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Q & A: Light from human bodies?

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Most recent answer: 07/24/2009
I read an article that said the human body emits light that is 1000 times lower than our eyes ability to detect it. so in theory if 1000 or 10000 people were place in a light tight room then would that room be visibly lit by their bodies?
- Steven Groves (age 18)
Kingston Jamaica
All warm bodies emit electromagnetic radiation.  Those, like the sun, that are extremely hot are incandescent and we can see them.  Those bodies, like us, have a temperature close to 37 oC emit only in the low infra-red region of the spectrum.      The reason for this has to do with the physics relationship between temperature and radiation spectrum. 
See:   for some gory details. 
Human eyes are pretty much insensitive to this kind of radiation. So, the answer to your question is no.   However if you put 1000 people together in a room it could get very warm.  A normal person emits about 100 Watts of heat.


Based on what you write, it sounds like if somehow you could get the light from all 10,000 people to come from the same direction,  there would be just enough visible component to detect. However, the light comes in from different directions and lands on different parts on the retina and remins below threshold. Mike W.

(published on 07/24/2009)

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