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Has knowledge changed perception of reality?

  1. Jul 15, 2003 #1
    When I first learned long ago that huge moon during moonrise is not optical distortion, but pure human mind produced illusion, I was quite astonished.

    http://www.amnh.org/naturalhistory/city_of_stars/21_full_moon.html [Broken]

    It is explained away by fact that for human, atmosphere above seems spherical and touching with horizon. Because we can see horizon only relatively close to us, it "seems" correct that objects at that distance must be closer that straight above. Now, because light from moon in the sky doesn't show any reduction in size, mind works it out that moon must be "as close" as sky above and as close as horizon, and it makes a "correction" due which we perceive moon literally huge.

    Probably many have read from books hot arguments in past between people who believed earth was flat and those who new already that its a sphere. Arguments were as simple as "walk up the hill and see yourself - its flat". I find it amusing, because as soon as I get some 20-30 feet elevation, I can immediately "see" curvature of horizon, and there is no question of such kind, at all.
    I can't remember how I perceived it as a child, but I know for sure that after a first flight by plane its been like that ever since.

    This made me really think if how we perceive reality with our eyes is strongly influenced by what we know about it? Mean, people in the past were not stupid liars, they really saw the flat earth. And we know its sphere, so we see it as a curved horizon. This mind game must be possible, as anyone who have seen huge moon on horizon can tell.

    But what are the limits of such influence on perception?
    Last edited by a moderator: May 1, 2017
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  3. Jul 15, 2003 #2
    That is fascinating Wimms, I never knew that, I always assumed it was just an optical distrotion like red skies.
    When it comes to the things we can't see, the abstract, the eyes are mostly the ability to reason.
  4. Jul 16, 2003 #3
    no more comments?
    I mean, if we'd see something completely alien, our mind would easily convert it into something familiar. How about space around us?
  5. Jul 20, 2003 #4
    Hello wimms,
    Great and intriguing title ! Do you know the book called "The Astonishing Hypothesis/The scientific Search for the Soul" by Francis Crick.
    There are lot's of things in there (you may not find it that surprising and astonishing but :)
    Perception changed by knowledge sounds correct to me from my personal experience of any kind...
    Think about simple sky observation at night. Is it not the same thing we found after a year, yes it is but there are some changes other than our eyes getting use to observing celestial bodies. It is not smt -imo- about observing just around. There is a hypothesis claiming that human vision is a 'made up'comment -may be you know- by the everything making up the mind. So the word of reality has to be discussed I guess. (In terms of the title) But I don't just mean the situation when we pick up according to our needs. What do you think?

    Last edited: Jul 20, 2003
  6. Jul 20, 2003 #5


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    quite interesting wimms...i think this is proof that the human senses are definitely subjective, and these senses are relied upon when interpreting the objective facts...
  7. Jul 20, 2003 #6

    Tom Mattson

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    That is fascinating. I always assumed it was an optical illusion. This assumption was bolstered by the few times I've seen the "huge moon" in movies (the only one I can think of right now is Contact with Jodie Foster, but I know there are more).

    Does the camera actually capture that image, or do they have to make the moon look big with special effects?
  8. Jul 20, 2003 #7
    If you think that's cool, you should check out the Einstein effect. It happens when the light is just right in the morning hours and shinning on a pool of fog. When your shadow falls on the fog, electric dancing rays of light seem to sprout out all around your shadow. Even more bizarre, if someone is with you neither of you can see each other's rays of light and the effect does not show up in photographs. I've seen it once myself and, believe me, it's enough to make someone become religious.

    One third of human brain is devoted to our vision which is arguably the best of any species. Technically, your eyes are the largest nerves and most exposed in the body. Something like eighty percent of what we see is just made up in the mind, so the idea that a great deal of what we see isn't real comes as no surprise.

    For example, only the sweet spot of the retenia picks up the pattern in say a carpet and the mind/brain fills in the same pattern for the rest of the carpet the eye perceives. That's why when you loose something small on a patterned carpet it can be so difficult to find. Your brain literally doesn't see it. Another example, when you see cars flying by in your peripheral vision they seem to stagger, this is the actual rate at which your eyes/brain take pictures. To achieve the fluid motion we perceive, the brain fills in all the gaps.
  9. Jul 21, 2003 #8
    Funny thing is that mind is deceived by captured image aswell. To convince oneself they offer to make 2 photos of the moon, one when its up in sky and one when its 'huge' including skyline. Then compare the photos - your mind tells you dammit, on horison it IS huge. Then take a ruler, and they'd measure exactly same size.. Cover the objects at horison, and moon 'clicks in place' to normal size.. I haven't tried that, but imagine could be quite a weird feeling..
    Important factor is the skyline, moon doesn't seem huge always.. it depends on what is seen on horison below it.

    Wuli, what are these electric dancing rays?
    Last edited: Jul 21, 2003
  10. Jul 24, 2003 #9


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    There's a distinction to be made between the moon illusion and your postulation that your knowledge / past experience has influenced how you see the horizon. With your horizon example, you are wondering if the conscious faculty of reason can affect our subjective perceptual experience (e.g. if you believe the earth is a flat then it will look flat). To that I might answer yes, but probably only in ways far more subtle than something as basic as the apparent sizes or shapes of objects. The conscious, deliberate reasoning of the horizon example isn't the same kind of 'reasoning' that occurs in the moon illusion. That is, no matter what you believe and no matter what arguments you recite in your mind, the moon illusion will persist (try it!); it's not a function of conscious belief, but rather is just a result of how the visual system itself is wired. A similar example is the Mueller-Lyer illusion (http://www.yorku.ca/eye/m-lillu.htm). Even after we rationally, objectively determine that these two lines are of equal length, they still look different sizes; it's just a heuristic hardwired into our brains to 'reason' that the >--< line must be longer than the <--> line of similar (in this case, equal) length.

    The brain basically constructs its whole perceptual worldview on such heuristics which function rationally/consistently in most cases (e.g. if an object is sitting on the horizon it is probably close to other objects on the horizon), but which occassionally break down in exceptional situations and thus produce astounding and confounding illusions like this moon illusion. It really brings you a long way towards understanding the relationship between consciousness and objective reality-- not just simply that 'things ain't what they seem,' but it also makes you appreciate how the brain has to build its perceptual model of reality from scratch. In a way it's more accurate to say that you look inside of yourself (at the pretty picture your brain paints for you) than to say you really see something external. The trick is that your insides map so well onto the outside.
    Last edited by a moderator: May 1, 2017
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