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Gerinski 
Prog Reviewer 
Joined: February 10 2010 Location: Barcelona Spain Status: Offline Points: 5154 |
 Posted: July 31 2013 at 07:34 |
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Well I do. I may find string theory a dead end as The Grand Unifying Theory of Physics, but if dozens of highly reputed physicists still believe that it may be, I will at least look at that option with some respect, after all who am I to tell.
You despised MWI with words sounding like "that's utter nonsense", I only remarked that reputed physicists support it.
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Dean
Special Collaborator 
Retired Admin and Amateur Layabout Joined: May 13 2007 Location: Europe Status: Offline Points: 37575 |
Posted: July 31 2013 at 08:14 |
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I haven't actually given my opinion on whether MWI is nonsensical or valid, I have simple said that in the context of this thread and in answer to Jim's question, MWI does not predict the existence of Alternate Realities, or even make them possible, or feasible.
If you want my layman opinion then I think it is an unlikely scenario if you take it at face value (which is not how it was ever intended but that is how most people interpret it) because time is not quantised nor is time event-driven so there would not be discrete worlds, universes, realities. Edited by Dean - July 31 2013 at 08:17 |
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Gerinski
Prog Reviewer
Joined: February 10 2010 Location: Barcelona Spain Status: Offline Points: 5154 |
Posted: July 31 2013 at 09:08 |
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It does predict alternate realities, that's the basic feature of the interpretation, at least in its "strong" form.
There are variations in the interpretation which we may call from "weak" to "strong". The "weak" view maintains that for example in the double-slit experiment, the universe splits in two briefly, in one universe the particle goes through one slit and in the other universe it goes through the other slit, but these alternate universes are very short-lived, if we were not observing the experiment they will interfere with each other and return to a single universe which is an interference pattern of both. If we were observing the experiment, they will decohere and only one of them will manifest and remain as "real", the other will be discarded (according to the probabilities dictated by Schoedinger's wavefunction equation). This is the "weak" interpretation in which "alternate realities" do not really exist, or more precisely they do but only for fleeting moments until they vanish. We are constantly surrounded by "shadow" alternative universes which quickly either merge or decay and disappear. The "strong" view is that if we attempt to observe the experiment (or if any other factor other than observation causes decoherence), both realities will persist and continue developing their course as two alternate universes, one in which the particle went through one slit and another universe in which it went through the other slit. So it's our observation (or some other unknown decoherence trigger) which splits the universe in different copies of itself. The strong view definitely predicts alternate realities (in fact as many as possible outcomes each quantum event in history has had to branch out). |
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Gerinski
Prog Reviewer
Joined: February 10 2010 Location: Barcelona Spain Status: Offline Points: 5154 |
Posted: July 31 2013 at 09:10 |
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And, I repeat, I am not a proponent of MWI, I just said to Jim that the sci-fi stories of alternate realities have some base on respectable scientific thoughts. Not more and not less.
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Dean
Special Collaborator
Retired Admin and Amateur Layabout Joined: May 13 2007 Location: Europe Status: Offline Points: 37575 |
Posted: July 31 2013 at 09:55 |
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Two problems with that: 1. it's not a prediction and 2. the "Alternate" is not a "Reality"
..and a simple bifurcation (two-way split) of quantum events does not lead to as many possible outcomes [as] each quantum event in history has had to branch out - it would lead to two to the power of each quantum event in history has had to branch out. If the first ever quantum event triggered two unverses then the next would occur in both, leading to four unverses - note this second bifurcation would not be the same event in both universes since an observation in Universe A would not trigger a decoherence in Universe B; it just happens to be the next event in Universe A and the next event in Universe B resulting from two seperate observation events (otherwise there would be a interaction between worlds and that apparently/allegedly does not happen). So the 3rd event in each of the four universes would result eight universes (2x4=2^3). However, there would not be a simple bifurcation, the number of worlds that would be created at each event is many (and that "many" is a big number) and the number of events in history is lots (and that "lots" is a very big number) so the resultant number of possible universes would be many to the power lots.
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Gerinski
Prog Reviewer
Joined: February 10 2010 Location: Barcelona Spain Status: Offline Points: 5154 |
Posted: July 31 2013 at 10:18 |
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Mmm, a prediction is usually something in principle testable so at the moment no, it's not a prediction but just a logical consequence of the interpretation. Why shouldn't the alternate universe be any less real that the other one? your current consciousness just happens to inhabit this one, there's nothing forbidding another Dean's consciousness experiencing different things.
I agree, the number of possible ramifications is likely infinite. Infinity is not necessarily unphysical, we just don't know, but it certainly raises eyebrows. But it is worth saying that ramifications are not all infinite, not "everything is possible" in the MWI. If a measurement (say spin) can only have two outcomes, up and down, the ramification will only result in two universes, not one more "in between up and down". Bigger philosophical issues come when we consider more mundane situations where many outcomes are possible, each with a certain probability (say the position of a particle in a box). The strong MWI says that as many universes as possible positions exist will emerge, but with distinct probabilities, so with distinct "survival chances". Universes with strong likelihood will persist harder than universes with little likelihood. The process by which universes with little likelihood are eventually discarded and universes with high likelihood are preserved is not yet postulated though.
