Many Worlds Theory: What is it & is it True?

[pallidin]

Greetings forum experts.

What is the Many Worlds theory? And, is there any evidence to suggest that it is wholly or partially correct?

Thanks

 

[UltanByrne]

Scientific American Cover Feature
May 2003 = Must read for you. (Plus check out my recent post at Mkaku.org's forums (hosted by this site) in the Theory of everything Forum).

Ultan

 

[pallidin]

Thanks. I will do that. Appreciate the direction.

 

[UltanByrne]

You bet!
Glad I could help...


Ultan

 

[Mk]

"Many physicists tried to explain the equations, Gordan said. each explanation failed for one reason or another. Then in 1957, a physicist named Hugh Everett proposed a daring new explanation. Everett claimed that our universe was one of an infinite number of universes existing side by side. each of these universes was constantly splitting. Everett called thsi the MANY WORLDS interpretation of quantum mechanics. His explination was consistant with the quantum equations, but physicists found it hard to accept though no one has ever shown it wrong. Everett had no patience with his colleages' objections. He insisted it was true whether you liked it or not.

Gordan took out a piece of paper and started drawing. Very simple experiment, been done for two hundred years. Set up two walls one in front of another, with the first wall having a single verticle slit in it

Now you shine a light at the slit. On the wall behind, you'll see a white line from light coming in through the slit.

Gordan continued to sketch, Now, say insted of one slit you have two. Shine a light, and on the wall you see-

Two vertical lines.

No, You'll see 5 lines of light and 6 bars of wall going black, white, black, white, black, white, black, white, black, white, black.

If you shine your light through four slits you get half as many bars as before, because every other bar goes black.

(yeah I still don't get it)

The light passing through the slits acts like two waves that overlap. In some places they add to each other and some places the cancel each other out. That makes a patern of alternating light and dark on the wall. What'w wrong with this is that this is a 200 year old explination, but since Einstein, we know that light consists of photons. Photons couldn't make this patern

Particles aren't simple as the way you have described them. Paricles can interfere with one another. In this case, the photons in the beam of light are interfering with one another to produce the same patern.

That seems logical, after all a beam of light is zillions of photons. It's not hard to imagine they world interact in some fashion. Nuh Uhh. One way to find out if that is true is to make a beam of light so weak only one photon comes out at a time, and put very sensetive detectors, so sensitive they can sense one photon. Now, there can't be any interaction with other photons. So the photons come through, one at a time. The detectors record where the photons land. What we see, is that the individual photons land only in certain places and never others. They only land where the bars of light were on the wall. They behave like they did in the beam of light. They are coming in one at a time. There are no photons to interere with them. Yet something still is interfering with them because they are making the usual interference pattern. So: What is interfering with a single photon. It has to be other photons , but where are they? We have detectors and they don't detect any photons. So where are they?

What he is saying is that single photon interference proves that reality is much greater that just what we see in our universe.The interference is happening, but we can't see any cause for it in our universe. Therefore, the interfering photons must be in other universes. That proves other universes exist. Sometimes they interfere with our universe.

Femember, within the multiverse the universes are constantly splitting which means that many other universes are similar to ours. And the similar ones interact. When we make a beam of light in our universe, beams of light are simultaneously made in many similar universes and the photons from those other universes."

The experiment in the passage has been done many times over the hundreds of years. All that was true, I believe it.

 

[slyboy]

Problems with many worlds

OK, here is a brief summary of the main reasons why many worlds has not been univerally accepted by physicists. I do not mean to suggest that these problems are not resolvable in the interpretation and indeed many attempts have been made. Nevertheless, the situation is not quite a simple as it is presented in popular accounts of the theory?

1) Where does the probability rule come from? If all possible universes exist in the wavefunction then why do we experience the outcomes of experiments according to the standard QM probability rule (Born's rule)?

2) Why does the universe split according to the basis in which we choose to measure in our experiments? In standard QM, there is nothing special about a particular basis, so this problem seems to indicate a priveliged role for measurements, which many worlds theorists are keen to remove from the theory?

3) In classical physics there is nothing to rule out that all possible universes exist, as in the many worlds interpretation. However, we are likely to regard this statement as an empty one, since it would have no effect on the physics we can do here in this universe. How does the many-worlds theory differ from this empty statement?

