Re: Extended Wigner’s Friend

[John Clark]

On Wed, Dec 5, 2018 at 10:57 PM Mason Green  wrote:

*> Ah, yes, multiple histories. Given only what we know now about the
> universe (and not what we “remember from before”, since our memories are
> actually just patterns encoded in our brain at the present moment),*


I've never understood the distinction some people make between many worlds
and many histories, if many worlds is correct then I have a unique history
the one I remember, but I have many different futures. Memories are part of
the universe and so is our subjective sense of the passage of time and that
needs an explanation. Yes the entire universe could have popped into
existence 2 seconds ago complete with memories of me in the second grade
and dinosaur bones in the ground but the simplest explanation is the past
existed.

*> what’s to stop us from thinking that entropy was higher in the past and
> things just spontaneously arranged themselves into the present low-entropy
> state? *


Because there are VASTLY more high-entropy states than low entropy states
(because there are more ways something can be disordered than ordered) so
the probability is overwhelming that the next state will have a higher
entropy than the one you're in now.  But entropy isn't always bad. Maximum
information
, or at least maximum
information that intelligence finds
interesting
,
 seems to be about

midway between maximum and minimum

entropy. Put some cream in a glass coffee cup and then very carefully put
some coffee on top of it. For a short time the 2 fluids will remain
segregated and the

entropy will be low and the information needed to describe it would be low
too, but then tendrils of cream will start to move into the coffee and all
sorts of spirals and other complex
and pretty
patterns will form, the entropy is higher now and the information needed to
describe it is higher
too
, but after that the fluid in the cup will reach a dull uniform color that
is darker than coffee but lighter than cream, the entropy has reached a
maximum but it would take less
interesting
information to describe it.

Another example is smoke from a cigarette in a room with no air currents,
it starts out as a simple smooth laminar flow but then turbulence kicks in
and very complex patterns form, and after that it diffuses into a uniform
featureless
very dull
fog.

*> To go into further detail, creatures who perceived time that way would
> not be able to maintain a sense of personal continuity or selfhood for very
> long,*


When we look at the arrow of time we see it pointing in one direction so we
remember the past but not the future and (if Many Worlds is correct) we
have  one unique past but many different futures; a being that looked at
the arrow of time and saw it pointing in the opposite direction would
remember the future but not the past and have one unique future but many
different pasts, and I don't see why that wouldn't generate a continuity of
selfhood just because it's going in the opposite direction.

*> I’m thinking I might write a story about beings who perceive time as
> parabolic, with their present selves at an entropy minimum: their language
> is structured so that they can only talk about possible pasts and not “the”
> past, and also they have words for all the Second Law-violating reverse
> processes that had to have occurred in the high-entropy majority of their
> possible pasts.To go into further detail, creatures who perceived time that
> way would not be able to maintain a sense of personal continuity or
> selfhood for very long, *


If the arrow of time were reversed you would discover different laws of
thermodynamics. For example you would remember that in the distant future,
that is to say a long way from your "now", perfume molecules "were" (the
most difficult part of time travel or reverse time thought experiments is
the grammar)  evenly distributed throughout the room, and you would
remember that in the more recent future the molecules were only in the
lower right part of the room, and you would remember that in the very
recent future (very close to your "now") all the molecules were confined
inside one small perfume bottle. You would then conclude that entropy
always decreases or remains the same. But as to how the bottle got into
that room in the first place well, you can make educated guesses but
essentially the past is unknowable, only the future is certain.

 John K Clark

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Re: Extended Wigner’s Friend

[Lawrence Crowell]

This result is really not that different from Bell's theorem on the loss of 
classical probability distribution in the violation of inequalities. There 
are Alice and Bob and their helpers, where if Alice gets a tails on a coin 
toss she prepares a state in |-> and if she gets heads she prepares 
1/sqrt{2}(|+> + |->). Now if this state is entangled in an EPR pair (say in 
the singlet state) with Bob, he then reads an output that is either |+> or 
with a .25 probability each a |+> or a |->. The helpers watching this 
situation will report on the coin toss and the states, which will depart 
from Alice and Bob's observations. This means the quantum outcome will 
disagree with the coin toss results of .5 probability head/tails, which is 
a classical expectation used to prepare the quantum states. 