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Dean
Special Collaborator
Retired Admin and Amateur Layabout Joined: May 13 2007 Location: Europe Status: Offline Points: 37575 |
Posted: July 31 2013 at 10:19 |
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And, as far as I know, MWI does not explain the double slit experiment at all. In your "weak" example the two universes interact (when they combine) to prodce the fringe pattern but MWI does not recombine the two universes. In your "strong" example in our reality the particle only went through one slit, in the bifurcated universe it went through the other - therefore there was no interaction and there is no fringe pattern. In the double-slit experiment the accumulation of particles produces a fringe pattern as if each particle went through both slits (as a wave would).
As I said, MWI is an illustration to allow us to interpret QM (or as Pat said, the mathematics)
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Gerinski
Prog Reviewer
Joined: February 10 2010 Location: Barcelona Spain Status: Offline Points: 5154 |
Posted: July 31 2013 at 10:36 |
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Yes it does, when we do not observe the experiment the two universes don't remain split, they immediately recombine in interference producing the fringe pattern and remaining as one universe.
Again, if we do not observe the experiment, the 2 universes (particle going through each slit) will interfere with each other and become a single universe with the interference (fringe). Only if we try to observe the experiment (or if any other unknown factor causes decoherence in the way observation does) will the universe split in two copies of itself. So, if we would assume that observation is the only process which can cause decoherence, we could say that the universe "knows whether we are looking at it or not". Personally I think that other processes other than observation can also result in decoherence, I don't know precisely which, but probably it would be safer to say that "the universe knows whether decoherence processes are active or not" and acts accordingly, interfering and recombining into a single universe if they are not and splitting in separate copies of itself it they are.
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Dean
Special Collaborator
Retired Admin and Amateur Layabout Joined: May 13 2007 Location: Europe Status: Offline Points: 37575 |
Posted: July 31 2013 at 10:52 |
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^ what you have described is not a splitting of reality nor is it MWI. MWI is not two differentiate worlds - they are not preexisting before the moment decoherence - it is the splitting of a single world - in that single world the particle appears to go through both slits as a wave would, we observe it at the detector where the fringe-pattern is formed in that same reality, that is the moment of decoherence since that is the moment of observation - this we know because the slits are a finite distance from the detector and the fringe patterning is proportional to that distance - the particle cannot predict the future so the fringing would occur whether the detector is there or not.
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Gerinski
Prog Reviewer
Joined: February 10 2010 Location: Barcelona Spain Status: Offline Points: 5154 |
Posted: July 31 2013 at 12:06 |
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Ha! don't you know about the 'delayed choice experiments' and the 'quantum eraser experiments'? Of course the particle can predict the future, it "knows" whether we are going to attempt to know which slit it went through or not, and it behaves accordingly, even before we have made the decision to check it or not. Some conclude that this is retrocausality, personally I would not go that far but honestly I do not have an explanation, what is clear is that the particle will behave differently if we attempt to know which path did it take or if we don't, and this is valid even if we made our decision after the particle crossed the slits. |
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Gerinski
Prog Reviewer
Joined: February 10 2010 Location: Barcelona Spain Status: Offline Points: 5154 |
Posted: July 31 2013 at 12:19 |
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No, if we watch which slit the photon or particle went though, you do not get a fringe pattern, only a cummulative set of dots in each slit's screen area. Only when we do not watch will the accumulation of particles, shot one at a time, produce a fringe pattern. And only when we attempt to know which slit the particle went through, the universe will split in two. Otherwise it will remain one single universe, a coherent interference of the two possibilities.
Edited by Gerinski - July 31 2013 at 12:25 |
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Dean
Special Collaborator
Retired Admin and Amateur Layabout Joined: May 13 2007 Location: Europe Status: Offline Points: 37575 |
Posted: July 31 2013 at 12:43 |
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If anyone is lost as to what Gerard and I are arguing over, it is this:
A popular-science explanation of what you can see is given here:
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Dean
Special Collaborator
Retired Admin and Amateur Layabout Joined: May 13 2007 Location: Europe Status: Offline Points: 37575 |
Posted: July 31 2013 at 13:52 |
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You cannot look back at the slit and see which one it went through. A telescope will see the point of origin (by direct line of sight only because it still only sees the photon once it arrives at the telescope - when we look at a distant star we see the photons as they hit our retina, and interpret that as a bright point of light on a 2D projection of the image in front of us, we do not see two light beams joining that point to our pair of eyes). A detector will see the point of "impact" of the arriving photon at the end of its journey. Neither telescope nor detector will see the photon (as a particle or a wave) at any time on the journey. Just because one telescope is focused on one slit it does not prove the photon did not travel through the other slit simultaneously (as if it were a wave) because it cannot "see" the other slit.
