Parallel universes make quantum sense?

[Devilin]

Parallel-universes-make-quantum-sense
The Everett, or many-worlds, interpretation
newscientist

? wouldn't this run out off energy extremely quickly

 

[cesiumfrog]

No, energy is irrelevant. The conservation laws you're thinking of obviously apply to macroscopic states individually. Would you claim energy is borrowed (from where?) every time we do a double-slit experiment (putting the photon into a superposition of being in multiple places at once)?

The experts seem to think the problem remaining with many-worlds is something to do with the interpretation of probability. I'm inclined to think the interpretation of probability remains a problem regardless of ones interpretation of QM.

 

[Devilin]

One would assume,that the energy was divided upon the split (but this couldn't happen)
If a particle held a virtually infinite amount of positions in a virtually infinite amount of universes wouldn't this would become problematic once the energy was released from these particles in one of a virtually infinite amount of universes

 

[JesseM]

One would assume,that the energy was divided upon the split (but this couldn't happen)
If a particle held a virtually infinite amount of positions in a virtually infinite amount of universes wouldn't this would become problematic once the energy was released from these particles in one of a virtually infinite amount of universes

There is no definite "split" in the many-worlds interpretation, just a universal superposition evolving continually according to the usual quantum rules. For complex systems like people, my understanding is that decoherence will cause different elements of the superposition to have almost no interference so there's no way for each version to notice the effects of the others in practice, but in theory there is always some small amount of interference so they are never truly isolated, the apparent split is just a subjective consequence of our limited ability to notice these effects. See Why do worlds split? from The Everett FAQ (which also deals with the question of energy conservation in question 22) or What is "A World"? from The Stanford Encyclopedia of Philosophy's entry on the many-worlds interpretation.

 

[quantum123]

This is very interesting:
That multiverse=> QM
Anyone has the original paper?

 

[Devilin]

Thanks for the replies & links

But I still have an issue with the energy

lets see if I can put it another way, I'm fine with superposition & conservation of energy

Thing is this, say you have an atom, a hydrogen atom in a sun, the atom is converted into energy via nuclear fusion, bye-bye atom, this hydrogen atom no-longer exists anywhere

Now as you have a virtual infinite amount of suns in a virtual infinite amount of alternative universes all sharing the same atom's all converting atom's into energy, wouldn't the energy be used up rather quickly, ie finite amount of atoms, divided by an infinite amount of energy extraction

 

[JesseM]

Thanks for the replies & links

But I still have an issue with the energy

lets see if I can put it another way, I'm fine with superposition & conservation of energy

Thing is this, say you have an atom, a hydrogen atom in a sun, the atom is converted into energy via nuclear fusion, bye-bye atom, this hydrogen atom no-longer exists anywhere

Now as you have a virtual infinite amount of suns in a virtual infinite amount of alternative universes all sharing the same atom's all converting atom's into energy, wouldn't the energy be used up rather quickly, ie finite amount of atoms, divided by an infinite amount of energy extraction

Do you understand how superpositions work in quantum mechanics? The fact that one element of the superposition gives up its energy in the form of high-energy photons or something does not somehow rob the other elements of the superposition of their energy, even if we are talking about a superposition of states for a single atom. And you can't confuse the number of actual atoms which are involved in the superposition with the number of distinct elements (eigenstates of whatever variable you're interested in) in the superposition--a single atom can be in a superposition of a huge number of different states. And if you're talking about states with well-defined energies (energy eigenstates), the different states aren't drawing from a common "pool" of energy, each one has its own energy. Conservation of energy in QM just means that the expectation value for energy--the sum of the energy of each state times the probability of that state--doesn't change over time for a closed system that's not receiving energy from outside or giving up energy to the outside.

Make sure you read question 22 of the Everett FAQ:

Q22 Does many-worlds violate conservation of energy?

First, the law conservation of energy is based on observations within each world. All observations within each world are consistent with conservation of energy, therefore energy is conserved.

Second, and more precisely, conservation of energy, in QM, is formulated in terms of weighted averages or expectation values. Conservation of energy is expressed by saying that the time derivative of the expected energy of a closed system vanishes. This statement can be scaled up to include the whole universe. Each world has an approximate energy, but the energy of the total wavefunction, or any subset of, involves summing over each world, weighted with its probability measure. This weighted sum is a constant. So energy is conserved within each world and also across the totality of worlds.

