Possible worlds and Everett's worlds
Joseph O'Rourke
(e.g., David Lewis) call a "possible world," and one branch
of Everett's superposition of worlds? This seems like a
topic on which some may have written previously; any
references would be appreciated.
Bob Bright
>Is there any clear relationship between what philosophers
>(e.g., David Lewis) call a "possible world," and one branch
>of Everett's superposition of worlds? This seems like a
No. (All of Everett's branches are supposed to be *actual*, and
moreover can evidently affect each other via reverse causation.)
>topic on which some may have written previously; any
>references would be appreciated.
It does seem like a likely topic, but I don't know of anything.
Anyone else?
BBB
--
Bob Bright | E-mail: bri...@ccu.umanitoba.ca
Dept. of Philosophy | FAX: (204) 261-0021
University of Manitoba | Voice: (204) 474-9105
Winnipeg, Man R3T 2M8 |
Mark Rosenfelder
I believe these are disparate concepts. The philosophers' "possible worlds"
would include worlds with a different physics-- worlds where the speed of
light is different, worlds without gravity, worlds with new forces, etc.
(I know things aren't usually stated this way, but it follows from the idea
that possible worlds include all imaginable worlds without internal logical
contradiction.) Everett's superimposed states are all however variations on
*this* world: the basic physics is the same in all "worlds", but the quantum
wavefunction has taken a different path in each.
Joseph O'Rourke
>oro...@sophia.smith.edu (Joseph O'Rourke) writes:
>
>>Is there any clear relationship between what philosophers
>>(e.g., David Lewis) call a "possible world," and one branch
>>of Everett's superposition of worlds?
>
>moreover can evidently affect each other via reverse causation.)
Even though all of Everett's branches are "actual," is there not
a sense in which they are possible worlds? Suppose first that macroscopic
brain events can be influenced by quantum effects, a big supposition
but not completely implausible. Suppose second that at a particular
time in history, a potential assassin of a world leader makes or
does not make the critical trigger-pull decision based on such a
quantum event. Does not then Everett's theory require that the
Kennedy-alive and Kennedy-dead worlds both exist as superpositions?
And if so, is this not similar to a philosopher's counterfactual
possible world?
John C. Baez
>Even though all of Everett's branches are "actual," is there not
>a sense in which they are possible worlds?
The notions of "actual" versus "possible" have to be quite carefully
defined in a manner suitable to quantum theory if we expect to get an
answer to this sort of question. Our naive notions simply won't cut it.
"Possible-probable, my black hen
Lays her eggs in the Relative When
She doesn't lay eggs in the Absolute Now
Because she's unable to postulate how."
(from The Space Child's Mother Goose.)
Ron Maimon
Resemblences such as these destroyed the credibility of this interpretation for
many years, and still keeps it rather underground in physics circles. They are
different in that Everett has a reason for believing these `worlds' exist, while
David Lewis is just bullshitting.
David Chalmers
>Even though all of Everett's branches are "actual," is there not
>a sense in which they are possible worlds? Suppose first that macroscopic
>brain events can be influenced by quantum effects, a big supposition
>but not completely implausible. Suppose second that at a particular
>time in history, a potential assassin of a world leader makes or
>does not make the critical trigger-pull decision based on such a
>quantum event. Does not then Everett's theory require that the
>Kennedy-alive and Kennedy-dead worlds both exist as superpositions?
>And if so, is this not similar to a philosopher's counterfactual
>possible world?
On the Everett account, neither world is counterfactual -- both are
actual. The trigger is both pulled and not pulled in different parts
of the actual world, although after the fact, limited creatures such
as we are only see part of what is going on (other parts of me, or
perhaps counterparts of me, are seeing other parts of what is going
on). The physics of our world is entirely deterministic, although
one can heuristically divide the world into lots of branches
(subworlds, if you like) which appear nondeterministic taken alone.
An easy way to see the difference between Lewis and Everett -- for
anything in one of Everett's subworlds, there will be something
to which both it and I are causally connected. There can be no
chain of causal connections between entities in two different possible
worlds of the Lewis variety -- if two things are causally related, they
are in the same world.
