Posted in August 2009

People emit visible light

Posted on 24 August, 2009

(A) Schematic illustration of experimental setup. (B–F) Images of ultraweak photon emission from human body. (B) Image of subject under normal light. (C) Image at 10:10 AM. (D) Image at 1:10 PM. (E) Image at 4:10 PM. (F) Image at 7:10 PM. (G) Image at 10:10 PM. (H) Daily rhythm of photon emission from face and body from 5 volunteers. (I) Typical thermographic image of subject from (B)–(G).

Researchers from the Tohoku Institute of Technology, Kyoto University and Kobe University have discovered that the human body emits extremely small quantities of visible light at levels that rise and fall over the course of the day.

Past research has shown that the body emits visible light 1,000 times fainter than what the human eye can perceive. This extremely weak light is found in virtually all living creatures and is thought to be a byproduct of biochemical reactions at the cellular level.

To learn more about the body's faint visible light, the research team -- led by Masaki Kobayashi of the Tohoku Institute of Technology -- used extremely sensitive cameras capable of detecting single photons. Five healthy male volunteers in their 20s were placed in front of the cameras in complete darkness for 20 minutes every three hours from 10 AM to 10 PM for three days. The researchers found that the amount of light emitted by the body fluctuated over the course of the day, and that its lowest point was at 10 AM and its peak was at 4 PM. According to the researchers, these fluctuations suggest that light emission is linked to our biological clocks and daily metabolic rhythms.

This research is an extension of the Inaba Biophoton project, a government-sponsored research effort focused on studying the ultra-weak light emitted from, transmitted in, and absorbed by biological tissue and cells. Unlike other known forms of relatively intense bioluminescence which can be seen by the human eye and which are created through processes involving specific substances, the "biophotons" at the center of this study originate completely from chemical activity within cells, and are not produced as a response to external light or other stimulation.

Since this faint light is linked with the body's metabolism, the findings appear to suggest that highly sensitive cameras could help doctors detect medical conditions.

Links:
- Strange! Humans Glow in Visible Light [Live Science]
- Imaging of Ultraweak Spontaneous Photon Emission from Human Body Displaying Diurnal Rhythm [PLos One]
- Inaba Biophoton Project [ERATO]