 

[benzun_1999]

Wierd thing

The weird thing about multiple world theory is that everything that could hppen in a second really happens in each of the world.
i read a book that claimed that time travel is possible using the multiple world theory. as there are chances of worlds which are still in 14th centuary.

-benzun

 

[LURCH]

I have allways has one major problem with the Everret Interpretation, it is alluded to in point #1 of Slyboy's post. The first rule of the Many Worlds view is that events in one universe cannot have an effect on events in another. That is why when we perform the "Schrodinger's cat" experiment, we do not open the box and see two cats; one dead and one alive.

The Everett Interpretation is an attempt to explain experimental results seen and measured many times by people in this universe. The dark and light bands produced by the double slit experiment have been measured by equipment, and seen by the naked eye. This proves that they cannot be the effect of some cause that is outside our universe.

 

[Argo]

I am very interested in the subject of other universes. I am currently reading timeline which has to do with quantum mechanics and w.e. So i thought id check up on it. I was also wondering if it is possible to make a light faint enough so that only one atom passes through at the time.

 

[UltanByrne]

I was also wondering if it is possible to make a light faint enough so that only one atom passes through at the time

I Don't want to look for the details of a particular experiment that did that, I'm pretty sure it has been done, regardless, I assume that your related question is whether the interference pattern would still show up if only one photon waws emited at a time... Yes it would, each 'atom' of light interferes with itself (as difficult as that may be to imagine)..

Ultan

 

[roy5995]

What would be some consequences of the many world theory?

Why is this theory so hard to believe?
I know that slyboy had some points, but can you explain them again? I didn't really understand what was meant.

 

[slyboy]

Problems with many worlds (at great lenght)

What would be some consequences of the many world theory?

Strictly speaking there are no 'consequences' of the many world theory that aren't given by the standard quantum formalism. We simply have to judge whether it is a simpler or more elegant interpretation of QM. Many interpretations contain features that are hard for physicists to swallow. In the case of many worlds, it is the vast multiplicity of seemingly unobservable universes. The interpretation has to provide significant benefits in clarity if we are going to accept this.

Having said this, many-worlds has proven to be useful in that the development of the first interesting quantum algorithm was an attempt by David Deutsch to show that many worlds must be true. We don't need many worlds to understand the algorithm, but this highlights how a diversity of approaches to QM can yield real results.

Why is this theory so hard to believe?

I don't think it is hard to believe; no more so than many of the other interpretations of QM. Some physicists believe that it is obviously the only way to interpret QM, notably David Deutsch. Many in the Quantum Computing community seem to agree on some level, but there is nowhere near universal acceptance amongst physicists as a whole.

I know that slyboy had some points, but can you explain them again? I didn't really understand what was meant.

OK, here is an attempt to explain them as simply as possible.

1) Probability rule: Many worlds says that whenever a quantum decision is made (for simplicity let's say that there are always two possible choices) the universe splits into two universes. For example, one where a particle goes to the left and one where it goes to the right.

However, QM predicts not only the possible alternatives, but also a probability associated to it. For example, there might be a 75% probability of the particle going left and a 25% probability of going right. How do we account for this if there are only two universes?

One way of doing this would be to say there are actually 3 universes where the particle goes left and 1 where it goes right. The probabilities are then given by the relative number of universes corresponding to each choice. This goes beyond the standard many-worlds approach originally proposed by Everett.

The problem with doing this is that the probabilities could conceivably be any number you like, so we might need a continuous infinity of universes for each quantum decision.

Other alternatives for getting quantum probabilities from many-worlds have been proposed, notably a decision theoretical approach by Deutsch. However, these also have their own problems.

2) The basis problem (this one is a bit more technical I'm afraid)

Imagine that we have a detector that tells us whether a particle goes left or right and there is a 50/50 chance of each possibility. One possible wavefunction for this would be:

|particle left>|detector left> + |particle right>|detector right>

Many worlds says that the two terms in this wavefunction represent a splitting across two different universes. However, in QM there is no special significance to this decomposition and we might equally well write:

(|particle left> + |particle right>)(|detector left> + |detector right>) + (|particle left> - |particle right>)(|detector left> - |detector right>)

This could be interpreted in a many worlds fasion by saying that we have two universes each of which has a different superposition for the particle and for the detector.

This may seem arbitrary, but it is not as stupid as it seems. One example that highlights this is the spin states of particles. In this case, (|left> + |right>) is often the same as the state |up>.

