Humans emit very small quantities of light

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Discussion Overview

The discussion revolves around the phenomenon of humans emitting very small quantities of light, particularly in the context of visibility, photon detection, and the nature of light emitted by the human body. Participants explore various aspects including the intensity of emitted light, the mechanisms of photon detection by the human eye, and comparisons to other light sources.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants note that humans emit light at levels that are 1,000 times less intense than what the naked eye can detect.
  • There is a discussion about the conditions under which dark-adapted eyes can detect individual photons, with some arguing that being naked may enhance photon detection due to pupil dilation.
  • One participant recalls a childhood belief that the graininess of photons in the dark was due to atoms in the air and questions whether the factor of 1,000 is probabilistic.
  • Another participant expresses curiosity about the contribution of black body radiation from humans compared to other forms of radiation, noting discrepancies in expected results.
  • Some participants discuss the minuscule nature of the radiation emitted by humans, including fluorescence from chemical traces on the skin.
  • There is a humorous exchange regarding visibility of stars in New Jersey, with one participant attributing it to light pollution and another joking about NASA's presence in the state.
  • Clarifications are made about the detection of photons by the human eye, with some stating that while individual photons can be detected, a neurochemical signal requires multiple photons to be perceived as light.
  • One participant describes their experience of seeing graininess in their vision and connects it to the perception of individual photons, while another compares this phenomenon to noise in digital photography.
  • There is a mention of the presence of photons in extremely dark environments, such as mines, due to various natural processes, including nuclear decay and cosmic rays.

Areas of Agreement / Disagreement

Participants express a range of views on the nature of light emitted by humans and the mechanisms of photon detection. There is no consensus on the specifics of photon visibility, the significance of black body radiation, or the conditions under which individual photons can be perceived.

Contextual Notes

Some claims about photon detection and visibility depend on specific conditions and assumptions that are not fully explored, such as the influence of light pollution and the physiological responses of the eye under varying light conditions.

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http://news.yahoo.com/s/livescience/20090722/sc_livescience/strangehumansglowinvisiblelight

Weeird!
But awesome.
 
Last edited by a moderator:
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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)
 
But if you're naked, your eyes are more likely to be dilated and you'll be better able to detect individual photons.
 
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?
 
Loren Booda said:
If we can "see" individual photons, is this factor of 1000 probabilistic?
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.
 
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

I would like to know how significant the difference between the black body radiation and this "other" radiation is
 
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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
 
mgb_phys said:
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

And this stuff is also described as being seriously miniscule. So I don't want to know what the relative difference is.
 
And I suppose I can't see any stars here in New Jersey because they went away?
 
  • #10
Pinu7 said:
And I suppose I can't see any stars here in New Jersey because they went away?
No it's because you can't see one photon/second from a star on top of 100,000 photons/sec from light pollution.
 
  • #11
mgb_phys said:
Dark adapted eyes can detect individual photons (you don't have to be naked)

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.
 
  • #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.
 
  • #13
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.
 
  • #14
it never gets completely pitch black anywhere,
Try being in a mine with your lamp turned off.

I can't see how it could get any darker. :)
 
  • #15
Alfi said:
Try being in a mine with your lamp turned off.

I can't see how it could get any darker. :)

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...
 
  • #16
Pinu7 said:
And I suppose I can't see any stars here in New Jersey because they went away?
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.
 
  • #17
negitron said:
There are still photons, including those of visible light, being emitted from various nuclear decay products, cosmic rays, thermal jitter and neutrino activity.
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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