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Humans emit very small quantities of light

  1. Jul 22, 2009 #1
    http://news.yahoo.com/s/livescience/20090722/sc_livescience/strangehumansglowinvisiblelight [Broken]

    Weeird!
    But awesome.
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Jul 22, 2009 #2

    mgb_phys

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    "1,000 times less intense than the levels to which our naked eyes are sensitive"
    Dark adapted eyes can detect individual photons (you don't have to be naked)
     
  4. Jul 22, 2009 #3

    BobG

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    But if you're naked, your eyes are more likely to be dilated and you'll be better able to detect individual photons.
     
  5. Jul 22, 2009 #4
    I believe this topic, more or less, appeared years ago on PF.

    As a child I thought the graininess of photons in the dark was actually atoms in the air.

    If we can "see" individual photons, is this factor of 1000 probabilistic?
     
  6. Jul 22, 2009 #5

    russ_watters

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    I would think so: just because you can "see" individual photons, that doesn't mean you can form an image with them. Our eyes do not store/accumulate photons the way a camera does.
     
  7. Jul 22, 2009 #6
    Well, I was curious how much visible light is emitted by a human simply due to black body radiation...but it's giving me a weird answer,

    http://img33.imageshack.us/img33/481/bodyg.png [Broken]

    I would like to know how significant the difference between the black body radiation and this "other" radiation is
     
    Last edited by a moderator: May 4, 2017
  8. Jul 22, 2009 #7

    mgb_phys

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    The short wavelength tail of a 310K black is going to be seriously tiny.
    This radiation is supposedly fluorescence from chemical traces on the skin
     
  9. Jul 22, 2009 #8
    And this stuff is also described as being seriously miniscule. So I don't want to know what the relative difference is.
     
  10. Jul 22, 2009 #9
    And I suppose I can't see any stars here in New Jersey because they went away?
     
  11. Jul 22, 2009 #10

    mgb_phys

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    No it's because you can't see one photon/second from a star on top of 100,000 photons/sec from light pollution.
     
  12. Jul 22, 2009 #11

    negitron

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    That's not entirely accurate. Although the light-sensitive cells in the retina are capable of responding to a single photon, a neurochemical signal is not sent to the brain until several photons have been detected within the span of about 100 ms.

    Cite.
     
  13. Jul 23, 2009 #12
    Just a small OT question..

    Whenever I look around and focus a bit, I notice my vision is grainy and it feels like I see individual photons.. I never knew until today what this was, so those are photons I'm seeing?
    If it gets dark there's always millions of small light particles that are barely visible, it never gets completely pitch black anywhere, but i can also see them in pure daylight.
     
  14. Jul 23, 2009 #13

    ideasrule

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    negitron's source also tells us that about 90 photons need to enter the eye for a flash of light to be detected, so it's impossible to actually see single photons. The graininess seen by octelcogopod is analogous to the noise in digital photos: in dark conditions, the eye boosts its sensitivity to the max, even if that means making frequent false detections.
     
  15. Jul 23, 2009 #14
    Try being in a mine with your lamp turned off.

    I can't see how it could get any darker. :)
     
  16. Jul 23, 2009 #15

    negitron

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    There are still photons, including those of visible light, being emitted from various nuclear decay products, cosmic rays, thermal jitter and neutrino activity. Of course, you need a photomultiplier tube to detect them...
     
  17. Jul 23, 2009 #16
    It's proof that NASA never went to NJ. The photos were staged in New Mexico which looks a lot like New Jersey if you squinch your eyes up real tight.
     
  18. Jul 23, 2009 #17

    mgb_phys

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    You can see thermoluminescence quite easily, unroll electrical tape or even tread heavily on some types of sand and you get a surprising amount of light.
     
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