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The duble slit expriment

  1. Apr 8, 2009 #1
    first of all im from israel so im sorry for the bad english :P

    ok.. in the duble slit expreminet when u open 2 slits the elctron go through them both.. and u place a measure device it shows that the electron go only through 1 slit.. but lets take a camera that films through which slit the electron go's... and u take the tape and send it to a person that located far away from there,, and the electron gun still shoots electrons, and the viewer that is far away wachtes the tape, do the function collapse? and suddenly the result changes? and the electron that is located far away knows that is been watched and change is course to go through only 1 slit? (and if it dose I think that u have a potential to measure how fast information travels).

    yours Nadav from israel.
  2. jcsd
  3. Apr 8, 2009 #2


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    You can't see the electrons with a camera unless you shine light on them of a high enough frequency, which is the same as a measurement. There will be no interference pattern if you do this.

    It has nothing to do with humans looking at videos or anything like that. Whether a human is present or not, if there is light of a high enough frequency to measure the electron's position, there will be no interference.
  4. Apr 8, 2009 #3
    so what u mean by that is that an observer has nothing to do with the collapsing of the function? and the electron makes a "decision" only because u shine a high frequency light on it?
  5. Apr 8, 2009 #4


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    Yes, it has nothing to do with a human/conscious observer.
  6. Apr 10, 2009 #5

    Hello. I'm new to the forum and surfed in from google looking for answers on this exact experiment. Is the above assertion conclusive? If so, could you please point me to some official sources of information that verify this?

  7. Apr 10, 2009 #6


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    Why would you need an 'official' source of information? Have you ever seen an electron? Obviously the electron detector is not a human eye. What matters is whether there's a detector and whether it is on or off. Not whether a human being bothers to look at at the result.

    It's not very difficult to verify that experimentally. Either you get an interference pattern or you don't.

    But there's little reason to - the quantum mechanical/physics definition of 'observation/measurement' has never had the same meaning as the casual, anthropocentric, everyday terms that imply human action. An atom bouncing off another can qualify as a QM 'measurement', even though you can't see it.
  8. Apr 10, 2009 #7


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    It certainly has nothing to do with the quantum mechanical explanation of the double slit experiment. I don't know what you mean by "official source", but you can look at any standard textbook on quantum mechanics; there won't be any mention of consciousness or human observer.

    In general though, some people do speculate about some relationship between quantum mechanics and consciousness, but keep in mind that none of this is part of the established quantum mechanics we have now.
  9. Apr 10, 2009 #8
    I'm sorry?? Firstly, I'm new here so I obviously need to familiarize myself with how dialogue takes place. In any case, the question as to "why" I need it is utterly irrelevant. An individual has a right to ask for information on this forum, does not she? If that's not how it works here, do let me know....

    When I said "official" I meant journal articles, accredited university produced literature, etc. I could find online and not a personal interpretation of "how thinks work". You're being slightly presumptuous don't you think? When I said "official" I was referring to the descriptions outlined in the rules here:https://www.physicsforums.com/showthread.php?t=5374 which were quite specific about sources of information.

    Enjoy your day.
    Last edited: Apr 10, 2009
  10. Apr 10, 2009 #9
    Hi - thanks for the response. When I said "official source" I meant journal articles, university papers, etc. Do you know of any specifically, as I'd like to explore them at my leisure? Tx!
  11. Apr 10, 2009 #10


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    I think the best place for you to look is a good book on quantum mechanics. Try the first few chapters of Feynman's lectures (volume 3). That should be an official enough source. Chapter 1 discusses the double slit experiment, and you should be able to follow most of it even if you don't have any background in physics.
  12. Apr 10, 2009 #11
    Tx - going to check it out!
  13. Apr 13, 2009 #12


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    I am glad you wrote that as I have read a lot of stuff that seems to give a special place to human consciousness in "Observing"!

    Would I be right in assuming that any deliberate or accidental circumstance that forces a particle to decide its location, momentum or spin would count as an "Observation"?

    Indeed is there a generally accepted definition of "Observation"?
  14. Apr 13, 2009 #13


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    If there is something in the (classical) environment that records the position of the particle, then it counts as an observation.

    This statement can be made more precise by defining the terms in it more carefully, but I think it is safe to say that we don't yet have a completely satisfactory understanding of the problem.
  15. Apr 13, 2009 #14
    "Observation" has many meanings. For example, getting information is an observation. But what for one is information - knowledge of some sort, for example, the answer to a puzzle, for another - it is not (he knew the answer, he is the author of the puzzle). So while pronouncing the answer one gets information, the other does not. So it is personal and subjective.
    Another meaning is getting some signal by a device. A human being can use this event to get information, but the device can work (react) itself.
    In the world most of quantum mechanical "observations" happen without involvement of humans. It's a human (subjective) feature to say "I feel only my own feelings", or "Before observation there is no information" and then to absolutize it to an abstract level.
  16. Apr 13, 2009 #15

    I found some interesting scientific research out of Cambridge University conducted by the Nobel Prize winner Brian Josephson http://www.tcm.phy.cam.ac.uk/~bdj10/ . Quite intriguing....

    I'm not a physicist myself, thought being the child of quite open-minded scientists (trained at the graduate level), part of my life "operating system" if you will is, Interroga Omnia, question everything.