Many worlds therefore has to provide an explanation of why one possible splitting occurs and not any other. Attempts to do this are usually based on decoherence, which is to do with the fact that the detector is a macroscopic object and thus its |left> and |right> states couple to the world differently. These explanations are not very convincing to me at the moment.

3) My third problem is not really that serious on a technical level. I'm just saying that we could describe classical physics in the same way as the many-worlds interpretation of QM. The fact is that we don't, because there are no benefits to introducing a multiplicity of universes in this case. Is the phenomenon of quantum interference really any more of a reason to postulate all these extra universes? I don't think so, but it would be a boring world if we all agreed.

 

[Phantom]

can anyone explain the device that is used to emit just one photon?

bet you can't eat just one. First, let me just be up front by disclosing that I have a huge problem with the efficacy of these interferometry models. The polarisers, the material in the instrument, the light emmitters, the detectors...all of it introducing unknown and in many cases, unmeasurable effects on particle collisions.

Its clear to me that these experiments have been put together with significant flaws for the last 30 years. Just because you only detect one photon does NOT mean that only one was emitted. And there is no way to have two detectors for the same particle. you would never know if there were originally two photons and one you never got or just the one, experimentally it is the same result and there is a major flaw in the great interference experiment. Even if you had two detectors for the same particle, you would never know if it was functional when the particle arrived.

This is a fundamental flaw of fourth order interferometry and also a result of reducing the real world to theoreticals again and again until it is assumed that the approximation is "close enough". Which is appallingly sloppy science for a group of people who are very concerned that their theories be nice and tidy.

In all of these experiments, there could be interfering particles which are not photons. There are also problems on the detector end of the apparatus. Measured resolution of one photon does NOT mean that every photon will be detected. It simply means that a photon was detected, not that all photons were detected. They come up with this equipment based on a timing scheme in which unless more than one photon is imaged during a certain interval after the laser being fired, it is assumed that there must have been no other photons. How would you know,for example, if your detector had a flaw that prevented a second late particle from being recorded if it arrived within a certain resolution period of the detector material? You wouldnt.

This is analagous to getting a letter in the mail and assuming that I sent you only one letter. Perhaps one was lost in transit, or it was delivered but I simply overlooked it.

Also consider the real world experiment of shining even coherent monochromatic light at a slit. Usually people talk about decoherence in the instrument. But the slit media itself ruins the integrity of coherence. Photons bounce off the edges of the solid material, refracting and reflecting every which way, because as everyone knows, there are no perfectly homogenous surface materials and anything three dimensional that has an edge is going to have protrusions at the atomic if not molecular levels. You might start with the best light you think you can attenuate, but you are going to get diffraction or diffusion patterns simply because you have imperfect surfaces on the edges of the slit. Of course there are interference patterns from this. This is classical EM; you don't need QT to predict the banded shadowing.

So who is to say that you are not simply seeing the results of an imperfect experiment? Single photon interference is quite simply an untestable theory. Unfortunately much of QT has been focussed on interpreting 3 decades of flawed data but no one has ever been able to repair this experiment. The Hong-Ou-Mandel device introduces the same macroscopic flaws as every other interferometer does. Wasting all this time obsessing over SPI is simply mental masturbatiion and an impediment to understanding the paradoxes of QT.

The fact that theorists have now come up with the multi-verse to explain what they see as quantum behavior of entangled pairs is completely at odds with Quantum Teleportation. Does anyone see the inconsistency here? Why would a separated sister particle change its spin in our universe when according to the multi-verse, its changing there? What would happen to our particle if someone in the multiverse changed their particle at the same time? I don't like the implications for symmetry here...some particles are symmetrical here,others in the multi-verse? That makes no sense to me at all.

I think the Many Worlds theory stinks. Its far too elaborate of a description to meet the test of Occams Razor. Why go to these elaborate lengths simply to chase down problems in QT? Let's start with the pesky photon and find out what's really going on there before we start adding 26 dimensions to the theory.

 

[McQueen]

No one can doubt that the many worlds theory exists. Every time we sit down at our computers there is the possibility of entering a realm of infinite possibilities. Yet from which direction do we approach this "reality" is it from our perceptions of the world as we see it (i.e physics ) or is it from a completely different perspective (i.e., that as we imagine it. On this question , I feel , rests the whole of the future of physics, and of our future.