I recall a paper by Brian Skyrms that tried to make a tenuous
connection between Lewis's and Everett's accounts. It appeared in
Philosophical Studies, I think, and is referenced in Lewis's book
_On the Plurality of Worlds_. My books and files are many miles
away, so I can't give you the full reference.
--
Dave Chalmers (da...@cogsci.indiana.edu)
Center for Research on Concepts and Cognition, Indiana University.
"It is not the least charm of a theory that it is refutable."
Ron Maimon
this is true, and its not a big leap. Quantum uncertainties magnify themselves
over time, and there is not only a Kennedy alive and Kennedy dead world, but a
world in which Kennedy spontaniously combusted in his car (admittedly a very
small possibility). But, this is a statement about physics.
It has absolutely no repercussions on morals, judgements, ideals, or any of the
other things philosophers deal with.
It can't be used to justify murder, because the guy is alive on some other part
of the wavefunction, it cannot be used to justify mandatory sentencing. It has
absolutely no relevance to the world. Why? because the world would look the same
with or without it. I can see the danger of philosophers thinking this is some
big and important result in philosophy when it really isn't.
Things like this make physicists very, very skeptical of Everett's interpretation.
So many stupid people talk about it.
(This is not a flame, and I'm not talking about you, but there are many really
stupid people who love the `many-worlds' interpretation for all the wrong reasons)
-Ron Maimon
Justin Smith
>In article <1993Aug4.1...@sophia.smith.edu> oro...@sophia.smith.edu (Joseph O'Rourke) writes:
>
>>Even though all of Everett's branches are "actual," is there not
>>a sense in which they are possible worlds? Suppose first that macroscopic
>>brain events can be influenced by quantum effects, a big supposition
>
This discussion is fascinating because I used to be acquainted with
some philosophers who were trying to use Everett's theory as a way
to give a `rigorous' meaning to `possible'. In other words, a world
is possible if there exists a causal chain of Everett branches connecting
it with our world.
One of the bizarre questions philosophers posed in this area was
``Could Socrates have been a turnip?''
and these philosophers felt one could rigorously say `No: not only
wasn't Socrates a turnip --- he also COULDN'T have been.'
(This is an example of the bizarre discussions that arise in
the more rarified regions of philosophy.)
--
_____________________________________________________________________________
Justin R. Smith Office: (215) 895-1847
Department of Mathematics and Computer Science Home: (215) 446-5271
Drexel University Fax: (215) 895-2070
Bruce Umbaugh
In article <1993Aug4.1...@sophia.smith.edu>, oro...@sophia.smith.edu
If I'm not mistaken, Everett holds that the "branching" worlds are
all *actual* ones. On at least some interpretations of modal logic,
possible worlds are non-actual.
--
Bruce Umbaugh bdu...@oduvm.cc.odu.edu
Dept. of Philosophy | Humanize the Internet: Ethernet
Old Dominion University | the Arts faculty.
Norfolk, Virginia 23529 USA | -- Peter Danielson
Joseph O'Rourke
>connection between Lewis's and Everett's accounts. It appeared in
>Philosophical Studies, I think, and is referenced in Lewis's book
>_On the Plurality of Worlds_.
Good memory!
Brian Skyrms.
Possible Worlds, Physics, and Metaphysics.
Philosophical Studies, 30 (1976) 323-32.
Avrom Faderman
>In article <1993Aug4.1...@sophia.smith.edu>, oro...@sophia.smith.edu (Joseph O'Rourke) writes:
>|> Even though all of Everett's branches are "actual," is there not
>|> a sense in which they are possible worlds? Suppose first that macroscopic
>|> brain events can be influenced by quantum effects, a big supposition
>|> but not completely implausible. Suppose second that at a particular
>|> time in history, a potential assassin of a world leader makes or
>|> does not make the critical trigger-pull decision based on such a
>|> quantum event. Does not then Everett's theory require that the
>|> Kennedy-alive and Kennedy-dead worlds both exist as superpositions?
>|> And if so, is this not similar to a philosopher's counterfactual
>|> possible world?
>
>this is true, and its not a big leap. Quantum uncertainties magnify themselves
>over time, and there is not only a Kennedy alive and Kennedy dead world, but a
>world in which Kennedy spontaniously combusted in his car (admittedly a very
>small possibility). But, this is a statement about physics.
