Help with correct description of Everettian QM

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Re: Help with correct description of Everettian QM

#21  Postby campermon » May 01, 2016 6:34 pm

DavidMcC wrote:
crank wrote:... My question was about the basic concept behind Everett.

You mean you aren't interested in whether or not it's nonsense?


Prove it.

:thumbup:
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Re: Help with correct description of Everettian QM

#22  Postby crank » May 01, 2016 7:04 pm

You understand Everettian interpretation is not the same as Tegmarks mathematical universe ideas, right? That it appears physicists are moving to Everett, as seen in earlier post by someone? You claim
Neither version is meaningful, because they are both based on Everett's false belief that the entire universe can be described by a single quantum state in the first place. The reality is that QM is inappropriate to large, massive systems.

but the first sentence is just an assertion, and the next is another assertion, a misleading one. Yes, QM is 'inappropriate', but not because it somehow doesn't apply, but because the calculations can't be done. I said this earlier. A shitload of physicists do think the universe is describable by a single state, so what am I to make of your assertion? I'm not a physicist, but I play a lot of their lectures on youtube, and what you say is at odds with what they say.
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Re: Help with correct description of Everettian QM

#23  Postby twistor59 » May 01, 2016 7:31 pm

I'm not a great fan of the Everett interpretation myself, but it is quite popular. Sean Carroll gives some discussion about the (in his opinion wrong) objections here
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Re: Help with correct description of Everettian QM

#24  Postby crank » May 01, 2016 7:41 pm

twistor59 wrote:I'm not a great fan of the Everett interpretation myself, but it is quite popular. Sean Carroll gives some discussion about the (in his opinion wrong) objections here

Your avatar leads me to think you're someone who should know, of course your posts make it clear, but is it not the case that really, no one has a clue at the moment what the correct interpretation of QM is, whatever even that may mean?
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Re: Help with correct description of Everettian QM

#25  Postby Cito di Pense » May 02, 2016 6:32 am

I'm immediately a fan of Carroll's 'acceptance' approach, to the extent that even whether or not it matters to me whether or not the MWI is valid involves a superposition of quantum states. That almost always helps me dispense with philosophy until some more facts come along to collapse the wave function into something I just have to live with.
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Re: Help with correct description of Everettian QM

#26  Postby aban57 » May 02, 2016 11:39 am

This discussion reminds me of one I had a couple times, regarding the multiverse "Hollywood interpretation". The idea was the same, meaning each of our decisions lead to the creation of distinct universes, one for each possible choice we could make. I always laughed at this idea, because to me, it was almost religious self-centeredness. How could our actions and decisions have so much impact on our universe ?
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Re: Help with correct description of Everettian QM

#27  Postby Cito di Pense » May 02, 2016 12:13 pm

aban57 wrote:This discussion reminds me of one I had a couple times, regarding the multiverse "Hollywood interpretation". The idea was the same, meaning each of our decisions lead to the creation of distinct universes, one for each possible choice we could make. I always laughed at this idea, because to me, it was almost religious self-centeredness. How could our actions and decisions have so much impact on our universe ?


You don't have to look at it that way. Think more, "You're a unique and special individual, just like everyone else."
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Re: Help with correct description of Everettian QM

#28  Postby crank » May 02, 2016 12:45 pm

aban57 wrote:This discussion reminds me of one I had a couple times, regarding the multiverse "Hollywood interpretation". The idea was the same, meaning each of our decisions lead to the creation of distinct universes, one for each possible choice we could make. I always laughed at this idea, because to me, it was almost religious self-centeredness. How could our actions and decisions have so much impact on our universe ?

The idea has nothing to say about decisions by anyone, it's about what is going on at the level of quantum interactions, however many of those might be involved in a person coming to some decision, which won't be 'one', the rest of your body will be generating, by wild ass guess of 1000 per cell, or 1017, 'decisions'.

Even if it was something like what you say, saying 'impact our universe' doesn't make any sense, it 'generates' 2 universes that are otherwise identical except for the decision you made, the 'impact' is exactly the same as it would unfold in 'our' non-Everettian universe depending on the choice made. And understand, before you had time for another thought, the number of further branchings would be a vast number I have no idea how to estimate, but we're talking numbers like googols.
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Re: Help with correct description of Everettian QM

#29  Postby DavidMcC » May 02, 2016 12:52 pm

campermon wrote:
DavidMcC wrote:
crank wrote:... My question was about the basic concept behind Everett.

You mean you aren't interested in whether or not it's nonsense?


Prove it.

:thumbup:

Prove what, campermon? Your post does not make sense.
I could guess that you are wanting me to "prove" that MWI is nonsense, right? If so, I have already mentioned the two very different versions of it: one in which the alternate universes exist, and one in which they do not. The latter could be seen as just an interpretation of probability calculations, but the former requires evidence: where are these alternated universes with alternate campermon's, etc? Thus, the burden of proof is not on me, but on the Everett camp.
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Re: Help with correct description of Everettian QM

#30  Postby aban57 » May 02, 2016 12:57 pm

crank wrote:
aban57 wrote:This discussion reminds me of one I had a couple times, regarding the multiverse "Hollywood interpretation". The idea was the same, meaning each of our decisions lead to the creation of distinct universes, one for each possible choice we could make. I always laughed at this idea, because to me, it was almost religious self-centeredness. How could our actions and decisions have so much impact on our universe ?

