Nude Physics 3: Luminosity

I’m neither physicist nor physician, so it’s only with a bit of creative license that I’m exploring, in this series of posts, certain physical properties of our bodies when nude. The first two posts in the series have featured concepts from physics that are perhaps more obviously applicable to our bodies: surface area to volume ratio, and torque. For the final two posts, I’m stretching the creative applicability a bit further without abandoning physical concepts.

Luminosity is a way of measuring brightness or intensity of light. There are many factors that enter into such a measurement, but one way it can be understood is as the “total luminous flux incident on a surface,” referred to as illuminance. The surface that interests me here is, of course, our skin, which we sometimes say “glows.” Whether in air or water, and accounting for a range of possibilities of reflection and refraction of light, our skin–in all of its available colors!–has a more intimate illuminant interaction with the sun than do our clothes.

Reflection, refraction, illuminance

Compared to other mammals, the relative hairlessness of humans literally highlights the sun’s touch. The fur or hide of a bear, moose, or even a wet otter, for instance, does not reflect light the way human skin does. Our simian cousins are much hairier than we are, with thinner skin. Animals such as rhinoceroses or elephants have little hair, but their hides are so tough and thick that they do not shine in the light the way human skin can. Only dolphins and whales–less so seals, and perhaps also some of the smoother-scaled reptiles–have body surfaces that reflect like human skin, but these surfaces lack the level of pigmentation in human skin that reacts to exposure by darkening. 

What might be the evolutionary relationship among greater surface of exposed skin, larger brains, levels of vitamin D production, and our fluctuating pigmentations? If we think of our bodies as extensions of our brains, then it only makes sense that so many of us recognize that we do our most creative and insightful thinking while naked outdoors. That’s when we’re producing vitamin D all over, we’re stimulated by the natural light and heat, and hopefully we’re developing a sun-kissed glow without burning–a healthy glow, we say–all while exposing the outermost reaches of our body/brain to the light.


There is something particularly powerful about the interplay of air and water in our skin’s illuminance. Whether from sea, stream, or sweat, the water on our skin intensifies absorption of sunlight while causing a glimmering optical effect that enhances the shine or glow. For many tropical indigenous peoples, the hypnotic effect of shimmering sunlight on rippling water formed part of a trance-like communication with the divine. To participate bodily in the effect, in other words to add the shine of the nude skin’s surface to the luminous interaction of light and water, was an ideal practice that gave rise to rituals such as the one made famous by the legend of El Dorado. In this kind of bathing ritual–like a transcendent skinny dipping–what is re-enacted is the resplendent birth of the creation of the Lake Mother and the Sun Father: glistening nude humanity.  

4 thoughts on “Nude Physics 3: Luminosity

  1. Will, there is something very powerful here at work in your post. If I am not mistaken, something at the archetypal level, at the level of ancient gods and goddesses from which we arise each time we relax into sleep, into water, into sunshine and moon\”shine\”.


  2. I agree, Roger – thanks for elaborating. I believe it is archetypal and therefore universal, even though at least one reader has remarked that he is too hairy for the shine effect to work without a body wax! I should specify that most tropical indigenous peoples simply have much less body hair than Europeans and Middle Easterners. But even in the case of El Dorado, the shine effect was enhanced by a coating of gold dust stuck to the skin with pine resin.


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