One way of viewing this result - that observed conserved quantities are conserved across the totality of worlds - is to note that new worlds are not created by the action of the wave equation, rather existing worlds are split into successively "thinner" and "thinner" slices, if we view the probability densities as "thickness".

 

[setAI]

The experts seem to think the problem remaining with many-worlds is something to do with the interpretation of probability. I'm inclined to think the interpretation of probability remains a problem regardless of ones interpretation of QM.

this is exactly what Deutsch's press release was about [here is another source btw ] he was announcing that he has shown mathematically that the "bush-like branching structure created by the universe splitting into parallel versions of itself " exactly reproduces the probabilities predicted by the Born rule- which is why Andreas Albrecht said: "This work will go down as one of the most important developments in the history of science"

 

[Demystifier]

this is exactly what Deutsch's press release was about [here is another source btw ] he was announcing that he has shown mathematically that the "bush-like branching structure created by the universe splitting into parallel versions of itself " exactly reproduces the probabilities predicted by the Born rule- which is why Andreas Albrecht said: "This work will go down as one of the most important developments in the history of science"

But can we actually see (on-line if possible) the details of the Deutsch's proof?

 

[setAI]

But can we actually see (on-line if possible) the details of the Deutsch's proof?

we are still waiting for the paper- this was just a press release

 

[Devilin]

Do you understand how superpositions work in quantum mechanics?

Hopefully you can enlighten me, ? how far does the empirical evidence go

 

[JesseM]

Hopefully you can enlighten me, ? how far does the empirical evidence go

This is a pretty big question, since the idea of quantum states being superpositions of eigenstates (the states a system is in when you make a measurement and get a definite answer) is very fundamental, basically any calculation you do in ordinary QM will involve superpositions of eigenstates, and thus every experimental confirmation of QM's predictions would count as a type of empirical evidence for this. For starters you might read http://www.ipod.org.uk/reality/reality_quantum_intro.asp and http://www.ipod.org.uk/reality/reality_quantum_casino.asp of http://www.ipod.org.uk/reality/reality_quantum_intro.asp primer on QM, or you might want to read a book like What Is Quantum Mechanics? which tries to introduce the basic math of QM without textbook-level detail, or the slightly more advanced Structure and Interpretation of Quantum Mechanics...maybe others here could recommend other introductory websites/books.

 

[xantox]

But can we actually see (on-line if possible) the details of the Deutsch's proof?

I'm not sure whether anything new was actually presented at the PI conference, possibly there has been a followup or a refinement. Deutsch-Wallace proofs are presented here http://www.arxiv.org/abs/quant-ph/9906015, here http://arxiv.org/abs/quant-ph/0211104 and here http://arxiv.org/abs/quant-ph/0312157, and also here http://arxiv.org/abs/quant-ph/0412194.

 

[Demystifier]

I'm not sure whether anything new was actually presented at the PI conference, possibly there has been a followup or a refinement. Deutsch-Wallace proofs are presented here http://www.arxiv.org/abs/quant-ph/9906015, here http://arxiv.org/abs/quant-ph/0211104 and here http://arxiv.org/abs/quant-ph/0312157, and also here http://arxiv.org/abs/quant-ph/0412194.

These results have also been criticized. See e.g.
http://lanl.arxiv.org/abs/gr-qc/9703089
http://lanl.arxiv.org/abs/quant-ph/9907024

 

[xantox]

These results have also been criticized. See e.g.
http://lanl.arxiv.org/abs/gr-qc/9703089
http://lanl.arxiv.org/abs/quant-ph/9907024

Indeed, and these objections were later answered by Wallace and Saunders.

 

[Demystifier]

Indeed, and these objections were later answered by Wallace and Saunders.

Indeed. Nevertheless, I believe it is safe to say that neither of the sides presented an absolutely convincing proof. The question is: whose arguments one finds more convincing?