The idea has nothing to say about decisions by anyone, it's about what is going on at the level of quantum interactions, however many of those might be involved in a person coming to some decision, which won't be 'one', the rest of your body will be generating, by wild ass guess of 1000 per cell, or 1017, 'decisions'.

Even if it was something like what you say, saying 'impact our universe' doesn't make any sense, it 'generates' 2 universes that are otherwise identical except for the decision you made, the 'impact' is exactly the same as it would unfold in 'our' non-Everettian universe depending on the choice made. And understand, before you had time for another thought, the number of further branchings would be a vast number I have no idea how to estimate, but we're talking numbers like googols.


So how does the "universe" choose which choice creates another universe, and which one goes on in the current one ? And how does my decision create an entire new universe, with 7 billion other people in it ?
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Re: Help with correct description of Everettian QM

#31  Postby crank » May 02, 2016 1:57 pm

You missed the whole point of the thread, the universes, one for every possibility of every choice, all exist simultaneously.
The use of 'choices' and 'branching' are really heuristics or some aid in understanding what is going on, the splitting doesn't really occur. The way you've stated the question makes no sense, no universes are created, there isn't a current one, and there isn't a new one. And why keep saying 'my decision'? I explained clearly, it has nothing to do with you making decisions, it's a quantum level event.

Plus, you realize that having 1017 'branchings' generated by shit going on in your body during any given heartbeat makes the issue of billions of people trivial? Billions is 10 to the 9th, your body is causing branching in numbers like 10 to the 17th, this is 100's of millions of multiples of the billions. You're not understanding the vast numbers of universes implied, in less time than you can have a thought, something like googols of universes branch out across the whole universe. [A googol is 10100]The heuristic can be both helpful and confusing, but what I'm saying is that the numbers of quantum decisions in a universe is a vast number, like many googols in a second, each of those make for googols more decisions in the next second. I think you need to think what that means, the billions of people just aren't of any significance whatsoever, none.
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Re: Help with correct description of Everettian QM

#32  Postby aban57 » May 02, 2016 2:14 pm

Sorry I misread your post. I was only referring to the "Hollywood interpretation", not to Everett's, for which I had no clue before I read this topic.
It sounds almost like some movie writer heard to speak about Everett's description, and turned it into what he thought would be a good idea for a sci-fi movie. Still pisses me off everytime I see that in a movie/TV show. Just like the "we use only 10% of our brain" nonsense.
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Re: Help with correct description of Everettian QM

#33  Postby crank » May 02, 2016 2:25 pm

aban57 wrote:Sorry I misread your post. I was only referring to the "Hollywood interpretation", not to Everett's, for which I had no clue before I read this topic.
It sounds almost like some movie writer heard to speak about Everett's description, and turned it into what he thought would be a good idea for a sci-fi movie. Still pisses me off everytime I see that in a movie/TV show. Just like the "we use only 10% of our brain" nonsense.

OK, I'm glad, because it seemed like you were really going off the road of lucidity. And I get the same way about an awful lot in movies, sometimes to the point of distraction. It's them that use only 10% of their brains, the rest of us are smart enough to use it all. Even movies that mostly try to get the science right,and hire someone like Carroll or Krause as advisers, will sacrifice their fidelity for a good scene. One big disgusted peeve for me is the sheer lunacy of a star wars universe where they're still running around with guns going pew pew pew.
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Re: Help with correct description of Everettian QM

#34  Postby aban57 » May 02, 2016 2:40 pm

back on topic, the first thing I thought when I read your post was this :

DavidMcC wrote:[
The reality is that QM is inappropriate to large, massive systems. It is only appropriate for very small, very low mass systems, such as atoms and molecules, unless the temperature is below a critical value. Once the energy difference between states of the whole system becomes less than thermal fluctuations, the model breaks down.


I didn't go deep into the QM field, but I knew that. I'm still trying to figure out how scientists of that level can overlook that. Or am I missing something ? :scratch:
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Re: Help with correct description of Everettian QM

#35  Postby crank » May 02, 2016 3:02 pm

aban57 wrote:back on topic, the first thing I thought when I read your post was this :

DavidMcC wrote:[
The reality is that QM is inappropriate to large, massive systems. It is only appropriate for very small, very low mass systems, such as atoms and molecules, unless the temperature is below a critical value. Once the energy difference between states of the whole system becomes less than thermal fluctuations, the model breaks down.