So, as a thought experiment:
The only way to see the photon at the slit is to put a pair of local detectors at the slits, there the photon will go through one of the slits and hit that local detector without interference (because that detector cannot detect photons from the other slit, hence no "local" interference can occur) - the photon will not then continue on its path unaffected to the distant detector because it has been subjected to an observer effect and been modified in some way - essentially it is a new photon that has not been through either slit at all, which is an explanation of why you would see a normal non-interference distribution at the far detector. Some other photons will go through the other slit and be detected by the other local detector, if they then continue on to the far detector they are again modified photons and will produce another non-interference distribution. Others, of course, will hit the spacer between the slits and not pass through at all and therefore not hit either local detector or the far detector.
That light behaves like a wave when you look for a wave and like a particle when you look for a particle should surprise no one, (well, it does not surprise me).
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Finnforest
Special Collaborator
Honorary Collaborator Joined: February 03 2007 Location: The Heartland Status: Offline Points: 16913 |
Posted: July 31 2013 at 18:32 |
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Physics students on Trek style beaming....still doesn't sound like I'll be able to beam to Dean's place for a beer anytime soon.....
 Instead of looking at it from the Trek angle of just zapping people around the universe, Leicester team member David Starkey says, “We decided to investigate the practicalities of teleportation as a means of everyday travel.” And the results are pretty astounding. The team determined just how much information would need to be moved by figuring out how much data humans are made of, including everything we’ve got going in the brain region. The team figured the sum total amounted to “2.6 times 10 to the power of 42.” This a number that humans couldn’t possibly count to in a lifetime, and is almost impossible to grasp with our data-filled minds. “We employed several approximations to determine the amount of data required in bits to fully store a human genetic code and neural information,” Starkey said, “and the signal to noise ratio of typical signalling equipment. Our results indicate the time scales to complete a full teleport of an individual are a little too lengthy at this time. Current means of travel remain more feasible.” You might not think that public transportation will get you where you need to go very quickly, but the transporter alternative will literally take forever. Scaling to bandwidth power, the team decided the energy needed to tele-send a person into orbit would take up to 4.5 times 10 to the power of 15 years, assuming a bandwidth of 29.5 to 30 gigahertz. In case you’re like me and can’t do massive calculations on the fly, this means the process would take 350,000 times longer than the existence of our 14 billion-year-old universe. I get shivers up my spine whenever I try and understand a time frame like 14 billion years, so to consider something even more time-intensive is enough to give me an aneurysm. I seriously doubt those Chinese scientists were thinking on this large scale when they started transporting photons at a speedy rate. -excerpt from GiantFreakingRobot website |
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Dean
Special Collaborator
Retired Admin and Amateur Layabout Joined: May 13 2007 Location: Europe Status: Offline Points: 37575 |
Posted: July 31 2013 at 19:23 |
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Star Trek transporters of course can transport 7 people at a time and hold many more in the transfer buffers while those seven are rematerialising and they can do it in a few seconds
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Finnforest
Special Collaborator
Honorary Collaborator Joined: February 03 2007 Location: The Heartland Status: Offline Points: 16913 |
Posted: July 31 2013 at 19:50 |
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^
I believe on one of the SG shows they even evacuated larger numbers of endangered folk via group transporting....though I can't recall the number |
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Gerinski
Prog Reviewer
Joined: February 10 2010 Location: Barcelona Spain Status: Offline Points: 5154 |
Posted: August 01 2013 at 04:23 |
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^^ As much as I respect those calculations, I still suspect that the universe may well hold some mysteries regarding information science and possibilities of compression. In a sense, the laws of physics themselves are a wonderful example of compression. Take the state of the whole universe at a certain time, and then we want to know what will happen in the next million years in the whole universe. The question might seem intractable if we think of it in terms of tracking the paths of each single particle in the universe, but it turns out that a few equations which can be written on a napkin are enough to tell the whole universe what it has to do during the next million years (the fact that we do not know the precise equations at the moment does not preclude the fact that we expect this to be the case).
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Dean
Special Collaborator
Retired Admin and Amateur Layabout Joined: May 13 2007 Location: Europe Status: Offline Points: 37575 |
Posted: August 01 2013 at 04:50 |
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That's not information compression, it does not even sound like information compression.
 Some of it even completely random:  |
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Icarium
Forum Senior Member 
VIP Member Joined: March 21 2008 Location: Tigerstaden Status: Offline Points: 34055 |
Posted: August 01 2013 at 05:01 |
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complex things can be simple and simple things can be complex.
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Gerinski
Prog Reviewer
Joined: February 10 2010 Location: Barcelona Spain Status: Offline Points: 5154 |
Posted: August 01 2013 at 05:21 |
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^^ So we can not exclude the possibility that the huge complexity of a human being, or at least certain aspects of it, might be reduced as from arising from some simple principles. The science of Complexity studies precisely the emergence of complex phenomena out of simple principles. There is no solid reason to believe that the complexity of a living organism is uncompressible in principle. Many features must emerge from simpler principles. So it might be enough to know those principles to reproduce traits of the organism from a simpler description of the basic data + the effect of those principles.
To tell somebody to build a Boeing 747 you do not need to tell him the position and type of each of its atoms, you can use drawings and specifications.
Edited by Gerinski - August 01 2013 at 05:23 |
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Gerinski wrote: