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Science

People Emit Visible Light 347

Posted by timothy from the lots-of-girls-I-know-glow-visibly dept.
An Anonymous Reader writes "The human body literally glows, emitting a visible light in extremely small quantities at levels that rise and fall with the day, scientists now reveal. Japanese researchers have shown that the body emits visible light, 1,000 times less intense than the levels to which our naked eyes are sensitive. In fact, virtually all living creatures emit very weak light, which is thought to be a byproduct of biochemical reactions involving free radicals."
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People Emit Visible Light More

People Emit Visible Light

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    • Re:Biblical? (Score:5, Insightful)

      by Tubal-Cain ( 1289912 ) on Thursday July 23, 2009 @03:00PM (#28799397) Journal
      I'm not sure halos are even part of Christian canon.

      • Re:Biblical? (Score:5, Informative)

        by Narcocide ( 102829 ) on Thursday July 23, 2009 @03:24PM (#28799705) Homepage

        They aren't, as such. What we know as a "halo" is more of a Hanna-Barbera cartoon knock-off of something that appears in a lot of early Christian art as a nimbus - a sort of glowing aura around Jesus and sometimes an accompanying Lamb. According to this wikipedia page [wikipedia.org] the concept was used earlier in a lot of other historical religious art too before becoming bastardized by pop culture's somewhat clumsy literal interpretation.

  • nothing special... (Score:5, Interesting)

    by Draque ( 1367509 ) on Thursday July 23, 2009 @02:12PM (#28798715)
    This isn't any kind of new or unpredicted phenomenon. Everything that emits heat emits some light. The chances that the wavelength of a photon emitted by a human being (while giving off normal heat) will fall within the visible spectrum is very low, but given that we emit billions and billions of photons on a regular basis, it's sure to happen every now and then. Get sensitive enough cameras, and you'll see that glow from everything that isn't at absolute zero.

    • Re: (Score:3, Insightful)

      by Anonymous Coward

      Er. Your argument is that because something emits enough photons, then some are bound to be inside the visible spectrum?

      That is not how light works. If you want a different wavelength, you need photons with different energy, and you need a different process.

      • Re:nothing special... (Score:5, Informative)

        by Bemopolis ( 698691 ) on Thursday July 23, 2009 @02:24PM (#28798899)
        No. His argument, correct but incompletely stated, is that any macroscopic object with a temperature emits a blackbody(-ish) spectrum which, since it spans the entire range of EM radiation, emits some light in the visible portion of the spectrum.

        • Rate is far too low for this (Score:5, Informative)

          by Roger W Moore ( 538166 ) on Thursday July 23, 2009 @03:20PM (#28799653) Journal
          Correct. Doing a quick back of the envelope calculation a human body will emit one photon with a wavelength of 600nm every 10 seconds. If we scale that up by a factor of 1,000 that would mean the human eye would need to be capable of seeing a flux of 100 photons/second per unit solid angle. This is well below the threshold of a human eye - you'd need a photomultiplier or low temp photon counter device to pick this up. So clearly this is not the source of light.

      • Re: (Score:2, Informative)

        by Draque ( 1367509 )
        You're right that they need different energies. If you graph the energies of photons emitted due to heat radiation, they'll form your typical bell curve, with the peak of the bell curve representing and energy level corresponding with infra-red radiation. That having been said... a few standard deviations from the center, you'll see the (very rare) photons emitted that have energy levels corrosponding with visible light. This happens when enough energy concentrates (by random, highly unlikely chance) to

        • Re:nothing special... (Score:5, Informative)

          by AndersOSU ( 873247 ) on Thursday July 23, 2009 @02:47PM (#28799231)

          not a bell curve [wikipedia.org]

          But it is a distribution, and the human body does radiate some visible photons. This phenomenon, however, is theorized not thermal radiation, but as something else.