This result does mean that if QM is universally applied then outcome have 
no strict objective basis, and if outcomes are thought of as objective then 
QM is not universally applied. This indicates there is no way QM can be 
made ψ-epistemic or ψ-ontic in a way that gives either consistency of QM 
universally or that there is an objective basis for measurements that is 
not subjective. ψ-epistemic and ψ-ontic interpretations are then in some 
way complementary ways of thinking about QM.

LC

On Monday, December 3, 2018 at 7:15:15 PM UTC-6, Mason Green wrote:
>
>
> There’s a new article in Quanta Magazine (
> https://www.quantamagazine.org/frauchiger-renner-paradox-clarifies-where-our-views-of-reality-go-wrong-20181203/)
>  
> about a thought experiment that poses trouble for certain interpretations 
> of quantum mechanics. 
>
> Specifically it implies that either 1. there are many worlds, 2. quantum 
> mechanics will need to be modified (as in objective collapse theories), or 
> 3. reality is subjective (solipsism?). Exciting stuff! 
>
> -Mason

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Re: Extended Wigner’s Friend

[Mason Green]

To go into further detail, creatures who perceived time that way would not be 
able to maintain a sense of personal continuity or selfhood for very long, 
since they have many future “selves” and past “selves”. So instead, they prefer 
to think of their future and past “selves” as other people more like cousins or 
family. A consequence of this is that they are always changing their names as 
time passes; they are literally becoming different people as time passes 
because each observer-moment is a different person blending into other people. 
“Schizophrenia with a vengeance”, indeed! Definitely a good sci-fi idea.

Thanks for the story idea, guys! I’d never have come up with it without this 
discussion.

-Mason

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Re: Extended Wigner’s Friend

[Mason Green]

Ah, yes, multiple histories. Given only what we know now about the universe 
(and not what we “remember from before”, since our memories are actually just 
patterns encoded in our brain at the present moment), what’s to stop us from 
thinking that entropy was higher in the past and things just spontaneously 
arranged themselves into the present low-entropy state? In other words, the 
second law of thermodynamics might not be true and the arrow of time could be 
more of a parabola with our present selves at the bottom. That ripe banana in 
your hand might have been rotten 6 days ago.

If multiple histories is true, then MOST (by probability amplitude) of the 
universe’s histories are paradoxical in this way, since there are more possible 
pasts with high entropy than there are with low entropy. Furthermore these 
counterintuitive histories might be weird in other ways (for instance, some of 
them might not feature a Big Bang or expanding universe at all, but rather the 
light distribution just fluctuated in such a way as to mimic one). Everything 
we think we know about “the past” might come into doubt if MWI and multiple 
histories are true. I once tried asking this question on Physics Forums but it 
got deleted for being too weird. Apparently they don’t like anything that 
upsets their common sense too much.

Actually I find the idea that the past is not as it seems to be oddly 
fascinating. I’m thinking I might write a story about beings who perceive time 
as parabolic, with their present selves at an entropy minimum: their language 
is structured so that they can only talk about possible pasts and not “the” 
past, and also they have words for all the Second Law-violating reverse 
processes that had to have occurred in the high-entropy majority of their 
possible pasts.

-Mason

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Re: Extended Wigner’s Friend

[Philip Thrift]

On Tuesday, December 4, 2018 at 2:09:06 PM UTC-6, Brent wrote:
>
>
>
> On 12/4/2018 1:02 AM, Philip Thrift wrote: 
> > 
> > Fay Dowker [ https://en.wikipedia.org/wiki/Fay_Dowker ] gives a short 
> > summary of "sum over histories" here (and why she prefers it to other 
> > interpretations). 
> > 
> > [ https://www.youtube.com/watch?v=Rj79kr6ekrI ] 
>
> She says she prefers it to Copenhagen because Copenhagen doesn't give an 
> picture of what happens between preparation and measurement. She says 
> she prefers it to Bohmian QM because it doesn't conflict with 
> relativity.  But she doesn't say anything about other interpretations 
> such as Everett's relative state interpretation. 
>
> Brent 
>



Thank goodness.


