Built on Facts

Glowing People

Here’s a neat little news article about humans glowing in the dark.

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.

Past research has 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.

We’re all glowing all the time throughout the entire spectrum as per Planck’s law. The radiation peaks very low in the infrared, by the time you’ve climbed up the spectrum there’s essentially no visible light emitted at human body temperatures. As such blackbody radiation isn’t what’s causing the observed glow here.

I don’t know enough about the science to say how likely the free radical hypothesis is, but on its face it’s not implausible. Chemical reactions tend to have roughly on the order of ~1 eV reaction energies, which is also generally around the visible part of the spectrum. It’s not at all implausible that a weak chemiluminescence could result.

Here’s the link to the actual photographs, which are sadly intensity plots and not true color. I’d be very interested in seeing a RGB composite.


  1. #1 Neil B ♪
    July 23, 2009

    Fascinating, and I’d like to see full-color pics of bioglow someday. But did Kobayashi take into account that there are asymptotic “tails” for the BB radiation spectrum? It means that in principle, much higher frequencies than the peak are being emitted by warm bodies, even if at low intensity – per the idealized formula at least. (I don’t think there’s even a cutoff per se – but in practice, it would be very hard for a room-temp. body to happen to give off an X-ray photon.) So that means, bodies at 300 K should be emitting a very few visible photons anyway from the extended thermal curve. It certainly should be calculated, to check against the purported human emission of natural light. Anyone check on this? (I could – too lazy/no time, sorry! 😉

  2. #2 Daniel
    July 27, 2009

    seems to me that the camera’s just picking up some near-infrared light.
    Ho hum.

  3. #3 Anonymous
    September 12, 2010

    This article fits with Fritz Albert Popp’s research of measuring biophotons with a sensitive light detector. It’s exciting to see more work done in this area.

  4. #4 Anonymous
    January 1, 2012

    I had a partner that glowed when he was happy? No camera, I have never seen it before this….Maybe this is the explanation, however I would of hoped it was more romantic than this…

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