Research shows humans emit photons !?!

[Royston]

Please see the Discovery article below...

 

http://dsc.discovery.com/news/briefs/20050905/handlight_print.html

 

"Not only the hands, but also the forehead and bottoms of our feet emit photons," Hiramatsu said, and added that in terms of hands "the presence of photons means that our hands are producing light all of the time."

 

The light is invisible to the naked eye, so Hiramatsu and his team used a powerful photon counter to "see"it.

 

The detector found that fingernails release 60 photons, fingers release 40 and the palms are the dimmest of all, with 20 photons measured.

 

The findings are published in the current Journal of Photochemistry and Photobiology B: Biology.

 

Can anyone explain this phenomenom ? I'll try and find the published article, but for the time being if anyone can explain how this occurs and more puzzling why these particular parts of the body...first time I've heard of humans emitting photons.

[5614]

Well humans emit IR (infrared) the whole time.

 

IR is part of the EM (electromagnetic) spectrum so IR is comprised of photons.

[YT2095]

Well humans emit IR (infrared) the whole time.

 

IR is part of the EM (electromagnetic) spectrum so IR is comprised of photons.

 

yeah, I was just going to say, Of Course we do!

even dead people will emit some as the body decays and certain chemical actions take place.

that part isn`t News

[Severian]

The detector found that fingernails release 60 photons' date=' fingers release 40 and the palms are the dimmest of all, with 20 photons measured.

[/quote']

 

I don't understand what this research is getting at. We must emit a huge number of photons from our bodies - not this tiny number!

[YT2095]

the only thing I can think of that maybe it`s of a certain Visible frequency that you emit?

and not the sort that fire dept and S&R unit cameras use to rescue you with, perhaps?

[Severian]

The article specifically said that they were not visible, but maybe they meant in terms of luminosity rather than wavelength. But even then, I would still expect more than this - any spectrum has a long tail.

[YT2095]

but when you consider a single photon even at a visible wavelength to the human eye, counts like 20 40 or 60 are hardly likely to be seen at all surely?

especialy spread over a comparitively "Wide area".

[Martin]

Well humans emit IR (infrared) the whole time.

 

IR is part of the EM (electromagnetic) spectrum so IR is comprised of photons.

 

5614 is certainly right about that

 

any warm object radiates infrared light (infrared is technically "EM radiation" but intuitively it's light that our eyes just happen not to be sensitive to)

 

the two laws involved date back to 1880 and 1905

 

around 1880 two Austrians (Stefan and Boltzmann) figured out the "black body radiation law" that says how the brightness of the heat glow depends on the temperature

 

http://en.wikipedia.org/wiki/Stefan-Boltzmann_law

 

around 1905 Einstein proposed that all light (including the heat glow off a warm object as a special case) comes in a bunch of separate energy packets---"photons"---it explained some things that couldnt otherwise be explained and was accepted as correct and won him the Nobel.

 

So if you put those two laws together you can get a rough idea of how many photons per second a square centimeter of your skin is radiating, just based on what temperature that area of skin is. Some properties of the skin enter in as detail, but a reasonably estimate is possible just with the 1880 law for a generic surface.

 

My feeling is that we ought to be able to FIGURE OUT how many photons per second come off a square centimeter of. say, your TONGUE, if you stick it out suddenly

 

Probably 5614 can do this. It shouldnt be too difficult to calculate.

 

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DIDN'T REALIZE THAT WHILE I WAS AWAY FROM THE COMPUTER A LOT OF PEOPLE REPLIED, so this post turns out to be somewhat redundant!

[Klaynos]

but when you consider a single photon even at a visible wavelength to the human eye' date=' counts like 20 40 or 60 are hardly likely to be seen at all surely?

especialy spread over a comparitively "Wide area".[/quote']

 

 

It is possible to see single photons (this can actually be done if you've got certain radioactive substances and a very dark room...)

[swansont]

...and the earth rotates on its axis. News at 11.

 

Once again, a science journalist does a bad job of reporting. Unfortunately, that's the norm, in my experience, rather than the exception. One might be surprised by the result, unless one had actually studied a little bit of science. The human body radiates on order of 100 Watts. Without knowing the wavelengths or counting intervals of the experiment, there's no way to really tell what's going on with the experiment. They should add an "Almost content-free!" disclaimer, like Kansas biology textbooks.

 

Odds are pretty good the experimenters knew about blackbody radiation and even told the reporter about it. But in my experience it is rare for the reporters to let the scientists check the articles for accuracy, and what the reporter thinks is important is rarely what the scientist does.

 

edit to add: One has to wonder if this is with the blackbody background subtracted, and the reporter forgot to mention that.

[YT2095]

Klaynos, although I agree with you wholeheartedly with the use of Scintialation counters and the likes, it doesn`t actualy apply to the OPs remit:

The light is invisible to the naked eye

I personaly wouldn`t like to put money on the idea that I could see a single photon (or 60 of them) unaided

[Sisyphus]

http://math.ucr.edu/home/baez/physics/Quantum/see_a_photon.html

 

So that question is settled with a definitive "sort of."

[swansont]

My feeling is that we ought to be able to FIGURE OUT how many photons per second come off a square centimeter of. say' date=' your TONGUE, if you stick it out suddenly

 

Probably 5614 can do this. It shouldnt be too difficult to calculate.

 

[/quote']

 

 

Couldn't wait. You actually need to use the Planck radiation formula. It makes a huge difference what the energy of the photons are - at 1 micron it's around 450/cm²s and drops quickly to be less than 1 in the visible and smaller out in the UV. I assumed a 1 nm bandwidth for detection.

[Skye]

They were looking at photochemistry, mainly photons emitted during redox reactions in and on the hand, with potential application in medical diagnostics. They spectrometer they used measured from 185 to 650 nm, I imagine to avoid IR.

[YT2095]

that`s interesting then, because since it covers UV, Plants are known to use UV also, as a means of comunication, and IIRC, certain insects that require plants or flowers (like Bees) have UV sensors, eyes that can see in the UV range too and I certainly know Moths can. I think the term is Bio-Luminescence (or something like that).

[Royston]

Please see the Discovery article below...

 

http://dsc.discovery.com/news/briefs/20050905/handlight_print.html

 

"Not only the hands' date=' but also the forehead and bottoms of our feet emit photons," Hiramatsu said, and added that in terms of hands "the presence of photons means that our hands are producing light all of the time."

 

The light is invisible to the naked eye, so Hiramatsu and his team used a powerful photon counter to "see"it.

 

The detector found that fingernails release 60 photons, fingers release 40 and the palms are the dimmest of all, with 20 photons measured.

 

The findings are published in the current Journal of Photochemistry and Photobiology B: Biology. [/i']

 

Can anyone explain this phenomenom ? I'll try and find the published article, but for the time being if anyone can explain how this occurs and more puzzling why these particular parts of the body...first time I've heard of humans emitting photons.

 

Yikes...'first time I've heard of humans emitting photons from their fingernails' I didn't realise I hadn't finished the sentence. I was going to carry on with 'it would make an alternative to those light up key fobs'. I've just found the rest of my post stuck in word.

 

I thought the concentration would be round the head, I really wanted to know why these particular parts of the body are being researched. If this is to be used for diagnosis why are they concentrating on these specific parts of the body. errr I guess I thought there was something 'special' about these 'parts'.

 

Just going through some of the replies, I thought it would be obvious that I understood where there's heat there's photons ??? My OP was badly worded so sorry about that, but still.

[Royston]

...and the earth rotates on its axis. News at 11.

 

Once again' date=' a science journalist does a bad job of reporting. Unfortunately, that's the norm, in my experience, rather than the exception. One might be surprised by the result, unless one had actually studied a little bit of science. [/quote']

 

Well yeah, this is why I couldn't understand that these emissions from 'particular' parts of the body were heralded as a 'new' discovery. I thought there was something, as I've already stated 'special' about these particular parts. My OP is misleading...sigh.

[swansont]

that`s interesting then, because since it covers UV, Plants are known to use UV also, as a means of comunication, and IIRC, certain insects that require plants or flowers (like Bees) have UV sensors, eyes that can see in the UV range too and I certainly know Moths can. I think the term is Bio-Luminescence (or something like that).

 

But one must differentiate between scattered light and emitted light. Insects that can see UV do so because plants and spider webs reflect strongly in the UV, but not necessarily because of any emission in ther UV. Flowers, bugs and webs can look very different when photographed in the UV. flower and butterfly example and many flowers listed here