- pt 

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Re: Extended Wigner’s Friend

[Brent Meeker]

On 12/4/2018 1:02 AM, Philip Thrift wrote:


Fay Dowker [ https://en.wikipedia.org/wiki/Fay_Dowker ] gives a short 
summary of "sum over histories" here (and why she prefers it to other 
interpretations).


[ https://www.youtube.com/watch?v=Rj79kr6ekrI ]


She says she prefers it to Copenhagen because Copenhagen doesn't give an 
picture of what happens between preparation and measurement. She says 
she prefers it to Bohmian QM because it doesn't conflict with 
relativity.  But she doesn't say anything about other interpretations 
such as Everett's relative state interpretation.


Brent

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Re: Extended Wigner’s Friend

[Bruno Marchal]

> On 4 Dec 2018, at 06:07, Brent Meeker  wrote:
> 
> 
> 
> On 12/3/2018 5:47 PM, Mason Green wrote:
>> Here’s a recent editorial I found in the magazine arguing against 
>> Many-Worlds on the grounds that it denies the reality of experience or the 
>> self. 
>> (https://www.quantamagazine.org/why-the-many-worlds-interpretation-of-quantum-mechanics-has-many-problems-20181018/)
>> 
>> Well, if we don’t want many-worlds or subjectivism, than the only other 
>> option looks like it’d be to modify QM itself. Some form of digital physics 
>> might work, otherwise we could have objective collapse (either random, or 
>> else there’s something/someone outside the universe choosing which path the 
>> universe follows).
> 
> Remember, QM is not compatible with general relativity.  It is often assumed 
> that the problem is finding a quantum theory of spacetime. But the long 
> sought theory may also require some modification of QM or otherwise throw 
> light on the measurement problem.  For example, Penrose's gravitationally 
> induced collapse might work out.

This, at least, postulates explicitly non-mechanism, which makes sense of its 
materialism.

Unfortunately Penrose’s motivation from Gödel is invalid (and can be seen as a 
confusion between []p and []p & p).

I am a priori open to his (non mechanist) theory of gravitation induced 
collapse, except I still don’t make much sense of it (maybe due to my 
incompetence).

Bruno



> 
> Brent
> 
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Re: Extended Wigner’s Friend

[Bruno Marchal]

> On 4 Dec 2018, at 03:24, Stathis Papaioannou  wrote:
> 
> 
> 
> On Tue, 4 Dec 2018 at 12:47, Mason Green  > wrote:
> Here’s a recent editorial I found in the magazine arguing against Many-Worlds 
> on the grounds that it denies the reality of experience or the self. 
> (https://www.quantamagazine.org/why-the-many-worlds-interpretation-of-quantum-mechanics-has-many-problems-20181018/
>  
> )
> 
> Well, if we don’t want many-worlds or subjectivism, than the only other 
> option looks like it’d be to modify QM itself. Some form of digital physics 
> might work, otherwise we could have objective collapse (either random, or 
> else there’s something/someone outside the universe choosing which path the 
> universe follows).
> 
> That article just claims, without explanation, that it would be impossible to 
> have consciousness if you were continually being duplicated. I don't think 
> you should accept this without further thought.

This assumes non-mechanism, which is indeed not much convincing at least as an 
hypothesis, unless they give a precise theory and how to test it. 

Bruno



> 
> -- 
> Stathis Papaioannou
> 
>  
> 
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Re: Extended Wigner’s Friend

[Philip Thrift]

On Monday, December 3, 2018 at 7:47:02 PM UTC-6, Mason Green wrote:
>
> Here’s a recent editorial I found in the magazine arguing against 
> Many-Worlds on the grounds that it denies the reality of experience or the 
> self. (
> https://www.quantamagazine.org/why-the-many-worlds-interpretation-of-quantum-mechanics-has-many-problems-20181018/)
>  
>
>
> Well, if we don’t want many-worlds or subjectivism, than the only other 
> option looks like it’d be to modify QM itself. Some form of digital physics 
> might work, otherwise we could have objective collapse (either random, or 
> else there’s something/someone outside the universe choosing which path the 
> universe follows). 
>
> -Mason



Keep in mind that "multiple histories" is (in a way) the time-reversed view 
of "many worlds":

*In the same way that the many-worlds interpretation regards possible 
futures as having a real existence of their own, the theory of multiple 
histories reverses this in time to regard the many possible past histories 
of a given event as having real existence.*
[ https://en.wikipedia.org/wiki/Multiple_histories ]

Fay Dowker [ https://en.wikipedia.org/wiki/Fay_Dowker ] gives a short 
summary of "sum over histories" here (and why she prefers it to other 
interpretations).

[ https://www.youtube.com/watch?v=Rj79kr6ekrI ]

- pt 

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Re: Extended Wigner’s Friend

[Brent Meeker]

On 12/3/2018 5:47 PM, Mason Green wrote:

Here’s a recent editorial I found in the magazine arguing against Many-Worlds 
on the grounds that it denies the reality of experience or the self. 
(https://www.quantamagazine.org/why-the-many-worlds-interpretation-of-quantum-mechanics-has-many-problems-20181018/)

Well, if we don’t want many-worlds or subjectivism, than the only other option 
looks like it’d be to modify QM itself. Some form of digital physics might 
work, otherwise we could have objective collapse (either random, or else 
there’s something/someone outside the universe choosing which path the universe 
follows).


Remember, QM is not compatible with general relativity.  It is often 
assumed that the problem is finding a quantum theory of spacetime. But 
the long sought theory may also require some modification of QM or 
otherwise throw light on the measurement problem.  For example, 
Penrose's gravitationally induced collapse might work out.


Brent

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Re: Extended Wigner’s Friend

[Brent Meeker]

You should read Scott Aaronson's take:

https://www.scottaaronson.com/blog/?p=3975

Brent

On 12/3/2018 5:15 PM, Mason Green wrote:

There’s a new article in Quanta Magazine 
(https://www.quantamagazine.org/frauchiger-renner-paradox-clarifies-where-our-views-of-reality-go-wrong-20181203/)
 about a thought experiment that poses trouble for certain interpretations of 
quantum mechanics.

Specifically it implies that either 1. there are many worlds, 2. quantum 
mechanics will need to be modified (as in objective collapse theories), or 3. 
reality is subjective (solipsism?). Exciting stuff!

-Mason



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Re: Extended Wigner’s Friend

[Stathis Papaioannou]

On Tue, 4 Dec 2018 at 12:47, Mason Green  wrote:

> Here’s a recent editorial I found in the magazine arguing against
> Many-Worlds on the grounds that it denies the reality of experience or the
> self. (
> https://www.quantamagazine.org/why-the-many-worlds-interpretation-of-quantum-mechanics-has-many-problems-20181018/
> )
>
> Well, if we don’t want many-worlds or subjectivism, than the only other
> option looks like it’d be to modify QM itself. Some form of digital physics
> might work, otherwise we could have objective collapse (either random, or
> else there’s something/someone outside the universe choosing which path the
> universe follows).
>

That article just claims, without explanation, that it would be impossible
to have consciousness if you were continually being duplicated. I don't
think you should accept this without further thought.

-- 
Stathis Papaioannou


Virus-free.
www.avast.com

<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

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Extended Wigner’s Friend

[Mason Green]

Here’s a recent editorial I found in the magazine arguing against Many-Worlds 
on the grounds that it denies the reality of experience or the self. 
(https://www.quantamagazine.org/why-the-many-worlds-interpretation-of-quantum-mechanics-has-many-problems-20181018/)

Well, if we don’t want many-worlds or subjectivism, than the only other option 
looks like it’d be to modify QM itself. Some form of digital physics might 
work, otherwise we could have objective collapse (either random, or else 
there’s something/someone outside the universe choosing which path the universe 
follows).

-Mason

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Extended Wigner’s Friend

[Mason Green]

There’s a new article in Quanta Magazine 
(https://www.quantamagazine.org/frauchiger-renner-paradox-clarifies-where-our-views-of-reality-go-wrong-20181203/)
 about a thought experiment that poses trouble for certain interpretations of 
quantum mechanics.

Specifically it implies that either 1. there are many worlds, 2. quantum 
mechanics will need to be modified (as in objective collapse theories), or 3. 
reality is subjective (solipsism?). Exciting stuff!

-Mason

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