    I'm always curious (suspicious???) when scientists say "the explanation isn't adequate, reasonable, etc", because alot of times that means "we don't like what this could mean" or something else "uncomfortable". Lastly, I've never been a slave to orthodoxy, the herd mentality, or my left brain faculties, so I'm naturally drawn to different ways of looking at things.

    I also saw some interesting videos on youtube featuring John Hagelin (Choate Rose Mary Hall, Dartmouth undergrad, Harvard Grad) who from what little I have read is/was considered one of the pioneers in String Theory and now seems to be doing a fair amount of scientific work involving Human consciousness. Here he addresses some pretty profound questions such as "what is consciousness", "what is it's role", etc.

    At any rate, this is all leisure for me so that could explain my attraction to the avante-garde.
  17. Apr 13, 2009 #16
    I think I know of a way to prove if consciousness affects the DSE or not. Set up the experiment, tell all the photons/electrons to go through the left slit ONLY, then sit back and watch the wave pattern develop. :wink:

    I have never understood how people assume that human consciousness affects the DSE....... If I could tell photons where to go, I would be a billionaire.
  18. Apr 13, 2009 #17
    Well, being the open minded person that you are, I'm sure you'll agree that just because YOU HAVEN'T understood how it may work, doesn't mean IT COULDN'T. When the Swedish scientist Emanuel Swedenborg in 1715 presented the Academy with his "Flying Machine", I'm sure the conversation went something like "I have never understood how people assume that something not born with wings could fly...".

    Needless to say we found out didn't we? http://en.wikipedia.org/wiki/Emanuel_Swedenborg

    That said, I make money not theories of physics so I am not bound by a strictly left brained paradigm.

  19. Apr 13, 2009 #18


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  20. Apr 14, 2009 #19
    Regarding the doublesplit experiment, I have been reading about it, and the conclusions that are drawn are not what I would expect. In the experiment where a single electron was injected in just one of the 2 slits, and it is "detected" that 1 electron exits from both slits, it begs the question on what method was used for detection.

    It gets even more interesting when another experiment was conducted and a single photon was shot in just 1 of the 2 slits, and it was "detected" that 1 photon exited from each of the 2 slits.

    I tend to ask why more often than not, and the double slit experiment begs so many questions.

    There looks to be a very obvious error when these experiments were conducted. In text books and online resources that describe this experiment, the illustrations are a bit 2 dimensional.

    I need a graphical example to what I am talking about, so I will reference the infamous wikipedia for an illustration:


    The above is a link taken from:


    Lets recreate this experiment, with either electron, or photon, and lets create a 3 dimensional test. Instead of having 2 slits with limited length, why not have pairs of slits going in 6 different directions. A hollow cube with paired slits on each side of the cube in the very center of each external face. The source of electron and photon is at the center of the cube. Lets agree that the source is at x,y,z 0,0,0 and the source is pointing to 0,0,100.

    A single electron and then a single photon is fired in 1 of the 2 slits at coordinates 0,0,100.

    With the understanding that a wave will propagate in a spherical fashion, will an electron or photon emerge out of any other slit? Specifically, slits at:


    Now, lets change that experiment up a bit, and cut 3 slits in their original experiments. The electron and then a photon is shot into the center slit. Which of the other 2 slits will it appear on the other side? Now lets extend that 3 slits to 36000 slits in a circle fashion, or even better, a cylinder fashion.

    An electron or photon is fired in slit 0. Which other slit will it exit out of, slit 1, slit 36000, or ???

    My guess? All of them.

    Here is the awesome part. If we do this enough times with single gold atoms, we'll be rich!

    Ok, seriously. A plain piece of cardboard with 2 slits does not have the capacity create matter, and I do not see how enough energy was emitted by releasing just one electron or even one photon to create an extra 1 by introducing a second slit.

    So, is it possible that the method of detecting these single electrons or single photons be erronous?
  21. Apr 14, 2009 #20

    I thought part of the Copenhagen interpretation had to do with the fact that phenomenon like the Schrodinger's cat thought experiment has to do with actual conscious thought?
  22. Apr 14, 2009 #21


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    No, the Copenhagen interpretation has nothing to do with consciousness.
  23. Apr 14, 2009 #22


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    Not really, there are entangled versions of the experiment in which there is a partner particle being detected at another spot.
  24. Apr 18, 2009 #23
    I agree with dx.
    Actually you see what you want to see. If you want to see wave nature you don't put any detector and find an interference pattern . But if u want to see the particle nature just put a detector which will send a photon which will return after hitting an electron(disturbing its motion) and this time you will not find any interference pattern. By this time because of that photon you know that through which slit the electron went. Here you see particle nature.
  25. Apr 18, 2009 #24
    Another point a single particle can also show interference pattern.
  26. Apr 18, 2009 #25
    Check this out!
    A new experiment was done with random number generators and some other twists. Seems wild!

    Can someone give a reader's digest version of some of the quantitative explanation?

    Here's the researcher's findings:

    The experiment is explained in physics world (is this a reputable magazine, I have no clue, as I am a bit of a n00b ;) )



    you can find other pdfs of the experiment, using the search phrase:
    filetype:pdf Jean-Fran├žois Roch
    Last edited by a moderator: Apr 24, 2017
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