>
>It has absolutely no repercussions on morals, judgements, ideals, or any of the
>other things philosophers deal with.
I'll agree that it has no ethical repercussions (at least, no direct
ones). I certainly _don't_ agree that it [by which I take you to mean
Everett's theory] has no philosophical repercussions whatsoever.
For example, a common argument against consciousness-as-program claims
is that only _conscious_ observers can collapse the wave function, and
it seems obvious that simply what _program_ you're running could have
no effect on something as physical as the wave function collapsing.
Therefore, these philosophers claim, consciousness must have a very
special physical place in the universe (Penrose, e.g., used this
argument).
This argument relies completely on the Copenhagen interpretation
(which Everett's theory is supposed to be an alternative to). If
Everett is right, the argument simply isn't valid. If he's wrong,
it's a much bigger deal (although there still might be some way around
it, I can't think of one).
>It can't be used to justify murder, because the guy is alive on some other part
>of the wavefunction, it cannot be used to justify mandatory
sentencing.
Agreed.
> It has
>absolutely no relevance to the world. Why? because the world would look the same
>with or without it.
No agreement on this one. In one case, certain events cause the Wave
function to collapse (and therefore have special physical standing);
in the other, the wave function never collapses.
> I can see the danger of philosophers thinking this is some
>big and important result in philosophy when it really isn't.
>
>Things like this make physicists very, very skeptical of Everett's interpretation.
>So many stupid people talk about it.
Just because some people draw false conclusions from X doesn't mean
all conclusions drawn from X are false.
--
Avrom I. Faderman | "...a sufferer is not one who hands
av...@csli.stanford.edu | you his suffering, that you may
Stanford University | touch it, weigh it, bite it like a
CSLI and Dept. of Philosophy | coin..." -Stanislaw Lem
John C. Baez
>If I'm not mistaken, Everett holds that the "branching" worlds are
>all *actual* ones. On at least some interpretations of modal logic,
>possible worlds are non-actual.
Actual-possible, my black hen, laid her eggs in a modal fen. I agree
with Bruce completely but urge on to people the task of defining
"actual" in a sense applicable to quantum mechanics. Certainly in
Everett's work on QM the (misnamed) "branches" are simply states which
can be linearly superposed to yield the given state. The first and
foremost thing is that QM itself doesn't tell you how to split up the
state into "branches"; our decisions about what count as interesting
observables affect how we decide to analyze a state of the universe into
a linear combination of states (what Zurek calls the "pointer basis" is
one choice - write the state as a linear combination of states in which
the pointer on your measurement apparatus points to a given number). So
- if anything is actual it's the state itself, not the "branches," but
even the state as a mathematical construct is merely something we choose
to model reality by, not reality itself (and this point, I believe,
continues to elude those who find QM incomprehensible), so we might as
well shrug and call the branches "actual."
There is, after all, a nonzero probability that the current state is in
one of these branches, after all!
Ron Maimon
|> In article <CBB37...@usenet.ucs.indiana.edu> chal...@bronze.ucs.indiana.edu (David Chalmers) writes:
|> >In article <1993Aug4.1...@sophia.smith.edu> oro...@sophia.smith.edu (Joseph O'Rourke) writes:
|> >
|> >>Even though all of Everett's branches are "actual," is there not
|> >>a sense in which they are possible worlds? Suppose first that macroscopic
|> >>brain events can be influenced by quantum effects, a big supposition
|> >
|> >On the Everett account, neither world is counterfactual -- both are
|>
|> This discussion is fascinating because I used to be acquainted with
|> some philosophers who were trying to use Everett's theory as a way
|> to give a `rigorous' meaning to `possible'. In other words, a world
|> is possible if there exists a causal chain of Everett branches connecting
|> it with our world.
|>
|> One of the bizarre questions philosophers posed in this area was
|>
|> ``Could Socrates have been a turnip?''
|>
|> and these philosophers felt one could rigorously say `No: not only
|> wasn't Socrates a turnip --- he also COULDN'T have been.'
|> (This is an example of the bizarre discussions that arise in
|> the more rarified regions of philosophy.)
|>
please stop talking about Everett and philosophy in the same breath (I know its
hard!) ^^^^
Everett is a serious scientist! Philosophers completely misunderstand him.
example- the Socrates, turnip dilemma. Yes, Socrates could have been a turnip.