 

[mgelfan]

Parallel-universes-make-quantum-sense
The Everett, or many-worlds, interpretation
newscientist

? wouldn't this run out off energy extremely quickly

MWI interpretation is speculative. Considerations of it can be wonderful exercises -- and if one does these exercises well enough one might even make some money (or a career ) from doing these exercises.

But for most of us I should think that worrying about all the metaphysical mumbo jumbo surrounding quantum theory is pretty much a waste of time? Isn't learning about the real world, and the way that quantum theory is used by physicists doing physics difficult enough?

 

[Demystifier]

Isn't learning about the real world, and the way that quantum theory is used by physicists doing physics difficult enough?

No!

 

[xantox]

Indeed. Nevertheless, I believe it is safe to say that neither of the sides presented an absolutely convincing proof. The question is: whose arguments one finds more convincing?

Yes, there is still no general agreement on the subject. The main difficulty being to decide whether the proof is (subtly) circular, or not.

 

[rewebster]

Indeed. Nevertheless, I believe it is safe to say that neither of the sides presented an absolutely convincing proof. The question is: whose arguments one finds more convincing?

that's quotable (not specifically to Wallace and Saunders, but when I'm thinking about anyone's 'theory')

 

[Viva-Diva]

Sorry to interrupt you scientists, but what does existence of parallel universe means for the lay person like myself?

Now if you again consider the movie "what the bleep do we know" does it all connect now?
Can you now give some attention to what the metaphysicts think?

Thanks,
Viva diva

 

[JesseM]

Sorry to interrupt you scientists, but what does existence of parallel universe means for the lay person like myself?

Well, in theory it means that for any outcome that could have gone differently if certain apparently random quantum events had gone differently--which thanks to the butterfly effect would probably include most events in history and in the lives of individuals--there should be a "world" where the outcome was different, like one where you went to a different school or where the British won the revolutionary war. But in practice, you can't visit these worlds so it doesn't make much difference to your life even if it's fun to think about (although you should consider that any time you take a risk which could lead to disastrous consequences, even if things turn out all right in your world, there's another where some poor version of you or the people around you have to suffer the worst-case consequences, so maybe that would make you less inclined to take such risks out of sympathy!) In any case, the new results discussed on this thread don't actually provide any evidence that the many-worlds interpretation is correct, if the press release is accurate they just solve some internal conceptual problems with the interpretation that were a barrier to some physicists being willing to take it seriously.

Now if you again consider the movie "what the bleep do we know" does it all connect now?

Nah, the many-worlds interpretation totally goes against the "observers can alter reality" thing that movie was promoting, since it dispels the idea of a "collapse of the wavefunction" upon observation which that idea was based on, and treats human observation as no different from other physical interactions. And as I understand it the many-worlds interpretation also removes the idea of a "nonlocal" connection between distant particles which I think the movie may also have been trying to draw metaphysical conclusions from. "What the Bleep" should not be taken too seriously as a guide to quantum physics, see here, here, http://dir.salon.com/story/ent/feature/2004/09/16/bleep/index.html and here for criticisms from a scientific point of view.

 

[ShadowWorks]

Lets say that somebody went back in time 100 no 1000 years and did a lot of messing around with time.

Come back to the world today and its a very different place today, ok we all get that.

Well so what.

Its only made a difference on this bubble of a planet, it has not changed a single thing in this solar system or Galaxy so I guess in the grand scale of things it would not change anything.

What is the problem?

 

[JesseM]

Lets say that somebody went back in time 100 no 1000 years and did a lot of messing around with time.

Come back to the world today and its a very different place today, ok we all get that.

Well so what.

Its only made a difference on this bubble of a planet, it has not changed a single thing in this solar system or Galaxy so I guess in the grand scale of things it would not change anything.

What is the problem?

Actually the many-worlds interpretation doesn't have anything specifically to do with time travel, it's basically just a consequence of trying to make the laws of quantum mechanics as simple as possible (avoiding the need for wavefunction collapse). David Deutsch is one many-worlds advocate who thinks if time travel were possible, it would take you to a different world as you describe, but other many-worlds advocates would say either that time travel is impossible or that you would always stay in the same history you started from, it would be impossible to "change" anything.