 

[graffix]

Hello All:
For those that believe in this theory, I am curious: What are the limitations of the many worlds theory? Infinite universes are spawning as I type this because I am sitting here typing instead of getting a cup of water or going out. So many universes, in fact, that it almost makes sense to ask what isn't possible? If we can't narrow it down this way, then the theory simply says that anything is possible. Can your limitations(of new universes) stop my immortality from happening (always wondered about the quantum immortality deal)?
*I don't have a stand on whether I believe it or not.. just very curious!

 

[Ontoplankton]

Originally posted by slyboy
Strictly speaking there are no 'consequences' of the many world theory that aren't given by the standard quantum formalism.

I'm not sure; what about Deutsch's quantum AI thought experiment, or approaches such as this?

1) Probability rule:

(...)

Other alternatives for getting quantum probabilities from many-worlds have been proposed, notably a decision theoretical approach by Deutsch. However, these also have their own problems.

What problems are these? (This is a nonrhetorical question, i.e. I'm not implying there aren't any problems.) Are there major problems that haven't been clarified by e.g. Wallace?

Many worlds therefore has to provide an explanation of why one possible splitting occurs and not any other. Attempts to do this are usually based on decoherence, which is to do with the fact that the detector is a macroscopic object and thus its |left> and |right> states couple to the world differently. These explanations are not very convincing to me at the moment.

What about approaches such as this?

Is the phenomenon of quantum interference really any more of a reason to postulate all these extra universes? I don't think so, but it would be a boring world if we all agreed.

An orthodox Everettist might say that he's not the one postulating universes, you're the one postulating them away. I'm inclined to agree with this: unless it's necessary to augment the Everett interpretation with extra structures (a fundamental probability measure, or something), it seems to me to be clearly simpler than other interpretations. It claims there is more stuff, but the universe doesn't seem to care about minimizing stuff, it seems to care about being simple (i.e. easy to specify).

I don't understand enough to make a firm judgement on the probability and preferred basis issues (which is why I'm only a tentative "believer") but Occam is a really awful argument against many-worlds. If that's what Occam means, you might as well use it as an argument for solipsism or geocentrism.

Also bad arguments are those of the form "many-worlds has no observational consequences, so it sucks", or even "many-worlds is not falsifiable, so it's false". These apply equally well to all other interpretations, which is why it's a philosophical issue. If the existence of many worlds is untestable, then so is the existence of only one world.

 

[slyboy]

I'm not sure; what about Deutsch's quantum AI thought experiment, or approaches such as this?

I'm not too familiar with these experiments, but I have seen an argument by Deutsch which says that many-worlds predicts that you could recohere the universes with sufficiently advanced technology. This might invalidate some interpretations, but it seems clear to me that any interpretation that says QM is in principle applicaple to any system of any size has no problems with this.

What problems are these? (This is a nonrhetorical question, i.e. I'm not implying there aren't any problems.) Are there major problems that haven't been clarified by e.g. Wallace?

There are approaches one can take to these problems. My point was that the arguments have not been universally accepted by physicists, mainly because most of them don't read articles by people like Wallace. This is, of course, no reason to doubt that the arguments might be correct. I am not an expert on his work myself, but I do remember falling asleep in an incomprehensible seminar he gave on the subject once. He is actually visiting my institute at the end of this month and I will try understand his approach while he is here.

I am generally fairly agnostic about quantum interpretations, but I do think that approaches such as Fuch's are worth considering as alternatives that are possibly simpler than many worlds.

 

[Phantom]

Occam is a GREAT argument against many worlds. Its a complexity test. Why should 20-something dimensions be more effective than say, 3?

Why would the universe be better served by creating a separate physical instance of itself for every fork in the possible chain of events? To me, many worlds implies that every time one thing occurs that represents determination, the universe creates every possible variant of the original event representing every possible outcome.

That defies explanation of purpose. After all, one would hardly argue that Schrodingers cat experiment is invalid because there are worlds represented where the cat is both live and dead, regardless of the determination made in the original universe.

If you were going to proceed fully down the many worlds path, the logical conclusion is that somewhere there is a world in which things fall up, constantly, another in which a tossed coin is always heads, and in which light is always polarized one direction. This defies our mathematical understanding of physical processes as well as mundane ones involving social or historical events. How many permutations would you have to have to allow for this kind of construction? I think the answer, in terms of dimensions, approaches infinity, since there will be a separate world based on every particle interaction that ever occurs.

 

[Pergatory]

Originally posted by Phantom
How many permutations would you have to have to allow for this kind of construction? I think the answer, in terms of dimensions, approaches infinity, since there will be a separate world based on every particle interaction that ever occurs.

"Approaches" infinity is kind of an understatement. I'd say more like far closer to infinity than we could possibly ever imagine, even just in one's own lifetime. No one denies the number of realities required for the Many Worlds theory.

My question is in regards to preserving energy. How can energy be preserved in a system where two realities are created from one?

 

[Phantom]

Yah, its got many contradictions that you would encounter in classic thermodynamics. Personally I think the idea probably began as an intellectual exercise regarding quantum indeterminancy in string theory and somehow got extrapolated to a macroscopic level.

However it came about, its certainly a very troubling theory from many angles, not the least of which is the thermodynamic entanglements.

I think its very poor science. Taking Everett seriously leads to many logical inconsistencies. Chasing after unification from a mathematical standpoint, has led to with all these untestable hypotheses. More bothersome is the fact that Everett sincerely believed that wavefunctions exist thermodynamically independent of observation. If Everett is correct, you should be able to control the entire universe with just your thoughts and your mind...the will can literally determine reality. This is a problem for me. Reality, or at least, our view of part of it, exists without us to observe it.

Copenhagen AND Everett are both incorrect. The effects they are trying to describe do not exist macroscopically. They may be nice ideas at the quantum level, but at our scale, cease to exist. Much as EM forces dissipate with distance...quantum effects are all but gone by the time you have gotten anywhere near even the molecular level.

but, on the other hand, untestable theories represent job security...its a nice gig for a theoretician.

 

[slyboy]

Although I am not a many worlds advocate, I think that some of your criticisms have been dealt with adequately by those who are.

Deutsch has a fairly good agrument in his book for why the vast majority of universes will obey the normal rules of physics. It is simply that the abnormal universes are extremely outnumbered, so it is incredibly likely that we will find ourselves in a 'normal' universe. If you think about a universe that splits every time someone tosses a coin, then there will be one universe where all the outcomes are heads. However, the law of large numbers ensures that the vast majority of universes have close to an equal number of heads and tails. This can be formalised using Shannon's notion of typical sequences.

As for thermodynamical, energy conservation and the Occam's razor issue, I think they are dealt with in FAQ.

Personally, I disagree with many-worlds more because it seems to be a fairly empty theory, offereing little possibility for further explanation or understanding of quantum phenomena and because of the technical issues I mentioned earlier.

In case you are interested, another good defense of the many-worlds view can be found at http://arxiv.org/abs/quant-ph/9609006

 

[Phantom]

My primary problem with MW theory, not just with the theory, but in the conjecture that someday there will be an empirical test, is that they incorrectly assume the validity of Copenhagen in order to prove MW.

"If we build reversible nanoelectronics (a pipe dream), then if the measurements agree all of the time, in contradiction to Copenhagen prediction, MW is proved".

however, what if Copenhagen isn't correct either?

The whole proof rests on shaky ground. They can't BOTH be correct, but supposing that MW is proved simply because Copenhagen is NOT, would be a simple fallacy.

Just because the measurements agree, does not demand that the wavefunction collapsed, split and then was restored. The other, less complex, simpler model is that it never collapsed at all and hence never changed.

Take for example, this excerpt "The machine was split into two states or different worlds, by the second measurement; one where it observed the electron with spin "left"; one where it observed the electron with spin "right"."

So, the second measurement collapses the wavefunction yet somehow the first measurement does not? Why would that be? Because its convenient for the theory but, however convenient, inconsistent.

I can't take this source seriously at all, and unfortunately this is about as solid as MW theory gets, from the material I have perused.

 

[Pergatory]

Great sources slyboy! Lots of good info in there. I read the first link, and something struck me as strange. A portion of the various violations of laws seem to be resolved by simply stating that new worlds don't "split" per se, but two previously-existing identical worlds take separate paths. So, while those two worldlines were identical up to that point and indistinguishable from each other on the collective wavefunction, they are now unique relative to each other. This fits with second law of thermodynamics, conservation of energy, etc.