There is, in quantum gravity, as far as we can see today, an amplitude for any
process to happen which conserves energy, momentum, angular momentum and charge.
this is because a black hole emits perfectly random radiation, and is its own
time-reverse. If I can throw socrates into a black hole, I should also be able to
see socrates come out of a black hole in the Hawking radiation. This is indeed
possible, but extremely unlikely since Hawking radiation is completely random.
There is an amplitude for a virtual black hole to form and swallow Socrates, and
reemit a turnip of the same mass charge momentum and angular momentum (a big
turnip, but a turnip nonetheless) and therefore there is a `world' where
Socrates becomes a turnip. As a matter of fact, there is a world where anything
happens, they are just very small measure worlds.
-Ron Maimon
Ron Maimon
|> [comp.ai.philosophy trimmed]
|>
|> In article <1993Aug4.1...@sophia.smith.edu>, oro...@sophia.smith.edu
|> (Joseph O'Rourke) says:
|> >
|> >Is there any clear relationship between what philosophers
|> >(e.g., David Lewis) call a "possible world," and one branch
|> >of Everett's superposition of worlds? This seems like a
|> >topic on which some may have written previously; any
|> >references would be appreciated.
|>
|> If I'm not mistaken, Everett holds that the "branching" worlds are
|> all *actual* ones. On at least some interpretations of modal logic,
|> possible worlds are non-actual.
|>
stop it! Youre making me sick!
Whether a world is "Actual" or "non-actual" makes absolutely no difference. If
you are a pattern of nerve cells and that pattern exists, but in a "non-actual~
world, that doesn't stop the world from being just as actual to you, the pattern
of cells.
Everett doesn't make any assumptions, except for the assumption that quantum
mechanics is correct. His is the only honest and true interpretation. Understand
it before you post it.
-Ron Maimon
Avrom Faderman
>In article <1993Aug6.1...@mcs.drexel.edu>, jsm...@mcs.drexel.edu (Justin Smith) writes:
>|> In article <CBB37...@usenet.ucs.indiana.edu> chal...@bronze.ucs.indiana.edu (David Chalmers) writes:
>|> >In article <1993Aug4.1...@sophia.smith.edu> oro...@sophia.smith.edu (Joseph O'Rourke) writes:
>|> >
>|> >>Even though all of Everett's branches are "actual," is there not
>|> >>a sense in which they are possible worlds? Suppose first that macroscopic
>|> >>brain events can be influenced by quantum effects, a big supposition
>|> >
>|> >On the Everett account, neither world is counterfactual -- both are
>|>
>|> This discussion is fascinating because I used to be acquainted with
>|> some philosophers who were trying to use Everett's theory as a way
>|> to give a `rigorous' meaning to `possible'. In other words, a world
>|> is possible if there exists a causal chain of Everett branches connecting
>|> it with our world.
>|>
>|> One of the bizarre questions philosophers posed in this area was
>|>
>|> ``Could Socrates have been a turnip?''
>|>
>|> and these philosophers felt one could rigorously say `No: not only
>|> wasn't Socrates a turnip --- he also COULDN'T have been.'
>|> (This is an example of the bizarre discussions that arise in
>|> the more rarified regions of philosophy.)
>please stop talking about Everett and philosophy in the same breath (I know its
>hard!) ^^^^
>example- the Socrates, turnip dilemma. Yes, Socrates could have been a turnip.
>There is, in quantum gravity, as far as we can see today, an amplitude for any
>process to happen which conserves energy, momentum, angular momentum and charge.
>
>this is because a black hole emits perfectly random radiation, and is its own
>time-reverse. If I can throw socrates into a black hole, I should also be able to
>see socrates come out of a black hole in the Hawking radiation. This is indeed
>possible, but extremely unlikely since Hawking radiation is completely random.
>
>There is an amplitude for a virtual black hole to form and swallow Socrates, and
>reemit a turnip of the same mass charge momentum and angular momentum (a big
>turnip, but a turnip nonetheless) and therefore there is a `world' where
>Socrates becomes a turnip. As a matter of fact, there is a world where anything
>happens, they are just very small measure worlds.
