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Am I missing something ?

  1. Feb 17, 2006 #1
    Firstly, I'm not a physicist nor even particularly clever, so please be gentle with me here : )


    Like many I have read and struggled to understand Schrodingers Cat and, whilst I've long since rejected the idea of a dead-alive cat (barring a strictly MWI manifestation of such a beast) there are still a few questions.

    For example, why on earth are we beating our heads over superpositions and non-locality when there appear to be NO corresponding observables. Isn't physics about developing and testing theoretic models which are consistent with the observable nature of things ?


    Q1.

    My first problem lies in an understanding of the idea of a superposition of states. If measurement of a quantum particle 'collapses' it into a definate state then how can we suggest that it was ever anything else. I'm certain no experiment has been able to show that such a superposition ever existed and thus, rightly or wrongly, I view the whole superposition argument as excess baggage.

    Is it any surprise that we hit problems with non-locality whilst trying to define a phenomenon that we admit cannot possibly be observed ? Thats not science, philosophy maybe, theology possibly ... but it's hardly good science.


    It seems to me that this superposition argument is more related to MWI (similarly unobservable). In which case the measurement would not so much solidify the state (which would be one of several coexisting but definate states) but rather confirm which state we ourselves inhabited.

    As for superpositions and entanglement I have not yet read anything which takes this beyond a purely figurative meaning. There has to be a sensible limit to how far we can pursue pure theory and I'm beginning to feel that we hit that limit a long time ago.

    Am I missing something important here ? Is there some experiment which shows the superposition as a measureable (albeit indirectly) phenomenon ?


    Q2.

    I'm familiar with the double-slit experiment, the implied wavefunction and the notion of its collapse into a definate state.

    But I find it dificult to class the double-slit experiment as a proof of superposition since there is no requirement that the particle itself is ever in a superposition, just that its 'path' is decided by and subject to some unknown statistical resolution. Certainly, theres not enough evidence to suggest the whole theoretical merry-go-round we currently find ourselves riding.

    Is it at all possible that the photon itself simply has no concept of the journey ? If a photon, once ejected, travels by definition at the speed of light what implications does this have on its notion of intervening space. Could it be said that a photon, from its own perspective, does not actually 'travel' at all ?

    If so, would this explain the wave-function ? A photon is both emited and absorbed at time t (subjective) and thus does not traverse the experiment in any classical sense ? Whilst such instantanous translation would appear to be ludicrous in the macroscopic world could the exchange itself be subject to quantum principles ? Has any experiment indicated whether the emission of a photon is entirely dependent upon it also being later absorbed in a predetermined way - Can they be the same event from the photons viewpoint ?

    Does any existing theory follow any similar line of thinking ?


    Of course, light isn't observed to travel instantaneously. I think postulating that instead of the mechanism of lightspeed exchanges being subject to intervening space that rather the concept of intervening space is somehow defined by the mechanisms of that underlying exchange is just as valid as accepting MWI or superposition of states and doesn't seem to bring with it any worries of breaking locality.

    Apologies if I'm making no sense at all. I'm just trying to work out whether this is science or sentiment. If its the latter, and it seems to be, then we can all have a go : )

    -G
     
    Last edited: Feb 17, 2006
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  3. Feb 17, 2006 #2

    ZapperZ

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  4. Feb 17, 2006 #3
    I've read that - I didn't want to contribute to the end of it as it appears to have taken a few turns already and become rather specific.

    What I'd like to ask instead is whether either the copenhagen or the multiple-world interpretations are strictly necessary or indeed even qualify as scientific theory. It seems to me that when you start stretching theory to this extent then you really need to go back to the basics and re-examine everything that lead you to that point.

    Whether some supposition of states exist until observed is quite irrelevant unless we can either observe it directly or use it to make some prediction which we can later verify through experiment. Neither the copenhagen nor the MWI leave this avenue open and thus are entirely unscientific... one might as well say that nothing existed until we opened schrodingers box and that the entire universe was then brought, kicking and screaming, into being as an attempt to resolve the state of the cat - And there you have it, not only an equally valid theory but also a good run at 'the purpose of existence' ... one which, I'm sure, would have pleased many ancient egyptians : )


    I think it is far more reasonable to say that problems presented illustrate only that we need to understand more fully the transition of a single photon in terms of its quantum nature and it's own 'experience' of the journey. Rather than just run with the notion that the universe exists for and because of the conscious observer and that a things exist in a supposition of states until someone cares to look. Perhaps it does, perhaps we're all Gods, creating our universe by virtue of being one of an number of possible arrangements of energy that is capable of musing over semi-dead cats.

    Personally, I think that postulating these unprovable scenarios is all rather 'last resort' thinking.


    Still, if anyone here can point me to some evidence that something truly can exist in a supposition of states until later resolved I really would love to hear it.

    For example ... Is there any experiment which shows that examining one part of a pair of entangled photons has ANY demonstrable effect on the other ? Indeed, can anyone derrive any potential behavioural or statistical prediction that could possibly give us an indication ? In the absence of any such avenue for experiment isn't this all just pseudoscientific claptrap ?


    -G
     
  5. Feb 17, 2006 #4

    ZapperZ

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    Note that there's a reason it is called a "copenhagen INTERPRETATION". It isn't part of the formalism of QM. The same goes with many world interpretation. These are not "theories". Do not confuse the two.

     
  6. Feb 18, 2006 #5

    vanesch

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    I particularly like the above statement. Various interpretations of quantum theory try to make sense of the FORMALISM of quantum theory. That is, they try to say what does, and what doesn't, correspond to "real things out there". And, depending on the choices, one gets different "stories". But these stories are not to be seen independently from the formalism, otherwise they sound really too much "made up".
     
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