today. Did physicists who
are/were MWI enthusiasts like Bryce DeWitt, John Wheeler, Sidney
Coleman, David Deutsch, Sean Carroll etc. overlook this or is it more
likely that Bruce's argument is simply wrong? Also there are many
physicists who are MWI critics, they never invoke that argument
against the MWI either.
I think QFT is only an approximate theory _because_ it assumes only
local interactions.
The constraints on non-local effects cannot get you to non-trivial
effects in Bell-type experiments.
Then in case of observations may take the position that observations
cannot be reversible. But since our brain can be simulated and you
could in principle run the simulation of a quantum computer, that
implies that observations can actually be reversible.
Only if your quantum computer never produces an output.
Right.
So, the irreversible aspects of observations in the real world have
nothing to do with the observations. Just like in the real world
there is always friction which affects the motion of objects. True
but things can also move in a perfect vacuum.
Now, in previous discussions the argument was made that you can't
consider a simulation of observers in a quantum computer because, by
definition, measurements must be irreversible. But that definition
is can then be argued to be unreasonable. One can argue that even in
the real world everything is in principle reversible. But then what
about IR photons? Well, that doesn't stand in the way for inn
principle reversibility either.
But then this whole argument then strayed into the unreasonable
domain, because the physics of what happens on my brain during
observations isn't affected by escaping IR photons and it can in
principle be simulated to arbitrary accuracy in a fully reversible
quantum computer.
I'm afraid you seem very inconsistent. Earlier you insisted that an
analysis had to include M81 and NGC215 as well as Alice, Bob, and
instruments. Now you, you just want to simulate the brains (and not
include any IR photons).
If one wants to discuss a particular experiment and draw conclusions
about possible violations of locality or something else, ten it's
important that all relevant degrees of freedom are included. Not doing
so can make the conclusions invalid. If I pretend that Alice and Bob
are reading two books and what they read is perfectly correlated then
the explanation for that may be that they visited the same library and
got copies of the same book there. Leave that out, and pretend that
the books may well have appeared out of thin air a their locations
(figuratively speaking, the point being that one may claim that the
origin of the books is irrelevant), then the non-local correlations of
what they read is a strange thing. The main point is then that the
non-local correlations can be explained using only local dynamos
starting from an initial state that does not contain any copies of
book at space-like separations.
None of this implies that a simulation of a brain must also include
the emission of IR photons to generate a conscious being that is
capable of making observations in his/her virtual world.
But drawing conclusions based on the reversibility of the brain (and the
universe) does.
Brent
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