Morpheus thanks for the link.Originally Posted by MorpheusSandman
This caught my eye:
•Identity Isn't In Specific Atoms, Three Dialogues on Identity:
Given that there's no such thing as "the same atom", whether you are "the same person" from one time to another can't possibly depend on whether you're made out of the same atoms
it may never try
but when it does it sigh
it is just that
good
it fly
As YesNo states, Schrodinger’s cat constituted a reductio ad absurdum to discredit quantum mechanics as a complete theory. Einstein agreed that this reductio succeeded, and insisted to his dying day that there were hidden variables in QM. Strictly, QM was false, he said, and he came up with a thought experiment intended to demonstrate this point, one that could not be carried out at the time, but was in fact carried out in the early 1980s. More about that in a bit.
Here is the problem. If we say that quantum particles have no properties prior to observation/measurement, then all of our cherished notions of reality are undermined. QM, in the Copenhagen Interpretation, undermines the following notions of reality:
Localism The idea that effects cannot propagate instantaneously across arbitrarily large distances. Einstein’s 1930s thought experiment showed this “spooky action at a distance” and he concluded this was absurd. It also seemed to conflict (though it actually does not) with the speed-of-light limitation on information transfer disclosed by his own relativity theory.
Realism The idea that there is a mind-independent reality. In Copenhagen QM, measuring quantum particles is precisely what gives them properties. Prior to measurement they are at best Aristotelian potentia endowed with potential to “be” something but are not actually anything. This prior measurement state is described mathematically by the wave function, in which the particles are “superposed” in every possible state, none of them actual until measurement. On the moment of measurement, the wave function is said to “collapse” and the particle takes on classical properties. So if Copenhagen QM is right, there is no mind-independent reality and a certain Berkeleyian ideality is introduced into the world.
Determinism QM is inherently indeterministic. One can calculate the probabilities of something happening when an observation is made, but the actual outcome is inherently random.
So if Copenhagen QM is right, the world is non-local, non-real and non-deterministic.
The problem is that we never encounter this in our ordinary every-day world, which seems to be local, real and deterministic. The cat thought experiment was a way to connect the microworld with the macroworld, and to demonstrate that if Copenhagen QM was correct, we can amplify the quantum state into the macrostate.
Skipping the details, the upshot is that if Copenhagen QM is right, we can amplify a state of indeterminate or superposed quantum particles up to a cat. Therefore the cat is in a state of superposition, neither alive nor dead, but a 50/50 probability of both until someone opens the box and looks. When someone opens the box, the cat’s wave function is randomly collapsed, in 50/50 probability, to either alive or dead. Both Schrodinger and Einstein thought this absurd and from this they concluded that QM is an incomplete theory and that there had to be hidden variables that guaranteed a mind-independent, deterministic and local reality.
Einstein’s thought experiment was finally put to actual test in the early 80s, armed with Bell’s Theorem, a mathematical tool developed after Einstein died. The experiment, and all experiments since, confirmed QM, ruled out hidden variables and refuted Einstein. An even stronger conclusion was drawn: even if Quantum Mechanics eventually turns out to be a false theory, no succeeding theory can restore localism and realism to the world. But this fact is contingent on a certain interpretation of QM – viz., Copenhagen.
Two years after Einstein died, Hugh Everett introduced the Many Worlds interpretation of QM. In so doing he completely restored localism, realism and determinism to physics, while keeping quantum mechanics a complete theory and without introducing hidden variables.
Simply put, the cat in the box is both alive and dead, in different versions of reality. When Sam opens the box, one version of Sam is entangled with a dead cat, and a different version of Sam is entangled with a live cat. So there are parallel universes.
Thus there is no wave-function collapse, no randomness, and no mind-dependent reality. Reality is every way that it can be, evolving deterministically according to the Schrodinger wave equation. There is also no spooky action at a distance under Many Worlds QM, because this phenomenon is introduced only by wave function collapse. There is no wave function collapse in MW, which is precisely why there are many worlds: All the potential worlds described by the wave function are real worlds, in their own quantum branch of reality.
Is there any way to decide which is correct, the Copenhagen QM or the Many Worlds QM? It seems that both lead to a description of reality that is hard to accept. Perhaps there is a third option.
My blog: https://frankhubeny.blog/
Yeah, I'd be interested to hear more from you, cioran. What has been done in the last few decades to attempt to test the various QM theories/interpretations? From what little I've read, it seems that MW is the most favored today, but I also know there's a lot of disagreement. I'm curious, though, as to how it would be possible to test such interpretations... if there are "many worlds" out there, where/how does one find the evidence?
"As far as we can discern, the sole purpose of human existence is to kindle a light of meaning in the darkness of mere being." --Carl Gustav Jung
"To absent friends, lost loves, old gods, and the season of mists; and may each and every one of us always give the devil his due." --Neil Gaiman; The Sandman Vol. 4: Season of Mists
"I'm on my way, from misery to happiness today. Uh-huh, uh-huh, uh-huh, uh-huh" --The Proclaimers
There many other options! Try John Gribbin's "Q is for Quantum" for an encyclopaedic breakdown that isn't too painful to read. He's also someone who very much favours the "all these theories are just models" approach that you like YesNo. Gribbin argues that there is no way to decide which interpretation is correct, they all "work", but they are all "hard to accept", given a Newtonian mind set. They all explain all the experiments, and deciding between them awaits someone to come up with ideas for other experiments. It isn't like the GR situation, where all it took was someone to get in a ship to go and observe an eclipse. No one has any (good) idea on how we could begin to design an experiment that would reveal the best interpretation, and there certainly aren't any good theoretical arguments to make one an obvious winner.
I'm trying to make sense out of these interpretations of QM. Here is the article I'm looking at now: http://en.wikipedia.org/wiki/Interpr...ntum_mechanics
It seems that the Many Worlds interpretation is the nuttiest of all: http://en.wikipedia.org/wiki/Many-worlds_interpretation
The obvious objections to it, such as Occam's Razor, conservation of energy, non-local instantaneous copying of the universe every time a photon hits someone's eye, make me think this would better be described as the "mad scientist" interpretation of QM.
My blog: https://frankhubeny.blog/
I'm not educated enough to enter into the discussion but I must say it's been very interesting reading the posts and the relevant links. I doubt I would have ever touched the subject of QM and MW had it not been for this thread so I'm glad that it's here. The idea of parallel universes is so exciting - but of course I'm sure I have watched that played out in a Red Dwarf episode! Now don't anybody curl their lip in contempt at me....
Before sunlight can shine through a window, the blinds must be raised - American Proverb
What about the observer of Schrodingers cat? Can he/she only exist (or not) when observed? Does this imply a so called 'infinite regress?'
I finished the Wikipedia article on Many Worlds.
So far, the Red Dwarf, that Delta40 suggested, or The Big Bang Theory look like the most appropriate universes for MW.
While following various links in the article I clicked onto "superdeterminism" where the experimenter is also completely determined through hidden variables and cannot even choose what questions to ask. I think this might have something to do with suggestions that russellb raised about the observer being part of the Schrodinger cat paradox, but it is getting late.
Last edited by YesNo; 11-12-2012 at 01:06 AM.
My blog: https://frankhubeny.blog/
Not a single one of these objections has the slightest force against the Many Worlds interpretation, and indeed every one of them betrays a total misunderstanding of it. Many Worlds is fully local and deterministic (unlike Copenahagen), and does not contradict the conservation laws. Nor does it contradict Occam's Razor at all. Not that the razor is any kind of law or anything to be paid much attention to in the first place.
Photographic memory applies here.
Just because you put something away and you do not see it does not mean your memory has not stored it.
There is a French saying that goes
''Loin des yeux loin du coeur'' meaning ''away from sight away from heart'' and of course I do not believe that for a second I could not my memory won't let me.
Last edited by cacian; 11-12-2012 at 04:12 AM.
it may never try
but when it does it sigh
it is just that
good
it fly
Al these interpretations (models) have their own supporters, not any of them are 'the truth', all of them 'work'. One model might be easier to use in one context, another in another, that's what working physicists do - use the model that works. They don't try and decide between them to see which is "best". Gribbin suggests the Copenhagen interpretation is not the right model to apply to the puzzle of Schrodinger's cat, but the many worlds interpretation works very well... So in trying to grasp the cat puzzle, I'd look at it through the lens of various interpretations and if one gets you to understanding it, then you can be happy! You then understand it! You don't have to understand it via all interpretations, because all interpretations work.
Many-worlds explains the cat so nicely, to a seven year old, that I recommend using that, and get over the "there's too many worlds!" complaint. I mean, there are too many galaxies, 100 billion when one seemed quite enough... so why not many worlds, why not multiverses... why not?
Why do you have to study this? Why not not just stick to practices? Why not read a nice 19th century novel that does make sense?
For the seven year old, if he hears about that darn cat, and asks about, I'd suggest he look into that after doing GCSE physics and read him Treasure Island... I mean you don't wan to encourage him to be a phycicist do you? There aren't any jobs in physics, and they don't get the girls...
No one understands quantum theory, as Richard Feynman said. All you get are "mad scientist" theories, as YesNo said, that will make you mad if you try and understand them. Of course the equations in this un-understandable theory work, so if you are a physicist you should "shut up and calculate" and gingerly adopt whatever Alice in Wonderland interpretation works for your problem at hand.
I have to study this because it is interesting and intricate at the same time. Reading a book does not generate as much excitement about the real world. Quantum does. It is about the environment the real world.
Lol well actually I do not want the seven year old to hear about the cat. It would upset him to find out an adult thought something so cruel to do a cat as part of a concept experiment.For the seven year old, if he hears about that darn cat, and asks about, I'd suggest he look into that after doing GCSE physics and read him Treasure Island... I mean you don't wan to encourage him to be a phycicist do you? There aren't any jobs in physics, and they don't get the girls...
Although the idea of a physicist is very appealing think of all the theories one can create and can impress the girls with.
I agree that no one understands it and that is the issue. Physics should be about understanding that something is exact.No one understands quantum theory, as Richard Feynman said. All you get are "mad scientist" theories, as YesNo said, that will make you mad if you try and understand them. Of course the equations in this un-understandable theory work, so if you are a physicist you should "shut up and calculate" and gingerly adopt whatever Alice in Wonderland interpretation works for your problem at hand.
I am one to believe there is an answer to everything.
I find for example that one can draw a a three sided linear triangle and yet when you build it you end up with something different.
The triangle one draws on a piece of paper is different from the triangle one builds because of 3d.
The same with a circle.
Again put a dot with a pencil on piece of paper and yet it is totally useless because a dot is irrelevant after that.
It would not be if it was not for the pencil.
it may never try
but when it does it sigh
it is just that
good
it fly
The Trainspotter's guide is about the real world. Is that exciting? Most popular quantum books are as tedious as the Trainspotter's guide, and as perplexing as Joyce. Give me Treasure island anyday, far more exciting... (and understandable...)
Good point - and what about poor Wigner's friend?Lol well actually I do not want the seven year old to hear about the cat. It would upset him to find out an adult thought something so cruel to do a cat as part of a concept experiment.
But uncertainty is built into QM - you can't have exact - ask Mr Heisenberg.I agree that no one understands it and that is the issue. Physics should be about understanding that something is exact.
The triangle on paper is 3d, although the vertical dimension is very small. How can you draw a proper triangle on a piece of paper?The triangle one draws on a piece of paper is different from the triangle one builds because of 3d.
Oh it is not about proper it is about the 'rough idea' like an architect or even a sketecher would do it on a piece paper.The triangle on paper is 3d, although the vertical dimension is very small. How can you draw a proper triangle on a piece of paper?
It is just a rough representation of a triangle the way we were taught at school when we talked arithmetics and theorems.
And so it is just three sides to it with a ruler and so if we cut it then one can see it is never the same copy as the one build for truth.
This is the only inexactness or uncertainty I am able to talk about.
The rest universe and humans are to be exact or at least how I see it.
And there is always an and to the most intriguing of all and that is the dot I mentioned earlier. Now that is uncertainty at its best. I see it and now I don't.
Last edited by cacian; 11-12-2012 at 11:42 AM.
it may never try
but when it does it sigh
it is just that
good
it fly
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