Human body literally glows, emitting a visible light in extremely small quantities

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

Past research has shown that the body emits visible light, 1,000 times less intense than the levels which can be seen with the naked eye. In fact, virtually all living creatures emit very weak light.

To learn more about this faint visible light, scientists in Japan employed extraordinarily sensitive cameras capable of detecting single photons. Five healthy male volunteers in their 20’s were placed bare-chested in front of the cameras in complete darkness in light-tight rooms for 20 minutes every three hours.

Schematic illustration of experimental setup that found the human body, especially the face, emits visible light in small quantities that vary during the day. B is one fo the test subjects. The other images show the weak emissions of visible light during totally dark conditions. The chart corresponds to the images and shows how the emissions varied during the day. The last image (I) is an infrared image of the subject showing heat emissions. Credit: Kyoto University; Tohoku Institute of Technology; PLoS ONE

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

Faces glowed more than the rest of the body. This might be because faces are more tanned than the rest of the body, since they get more exposure to sunlight.

humans give off radiation. Humans give off mostly infrared radiation, which is electromagnetic radiation with a frequency lower than visible light. This effect is not unique to humans. All objects with a non-zero temperature give off thermal radiation.

And because a temperature of exactly absolute zero is physically impossible, all objects give off thermal radiation. We have to be careful here. Thermal radiation is not the exact same thing as infrared radiation. “Thermal radiation” is all the electromagnetic waves given off by an object because of its temperature, and includes radio waves, infrared waves, and even visible light. Infrared waves are only one part of thermal radiation.The two tend to get confused because most of the thermal radiation is infrared radiation for temperatures that are comfortable to humans. As an object gets hotter, the peak of its thermal radiation shifts to higher frequencies. The sun is hot enough that most of its thermal radiation is emitted as visible light and near infrared waves.


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