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People Emit Visible Light

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."

38 of 347 comments (clear)

  1. nothing special... by Draque · · Score: 5, Interesting

    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.

    1. Re:nothing special... by Anonymous Coward · · Score: 3, Insightful

      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.

    2. Re:nothing special... by Bemopolis · · Score: 5, Informative

      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.

      --
      "I guess the moral of the story is, don't paint your airship with rocket fuel." -- Addison Bain
    3. Re:nothing special... by geekgirlandrea · · Score: 5, Informative

      See Planck's law. 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.

    4. Re:nothing special... by smellsofbikes · · Score: 4, Informative

      Read about Planck's Law. 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.

      --
      Nostalgia's not what it used to be.
    5. Re:nothing special... by AndersOSU · · Score: 4, Informative

      not a bell curve

      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.

    6. Re:nothing special... by momerath2003 · · Score: 3, Informative

      The chance of emission at higher energies decreases exponentially. You're getting far, far, far more exposure to ionizing radiation from the naturally radioactive potassium in others' bodies than by their black-body emission.

      --
      I had but a simple dream, to destroy all humans.
    7. Re:nothing special... by Tubal-Cain · · Score: 3, Insightful

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

      /me checks electromagnetic spectrum

      Looks like extremely low-energy photons are radio.

      Assuming it actually is a bell curve.

  2. Establish in 2005 by eldavojohn · · Score: 5, Informative

    I thought this was discovered and establish in 2005 by Mitsuo Hiramatsu, a scientist at the Central Research Laboratory at Hamamatsu Photonics. 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?

    --
    My work here is dung.
    1. Re:Establish in 2005 by Anonymous Coward · · Score: 3, Interesting

      It was discovered in 1923 by a Russian scientist, Alexander Gurvitsh. It was re-discovered in the 70s by a German physicist named Fritz-Albert Popp. This stuff is really old, they discovered nothing new. Popp proposes that this emission is very different from typical black body radiation.

    2. Re:Establish in 2005 by schon · · Score: 5, Funny

      It was re-discovered in the 70s by a German physicist named Fritz-Albert Popp

      Soo.. you're trying to tell us that this is just some sort of Popp-physiology?

      /me ducks

  3. Michael Stipe was right! by scubamage · · Score: 5, Funny

    So, I guess we really are all "Shiny Happy People!" I suppose next we should begin holding hands.

    1. Re:Michael Stipe was right! by clone53421 · · Score: 3, Informative

      A flu mask is really only effective at stopping yourself from spreading germs when you're sick. It isn't really going to help keep you from getting sick from other people's germs.

      --
      Alexander Peter Kristopeit bought his basement from his mommy for one dollar.
    2. Re:Michael Stipe was right! by swillden · · Score: 4, Funny

      I'm not touching anyone.

      And we appreciate that.

      --
      Note to ACs: I usually delete AC replies without reading them. If you want to talk to me, log in.
  4. New definition of visible. by 140Mandak262Jamuna · · Score: 4, Funny
    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."

    --
    sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
    1. Re:New definition of visible. by thisnamestoolong · · Score: 5, Informative

      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.

      --
      To the haters: You can't win. If you mod me down, I shall become more powerful than you could possibly imagine
  5. Master Yoda called this... by Casharelle · · Score: 5, Funny

    Master Yoda called this back in The Empire Strikes Back: "Luminous beings are we...not this crude matter!"

  6. As I always suspected by Bemopolis · · Score: 5, Funny

    People are visible, but they aren't all that bright.

    --
    "I guess the moral of the story is, don't paint your airship with rocket fuel." -- Addison Bain
    1. Re:As I always suspected by snspdaarf · · Score: 3, Funny

      I guess that's why Dad always said, "Rise and Shine!"

      --
      Why, without your clothes, you're naked, Miss Dudley!
  7. Re:1,000 times too faint to see? by amicusNYCL · · Score: 5, Informative

    Visible in this context doesn't mean perceptible, it's describing the wavelength, not the intensity. The light is very low intensity that has a wavelength within the visible spectrum.

    --
    "Our two-party system is like a bowl of shit looking at itself in a mirror." - Lewis Black
  8. Mood rings! by scubamage · · Score: 5, Insightful

    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.

    1. Re:Mood rings! by Anonymous Coward · · Score: 4, Funny

      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?

  9. Nothing special aside from what was in TFA by interkin3tic · · Score: 3, Informative

    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.

  10. Re:Biblical? by Tubal-Cain · · Score: 4, Insightful

    I'm not sure halos are even part of Christian canon.

  11. Re:Your missing the point by geekboy642 · · Score: 3, Informative

    You lie. That film had ONE main part. Any evidence of some kind of 'sequel' was planted by the machines to confuse your mind.

    --
    Just another "DOJ fascist authoritarian totalitarian bootlicker" -- Zeio
  12. Re:Your missing the point by killthepoor187 · · Score: 5, Funny
  13. Absolutely. by jeffb+(2.718) · · Score: 4, Funny

    How humbling, though, to realize that a four-watt nightlight harbors something like a billion times more chi than you do.

  14. Re:Biblical? by Magic5Ball · · Score: 5, Interesting

    Not really a halo...

