Friday, April 13, 2007

My Glowing Hands

A few years ago I went "caving" in a lava tube in Hawaii. It was a fun experience and I usually enjoy getting underground. Our guide showed us something strange. We all turned off our lights and it was truly pitch black. We'd all had this experience before. I remember it best while on a tour of a gold mine in California but I'm sure we did the same thing when I went caving with my mom as a much younger kid. On to the weirdness.

The guide had us hold up our hand in front of our faces. What's weird? We could see them. Keep in mind this should be impossible. There was no light source in the cave whatsoever. The walls were black lava.

In the immortal words of Nigel Tufnel "It's like, how much more black could this be? And the answer is none. None more black.

Still though, we could all see our hands. The guide had no explanation though he did note that you can only see your own hand. He thought it had something to do with each person being in tune with their own electrical system which sounded like a bunch of bunk to me, More likely, I thought, it is all your imagination. Sort of a visual hallucination ala phantom limb syndrome. Wait though, my brother and I experimented and sure enough, we could see each others hands. Our guide had never seen this before though he admitted he had never had brothers try. Weird.

Since that time I've gone into caves with other folks and we always do the pitch black bit. When I tried this recently with some kids in my Youth Adventure Corp, sure enough, the kids could see their hands.

Eyes work by picking up photons so it seems that there has to be photons bouncing off your hands somehow. I thought about your eyes being sensitive to a little infrared but I couldn't find any research on that. According to this article, "Retinal sensitivity sometimes extends (with very low sensitivity) to 1000 to 1050 nm. Note that if your eyes were sensitive to much longer wavelengths you would look through a sort of "infrared fog", since you would see heat energy everywhere."

Sources vary but the lower limit of what is considered infrared is generally between 700 and 800 nm. So, in theory, very sensitive dark adapted eyes could pick up some sort of infrared. I believe this is called "near infrared" though there aren't hard and fast rules. The human hand emits infrared at 8,000 to 14,000 nm. That is well outside what humans can possibly detect. Back to square one.

The other day I was searching for something completely different online and I came across a new study. Dr Mitsuo Hiramatsu, a scientist at the Central Research Laboratory at Hamamatsu Photonics in Japan announced that human hands emit photons.

An article in Discovery News suggests that, "Fingernails release 60 photons, fingers release 40 and the palms are the dimmest of all, with 20 photons measured." Unfortunately the article doesn't say what kind of rate that is. 40 photons per what unit of time? I know from my Astronomy work that the dark adapted eye can detect very few photons but without rate information I can't tell if this is the answer to my glowing cave hand mystery. The full research article on the glowing hands is here but I'm too cheap to pay for it.


1 comment:

Timothy said...

Hi Kirk,

I have noticed the same thing when in pitch black in caves. For me it doesn't have to do with any relation, I can make out the people near me... They appear darker than the dark around them. Have you done any more research on this? I am currently trying to find published research on this phenomena and as of yet have not found anything solid. If you are still interested in this, email me at and I'll share what I find as I come across it. If anything, I may just have to motivate someone in our psychology department (Colorado State University) to do a little study on this :)