Yes, but would this turnip _be_ Socrates? The main problem I see with
using Everett to answer questions like "could Socrates have been a
turnip" is that all Everett gives us is an internal description of
other worlds--It doesn't necessarily point up identities between those
worlds and this.
So, maybe Everett can tell us if there could have been a turnip that
shared properties X,Y,and Z with Socrates, but the (in my mind) most
interesting question is what (if any) X, Y, and Z would be necessary
to make that turnip _Socrates_, and to answer _this_ question, I'm
afraid we must stick with metaphysics--our physicist friends probably
won't be able to help us very much.
Michael R. Hand
> > If I'm not mistaken, Everett holds that the "branching" worlds are
> > all *actual* ones. On at least some interpretations of modal logic,
> > possible worlds are non-actual.
>
> stop it! Youre making me sick!
Poor guy. Somebody makes a decent (if hesitant) response to a reasonable
question, and it makes Ron sick.
> Whether a world is "Actual" or "non-actual" makes absolutely no dif-
> ference. If you are a pattern of nerve cells and that pattern exists,
> but in a "non-actual~ world, that doesn't stop the world from being
> just as actual to you, the pattern of cells.
Ron seems thinks that the indexical theory of actuality is news, and
that it somehow refutes the earlier posting. Nope to both. (Only the
latter point is *relevant*, of course.)
> Everett doesn't make any assumptions, except for the assumption that
> quantum mechanics is correct. His is the only honest and true inter-
> pretation. Understand it before you post it.
"Understand it before you post it"? Learn something about recent
(i.e. past 25 yrs) metaphysics of modality. Practice what you preach.
B-o} M
-------------------------------------------------------------------
These are things that we shall try and discover.
But these are things we must not take seriously.
-- Samuel Beckett
-------------------------------------------------------------------
Michael Hand (409)845-5660, fax (409)845-0458
Philosophy Dept, Texas A&M Univ, College Station TX 77843-4237, USA
ha...@tamuts.tamu.edu mh...@tamu.edu
Ron Maimon
(grumble)
ok this is a legitimate philosophical question.
However, I call a question legitimate only if the answer `no' would make
me do something different than the answer `yes'. I don't think this question
or related questions qualify.
-Ron Maimon
Ron Maimon
|> rma...@npac.syr.edu (Ron Maimon) writes:
|>
|> > Whether a world is "Actual" or "non-actual" makes absolutely no dif-
|> > ference. If you are a pattern of nerve cells and that pattern exists,
|> > but in a "non-actual~ world, that doesn't stop the world from being
|> > just as actual to you, the pattern of cells.
|>
|> Ron seems thinks that the indexical theory of actuality is news, and
|> that it somehow refutes the earlier posting. Nope to both. (Only the
|> latter point is *relevant*, of course.)
|>
point well taken. I was a bit upset by earlier posts regarding Everett, and I
wrote an undeserved flame. Apologies.
p.s. If anyone can find some way to show that what I said, concerning the matter
of existance relative to your own pattern of cells, is wrong I would be happy to
see it.
-Ron Maimon
Benjamin J. Tilly
av...@Csli.Stanford.EDU (Avrom Faderman) writes:
>
> Yes, but would this turnip _be_ Socrates? The main problem I see with
> using Everett to answer questions like "could Socrates have been a
> turnip" is that all Everett gives us is an internal description of
> other worlds--It doesn't necessarily point up identities between those
> worlds and this.
>
Depends on how you define Socrates.
> So, maybe Everett can tell us if there could have been a turnip that
> shared properties X,Y,and Z with Socrates, but the (in my mind) most
> interesting question is what (if any) X, Y, and Z would be necessary
> to make that turnip _Socrates_, and to answer _this_ question, I'm
> afraid we must stick with metaphysics--our physicist friends probably
> won't be able to help us very much.
>
I agree. What the exact definition of Socrates should be is unlikely to
be of any interest for them. As a matter of fact *I* do not find it to
be of interest. Why are the philosophers talking about it? :-)
Ben Tilly
Avrom Faderman
>In article <1993Aug8.0...@Csli.Stanford.EDU>
>av...@Csli.Stanford.EDU (Avrom Faderman) writes:
>> Yes, but would this turnip _be_ Socrates? The main problem I see with
>> using Everett to answer questions like "could Socrates have been a
>> turnip" is that all Everett gives us is an internal description of
>> other worlds--It doesn't necessarily point up identities between those
>> worlds and this.
