The light is in our eyes...

Discussion in 'Physics & Math' started by Quantum Quack, May 21, 2017.

  1. Seattle Valued Senior Member

    Messages:
    2,573
    As pointed out above, seeing is done in the brain. It tries to help fill in the gaps. You have a blind spot in each eye (where the nerve bundle comes in) but it is at a different spot in each eye so it's an issue only when you close one eye and look a certain way.

    You can find the blind spot and make the tip of your finger disappear when you do it right but even in this case you still get a background image that seems to fit. This is just your brain making it up.
     
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. Quantum Quack Life's a tease... Valued Senior Member

    Messages:
    17,542
    Thanks guys...
    ok the key word I needed was refraction, I did what I should have done before posting and googled you tube.
    and found this classic:

    presume circa 1950s -60s B&W 10 minutes-ish
     
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. Quantum Quack Life's a tease... Valued Senior Member

    Messages:
    17,542
    The question though is why the image appears to be "over there" and not inside my eye.... (there is a scientific term for this issue but I simply can not remember it...)
     
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. sweetpea Registered Senior Member

    Messages:
    776
    Because of the structural arrangement of the lens and receiving surface at the back of the eye, an inverted image forms. The brain corrects this to right way up. How does the brain know what is right way up...via experience over its millions of years of evolution dealing with its environment via its senses. The same goes for depth perception. You don't 'see' space, your brain knows how to interpret information, that is parallax.
    Again, how does it know...experience over its millions of years of evolution. Seattle did mention evolution.
    If your in a darken room with just a distant sphere light source, and the sphere is equally bright all over, you may have difficultly knowing it's not a flat disk also equally bright all over.
    Edit to add...If you showed a baby a photo of parallel train lines meeting at a point in the distance, would the baby know that point is in the distance...brain experience of the eye.
     
    Last edited: May 21, 2017
  8. Michael 345 Valued Senior Member

    Messages:
    3,755
    You might be looking for Aniseikonia

    which I don't think answers your question exactly

    https://en.m.wikipedia.org/wiki/Aniseikonia

    Please Register or Log in to view the hidden image!

     
  9. river

    Messages:
    9,793
    What do you mean by " image appears to be " over there " and not inside my eye ?
     
  10. Quantum Quack Life's a tease... Valued Senior Member

    Messages:
    17,542
    Just to clarify...

    the following image although for all intents and purposes quite correct, can be misleading:

    Please Register or Log in to view the hidden image!



    It shows the reversed image on the retina and the source.

    yet the following image describes all we actually experience:

    Please Register or Log in to view the hidden image!



    According to well understood theory, we do not actually see the source we only see the light that the source emits. ( on our retina)
    How are we able to say we are seeing the source?
    How do our light effect models allow for us to see the source (at location, "over there") even if historical ( ie. astronomy).

    BTW apologies for any confusion as I am trying to find out how to ask the question.
    images taken and modified from posted video as we go...
     
    Last edited: May 21, 2017
  11. river

    Messages:
    9,793
    How are we able to say we are seeing the source?

    Because the source is specific .

    Sky is not confused with a rock .

    Water is not confused with iron .

    BTW, B&W , NO problem
     
  12. Quantum Quack Life's a tease... Valued Senior Member

    Messages:
    17,542
    but you are only seeing the light in your eyes. Certainly not the source (directly)
     
  13. river

    Messages:
    9,793
    Yet the source directly is the source of light , from that source .
     
  14. Quantum Quack Life's a tease... Valued Senior Member

    Messages:
    17,542
    no it is only the light that is emitted.
    eg
    Star in the sky...
    Are we seeing the star or the just the light it emits?
     
  15. Quantum Quack Life's a tease... Valued Senior Member

    Messages:
    17,542
    I'll post the example image again.
    Claim:
    This is all we see (experience) of the source:

    Please Register or Log in to view the hidden image!

     
  16. river

    Messages:
    9,793
    The star .

    Notice that any light from a star is focused to that point of source .
     
  17. exchemist Valued Senior Member

    Messages:
    6,637
    When we say that we "see" anything, what we mean by that is that we detect enough light from it (a) to form an image on our retina and (b) which our brain can process in a comprehensible way.

    So it seems to me that the distinction you are making is not a real one.
     
  18. Michael 345 Valued Senior Member

    Messages:
    3,755
    The image on the retina is the light from the source hence represents the source

    By the way while the image is shown correctly upside down should it also be transposed left to right?

    About 40 years ago I watched a movie from The Moody Institute where someone was fitted with prism glasses which turned everything upside down

    After only a few days his vision reverted to normal while wearing the glasses

    He was able to pilot a plane with the glasses on

    At the end of the experiment with the glasses removed his view again became upside down

    This only lasted a short time also before reverting to normal

    But I do grasp your idea of why do we see the source out there

    Not exactly unknown or unexplained are you aware that light is invisible?

    You cannot see light in its raw form

    You can only see light if emitted from or bounces off a source

    Need more thought on in the eyeball puzzle

    Please Register or Log in to view the hidden image!

     
  19. Quantum Quack Life's a tease... Valued Senior Member

    Messages:
    17,542
    In the case of a star the actual star isn't even in the location we "see" it to be... some cases millions of years have passed since the light impacts upon our retinas and the star has moved from it's original position.
     
    danshawen likes this.
  20. danshawen Valued Senior Member

    Messages:
    3,942
    Well, for one thing, if you used one of those new, fancy femtosecond shutter speed cameras, you would not only see that silhouette against the light beyond the door. You would also see what exactly was around the edges of the long sides of that door. This is possible only because light also has the properties a wave phenomenon. The door with a silhouette is actually a double slit.

    When you observe one side of the slit, you decohere the other, so it will require more than one exposure with your femtosecond camera to see everything there is around both corners of the sides of the door. The direction you observe matters.
     
    Last edited: May 21, 2017
  21. danshawen Valued Senior Member

    Messages:
    3,942
    Because of the Ehrenfest paradox, if that star appears at 180,000 ly distant on the other side of the Milky Way, you also actully see a Lorentz distortion (contraction) of the distances aeons ago between that star and the stars in relative motion along either side of it.

    If you are on the rim of a relativistic merry-go-round, any element of the rim with an instantaneous velocity component that is opposite yours will begin to Lorentz contract, and the point on the other side of the rim directly opposite your position will have maximal contraction. The amount of the contraction would be independent of the direction of spin.

    Distance perspective for closer objects, in your eye or in any optical instrument, is simply an artifact of the inverse square law, of course. Sorry, if that was all you were going for, it's just too simple. I think I know you better than that, QQ.
     
    Last edited: May 21, 2017
  22. karenmansker HSIRI Banned

    Messages:
    638
    NOT completely true . . . . . one can 'judge distances' by mental comparison of apparent observed size relative to known size. Things farther away are generally perceived as smaller.
     
    danshawen likes this.
  23. river

    Messages:
    9,793
    Disagree .

    Yeah well there is parallax and precession . Which understands the movement of stars.
     

Share This Page