 

[Viva-Diva]

Nah, the many-worlds interpretation totally goes against the "observers can alter reality" thing that movie was promoting, since it dispels the idea of a "collapse of the wavefunction" upon observation which that idea was based on, and treats human observation as no different from other physical interactions. And as I understand it the many-worlds interpretation also removes the idea of a "nonlocal" connection between distant particles which I think the movie may also have been trying to draw metaphysical conclusions from. "What the Bleep" should not be taken too seriously as a guide to quantum physics, see here, here, http://dir.salon.com/story/ent/feature/2004/09/16/bleep/index.html and here for criticisms from a scientific point of view.

All said and done, I have been able to attract small and big things into my life just by changing my thinking. It is so spooky and works like magic. I have a scientific rational mind too, but I tried this only when I had hit rock bottom in my life. Thats when I said, well since nothing is working let me try this metaphysics thing. And lo and behold, it worked!
I don't know the reason behind it. I don't even know if any science is involved in this phenomenon. But it worked for me, so I am not complaining :-)

 

[ShadowWorks]

All said and done, I have been able to attract small and big things into my life just by changing my thinking. It is so spooky and works like magic. I have a scientific rational mind too, but I tried this only when I had hit rock bottom in my life. Thats when I said, well since nothing is working let me try this metaphysics thing. And lo and behold, it worked!
I don't know the reason behind it. I don't even know if any science is involved in this phenomenon. But it worked for me, so I am not complaining :-)

Your talking about the power of attraction or prayer?

Will there is another reason why they work and its nothing magical, its subconscious programming and its fair enough because I know it works and I am not even religious.

 

[Viva-Diva]

Your talking about the power of attraction or prayer?

Will there is another reason why they work and its nothing magical, its subconscious programming and its fair enough because I know it works and I am not even religious.

Thanks Shadow Works That was really nice coming from a scientist like you. I am happy

What in your opinion is subconscious programming and why do you think it work for you?

Thanks,
Viva-Diva

 

[vanesch]

Sorry to interrupt you scientists, but what does existence of parallel universe means for the lay person like myself?

Nothing at all. If the theory is well set up, it shouldn't (most of the time) make any difference at all.

 

[vanesch]

(although you should consider that any time you take a risk which could lead to disastrous consequences, even if things turn out all right in your world, there's another where some poor version of you or the people around you have to suffer the worst-case consequences, so maybe that would make you less inclined to take such risks out of sympathy!)

In fact, and that's where it is fun to read some papers by Deutsch, although I sometimes think he's making too much fuzz about it, the existence or not of many worlds shouldn't make any difference to a rational decider. If that rational decider makes the balance of "gain versus cost" for a certain action, then there will be more gain, on average, over the different worlds than that there will be costs. Ok, in some "worlds" the costs will be higher, but these worlds are less probable.

You cannot be "compassionate" about the slightest "world" given that there are miriads of terrible things that happen with very high improbability in that case. As a way of speaking, there's always a world somewhere where (bad luck, really low probability) all the air molecules tunnel out of the room where you are sitting and you die asphixiated.

So you better optimize for the "big" worlds (big in Hilbert norm), and that comes down to make rational decisions.

 

[JesseM]

In fact, and that's where it is fun to read some papers by Deutsch, although I sometimes think he's making too much fuzz about it, the existence or not of many worlds shouldn't make any difference to a rational decider. If that rational decider makes the balance of "gain versus cost" for a certain action, then there will be more gain, on average, over the different worlds than that there will be costs. Ok, in some "worlds" the costs will be higher, but these worlds are less probable.

You cannot be "compassionate" about the slightest "world" given that there are miriads of terrible things that happen with very high improbability in that case. As a way of speaking, there's always a world somewhere where (bad luck, really low probability) all the air molecules tunnel out of the room where you are sitting and you die asphixiated.

So you better optimize for the "big" worlds (big in Hilbert norm), and that comes down to make rational decisions.

Well, a hypothetical "compassionate" person might be more worried about minimizing the number of worlds where there was a "cost" (pain) as opposed to maximizing the number of worlds where there was a "gain" (pleasure)...it's true there will always be some worlds where terrible things happen, but you can attempt to minimize them with your actions. I'm not saying this is the most rational strategy, but it might be preferred by some people.