>Depends on how you define Socrates.
I agree, but an awful lot of people don't. For example, Kripke (in
_Naming_and_Necessity_) argued that what properties are necessary to
be water has little to do with how we define "water."
"How you define Socrates" is not a trivial question--although
we can make up any definition we want, there will still be the
question of whether this definition is what we _ordinarily_ mean by
"Socrates." Finding out what we _ordinarily_ mean is quite hard. Just
because we know it when we see it doesn't mean we can define it.
>> the (in my mind) most
>> interesting question is what (if any) X, Y, and Z would be necessary
>> to make that turnip _Socrates_, and to answer _this_ question, I'm
>> afraid we must stick with metaphysics--our physicist friends probably
>> won't be able to help us very much.
>I agree. What the exact definition of Socrates should be is unlikely to
>be of any interest for them. As a matter of fact *I* do not find it to
>be of interest. Why are the philosophers talking about it? :-)
It's identity theory. We're trying to figure out what the core of
particular objects are. In general, this is to come up with an
ontology (description of what things exist). Ontology just _is_
interesting to some people (like me). But of course there's a more
immediate question: Why might it be relevant to this group?
Well, suppose we "downloaded" Socrates' brain onto a computer
simulation. Would that simulation _be_ Socrates? (To make this seem
a bit less academic, replace "Socrates" with "you"). A relevant
question if you're considering whether to download your brain and
simultaneously destroy your body in a quest for immortality.
Jonathan Cohen
This becomes interesting as an ontological matter as soon as one works
in a quantified modal logic with identity, for one wants to evaluate
the truth of expressions like:
Nec. (Socrates ~= turnip)
As someone else may have mentioned, a classic source on these and
related problems is Kripke's _Naming and Necessity_. This text
represents one of the most important and first attempts to give a
coherent philosophical interpretation of the quantified modal logics
developed in the sixties by Kripke and others.
--
University of Chicago phone: (312) 955 1792
email: jd...@cs.uchicago.edu
Stan Friesen
|>
|> For example, a common argument against consciousness-as-program claims
|>
|> This argument relies completely on the Copenhagen interpretation
|> (which Everett's theory is supposed to be an alternative to). If
|> Everett is right, the argument simply isn't valid. If he's wrong,
|> it's a much bigger deal (although there still might be some way around
|> it, I can't think of one).
How about: any physical system with certain properties is an
'observer' in the QM sense. For instance, a photographic plate
probably qualifies as an 'observer'. (Note, in this interpretation
the term "observer" is rather a misnomer).
|> > It has
|> >absolutely no relevance to the world. Why? because the world would look the same
|> >with or without it.
|> No agreement on this one. In one case, certain events cause the Wave
|> function to collapse (and therefore have special physical standing);
|> in the other, the wave function never collapses.
In fact, that seems to be the *only* difference.
Otherwise the many-worlds and the Copenhagen interpretation
are the same.
--
sar...@teradata.com (formerly tdatirv!sarima)
or
Stanley...@ElSegundoCA.ncr.com
The peace of God be with you.
Warren G. Anderson
> this is because a black hole emits perfectly random radiation, and is its own
> time-reverse. If I can throw socrates into a black hole, I should also be
> able to see socrates come out of a black hole in the Hawking radiation. This
> is indeed possible, but extremely unlikely since Hawking radiation is
> completely random.
Do you know something the rest of us don't? CPT invariance of black hole
radiation is one of the hottest topics on the market these days. Indications
are that an initial pure state can fall into a black hole and lead, through
Hawking radiation, to a final mixed state. This is commonly known as the
black hole information loss problem. This loss of unitarity is very
disturbing, and there are many people working to find a mechanism by which
this problem might be overcome. No suitable candidate has been adopted yet,
there are certain drawbacks to having only a semi-classical theory at late
times in the evaporation process.
In article <1993Aug7.2...@newstand.syr.edu> rma...@npac.syr.edu (Ron
Maimon) writes:
> Understand it before you post it.
