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The Double Slit Experiment Blows My Mind

  1. Jun 18, 2012 #1

    This is seriously the most amazing thing ever. Pretty cheesy experiment, but amazing results. It still makes no sense to me how an observer completely changes the outcome. Its like the electron has a mind!
    Last edited by a moderator: Sep 25, 2014
  2. jcsd
  3. Jun 18, 2012 #2


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    It makes more sense when you realize that an observation is an interaction between the particle and its environment (that leaves a record of what just happened somewhere in the environment). So it's not a matter of "just looking", as the video suggests. But the double-slit experiment is still pretty amazing.

    The the rest of the video is accurate enough, but the movie it's from is not. So if you've seen it, please disregard everything else they said.
  4. Dec 5, 2012 #3
    The double slit experiment amazes me too, and it blows my mind every time I come across it even through I studied this stuff decades ago as physics student. To see how crazy this really is I would like to know what the result of the following thought experiment should be: Assume we build a robot that can assemble a simple contraption reproducing the experimental setup of the double slit experiment. The experimental setup should be such that only one or as few electrons as possible are sent into the double slit region at a time, and an array of sensors registers the incidence of electrons. Each experiment ends after sending only one or very few electrons through the double slit, and the information from the sensors is written down or registered in some computer. The experiment is reproduced a few ten or hundred thousands times in several places, using different robots that carry it out, different actual apparatus and sensors, but the design, dimensions, and parameters are identical (within manufacturing variations). Also identical is the protocol as it is carried out by a small robot with a fixed programming. Optimal would be if the entire experimental setup could be purchased cheaply in toy stores, so that the experiment can be carried out in many places and many people. All the sensor data from all the experiments are gathered after a few years and evaluated: Does the interference pattern still show up?
    If yes (which I find very plausible) I would say it is true that we have an experiment for which the math makes exactly the right predictions. I think I even understand that math quite well. But the experiment would also confirm that nothing is explained by it.
  5. Dec 5, 2012 #4
    the probability amplitude woulld be the same for all the setups, and people have performed the DSE with 1 photon at a time and seen the diffraction grating in such cases.
  6. Dec 15, 2012 #5
    I think the point of rewtnode's thought experiment, dipstik, is that each experimental apparatus only performs the experiment once, with a single photon. Where that photon hits the detector is recorded in some central database, and then the apparatus is destroyed (or at least never used again). Then, later, after thousands of experiments have been done by thousands of unrelated apparatuses in thousands of unrelated locations, the results of where each photon hit the sensor are tallied up. Does the interference pattern appear?

    That's an interesting thought. I'd think it would. If the location of the photon hitting the detector is purely statistical, then it's the same as having thousands of people roll dice all over the world at different times and comparing results to see if each result still comes up 1/6th of the time. The answer for dice is an obvious yes, and is proven by casino profits in gambling towns. The double slit version of the experiment should actually be pretty easy to test on a smaller scale than the one described. I think the astonishing thing would be if the pattern DIDN'T appear. That would be like discovering that if a thousand people roll a six sided die once and then throw it away and then compare results then they will all roll 3.
  7. Dec 15, 2012 #6


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    You would have to remake the apparatus exactly, at least within a fraction of a wavelength of the same distances. Not too hard with radio waves, but pretty tough with light.
  8. Dec 15, 2012 #7


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    Indeed, the Double-Slit Experiment is the most intruiguing feature of quantum physics that buffles anyone that encounters it.
    Have you ever thought that in the future it'll maybe be possible to observe the wave-nature of supermacroscopic objects, even intelligent organisms? What would we feel if they threw us (our body) in a double-slit-like experiment and observed that we went through both slits? Ofcourse we probably wouldn't feel/see/hear anything because we would be completely isolated from any enviroment.
    Maybe some of you read this, and say: "You just ascribed a wavefunction to a whole human!!", and think that this is so impossible. But it's not! It's not impossible if you know what objects have "gone through both slits" in the laboratory the recent years!
    We know that photons behave like waves, electrons, single atoms, ..even molecules! Did you know that the molecule C60 fullerene comprised by.. 60 atoms have "gone through both slits"? If you hear this for the first time, you're probably like.. "Really!??!". But it doesn't stop there!
    The experiments have advanced so much that physicists in Vienna have succesfully prepared the molecule TPPF152 C168H94F152O8N4S4 , a bound system of 430 atoms!!! and size ~5 nanometers, in a superposition of two positions with separation 2 orders of magnitude larger than the size of the molecule itself! In other words, the wavefunction of this gigantic 430-atom molecule spread out and covered an area 100 times larger than the molecule itself. It's so mind blowing..
    You can see the molecules by yourself in the following Nature (Open) article,
    http://www.nature.com/ncomms/journal/v2/n4/full/ncomms1263.html .
    The biggest one that i'm referring to is the one that has two feet, two arms and a head! :tongue: Not kidding, it's not hard to imagine this being an actual person..

    Let's suppose for a moment that quantum mechanics is so correct that if you isolate a gigantic object (e.g. human or even a dinosaur), no matter how big, from the enviroment , its center-of-mass wavefunction will start spreading out covering space orders of magnitude larger than the size of the object itself (i don't care about the time that will take). Now, think of Bohm's pilot-wave theory. It says that when in superposition the "actual particle" is moving like crazy in random trajectories driven by a quantum potential. Isn't it quite awkward if you apply this interpretation to a big object? If we someday achieve superposition of a human, then a quantum potential is going to drive the whole person around like crazy through impossible trajectories even exceeding the speed of light. It's so non appealing... even if it stands mathematically.
  9. Dec 16, 2012 #8
    I did read that in Stephen Hawking's new book. Simply amazing that even C60 behaves this way. So the stuff that we're made up of are all in superposition...what does that say about us and true reality?
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