        • Re: (Score:2)

          by lawpoop ( 604919 )

          they'll form your typical bell curve, with the peak of the bell curve representing and energy level corresponding with infra-red radiation... This happens when enough energy concentrates (by random, highly unlikely chance) to create a photon with much higher energy than is typical for a radiating body.

          So what process creates the other half of the bell-curve, the photons at a lower energy than infra-red radiation?

      • Photons only come in quantum energy levels when they are generated from a quantum process. Conversely, blackbody radiation is a probability distribution of energy levels.

      • Re:nothing special... (Score:5, Informative)

        by smellsofbikes ( 890263 ) on Thursday July 23, 2009 @02:44PM (#28799189) Journal
        Read about Planck's Law [wikipedia.org]. It predicts the distribution of photons by frequency dependent on temperature. The scale is from wavelength = 0 to wavelength = inf, but the distribution is an asymmetric peak that goes to shorter wavelengths as the temperature increases. The extremely large majority of photons emitted by an object at 293K will be in the infrared, but a few will be visible, ultraviolet, and x-ray.

        • X-rays, hmm, so being in crowded places does increase the exposure to harmful radiation. I always knew that one should avoid crowds and now it is confirmed. That also means that, given enough people, one can demonstrate an attack using photonic means.

          [tinfoilhat_hat]Makes me wonder when an overzealous politician picks it up and limits demonstrations to few people to lower exposure to radiation.[/tinfoilhat_hat]

    • Re: (Score:3, Insightful)

      by dgatwood ( 11270 )

      Just to be pedantic, you'd have to move it into a colder room or it won't be distinguishable from the background emissions of everything else. The only things that could possibly be distinguishable would be things that produce their own heat, whether electrically or chemically.

    • The important thing here is we just discovered the solution to the energy crisis, all we need are MORE people.
      Think about it; if 1 person emits light 1000 times too faint to see, that means 1000 people emit exactly enough light to see. All I need are 1000+ Chinese people willing to stand around in my hallway for a couple pennies a month and I don't need a nightlight to find my way to the pisser at 4am anymore!!!

    • Re: (Score:3, Informative)

      by Eukariote ( 881204 )

      This isn't any kind of new or unpredicted phenomenon.

      It is definitely unpredicted by conventional theory. The visible part of the black-body radiation spectrum (which you seem to be referring to) for an object at human-body temperature is far less than 1/1000th of what is still visible. These emissions are therefore not thermal. And the is no other conventional theory that mandates such emissions.

    • Re: (Score:2)

      by Quaoar ( 614366 )
      These results are specifically about the deviation of the spectrum produced by a human from a black body, and how that varies throughout the day. For a blackbody, the number of photons coming out as visible radiation is 1/10^3000 the total number (assuming a body temperature of ~280K, the number is so tiny because visible photons fall into the exponential Wein tail of the BB distribution), so you would naÃvely predict that no human has ever emitted a visible photon. Ever. So yes, it is something speci

    • Re:nothing special... (Score:5, Informative)

      by geekgirlandrea ( 1148779 ) <andrea+slashdot@persephoneslair.org> on Thursday July 23, 2009 @02:36PM (#28799073) Homepage
      See Planck's law [wikipedia.org]. The power density at a given wavelength is inversely proportional to an exponential function of the photon energy, for wavelengths short compared to the peak. For humans (37 celsius), the peak lies at about 9.3 microns. If this were thermal radiation from a blackbody spectrum, the exponent for the longest visible wavelengths would be about 66.3, corresponding to about 1.9 * 10^-20 W/m^2 of radiated power in the visible spectrum, assuming perfect emissivity. If a typical human has a surface area of 2 m^2, that's around one thermal photon every ten seconds in the visible spectrum. This is many more than 1,000 times too dim to see. The photons referred to in the article come from chemical reactions, not thermal radiation.

    • Re: (Score:2, Funny)

      by fmita ( 517041 )
      Yes, but you're talking about a blackbody spectrum, whereas the article is implying that this is something else (photons released by chemical reactions, not by the thermal jiggle of charge). See http://en.wikipedia.org/wiki/Biophotons [wikipedia.org]

    • Nothing special aside from what was in TFA (Score:4, Informative)

      by interkin3tic ( 1469267 ) on Thursday July 23, 2009 @02:58PM (#28799367)

      The summary, most commenters, and largely the article itself seem to be missing the big point here

      The researchers found the body glow rose and fell over the day, with its lowest point at 10 a.m. and its peak at 4 p.m., dropping gradually after that. These findings suggest there is light emission linked to our body clocks, most likely due to how our metabolic rhythms fluctuate over the course of the day...

      Since this faint light is linked with the body's metabolism, this finding suggests cameras that can spot the weak emissions could help spot medical conditions

      So yes, people glow, and yes, this was known previously. The point of the research is that this can be used, for studying circadian rythms and maybe identifying problems with it and metabolism. The scientist quoted is billed as a "circadian rhythm biologist," you've got to think he's probably not studying this to find out if people glow or not.

      The information in the summary is thirdhand at best: whoever makes the summary makes it from an article, which in this case wasn't primary literature from the actual scientists but was AOL news or whoever "imaginova corp" is interviewing several japanese scientists about their work. AOL news seems to have misunderstood the research that they were writing about.

  • Establish in 2005 (Score:5, Informative)

    by eldavojohn ( 898314 ) * <eldavojohn@gm a i l . com> on Thursday July 23, 2009 @02:13PM (#28798721) Journal
    I thought this was discovered and establish in 2005 by Mitsuo Hiramatsu, a scientist at the Central Research Laboratory at Hamamatsu Photonics [quantumbalancing.com]. The only new information I recognize is that it varies by time of day, not that people emit visible light. Did this new study find anything else out additionally or just make pretty pictures that show it?

  • Michael Stipe was right! (Score:5, Funny)

    by scubamage ( 727538 ) on Thursday July 23, 2009 @02:13PM (#28798731)
    So, I guess we really are all "Shiny Happy People!" I suppose next we should begin holding hands.

  • An "aura"? (Score:2, Interesting)

    by Viper2026 ( 648272 )
    Whod've thunk it...

  • New definition of visible. (Score:5, Funny)

    by 140Mandak262Jamuna ( 970587 ) on Thursday July 23, 2009 @02:16PM (#28798775) Journal
    So the allegedly emitted light is 1000 fainter than what human eyes can see. Then why call it "visible", meaning viewable, seeable, ocularly pursuable (thanks Charles Dickens, Tale of Two Cities ... it has been a long time since I had the pleasure of ocularly pursuing you ... is Dickenesque for long time no see) ?

    May be I can use this definition to claim my code is fully documented when the sole documentation is a line of comment that says, "Someday I should document this insane hack."

    • Its visible to kitties and puppies, of course. I think. Maybe.

    • Re: (Score:3, Informative)

      by amRadioHed ( 463061 )

      From wikipedia [wikipedia.org]: "The visible spectrum is the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light."

    • Re:New definition of visible. (Score:5, Informative)

      by thisnamestoolong ( 1584383 ) on Thursday July 23, 2009 @02:24PM (#28798913)
      The terms are a bit confusing, but the term "visible" light has nothing to do with magnitude, it only refers to light with a particular wavelength, roughly 380 to 750 nm, which our retinas happen to be sensitive to. The term visible is not meant to differentiate visible light from invisible light, but rather to differentiate these waves from radio waves, infrared, ultraviolet, X rays, microwaves, and gamma rays. So yes, even if the light cannot be seen, if it is in that particular spectrum, it is visible light.

      • Right on.. It would help if popular culture could just call it all EM Radiation [wikipedia.org], and call "visible light" EM Radiation in the visible spectrum, but the term radiation scares people. Maybe as an acronym, EMR and EMR-V would be less frightening. Nonetheless, it would be more technically accurate, and remove the ambiguity of the term "light".

      • , it only refers to light with a particular wavelength, roughly 380 to 750 nm, which our retinas happen to be sensitive to.

        Our eyes happen to be sensitive to. Our retinas are sensitive to UV, but the cornea filters out some UV light: as much as we normally see absent looking at the Sun, etc.

    • There are two factors when considering light. The number of photons and the wavelength of each photon. In this experiment the first one makes the light they are considering faint. The wavelength of those few photons is what makes them in the visible spectrum. Or another way to look at is ultraviolet light from the sun is fairly intense outside, but we don't see it because our eyes aren't designed to detect that wavelength. The neat part, that is probably most useful, is that it detects how the metabolism is

  • Master Yoda called this... (Score:5, Funny)

    by Casharelle ( 746564 ) on Thursday July 23, 2009 @02:19PM (#28798821)
    Master Yoda called this back in The Empire Strikes Back: "Luminous beings are we...not this crude matter!"

  • As I always suspected (Score:5, Funny)

    by Bemopolis ( 698691 ) on Thursday July 23, 2009 @02:20PM (#28798841)
    People are visible, but they aren't all that bright.

  • It's the Midi-Chlorian

    duh

  • Biophotons (Score:3, Interesting)

    by Eukariote ( 881204 ) on Thursday July 23, 2009 @02:26PM (#28798935)
    Similar "biophoton" phenomena have been studied in the past at the International Institute of Biophysics [lifescientists.de]. It is most interesting as conventional theories do not predict such emissions.

  • Obligatory (Score:2, Funny)

    by Dunbal ( 464142 )

    "Luminous beings are we, not this crude matter." - Yoda

  • We're made of the elements found in stars...
    http://en.wikipedia.org/wiki/Delenn [wikipedia.org]
    http://www.youtube.com/watch?v=iE9dEAx5Sgw [youtube.com]

    Though I don't think we necessarily glow brighter if we have a good idea. :-D

  • You plonks just sparkle. We shine.

    Oh, and to E.T.: I've got your ouch right here.

  • Mood rings! (Score:5, Insightful)

    by scubamage ( 727538 ) on Thursday July 23, 2009 @02:39PM (#28799107)
    So, since this light is directly related to biological processes, that means in theory it should be tied to mood. For instance, clinical depression is tied to a general depression of all physiological processes. So, it would stand to reason that if you're down, you would emit less light. Someone who is euphoric should look (relatively) like a lightbulb in comparison. I know in the article it says that the amount and color of light varies, I wonder if this would lead towards a mood-ring style ability to read emotions. For instance, someone who is emitting a "pensive" light spectrum, along with other biological cues like sweat, and fidgiting may be a good suspect for scrutiny.

    • Re:Mood rings! (Score:4, Funny)

      by Anonymous Coward on Thursday July 23, 2009 @03:00PM (#28799403)

      For instance, someone who is emitting a "pensive" light spectrum, along with other biological cues like sweat, and fidgiting may be a good suspect for scrutiny.

      So you're saying we should judge people by the color of their skin?

    • "Hi there, how are you? Oh, wait- Let me get out my spectrometer!"

    • Re: (Score:3, Insightful)

      by merreborn ( 853723 )

      So, since this light is directly related to biological processes, that means in theory it should be tied to mood. For instance, clinical depression is tied to a general depression of all physiological processes. So, it would stand to reason that if you're down, you would emit less light. Someone who is euphoric should look (relatively) like a lightbulb in comparison. I know in the article it says that the amount and color of light varies, I wonder if this would lead towards a mood-ring style ability to read

  • Comment removed based on user account deletion

  • Something in my kit of salvage electronics which I could never figure out what to use it for, to try and detect the presence of these "humans".

    Now if only I can only safely generate the 1000-2000 volts to drive it.