Indeed :-).
--
########################## _`|'_ ##############################################
## Warren G. Anderson |o o| "... for its truth does not matter, and is ##
## Dept. of Physics ( ^ ) unimaginable." -J. Ashbery, The New Spirit ##
## University of Alberta /\-/\ (ande...@fermi.phys.ualberta.ca) ##
Avrom Faderman
>In article <1993Aug6.2...@Csli.Stanford.EDU>, av...@Csli.Stanford.EDU (Avrom Faderman) writes:
>|>
>|> For example, a common argument against consciousness-as-program claims
>|> is that only _conscious_ observers can collapse the wave function, ...
>|>
>|> This argument relies completely on the Copenhagen interpretation
>|> (which Everett's theory is supposed to be an alternative to). If
>|> Everett is right, the argument simply isn't valid.
valid, but it has a false premise. It's wrong, anyway, which is the
important thing.
>|> If he's wrong,
>|> it's a much bigger deal (although there still might be some way around
>|> it, I can't think of one).
>How about: any physical system with certain properties is an
>'observer' in the QM sense. For instance, a photographic plate
>probably qualifies as an 'observer'. (Note, in this interpretation
>the term "observer" is rather a misnomer).
I wonder how a photographic plate would qualify. What does a
photographic plate do on a subatomic level that would collapse the
wave function? Wasn't it Penrose's point (although of course if you
reject the Copenhage interp. this point is groundless) that brains did
something fancy that we didn't yet understand that resulted in wave
functions collapsing? If this were true, this would be a very
materials-based (to use a term from another thread) property of
brains, and I don't see how photographic plates would share it.
I thought that if you put a photographic plate into the box,
Copenhagenists claimed the plate (as well as the cat) would be in a
superposition of states until a conscious observer opened the box up.
Don't ask me what happens if you put a human into the box; I always
thought this would be a good argument against Copenhagen.
>|> No agreement on this one. In one case, certain events cause the Wave
>|> function to collapse (and therefore have special physical standing);
>|> in the other, the wave function never collapses.
>
>In fact, that seems to be the *only* difference.
>Otherwise the many-worlds and the Copenhagen interpretation
>are the same.
Probably. But for ai.philosophers, this is an important difference.
Benjamin J. Tilly
s...@tools3teradata.com (Stan Friesen) writes:
> |> > It has
> |> >absolutely no relevance to the world. Why? because the world would look the same
> |> >with or without it.
> |> No agreement on this one. In one case, certain events cause the Wave
> |> function to collapse (and therefore have special physical standing);
> |> in the other, the wave function never collapses.
>
> In fact, that seems to be the *only* difference.
> Otherwise the many-worlds and the Copenhagen interpretation
> are the same.
>
That is *not* a small difference though. If the Everett interpertation
is wrong then there has to be a collapse at some point. That collapse
should have an explanation. The explanation for that collapse would
have to be some addition to our physical theories. That means that
there is new phsics out there waiting to be discovered that leaves the
very small alone and changes the rules significantly by the time that
it gets to our level. I think that anyone who seriously believes this
should be trying to work out what this new exiting physics is and
trying to find experiments to verify their theories!
All serious suggestions on this topic are welcome.
Ben Tilly
Ron Maimon
|>
|> How about: any physical system with certain properties is an
|> 'observer' in the QM sense. For instance, a photographic plate
|> probably qualifies as an 'observer'. (Note, in this interpretation
|> the term "observer" is rather a misnomer).
|>
This would be just peachy if QM ever predicted collapse through the action of
atoms with other atoms. But that never happens. QM can describe a photographic
plate very well.
|> |> > It has
|> |> >absolutely no relevance to the world. Why? because the world would look the same
|> |> >with or without it.
|> |> No agreement on this one. In one case, certain events cause the Wave
|> |> function to collapse (and therefore have special physical standing);
|> |> in the other, the wave function never collapses.
|>
|> In fact, that seems to be the *only* difference.
|> Otherwise the many-worlds and the Copenhagen interpretation
|> are the same.
|>
and what a difference it is! this is the one contentious point of quantum
mechanics! It causes EPR `paradoxes', Scroedinger's cat `paradoxes',
observer=physical system `paradoxes' ......
-Ron Maimon