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Murshid Salam

Program Controller, Ericsson India Global Services Pvt. Ltd.

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In double slit experiment of Thomas Young, why do electrons (particles) behave like waves when we aren't observing them?

In double slit experiment of Thomas Young, electrons (particle) behaves like a particle when they are under observation. But how they suddenly behave like a wave when we do not observe them.

Topics: quantum superposition
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  • Barry Palmer 50+

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    Jul 20 2012: In my very humble opinion, quantum mechanics is a bunch of math that can make amazingly accurate predictions, and that math is a huge achievement. But we have zero understanding of what is actually going on. I think we limit ourselves by thinking in terms of waves and particles. What we call subatomic 'particles' act LIKE particles and act LIKE waves, but I suspect that they are neither, and our limited imaginations cannot figure out what they are.
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      David Hamilton 50+

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      Jul 22 2012: My favorite explanation, is that there is something fundamentally flawed in either human perception, or much more simply the human eye, and we've built it into our tests.
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        Marius Moe

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        Jul 31 2012: Actually, it's the detectors in the test themselves.

        As an analogy, imagine trying to find the position of a marble in a dark room, by hitting it with another marble. It's kind of hard to do without interfering with the marble that you hit.

        Earlier this year, researchers managed to do the experiment using more advanced technology and tools, so they could observe which slit it went through without interfering with the wave-like properties of the particle. Nothing about our eyes, just a huge refinement of the detection system in the test itself.

        Here's an article that talks a little about it:
        http://arstechnica.com/science/2012/05/disentangling-the-wave-particle-duality-in-the-double-slit-experiment/

    • Erik Dahlberg

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      Jul 27 2012: I agree with this view. We most def limit ourselves when trying to extrapolate quantum phenomena to our world. The wave and the particle are only pictures we use, abstractions. I don't believe that the act of observation has anything "magical" to it as in "the object cares about how it's being observed". The choice of viewpoint simply brings certain characteristica into view.
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      Carl Shaw

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      Jul 29 2012: I agree Barry, I think that as others have suggested, that light is neither particle nor wave. However, this does not explain how the results of an experiment may be determined by consciously observing it.

      I think we are looking at two problems: 1/light is neither wave nor particle. 2/ There is also a significant/pivotal part played by consciousness in all this.

      • Barry Palmer 50+

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        Jul 29 2012: Personally, I am philosophically opposed to the idea that observation per se plays any role in the outcome of these experiments. If you analyse all aspects of these experiments, it is clear that this idea is a conclusion, not an observation. I believe this conclusion is incorrect because we do not have a full understanding of what is actually occurring.. I believe the first mistake was interpreting the uncertainty principle as a property of the universe; I think it is just a limitation of what is knowable. A second mistake is not appreciating our ignorance of the true nature of subatomic particles. Also, I suspect there are other unknown phenomena affecting these experiments. The result is false conclusions. These mistakes stem from human hubris. Scientists have a desperation to understand and publish; their human needs cause them to put onto paper ideas and conclusions which are based on what they know. If you take a step back and look at the bigger picture, and also take into consideration the unknowns, their conclusions are not so conclusive.

        All that being said, I could be wrong, and consciousness could be playing a role. But that cannot be considered a fact until we understand how consciousness is involved. Until then, it is just one possibility. Considering the history of science, I think it is very improbable. The universe does not need observers to function. Subatomic particles don't care about us.

        I admit that I have only a layman's understanding of quantum mechanics. My strong opinions stem from a good grasp of logic and knowledge of the history of science. Many scientists have made the same kinds of mistakes that I see being made again and again. I recently saw a documentary in which a few rogue physicists are also looking for alternative explanations.
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          Carl Shaw

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          Jul 29 2012: Hi Barry, I try to drive philosophical objections away from my thoughts whilst I am considering a subject. Truth is blind to philosophical approach.
          Physics adopts the philosophical approach that all comes from the material. This is a severe, unnecessary and arbitrary restriction in the search for knowledge. Adopting this it finds the answer it wants (i.e. all stems from a big-bang) even if to do this it needs to invent vast quantities of imaginary dark matter and energy to support this idea.
          If science was free to discover our origins without any philosophical assumptions restricting the answer, it might find a different origin. Perhaps consciousness is our origin?
          If a hammer is the tool available then every problem is a nail.
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        Marius Moe

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        Jul 31 2012: The double slit experiment was done earlier this year, both observing which slit the particle went through, and observing without interfering on it's wave-like properties. Consciousness didn't seem to have anything to do with it, just the detection technique, which now is much more advanced.

        http://arstechnica.com/science/2012/05/disentangling-the-wave-particle-duality-in-the-double-slit-experiment/
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          Carl Shaw

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          Aug 1 2012: Hi Marius,
          The article you reference raised my attention. I found c copy of the original paper at http://www.pnas.org/content/early/2012/05/23/1201271109 .
          It appears the article isn't strictly representative of the experiment that was carried out. The experiment is an amalgamation of TWO experiments. The particle which interferes is a particle from experiment 1, whereas the particle which is detected as going through a particular slit is from a second experiment 2.
          In conclusion the authors write:
          "However, the EPR discussion (3) or the delayed-choice experiment (22) have taught
          us that quantum objects do not have a reality independent of a
          measurement as summarized (29) by the phrase “one cannot consider
          quantum properties as being ’real,’ in the sense of ’objective
          reality.’”
          John A. Wheeler (3), paraphrasing Bohr, expressed this fact
          most vividly by saying “No elementary quantum phenomenon is
          a phenomenon until it is a recorded phenomenon brought to a
          close by an irreversible act of amplification.”
          In this sense our experiment can also be interpreted as another
          confirmation of the nonobjectifiability of quantum mechanics or,
          as stated by Torny Segerstedt, “Reality is theory.” "

          A similar recent experiment (http://arxiv.org/abs/quant-ph/9903047) uses similar materials but a different experimental arrangement such that THE SAME PHOTON can be measured in 1 single experiment. Availability of the results of the experiment (conscious observer) DID still seem to have significance.

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