Re: The multiverse is unscientific nonsense??

[Brent Meeker]

On 11/25/2023 12:12 PM, John Clark wrote:



On Fri, Nov 24, 2023 at 5:51 PM Brent Meeker  
wrote:




>> And the best response to my challenge that you could come up
with was:
"/The explanation is in print which is classica/l"



/> Can you tell the difference between the above and "The
explanation is classical and is in print." /


Yes. The print is classical but the explanation is not. I also know 
the difference between the cat is in the hat and the hat is in the cat.


> /I never said there were not explanations using quantum concepts
like Hilbert space and the Born rule. /


Therefore you were never able to do what I challenged you to do, which 
was "Using only classical concepts explain to me how and why the 
Quantum Eraser Experiment works."


/> This started with me pointing out, like Bohr, that all science:
experiments, records, results, theories are necessarily in a
classical world. /


NO.  Records of the results of experiments are written down 
classically, but the theories needed to predict those results must be 
quantum mechanical, and a quantum interpretation is needed to 
understand why those theories are so good at making correct predictions.


/> To say that those theories may postulate quantum world does not
invalidate it./


That depends on whatthe pronoun "it" in the aboverefers to.

  John K Clark    See what's on my new list at Extropolis 

This started with my point that we test, observer, infer, write papers, 
attend conferences, discuss and write down theories, all in a classical 
world.  Everything we know about QM comes from observations, each of 
which is seeing a result, not a superposition of results.  This is the 
basis of the Copenhagen interpretation.  Do you disagree with any of that?


Brent


iyu

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Re: The multiverse is unscientific nonsense??

[John Clark]

On Fri, Nov 24, 2023 at 5:51 PM Brent Meeker  wrote:

>
> >> And the best response to my challenge that you could come up with was:
>> "*The explanation is in print which is classica*l"
>>
>
> * > Can you tell the difference between the above and "The explanation is
> classical and is in print." *
>

Yes. The print is classical but the explanation is not. I also know the
difference between the cat is in the hat and the hat is in the cat.

 > * I never said there were not explanations using quantum concepts like
> Hilbert space and the Born rule. *
>

Therefore you were never able to do what I challenged you to do, which was
"Using only classical concepts explain to me how and why the Quantum Eraser
Experiment works."


> * > This started with me pointing out, like Bohr, that all science:
> experiments, records, results, theories are necessarily in a classical
> world. *
>

NO.  Records of the results of experiments are written down classically,
but the theories needed to predict those results must be quantum
mechanical, and a quantum interpretation is needed to understand why those
theories are so good at making correct predictions.

* > To say that those theories may postulate quantum world does not
> invalidate it.*
>

That depends on what the pronoun "it" in the above refers to.

  John K ClarkSee what's on my new list at  Extropolis

iyu

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Re: The multiverse is unscientific nonsense??

[Lawrence Crowell]

On Wednesday, November 22, 2023 at 6:23:48 AM UTC-6 John Clark wrote:

On Tue, Nov 21, 2023 at 7:45 PM Brent Meeker  wrote:

>> There is plenty of direct evidence that quantum weirdness exists, even 
the father of the Copenhagen Interpretation Niels Bohr admitted that "*Anyone 
who is not shocked by Quantum theory does not understand it *". Something 
must be behind all that strangeness and whatever it is it must be odd, very 
very odd. Yes, many world's idea is ridiculous, but is it ridiculous enough 
to be true? If it's not then something even more ridiculous is. As for the 
Copenhagen interpretation, I don't think it's ridiculous, I think it's 
incoherent, and if you ask 10 adherents what it's saying you'll get 12 
completely different answers, but they all boil down to "*just give up, 
don't even try to figure out what's going on*". But I think one must try.

 

* > I think that's very unfair to Bohr.  His basic observation was that we 
do science in a classical world of necessity.* 


Bohr was a great scientist but I think he was a lousy philosopher.  Bohr 
thought there was a mystical interface between quantum events and conscious 
awareness, some call it the "Heisenberg Cut", but neither Bohr nor 
Heisenberg could explain the mechanism behind this mysterious phenomenon 
nor could they say exactly, or even approximately, where the hell the 
dividing line between the classical world and the quantum world is. By 
contrast Many Worlds has no problem whatsoever explaining the mechanism 
behind the Heisenberg cut or where the dividing line is because the 
Heisenberg cut does not exist and there is no dividing line, everything is 
quantum mechanical including the entire universe.  I think this is the 
reason the Many Worlds interpretation is more popular among cosmologists 
than among scientists in general.


The Heisenberg cut is a weakness with the Copenhagen Interpretation. 
However, all interpretations of QM when chased down their rabbit holes lead 
to nests of problems that fail to close.

LC
 


 > *Only in a classical world can we make measurements and keep records 
that we can agree on.  *


But the Copenhagen adherents can't agree even among themselves what a 
"measurement" is or what a "record" means, but Many Worlds people are in 
agreement, all measurements are a change in a quantum state but a quantum 
change is not necessarily a measurement.   
  

> *when we study the microscopic world we must use quantum mechanics, but 
our instruments must be classical. *


We can pretend our instruments are classical, in our everyday life we can 
pretend that everything is classical, but we've known for nearly a century 
that is just a useful lie we tell ourselves because reality is not 
classical, it is quantum mechanical.   
 

*> You can treat a baseball as a quantum system composed of elementary 
particles; but your measurements on it must still give classical values. *


As I said before, you can live your entire life by pretending that 
classical physics is all there is and in fact billions of people have had 
successful lives doing so, but that doesn't make it true. In theory 
classical measurements can be exact, but quantum measurements cannot be 
even in theory. If we wish to study the fundamental nature of reality we're 
going to need to perform experiments with things when they are in very 
exotic conditions that we will never encounter in everyday life, and when 
we perform these difficult experiments we find the things get weird, very 
very weird, and that demands an explanation. And waving your hands and 
saying there is a Heisenberg cut is not an explanation.


* > Since the development of decoherence theory this boundary can be 
quantified in terms vanishing of cross-terms in a reduced density matrix. *


Forget theory, every time the precision of our quantum *EXPERIMENTS* 
improves the lower limit of this mythical boundary between the classical 
world and the quantum world gets larger, I think it's as large as the 
entire universe.  
 

> *What is left unexplained, in MWI as well as Copenhagen, is the 
instantiation of a random result with probability proportional to the 
diagonal elements of the reduced density matrix.*


If the concept of "probability" is to make any sense and not be paradoxical 
it must be a real number between 0 and 1, and all the probabilities in a 
given situation must add up to exactly 1. Gleason's theorem proved that 
given those restraints, probability can always be expressed by the density 
matrix, that is to say the Born Rule. So the real question is; 
Schrodinger's equation is completely deterministic so why do we need 
probability at all? The Copenhagen people have a range of answers to that 
question, some say Schrodinger's equation needs to be modified by adding a 
random element, but they can't agree on exactly what it should be, others 
say it is improper to even ask that question, but they can't agree among 
themselves exactly why it is improper.  

Re: The multiverse is unscientific nonsense??

[Lawrence Crowell]

On Sunday, November 19, 2023 at 10:26:58 PM UTC-6 Brent Meeker wrote:

There seems to be a conflation between the multiple worlds of Everett and 
the eternal inflation of a multiverse.

Brent


Max Tegmark thinks there is a high level multiverse of this form involving 
MWI. The problem is that we will never be able to know, and MWI is an 
interpretation that is auxiliary to QM and really not necessary. 

LC
 


On 11/19/2023 4:49 PM, Lawrence Crowell wrote:


The real problem is that anything involving the multiverse, say some 
quantum field signature from the earliest quantum cosmology, is stretched 
by inflation into a red-shifted spectrum beyond measurability. The 
multiverse is consistent with inflationary cosmology, which is supported by 
data, but information about the multiverse may never be detected. 

LC 

On Saturday, November 18, 2023 at 5:58:15 AM UTC-6 John Clark wrote:

*I read an article called The multiverse is unscientific nonsense 
 by 
Jacob 
Barandes, a lecturer in physics at Harvard University, and I wrote a letter 
to professor **Barandes commenting on it. He responded with a very polite 
letter saying he read it and appreciated what I said but didn't have time 
to comment further. This is the letter I sent: *
===


*Hello Professor Barandes *

*I read your article The multiverse is unscientific nonsense with interest 
and I have a few comments:*

*Nobody is claiming that the existence of the multiverse is a 
proven fact, but I think the idea needs to be taken seriously because: *

*1) Unlike Bohr's Copenhagen interpretation, the Many Worlds theory is 
clear about what it's saying. *
*2) It is self consistent and conforms with all known experimental 
results. *
*3) It has no need to speculate about new physics as objective wave 
collapse theories like GRW do.*

*4) It doesn't have to explain what consciousness or a measurement is 
because they have nothing to do with it, all it needs is Schrodinger's 
equation.   * 


*I don't see how you can explain counterfactual quantum reasoning and such 
things as the Elitzur–Vaidman bomb tester without making use of many 
worlds. Hugh Everett would say that by having a bomb in a universe we are 
not in explode we can tell if a bomb that is in the branch of the 
multiverse that we are in is a dud or is a live fully functional bomb.  You 
say that many worlds needs to account for probability and that's true, but 
then you say many worlds demands that some worlds have “higher 
probabilities than others" but that is incorrect. According to many worlds 
there is one and only one universe for every quantum state that is not 
forbidden by the laws of physics. So when you flip a coin the universe 
splits many more times than twice because there are a vast number, perhaps 
an infinite number, of places where a coin could land, but you are not 
interested in exactly where the coin lands, you're only interested if it 
lands heads or tails. And we've known for centuries how to obtain a useful 
probability between any two points on the continuous bell curve even though 
the continuous curve is made up of an unaccountably infinite number of 
points, all we need to do is perform a simple integration to figure out 
which part of the bell curve we're most likely on. *

*Yes, that's a lot of worlds, but you shouldn't object that the multiverse 
really couldn't be that big unless you are a stout defender of the idea 
that the universe must be finite, because even if many worlds turns out to 
be untrue the universe could still be infinite and an infinity plus an 
infinity is still the an infinity with the same Aleph number. Even if there 
is only one universe if it's infinite then a finite distance away there 
must be a doppelgänger of you because, although there are a huge number of 
quantum states your body could be in, that number is not infinite, but the 
universe is. * 


*And Occam's razor is about an economy of assumptions not an economy of 
results.  As for the "Tower of assumptions" many worlds is supposed to be 
based on, the only assumption that many worlds makes is that Schrodinger's 
equation means what it says, and it says nothing about the wave function 
collapsing. I would maintain that many worlds is bare-bones no-nonsense 
quantum mechanics with none of the silly bells and whistles that other 
theories stick on that do nothing but get rid of those  pesky other worlds 
that keep cropping up that they personally dislike for some reason. And 
since Everett's time other worlds do seem to keep popping up and in 
completely unrelated fields, such as string theory and inflationary 
cosmology. * 


*You also ask what a “rational observer” is and how they ought to behave, 
and place bets on future events, given their self-locating uncertainty. I 
agree with David Hume who said that "ought" cannot be derived from "is", 
but "ought" can be derived from "want". So if an