However, it seems to suggest that in the instant that the universe began, every possible worldline was created for every probability that would ever occur. In other words, history has been pre-determined, and we are merely living out one of those worldlines to whatever its determined outcome may be. This suggests that we don't control our destiny, etc., all the usual fate stuff. It would also suggest that if either time or the universe were infinite, then so must be the number of worldlines. The same is true for time travel, even if both time and universe are finite, time travel would also create an infinite number of possible worldlines. Those are some heavy implications! Another source for my doubt (and interest) in Many-Worlds theory.

 

[slyboy]

I think there is a common fallacy in Phantom's reply, which is to associate the Copenhagen interpretation with the textbook version of QM.

Copenhagen has a notion of the 'Heisenberg cut', which is the distinction between the system you are treating quantum mechanically and the measuring device you are treating classically. However, both Bohr and Heisenberg argued that the precise location of this cut is completely arbitrary and the physics described is the same where-ever you choose to put it. An extreme example is to put the Heisenberg cut at the level of the whole universe, from which you get the many-worlds interpretation. Thus, I think that any criticism of many-worlds applies equally to Copenhagen and that they cannot be distinguished by any of the proposed experiments.

The usual textbook version of QM, with an explicit projection postulate, is much closer to von-Neuman's formulation. He recognised that you can't generally describe a measurement yielding a definite result from unitary dynamics, so was forced to introduce the projection postulate explicitly. This, one could argue, should yield different predictions from many-worlds.

I don't agree with all of Pergatory's arguments either, specifically about determinism. Classical physics is deterministic and many philosopher's came up with arguments for why we can have free-will or at least appear to have it in such a universe. The issue seems to be largely independent of determinism, since I don't see how genuine randomness leads to free-will either. One has to postulate that the mind can have some control over the collapse of the state-vector, which would conflict with current understanding of QM (Squires made some speculations on this point Squires ).

To me, the issue of free-will is largely independent of physics and I don't think we can resolve the problem by the method of scientific enquiry. I would be happy to be proved wrong on this point, but currently I don't think there is a good argument for a connection between QM and free-will.

 

[Kazuya]

My main concern for flawed experiments being the source of interference patterns is that such variable experiments can produce almost exact results (well, how exact is QM?). By this I mean differing light sources and conditions, which, although greatly similar, are ultimately different.

I generally attempt to assume that interference patterns occurring from single photon experiments (although impossible) would be due to the wave-nature of particles. This requires us to postulate about the structure of waves or particles of incredibly small size (quarks, leptons, gluons, etc.) and is a task which I am not fitting of. Thus, I ignore it, searching for explanations using macroscopic examples instead. If a particle is indeed a particle yet possesses wave-like behavior, I imagine it as a ball moving in a wave-form but as a single entity. Example: this ball exists in open space, devoid of interactions. It moves with a sinosoidal wave pattern regardless of direction or speed. There are many complications involved with this image of a wave-particle, many of which I am not yet capable of handling. Perhaps when I have actually finished my degree I will have more insight in this area =/

Until than, everything is magic. Yes, everything.

 

[slyboy]

Your view bears some similarity to de-Broglie's view of the wavefunction. He viewed everything as a wave, but additionally a wave can have a sharp peak (singularity) which interacts nonlinearly with the rest of the wave and can be interpreted as a particle.

This view has differing predicitions from QM, since it predicts the existence of "empty" waves, which contain no singularities, but can be used to affect the singularities in other waves. Some experiments have been done to test the theory, but the accuracy is not yet great enough to rule it out. However, most physicists interpret the current results as evidence against the theory, since no interference patterns from "empty" waves were observed. Proponents point out that the results are also consistent with intereference patterns with low visibility, which could well be caused by the noisy nature of the experiments.

 

[graffix]

I'm perpared to be laughed at here, but I was wondering how popular is the Quantum Immortality theory in here... At first it sounds like a crazy idea, but I just thought about all the near death experiences I've had and of course I always survived! In retrospect it makes sense but looking ahead, it doesn't... I'm not comfortable with the idea that I'll survive to live up to say even a thousand years. Could something change once a probability for a certain outcome gets to be so small in MWI? Are there any theoretical boundaries?

