Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Shooting humans through a giant double slit experiment

  1. Dec 4, 2009 #1
    Lets say some aliens scaled up the two slit experiment to an enormous size. It is so large that shooting 100kg masses of carbon through the slits creates a diffraction pattern. The aliens then decide to replace the carbon with some captive humans and shoot them through the slits to see what happens. Do you believe the aliens would still see a diffraction pattern?
  2. jcsd
  3. Dec 4, 2009 #2
    If the aliens can successfully get a diffraction experiment to work with 100kg blocks of carbon at room temperature, then they should be able to do it with humans too under the same conditions.

    For it to work, they'd have to turn the lights off, and evacuate the chamber, so the human would have to be in some capsule so that he can still breathe. You'd hope he isn't emitting too much thermal radiation, but you'd have the same problem with the carbon block.
  4. Dec 4, 2009 #3


    User Avatar
    Science Advisor
    Gold Member

    No reason why it shouldn't work in principle.
    However, from a practical point of view decoherence would -as far as we know- prevent you from performing the experiment with anything that big; a human would couple too strongly to the environment.

    I guess it MIGHT be possible to repeat the double slit experiment with e.g. a small virus (it has been done with C60 which is a very big molecule). although EM coupling (essentially thermal radiation) is a big problem for something even of that size.
  5. Dec 5, 2009 #4
    Do you think it makes a difference to use humans, because humans are "observers" ? If it works for carbon, it works for humans. Nature doesn't care about our consciousness.
  6. Dec 5, 2009 #5
    You can't get any visible diffraction patterns with macroscopic bodies. If anything, you shouldn't go "really big", you should go really small and really slow. Distance between peaks and troughs in the diffraction pattern is inversely proportional to the mass, to the velocity, and to the distance between the slits.
    Last edited: Dec 5, 2009
  7. Dec 5, 2009 #6
    Quantum Mechanical textbooks are often very unclear on what defines an observer. But if you where to carry out a diffraction experiment using humans, then they would have to be prepared in a state where they cannot be considered to be observers. You could ask the same question you are pondering, by considering if it's possible to carry out diffraction questions using photon detectors. If you carried out the math I would assume you come to the conclusion that it's possible, but only when the detectors become incapable of detecting.
    I think you could do this by considering the outcome of a traditional double slit experiment, but then adding a photon collision midway (the observation).
  8. Dec 5, 2009 #7


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Larger mass means shorter wavelength, so in the human diffraction experiment (if the humans are to be treated as "particles") the slits would have to be much narrower than the ones in an electron diffraction experiment. When you shoot a human through such a slit, what comes out on the other side won't be human. It will be radiation, consisting of many different species of particles. These particles will have a wide range of momenta, and some of them might decay to lighter particles on the way to the detector. This will make it very hard to find anything that looks like a diffraction pattern in the dectector results. But I suppose there will be a peak in the velocity distribution of each species of stable particles, so the detector results should at least contain such patterns, but they will be very difficult or impossible to see due to the "noise" from all the other particles.
  9. Dec 5, 2009 #8


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    No difference at all.

    It's not going to work for carbon either, for the same reason. (See my previous post).
  10. Dec 5, 2009 #9


    Staff: Mentor

    You would need some serious advances in cloning too, in order to prepare a suitable ensemble of identical humans. :smile:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook