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."
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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."
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."
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.
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.
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.
by Anonymous Coward
on Thursday July 23, @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?
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
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.
And you're playing a semantic trick where you take a word with multiple definitions, and change the definition you're using from the one that was clearly implied by the original context.
In the headline "People Emit Visible Light", "Visible" means "in the visible portion of the spectrum". "Visible Light", especially in a scientific context, usually means "light which is in the visible portion of the spectrum".
I don't think that's obvious... well, other than the fact that they don't emit visible light by the definition I'd normally assume was meant. Since I can look around and see that they don't...
It's extremely obvious if you're aware of the meaning of "visible light" in a scientific context. Anytime you see the phrase "visible light" in the same sentence as "scientists say" or "researchers have shown", then it is nearly 100% certain that this is the intended meaning. The clincher would be if you consider the
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 [merriam-webster.com].
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.
And you're assuming that Slashdot headlines are viewed as Scientific forum (capitalization used to emphasize your bias).
When the sentence containing the phrase in question also includes the phrase "scientists reveal" and the next sentence includes "researchers show", then it is probably safe to interpret it in a scientific context.
I will admit that I am biased towards thinking that most slashdotters would have attended and been interested enough to pay attention to high school or entry-level college physic
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.
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.
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.
Not that I really feel the ability to see auras would prove God or psychics or anything, but your conclusion is making an assumption that has no basis.
Just because we can see a dim light, does not mean that a bright one would blind us. It tends to be true due to the way our iris works, but even in bright indirect sunlight we can see dim directed lights, and there is no saying that the iris would filter out all of a dim directed light.
90% of our filtering goes on in our brains anyway. We filter away inform
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.
"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.
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.
by Anonymous Coward
on Thursday July 23, @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.
nothing special... (Score:5, Interesting)
Re: (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.
Re:nothing special... (Score:5, Informative)
Parent
Rate is far too low for this (Score:5, Informative)
Parent
Re: (Score:3, Funny)
Tell 'em they'll get lighter.
Leveraging homographs [wikipedia.org] for fun and PROFIT!!!
Re:nothing special... (Score:5, Informative)
Parent
Re:nothing special... (Score:4, 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.
Parent
Re:nothing special... (Score:5, Informative)
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.
Parent
Re:nothing special... (Score:4, 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 [slashdot.org].
Parent
Re: (Score:3, Insightful)
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.
Re: (Score:3, Informative)
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:nothing special... (Score:5, Informative)
Parent
Nothing special aside from what was in TFA (Score:4, Informative)
The summary, most commenters, and largely the article itself seem to be missing the big point here
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.
Parent
Re: (Score:3, Funny)
Re:Your missing the point (Score:4, 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.
Parent
Re:Your missing the point (Score:5, Funny)
http://xkcd.com/566/ [xkcd.com]
Parent
Establish in 2005 (Score:5, Informative)
Re: (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.
Re:Establish in 2005 (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?
Parent
Michael Stipe was right! (Score:5, Funny)
Re:Michael Stipe was right! (Score:5, Funny)
I'm not touching anyone.
And we appreciate that.
Parent
Re:Michael Stipe was right! (Score:4, 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.
Parent
New definition of visible. (Score:5, Funny)
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."
Re: (Score:3, Informative)
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)
Parent
Master Yoda called this... (Score:5, Funny)
As I always suspected (Score:5, Funny)
Re:As I always suspected (Score:4, Funny)
Parent
Biophotons (Score:3, Interesting)
Mood rings! (Score:5, Insightful)
Re:Mood rings! (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?
Parent
Re: (Score:3, Insightful)
Uh, duh. (Score:3, Insightful)
Anybody that's ever taken LSD could have told you that!
Re:1,000 times too faint to see? (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.
Parent
Re: (Score:3, Informative)
And you're playing a semantic trick where you take a word with multiple definitions, and change the definition you're using from the one that was clearly implied by the original context.
In the headline "People Emit Visible Light", "Visible" means "in the visible portion of the spectrum". "Visible Light", especially in a scientific context, usually means "light which is in the visible portion of the spectrum".
Re: (Score:3, Informative)
I don't think that's obvious... well, other than the fact that they don't emit visible light by the definition I'd normally assume was meant. Since I can look around and see that they don't...
It's extremely obvious if you're aware of the meaning of "visible light" in a scientific context. Anytime you see the phrase "visible light" in the same sentence as "scientists say" or "researchers have shown", then it is nearly 100% certain that this is the intended meaning. The clincher would be if you consider the
Re:1,000 times too faint to see? (Score:5, Insightful)
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 [merriam-webster.com].
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.
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.
Parent
Re: (Score:3, Informative)
And you're assuming that Slashdot headlines are viewed as Scientific forum (capitalization used to emphasize your bias).
When the sentence containing the phrase in question also includes the phrase "scientists reveal" and the next sentence includes "researchers show", then it is probably safe to interpret it in a scientific context.
I will admit that I am biased towards thinking that most slashdotters would have attended and been interested enough to pay attention to high school or entry-level college physic
Re:Biblical? (Score:5, Insightful)
Parent
Re:Biblical? (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 [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.
Parent
Re:Biblical? (Score:5, Informative)
Also a lot of people don't know this but the Super Devil doesn't appear anywhere in the Bible.
Parent
Re:Biblical? (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.
Parent
Re:Biblical? (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.
Parent
Re: (Score:3, Interesting)
Not that I really feel the ability to see auras would prove God or psychics or anything, but your conclusion is making an assumption that has no basis.
Just because we can see a dim light, does not mean that a bright one would blind us. It tends to be true due to the way our iris works, but even in bright indirect sunlight we can see dim directed lights, and there is no saying that the iris would filter out all of a dim directed light.
90% of our filtering goes on in our brains anyway. We filter away inform
Re:Biblical? (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.
Parent
Re:Biblical? (Score:5, Insightful)
Parent
Re:Biblical? (Score:4, 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.
Parent
Re:Biblical? (Score:5, Informative)
Parent
Absolutely. (Score:5, Funny)
How humbling, though, to realize that a four-watt nightlight harbors something like a billion times more chi than you do.
Parent
Re:Can't the eye detect single photons? (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.
Parent