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50 Years of the Multiverse Interpretation
Posted by
Zonk
on Fri Jul 06, 2007 08:16 PM
from the one-of-my-favorite-verses dept.
from the one-of-my-favorite-verses dept.
chinmay7 writes "There is an excellent selection of articles (and quite a few related scientific papers) in a special edition of Nature magazine on interpretations of the multiverse theory. 'Fifty years ago this month Hugh Everett III published his paper proposing a "relative-state formulation of quantum mechanics" — the idea subsequently described as the 'many worlds' or 'multiverse' interpretation. Its impact on science and culture continues. In celebration, a science fiction special edition of Nature on 5 July 2007 explores the symbiosis of science and sf, as exemplified by Everett's hypothesis, its birth, evolution, champions and opponents, in biology, physics, literature and beyond.'
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So in another universe of the multiverse... (Score:2, Funny)
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Who wants to loan me their account at Nature so I can log in?
Re:So in another universe of the multiverse... (Score:5, Funny)
Try one username/password combination at random. At least one of your instances will get in.
Parent
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Can I now borrow your username and password for that universe?
Re:So in another universe of the multiverse... (Score:5, Funny)
Parent
I am embarrassed to say.. (Score:2)
Nothing for you to see here. Please move along. (Score:3, Funny)
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SF (Score:3, Funny)
Wait, no, that's not why. It's because they're the same thing.
Oh, great! (Score:4, Insightful)
Just what we need; the knowledge that there are an infinite amount of dupe posts in the multi-verse.
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Funny thing is, in the almost-this other universe everyone who parties on a Friday night is a geek loser, and social people all post on Slashdot every day.
Now the only thing you gotta do, is devise a machine that lets you two swap the universes.
MWI is cool and all.... (Score:3, Interesting)
Quantum mechanics does weird stuff when you measure it (probability field of position/velocity).
When something is measured, it collapses it... What causes the collapse?
Perhaps consciousness?
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Greg Egan wrote a book [wikipedia.org] on that topic. Aliens were relying on non-collapsed wave functions as a part of their normal life. New instruments like the Hubble Telescope were causing mass genocide in the observable universe, which got some aliens pretty pissed off.
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The premise of encasing the solar system reminds me of a book I read where earth was encased for, IIRC, a similar reason. I just googled around until I found it. It's Spin [wikipedia.org] by Robert Charles Wilson.
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There is no good reason to believe that such a thing exists.
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Re:MWI is cool and all.... (Score:4, Interesting)
Going beyond the semantic issue, the GP seemed to be implying that consciousness is something special, some unknown part of nature.
However, suppose that you ask a person if they are sane. Should you believe their answer? The only means you have to evaluate the experience of your own consciousness is your own consciousness itself. If your consciousness wasn't some supernatural thing but instead was a little program in your brain to fool you into protecting your existence above all else by creating the illusion of being something special and supernatural, you wouldn't be able to tell the difference.
Now consider everything that we know about reality. Does the universe work more like a precise machine or more like some transcendental mystical metaphysical drug hallucination? Consider everything we know about the mechanics of the brain. It is organized a lot like and its components are a lot like a computer. Is this a description of a ghost trap or of a computational device?
The Earth sure does look flat, though, doesn't it?
Parent
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Well, good for you. Of course, your explanation above is the exact equivalent of someone telling me that they believe in God and thumping "the good book", or that they believe in magic. You may belie
Re:MWI is cool and all.... (Score:5, Informative)
Parent
Re:MWI is cool and all.... (Score:5, Funny)
Parent
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But I'd like to know what consists a measurement.
Generally at the quantum level, a measurement or observation is when you bounce a particle (usually a photon) off another particle.
It's similar to how you see things. Light bounces off of a thing, and that light bouncing into your eye is how to observe and measure things. Just lower the scale to a single photon of light (or even a smaller particle) and youre set.
The reason you can't measure all the details of a particle at this level is because when the photon you bounce off it actually hits the particle
Re:MWI is cool and all.... (Score:4, Informative)
The reason you can't measure all the details of a particle at the same time is NOT because photons bounce off of it and disturb it. The reason you can't measure all of the details of a particle at the same time is because that is JUST THE WAY IT IS. It has nothing to do with interference from other particles. There is no "reason" for it. No one knows why it works that way. It's called "complementarity", and it's the fundamental quantum mystery.
Parent
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Rather, all the *possible* outcomes of a quantum measurement do happen: each one in a different universe.
When you measure one particular outcome, that means that you are in the particular universe where you measure that outcome: by definition.
A measurement consists in an event that translates "quantum information" into "classical information": quantum information is very complex
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Re:MWI is cool and all.... (Score:5, Informative)
No in the MWI the wavefunction does NOT collpse. This is the whole point of the MWI, in the Copenhagen interpretation the wave function collapses on a measurement to a single state. In the MWI a measurement splits the world into two different states there is no collpse of the wavefunction.
The Copenhagen interpretation abolishes physical reality and brings in the idealist concept of a conscious observer collapsing the wavefunction. The MWI restores physical reality in quantum mechanics.