 

[Phantom]

Actually, the Quantum Immortality theory is one of the more attractive theory sets of MW, to me. Like you, I often wonder that if MW is valid, are there many world lines where I am dead because I didnt survive my accidents or close calls were actually accidents? I've actually had that thought in the few seconds right after an accident. Like "whew that was a close one. Hey...I wonder if I am really dead in my world and this is a new one?"

And thinking about this gives me a headache, because I tried to consider this as a binary system, (0=dead, 1 = alive) but then I realized there is an equally valid third condition in which I simply don't exist and never did!

So I am tempted to say that the most popular models of Quantum Immortality presuppose too much, because in all observable systems, the subject exists. And that's quite frankly just a really big leap.

I think the very precariousness of our existence here (our distance from Sol and its size/intensity, the heating and subsequent cooling that produced the right atmospheric and electromagnetic conditions for life to begin here, our rotation of course, and so many other things) should give us an idea of how very locally determinant our existence is to begin with.

The things that happen to us might seem chaotic and whimsically improbable, but that's because we're comparing it to an expectation of some kind of order. What if, our existence here is simply a strange and random fluke in MW? What if we are that 1 in 1 trilion worlds where we exist at all?

My gut says if MW is valid, in 99.9999% of the worlds, our beautiful blue planet is either a charred cinder or an icecube.

 

[lslars31]

The weird thing about multiple world theory is that everything that could hppen in a second really happens in each of the world.
i read a book that claimed that time travel is possible using the multiple world theory. as there are chances of worlds which are still in 14th centuary.

-benzun

Timeline by chance?

 

[vanesch]

It might be interesting to note that the complexity of "many worlds" is nothing else but the complexity of the quantum mechanical superposition principle.
The "many worlds" configuration space of 2 electrons is nothing else but the product hilbert space of each electron individually ; and if you go to QFT, then the MW statespace is nothing else but the statespace of fields (the hilbert space spanned by all possible configurations of fields). When doing "orthodox" QM, you do not seem to object to the fact that we work with "superpositions of histories" (it is the very core postulate of QM). MW just applies this principle to the whole universe.
So it is not SO exotic ; you do MW when you make up superpositions in QM.
In fact, MW even reduces that complexity by assuming that once worlds "split", they do not interfere anymore. I understand this as exactly what decoherence says.
If I understand well, in MW, an "observer" (a mind ?) traces out one particular "path" through all these "splittings".
However, the problem I have with MW is not its "complexity". It is how you get out the right probabilities when having combinatorial "choices".

cheers,
Patrick.

 

[graffix]

Phantom: Yeah, how very lucky we were to be here is mindblowing... MWI will say that all those other trillion worlds with no life forms exists... but do they really? Everything in Quantum Physics talks of superposition and how it collapses when a mind observes it. Forgive my lack of understanding in this subject, but if those worlds have no one to observe them, aren't they in a infinite state of superposition (until someone can travel into that world and at that time collapse it into one reality)? Also, how did the big bang pan out the way it did, if there was no one observing it, shouldn't our universe have been in a state of superposition? I'm not a physics major or anything (didn't take it in college) so forgive me if I'm missing some vital fundamentals!

 

[pallidin]

I am not one who favors "observation" being the determinate factor in the MWT split. If a splitting occures, it would seem to me that is a consequence of action, as opposed to the mere thought of action.
That is, only reality can potentialize tangental aspects of it.

 

[graffix]

Pallidin: Hmmm I never thought about it. I can definitely see action as something that would cause a MWT split (ie a guy in a motorcycle cutting someone off). I always thought observations by their very nature collapses superpositions, though, like in the two slit experiments? Then I realized I'm having a hard time defining an 'action' and 'observing' because in those experiments setting up the experiment can be seen as actions. It usually goes like: we think of the action, perform the action, we observe the results. I'm not even sure if time even has anything to do with it. But anyway going back to my possibly stupid question of big bang, who or what caused (by action or observing) the collapsing of superpositions back then? Or is it more like 'since I am here, it must of have been...'? This is messing with my head. Now I question if the collapsing of worlds by our choices is even a similar phenomenon as the existence of other worlds that contain no life, no observers?

 

[pallidin]

Well put, graffix. I especially like the way you pointed out that experiments designed to look at "observation-only" criteria are, in fact, prior-mode action based. Outstanding!
Your statements should lead some to seriously consider wherther or not a pure observational platform is even possible in some(or any!) experiments. Nice call.