I didn't go deep into the QM field, but I knew that. I'm still trying to figure out how scientists of that level can overlook that. Or am I missing something ? :scratch:

DavidMcC is way overstating this. QM applies everywhere, it's just not practical at the macroscopic levels. Really more like impossible, there are on the order of 1027 atoms in everyday objects, the equations/solutions needed for fairly simple interactions of a few electrons, photons, protons, etc, can get too intractable very quickly, 1027 particles interacting and forget about it. Newton does quite nicely. But, the macro systems are still obeying QM, it is still the theory underlying pretty much everything, it just won't make nice with relativity. Your smart phone is one of the very few things normal human beings interact with that actually require both theories to work, QM for all the electronics, and GR for the GPS.
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Re: Help with correct description of Everettian QM

#36  Postby twistor59 » May 02, 2016 3:09 pm

crank wrote:
twistor59 wrote:I'm not a great fan of the Everett interpretation myself, but it is quite popular. Sean Carroll gives some discussion about the (in his opinion wrong) objections here

Your avatar leads me to think you're someone who should know, of course your posts make it clear, but is it not the case that really, no one has a clue at the moment what the correct interpretation of QM is, whatever even that may mean?


My understanding at the moment is that pretty much all of the mainstream interpretations give the same predictions for the results of any experiment that you can conceivably do. So as far as experiment is concerned, there's not much to choose between them. I'm fairly pragmatic (an engineer), so what I would mostly care about is getting predictions for the results of repeatable experiments. To do this I wouldn't have to worry about the issues that get people passionate about Everett. It all gets bound up with the issue of what probabilities really mean, and I get confused!
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Re: Help with correct description of Everettian QM

#37  Postby twistor59 » May 02, 2016 3:18 pm

aban57 wrote:This discussion reminds me of one I had a couple times, regarding the multiverse "Hollywood interpretation". The idea was the same, meaning each of our decisions lead to the creation of distinct universes, one for each possible choice we could make. I always laughed at this idea, because to me, it was almost religious self-centeredness. How could our actions and decisions have so much impact on our universe ?


You could always opt for the "Bollywood Interpretation". The music is much more fun. :cheers:
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Re: Help with correct description of Everettian QM

#38  Postby crank » May 02, 2016 7:21 pm

twistor59 wrote:
crank wrote:
twistor59 wrote:I'm not a great fan of the Everett interpretation myself, but it is quite popular. Sean Carroll gives some discussion about the (in his opinion wrong) objections here

Your avatar leads me to think you're someone who should know, of course your posts make it clear, but is it not the case that really, no one has a clue at the moment what the correct interpretation of QM is, whatever even that may mean?


My understanding at the moment is that pretty much all of the mainstream interpretations give the same predictions for the results of any experiment that you can conceivably do. So as far as experiment is concerned, there's not much to choose between them. I'm fairly pragmatic (an engineer), so what I would mostly care about is getting predictions for the results of repeatable experiments. To do this I wouldn't have to worry about the issues that get people passionate about Everett. It all gets bound up with the issue of what probabilities really mean, and I get confused!


I think that's a yes, probably :grin:

But,while you're shutting up and calculating, you're not extremely curious? I'm not knowledgeable enough to be passionate about any of the given choices, but still passionately curious about it all. I would bet most on 'none of the above', that whatever they figure out is going to be weirder than anything they're thinking, and simpler somehow.
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Re: Help with correct description of Everettian QM

#39  Postby twistor59 » May 02, 2016 7:40 pm

crank wrote:
But,while you're shutting up and calculating, you're not extremely curious? I'm not knowledgeable enough to be passionate about any of the given choices, but still passionately curious about it all. I would bet most on 'none of the above', that whatever they figure out is going to be weirder than anything they're thinking, and simpler somehow.


Yes, I do have some curiosity: I imagine the final answer will involve something we don't know about yet. Something to do with spacetime and information maybe? I don't really know! I find trying to understand the parts of physics that are already well established to be challenging enough for the moment. :lol:
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Re: Help with correct description of Everettian QM

#40  Postby DavidMcC » May 03, 2016 4:48 pm

crank wrote:
aban57 wrote:back on topic, the first thing I thought when I read your post was this :

DavidMcC wrote:[
The reality is that QM is inappropriate to large, massive systems. It is only appropriate for very small, very low mass systems, such as atoms and molecules, unless the temperature is below a critical value. Once the energy difference between states of the whole system becomes less than thermal fluctuations, the model breaks down.


I didn't go deep into the QM field, but I knew that. I'm still trying to figure out how scientists of that level can overlook that. Or am I missing something ? :scratch:

DavidMcC is way overstating this. QM applies everywhere, it's just not practical at the macroscopic levels. Really more like impossible, there are on the order of 1027 atoms in everyday objects, the equations/solutions needed for fairly simple interactions of a few electrons, photons, protons, etc, can get too intractable very quickly, 1027 particles interacting and forget about it. Newton does quite nicely. But, the macro systems are still obeying QM, it is still the theory underlying pretty much everything, it just won't make nice with relativity. Your smart phone is one of the very few things normal human beings interact with that actually require both theories to work, QM for all the electronics, and GR for the GPS.

Re the bolded bit: wrong. If the coherence length is shorter than the distance between particles, then no wavefunction applies, and it is a classical system. OK?
EDIT: Also, the coherence length goes down as the mass goes up.
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