 

[vanesch]

it's true there will always be some worlds where terrible things happen, but you can attempt to minimize them with your actions.

... and then another you in another world will take exactly the opposite attitude, so all pain for nothing...

 

[JesseM]

... and then another you in another world will take exactly the opposite attitude, so all pain for nothing...

That would be an argument for moral nihilism! Just because there is some world where you become a serial killer that doesn't mean you might as well do it here, since after all your decisions are shaped by personality and beliefs and these things make some actions far more likely than others. David Deutsch expresses his attitude towards morality in the context of the MWI http://www.kurzweilai.net/articles/art0268.html when he says "By making good choices, doing the right thing, we thicken the stack of universes in which versions of us live reasonable lives. When you succeed, all the copies of you who made the same decision succeed too. What you do for the better increases the portion of the multiverse where good things happen."

 

[vanesch]

That would be an argument for moral nihilism! Just because there is some world where you become a serial killer that doesn't mean you might as well do it here,

We're drifting away here, but no. Would you like to live the (observed) life of a serial killer or not ? If you think it is a good thing, then be a serial killer ; if you don't like it, then don't be one. If you do what you think is good for YOU (the copy you happen to be), then it will also be "good" for a sizable fraction of worlds. If you think it is not good for you, then you should try to avoid it, and it will then also be avoided in a serious fraction of worlds. As such, it really doesn't matter whether there are copies around or not. You take the risks, and you do the things of which you expect (in the statistical sense) to bring you benefit, and then it will bring benefit to the larger portion of worlds in which you have copies.

If you want to increase the size of the worlds where you, according to one or another standard, are making benefits, and you want to minimize the size of the worlds where you will suffer loss, then you simply have to behave the way you'd behave in a mono-universe world with probabilistic laws, and try to optimize the statistically expected benefit for yourself (using whatever criterium you like).

As such, the existence or not of other universes doesn't matter at all. And you're really not "responsable" for what might happen to your copies in other worlds, as in the largest part of them, you don't even exist.

 

[JesseM]

We're drifting away here, but no. Would you like to live the (observed) life of a serial killer or not ? If you think it is a good thing, then be a serial killer ; if you don't like it, then don't be one.

So you think the effect of my actions on others is irrelevant? (and yes, this is drifting from the main thread topic, maybe it'd be better if the posts on morality and the MWI were split off and moved to the philosophy forum...) If so I'd disagree, whatever decisions now influence the total number of copies stemming from this moment, and can influence the number of copies of people around me who are affected positively or negatively by my choices. This is exactly David Deutsch's argument, as I understood it.

If you want to increase the size of the worlds where you, according to one or another standard, are making benefits, and you want to minimize the size of the worlds where you will suffer loss, then you simply have to behave the way you'd behave in a mono-universe world with probabilistic laws, and try to optimize the statistically expected benefit for yourself (using whatever criterium you like).

It's true that if you're most concerned with avoiding causing suffering, then even in a single probabilistic universe you should avoid taking risks which could lead to such suffering, so for a perfectly rational being the existence or nonexistence of other worlds shouldn't affect their moral choices. Still, the real existence of other worlds where a particular risk--say, not wearing a seatbelt on one car trip--leads to such suffering might make the issue a little more emotionally vivid for some people, and encourage them to actually try to live up to their moral standard at all times, which we as not-perfectly-rational-beings have trouble doing.

 

[vanesch]

So you think the effect of my actions on others is irrelevant?

In as far as those others are purely hypothetical, and there's no chance for you to ever observe any effect of your goodness or your evil on them ? My personal stance on that is: couldn't care less! As a cure to this kind of considerations, take on a solipsist view, which is also totally compatible with quantum theory: there are no others! Do you think that the effect of your actions on your own figments of imagination have any importance - in as far as they don't influence in any way the further experiences you may live ?

So let us not push things too far. The MWI view on quantum mechanics is a way of giving "ontological" (and hence hypothetical) substance to some formulas written on paper which work very well in the lab (quantum mechanics) in order for us humans to grasp a bit better how this formal machinery works. This is a far cry from having moral considerations for these "mental pictures" ! After all, we don't know what will be the next physical theory, and what "ontological" pictures its formalism will eventually suggest.