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The Mechanism of Seeing

  1. Feb 22, 2010 #1

    JK423

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    I'd like to share with you some current thoughts that i had.

    Say we are 1-Dimensional. Our "eye" is at the O point, and there is an atom on some distance 'x' from our eye.
    The atom emits a photon, which comes into our eye and we detect it - we see a flash.
    Can we have any clue about the initial emmittion point of that photon? From which distance 'x' from our eye was emitted? Or rephrasing: Can we know where the atom is just by detecting the photon?
    The answer is 'No' ofcourse.

    But that seem to be contradicting!!
    In our ordinary life we see Objects. And actually, we see the colour of those objects coming right out of their surface! That means that we know where the atoms -that emit the photons- are located! But didnt we say just before that by detecting a photon we cannot know the point from which it was emmited?? Why do we see what we see?
    -Imagine you are in outer space. No stars no nothing, just black. And suddenly a ball is lightened. Can you say at which distance approximately this ball is?
    The answer is No! It can be a small ball close to you, or it may be a huge ball in the size of galaxies light years from you! You cannot know.
    However, when you see a basketball in your everyday life, you know that its there and not in the andromeda galaxy.
    The are numerous such examples.

    I concluded in this: If you dont have a reference point, you cannot know any distance. In our everyday life, we have numerous such points to refer. Our brain processes all this information and gives us the feeling that we know what the distance is.
    -When we move our head, and we actually move according to the object, then we know that the object is close to us.
    -We're 'measuring' distances by comparing the sizes of the objects to others to which we are familiar with. If you think about it, we do that all the time without thinking about it.
    This is what breaks the symmetry of the original problem!

    And one last example:
    Say, again, you are in outerspace (there are no reference points there!)
    One eye is closed and your head is still -you cannot move it at all.
    Now you see a glowing ball -like before. The question is: Can we know where it is?
    The answer is absolutely know. Now that you cannot move your head at all, the glowing ball could actually be VERY small and only some nanometers away from your eye, or it could be so HUGE many ligt years away! You certainly cannot know, as you cannot know where the atom that emits the photon is. Its basic physics, this is what we should expect to happen.
    And i kind of explained to you why this is not happening in our everyday life.


    What do you think?
     
    Last edited: Feb 22, 2010
  2. jcsd
  3. Feb 22, 2010 #2

    russ_watters

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    It is part having a reference and part binocular vision.
     
  4. Feb 22, 2010 #3

    JK423

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    Well, certainly binocular vision plays a role in order to see in 3D (two sides of an object simultaneously). But i didnt refer to it because even with one eye closed you can still tell the distance in the everyday life.
     
  5. Feb 22, 2010 #4
    It is much more difficult with one eye. A sense of distance is still gained from the minute amount of parallax achieved by moving your head from side to side.
     
  6. Feb 22, 2010 #5

    JK423

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    Certainly, i talked about that in my last example:
    But still, the main contribution to the distance 'feeling' is still the reference points (which has to do with the size of objects, how their size varies when they move away or close to you etc).
    Moving your head clearly contributes when the object is close to you. But when far away, nothing.
     
  7. Feb 22, 2010 #6
    The brain uses a number of clues to work out the distance to an object, not just light but also sound. Either way, parallax is important. (In the case of sound it would be the difference between the sound from the same source entering the two ears.)

    Yes, I agree with your general proposition that there is no innate distance information in a single photon reaching the eye from a source. Distance is something we humans have to find by induction, using a number of clues. It only works for small distances, which of course, from a survival point of view, is all that is necessary to know how far away that dangerous tiger was or that car is on the road.
    We didn't need to know whether the Moon or Sun was nearer!
    Those distances are deduced from other information. Parallax, though, is still used for some astronomical distance measurement.
    There is no parallax in your one dimensional world, as it needs a displacement at right angles to the line between you and the object to function. It needs 2 dimensions to work.
     
  8. Feb 22, 2010 #7

    JK423

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    I agree with you totally :approve:
     
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