  • . . . to replace that old 25W bulb? I've been experimenting with these newfangled florescent thingies, but the labels always seem to lie like rugs: 1W = 1000GW!

    Maybe I need to know how *bright* the things actually are. Like, how many humans would I need to illuminate the Library of Congress? That would seem like appropriate Slashdot units.

  • Careful analysis tells me it is absolutely necessary for the survival of the human race to investigate photon emission from women. Since cloth would interfere with measurements, experiments will have to be clothing-free, and in a dark room. Volunteers are needed, apply now. Scientific requirements show a need for women between 18 and 40 with large busts. No pay, but refreshments will be served in sufficient quantities to achieve experimental results.
  • I'm still applying for a grant to research this, but I'm told people also emit a scented gas! Part of my research will focus on this 'silent but deadly' scenario as it appears this scent is not always accompanied by sound.

  • FTA: "...In fact, virtually all living creatures emit very weak light, which is thought to be a byproduct of biochemical reactions involving free radicals."

    This explains why the city of Berkeley (California) shows up so bright on satellite photos taken at night. Way too many free radicals.

    (and I should know... I grew up there!)

  • The human body literally glows, emitting a visible light in extremely small quantities at levels that rise and fall with the day,

    Thank goodness. I thought it was just me who had nocturnal emissions.

  • Uh, duh. (Score:3, Insightful)

    by pi_rules ( 123171 ) on Thursday July 23, 2009 @03:30PM (#28799793)

    Anybody that's ever taken LSD could have told you that!

  • I read that somewhere once...fact or fiction? If fact, then how can any light in visible wavelengths be "1000x" under the detection threshold of the human eye?

    • Re:Can't the eye detect single photons? (Score:5, Informative)

      by Anonymous Coward on Thursday July 23, 2009 @04:10PM (#28800313)

      Close. A single photon is capable of making a single cell (rod) in your retina fire. To actually perceive light, you need around 9 or 10 rods to fire at around the same time. Problem here is that only around 10% of the photons entering your eye end up striking a receptor - the rest are reflected off of the cornea, get absorbed in the vitreous humor (fluid inside the eye), or pass through the retina without striking a spot where a receptor is located.

  • Two Theories (Score:3, Insightful)

    by DynaSoar ( 714234 ) on Thursday July 23, 2009 @08:32PM (#28802717) Journal

    1. The rods of the human retina can react to a single photon. However, to be consciously perceived between 5 and 10 photons must be detected within 100 milliseconds. To pick up light that's 'visible', but "1,000 times less intense than the levels to which our naked eyes are sensitive" ('Which is, of course, impossible. -- Hitchhiker's Guide) the researchers in TFA are claiming to detect small fractions of a photon (repeat HHG assertion here).

    As stated, the above applies to conscious perception. A normally non-conscious perception via an alternate visual channel has been proven to exist. This 'blindsight' has been discussed here previously http://science.slashdot.org/article.pl?sid=08/12/24/2330245 [slashdot.org] . It has been shown to not only exist in the sighted, but can be trained in them so to become functional. There was a school for this in New Mexico that was written up in Co-Evolution Quarterly almost 20 years ago. In the discussion thread here, more than one person admitted to having developed or noticed having this ability.

    2. The spirit of we two legged can become attuned to the spirit of the four legged, and so the hunter can find prey in darkness, and one can also avoid becoming hunted. Likewise, we can feel the spirit of the standing people (trees) and so find our way between them with surprising speed. Although it works as though it were sight, because it is a working of the spirit, the impressions received are not detected as visual images to the mind, but only to the spirit.

    I've got a lot of academic training in #1. I've got some training, and have ancestors with a lot more in #2. They may be incompatible, but since no viewpoint perfectly and completely describes reality, none can be said to be the only truth. In any case, learning to use dark sight doesn't require believing either.

    Still, there ain't no such as pieces of photons.

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