    At least not to most people. Assuming that light sensitivity and light emission are independently normally distributed in the population, it's entirely possible that extremely sensitive individuals can see the light coming off the extremely bright individuals. Further, it is possible for genetically isolated populations to have gained extreme sensitivity or extreme brightness through the usual biological mechanisms, or if such traits were selected for through cultural or religious practices. Also, consider that relatively unstressed young Japanese men may not be fully activating whatever metabolism or physiology issues the light. There may be something to metabolism around "afterglow", women glowing when they're pregnant, unusual mental capacity, etc. which could easily generate 10 or 100 x the intensity observed in this study, and thus be observable by many people. (All sorts of biological processes span several orders of magnitude in concentration, intensity, energy, etc., and plenty of other bio-luminescent organisms show that the energy levels required to emit naked eye visible light are mostly not harmful to the organism.)

    Whether we are consciously aware of the brightness of others, or if we do anything with that information are topics for future study.

    --
    There are 1.1... kinds of people.
  15. Rate is far too low for this by Roger+W+Moore · · Score: 5, Informative

    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.

  16. Re:Biblical? by Narcocide · · Score: 5, Informative

    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 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.

  17. Re:Biblical? by gilleain · · Score: 4, Insightful

    it's entirely possible that extremely sensitive individuals can see the light coming off the extremely bright individuals.

    If there are people who have vision that is 1,000 times normal, then they must get blinded by the sun really easily...

    There may be something to metabolism ... which could easily generate 10 or 100 x the intensity observed in this study, and thus be observable by many people.

    Conversely, the 'brights' (don't tell Dawkins about this!) would be producing lots more free-radicals than normal. I sure hope they also have more efficient repair mechanisms in place to mop them up.

  18. Re:Can't the eye detect single photons? by Anonymous Coward · · Score: 5, Informative

    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.

  19. Re:Biblical? by JAZ · · Score: 3, Funny

    "1,000 times less intense than the levels to which our naked eyes are sensitive"

    yeah apparently Japanese scientists have a different definition of visible than I do. I always had that stupid "if I can see it then it is visible, if I can't see it then it isn't visible".

    I bet it is just like with cellular mitosis: audibly noisy when my cells divide, just so quiet that I can't personally hear it.

    --


    "Karma can only be portioned out by the cosmos." -- Homer Simpson
  20. Re:Biblical? by rumith · · Score: 5, Informative

    Usually "visible light" means "electromagnetic radiation with wavelength lying in (approximately) 380-750nm range". At least that's what they taught us in the university. Somehow, I find this definition much more logical than yours, no offense meant.

  21. Re:1,000 times too faint to see? by Chris+Burke · · Score: 4, Insightful

    Whatever researchers may use it to mean, the majority of people will probably be inclined to use the dictionary definition, and the most common one, if you don't clarify:

    1 a: capable of being seen <stars visible to the naked eye> b: situated in the region of the electromagnetic spectrum perceptible to human vision < visible light>

    Wait. You're telling me that the majority of people will use definition 1a, and only 1a, without even considering 1b, even though 1b specifically and directly refers to the exact phrase being used -- "visible light"?

    You're telling me that the majority of English speaking people do not ever consider the multiple definitions that nearly every word in our language has, and choose based on contextual clues what the most likely intended meaning is? I don't buy that for a second. You know why? Because just now, without even thinking about it, you automatically processed the word "buy" and based on the contextual clues chose meaning number 5.

    This has nothing to do with people choosing the first definition from a dictionary as opposed to the second, because nobody was looking in a dictionary. This has to do with people not knowing a scientific term so common and non-obscure it's definition 1b in said dictionary.

    So basically, if you mean "light in the visible spectrum", just say that. "Visible light" will be interpreted by most people according to the 1a definition of "visible", not the 1b definition. It comes first because it's common...

    Okay, once again I'm surprised, and again I admit it must just be the fault of my perception.

    I would never have guessed that people who have no idea what "visible light" means would find the phrase "light in the visible spectrum", or even just "spectrum" meaningful. I wouldn't have thought those people even knew that the stuff outside the visible spectrum was light. So you're telling me that people know that the colors in a rainbow and X-rays and radio waves are all the same thing, they're all light, but at the same time have no idea what "visible light" could mean? I really never would have expected that.

    I guess this illustrates one of the difficulties of writing about technical material for a layman audience -- remembering what it was like to be a layman, and thus what a layman would understand, when that could have been a long time ago. As far as I can remember, I learned about the EM radiation spectrum that includes X-rays, radio waves, infrared, and the light our eyes are sensitive to along with the phrase "visible light" to describe the latter section of the spectrum in a single class session in high school physics. So it would never have occurred to me that you could expect your audience to know one and not the other.

    --

    The enemies of Democracy are
  22. Re:Biblical? by Anonymous Coward · · Score: 5, Funny

    What does color have to do with this?

    Well if you're black, this means you're probably going to be more popular at raves.

  23. Re:Biblical? by Chris+Burke · · Score: 4, Informative

    Also a lot of people don't know this but the Super Devil doesn't appear anywhere in the Bible.

    --

    The enemies of Democracy are
  24. Re:Biblical? by reboot246 · · Score: 4, Insightful

    No, what I'm saying is that the proposition, "People Emit Visible Light", is a crock. I take words seriously. When they say "visible", I take it to mean "VISIBLE". If they meant to say, "people emit light in the visible part of the spectrum", then they should have said exactly that. Words have meanings.