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Is the world really colourless?

  1. Apr 7, 2009 #1
    I have a question that's bothering me,thought some of you on this forum might have an answer: We see things because (a) they either emit light or (b) they reflect light. Now, visible light is part of the electromagnetic spectrum which put simply is an orderly classification of electromagnetic waves with respect to their frequencies/wavelengths. Now, as I understand it, our eyes can 'see' visible light because they detect electromagnectic waves with a particular frequency (that of visible light) and generate an electrical signal, which is sent to the brain. The brain then interpretes this signal and voila, we get an image. Is colour then a creation of the brain? Is the world in reality colourless?
     
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  3. Apr 7, 2009 #2

    Danger

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    Welcome to PF, Prearius.
    Essentially, you are correct. The concept of colour is a human construct, based upon the way that we perceive EM radiation. That is not to say that the world is colourless (all wavelengths are abundant), but the word has no meaning outside of human perception.
     
  4. Apr 8, 2009 #3

    russ_watters

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    I would adjust that last part to say 'the perception of color is different for different animals'. Google for animal color vision and you'll find links that simulate what colors look like to animals: http://www.colormatters.com/kids/animals.html
     
  5. Apr 8, 2009 #4

    Danger

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    I agree completely about the perception, but the concept of colour is human.
     
  6. Apr 8, 2009 #5

    vanesch

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    As far as we know, every "concept" is human :smile:
     
  7. Apr 8, 2009 #6
    I have always found this fascinating.

    I understand how it is we are able to determine somewhat what colors some animals can see, but how are we able to determine eyesight for animals that see outside of the visible spectrum? Dolphins-Ultrasound, Bees-Ultraviolet.

    Is this also determined by cones?
     
  8. Apr 8, 2009 #7

    Danger

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    Touche... :biggrin:
    Goliath... ultrasound is not technically part of the EM spectrum.
     
  9. Apr 8, 2009 #8
    About 6% to 8% of males, and about 1% of females, are color blind due to either brain or nerve damage. Military like to have color blind people in their ranks, because color blind peole are better able to spot camouflage.
     
  10. Apr 8, 2009 #9
    If you had a mass of neutrons, like, enough neutrons to occupy 1 liter of space (say in a sphere), what color would it be (just neutrons).

    Would it be white (reflect all light), black (reflect no light, possible due to its incredibly large mass) or transparent (no electrons jumping around to produce photons, so it just goes right through)?
     
  11. Apr 8, 2009 #10
    I'd propose this as "the question of the year" :smile:
     
  12. Apr 8, 2009 #11

    vanesch

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  13. Apr 8, 2009 #12

    Danger

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    Since it would essentially be a very small neutron star, I suspect that the reflected light would be gravitationally red-shifted to a large degree.

    edit: Nice link, Vanesch. I just spotted it after posting.
     
  14. Apr 8, 2009 #13
    Awesome!
     
  15. Apr 8, 2009 #14
    Almost everything (but not necessarily everything) is relative to human perception. Ultimately, the only camera angle we have of the universe is the human mind. Thus, you could probably assume that there are features of nature out there beyond our detection; for example, if we did not evolve to perceive light, how long would it take us to realize the existence of electromagnetic waves? Concepts like this (those involving the level of limitations of our perception) could extend to dark matter and so forth.
     
  16. Apr 8, 2009 #15
    Sound is the same way as color, you could say that there is no such thing as sound, it is just vibrations picked up by little bones in our ear.
     
  17. Apr 8, 2009 #16
    Now, that's interesting. A group survival trait. Do you have a link?
     
  18. Apr 8, 2009 #17

    russ_watters

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    No, not really. Sound and light are both continuous spectrums, but sound is not divided into discrete groupings of frequencies by our ears, unlike our eyes.

    Regarding the simulations of the differing color vision, the separation of frequencies into colors is accurately depicted by the simulations - what is not (as suggested) is how those colors actually appear to us. Consider this:

    We have red, green, and blue photoreceptors in our eyes. What would happen to our perception of color if our brains were re-wired to make the red ones appear green and vice versa?
     
  19. Apr 8, 2009 #18

    DaveC426913

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    You want to wow your mind, look up tetrachromats.
     
  20. Apr 9, 2009 #19
    I am not all that familiar with Synesthesia, having read just a few things. The colors that these individuals associate with sounds, would these colors be only produced by the mind, or could it be possible they are somehow optically viewing these sound waves?

    Do they see still the sounds if their ears are covered? How about their eyes? I haven't found anything that specifically touches on this aspect.
     
  21. Apr 9, 2009 #20
    That ultimately everything is relative to human perception is a brilliant concept. Correct me if I'm wrong, but I think that's somehow related to the observer problem in quantum mechanics (in essence, a state changes merely by looking at it). That's quite puzzling.
     
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