Let's take the Schrodinger cat thought experiment: <cat alive|cat dead>
This gives rise to the density matrix:
cat alive ...................... cat alive + cat dead
cat alive - cat dead ..... cat dead
The CI supporters would say the MWI didn't explain why we don't see the off diagonal mixed states. But the modern approach to the measurement problems in MWI uses the concept of decoherence which is the interaction of the isolated quantum states with the macro environment. It has been shown that the mixed states are destroyed by interference when decoherence from interaction with the environment occurs. Thus in this experiment the world is split into two, one where the cat is alive and one where it is dead.
The decoherence approach in conjunction with the MWI abolishes the necessity of observers and restores the independent physical reality abolished the the CI. The proliferation of many worlds is the price we have to pay for physical reality and the unitary evolution of the wavefunction.
Parent
*Interpretation* (Score:3, Informative)
I like SF as much as probably most people here, but I can't see the scientific significance.
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The many-worlds hypothesis does have some serious problems, such as how a universe with probability p and one with probability -p cancel each other out. (The branching would have to happen "after" the cancellation.)
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So, being 'inside' the universe and taking its measurements from the inside only gets us so far. Beyond that, we have theories about the nature of the universe, but they can't be shown to be true or untrue. There are theories that are certainly untrue, but there are al
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No faster-than-light travel, causality, single-valued universe. Pick any two. That'll give you your preferred QM interpretation. (Hint: FTL = CI, backward causality = TI [wikipedia.org], more or less, and multi
Mirror, Mirror (Score:5, Funny)
Personal experience of the Multiverse (Score:3, Interesting)
I've observed many times that I "should have" died. It struck me that, perhaps, I did die in an alternate universe, but I (whatever I "is") continue on in at least one of the multiverses. In those multiverses in which "I" experience the death of a close friend or family member... well... that just is how it goes. But they, too, continue in an instance of the multiverse. Perhaps I do not.
Anyway... "They're coming to take me away, ha ah..."
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I had to look closely to see if you had used the letter J [wikipedia.org]
Re:Personal experience of the Multiverse (Score:5, Interesting)
Luckily he made it out alive. But he suffered severe PTSD for a few years afterwards. He would just be walking to the grocery store and be suddenly struck with the terrifying reality that he wasn't walking to the store at all -- this was the final hallucination of his mind moments before he perished in the apartment fire. Instead of his past flashing before his eyes, this was his mind's final, desperate attempt to comfort itself, by creating a reality where he lived out the rest of his life.
I try not to think about it because it's creepy. If I really start to think about it I get terrified.
Parent
Wanna hear something really disturbing? (Score:2)
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Re:Personal experience of the Multiverse (Score:4, Interesting)
Note that this is not a very exciting kind of immortality. Especially since a goodly number of worldlines coming from here will produce computronium [wikipedia.org]. At least some of which will simulate you, yes you personally for an unspeakable amount of subjective time (possibly infinite if even one non-zero probability path leads to that outcome), during which you will in some cases experience what can only be described as "as close to a literal heaven as you can get", and in other cases "as close to a literal hell as you can get", and the full range of things in between. If Quantum immortality is "true", there are things worse than death, and we will more or less all get to experience them on some worldline.
Note further that it is not meaningful to wish that "you" will end up in one of the good cases; if QI is true, all cases lie in your future equally. "You" will end up in the good and the bad and the inbetween, all at once. Perhaps some people consider this a form of escapism, but it is also fairly horrifying if you follow the implications out beyond "In some very real sense, I can not experience death."
Parent
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Probably the most interesting practical question is what percentage of futures include all our lost family members and f
Shoot (Score:2)
Anyone who knows if they'll be selling this one in other universes?
Old (Score:5, Informative)
It would be nice if scientists, when talking to non-scientists, drafted lively images like this one. IMHO, it would go a long way in bridging the gap between them and "normal" people, who don't think in terms of numbers and mathematical concepts.
Late to the party, but... (Score:2)
All of them?
Take me to the parallel universe... (Score:2)
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Isn't being a physicist enough of a punishment in itself?
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Re:50 year of an untestable hypothesis (Score:4, Insightful)
Sorry, your computer now refuses to work because it no longer obeys quantum mechanics. The electrons are just stuck at the N-P junctions and nothing happens because they're all in a fully defined position with no way of jumping across it at the energy levels they have. Bump the energy up, and they behave classically and just burn their way through without any of the nice semiconductor properties that make computation with them possible.
On the upside, now you'll have a lot more time to tar and feather the quacks who made your nonfunctional computer!
Parent
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Big red button x 6000000000 (Score:2)
But lets assume for argument sake that nobody does. People will quickly learn that nobody will push their button, and nobody will seriously care that others have them. We will be in much the same place we are right now.
That's the problem with the current (and former) arms race. We weren't willing to "push the button" (meaning nuke Russia), and Russia wasn't either. Both countries were reduced to non-nuclear m
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I think the point was that there will be -some- universe where nobody pushes the button---we can ignore the dead non-utopians who did.