The Art and Science of Shadows

What is it about shadows we find so magical? Adults and children, alike, are lured by projections on the wall, or the figures striding alongside us on sidewalks, all beckoning us to an otherworld where doppelgängers take on lives of their own, existences we can only begin to imagine. 

The shadow is where mystery resides. It is the unknown and the unseen. It is where nefarious beings lurk, and it’s also where hope and creativity nestle. According to Jung, our shadow is our dark, repressed self, but it’s also “the seat of creativity,” where potential lives. It is the well from which ideas flow unfettered. Hades, god of the underworld, has been referred to as Lord of the Shadow and also Lord of the Shades, which, in literature, are the spirits of the dead, our ghosts. But by the same token it’s where our subconscious dwells, our personal ghosts, the depths of our psyche.  

In art, it is, in concert with its counterpart light, a language unto itself. In drawings, paintings, and photography, it is the shadows that give shape and depth to light. In chiaroscuro, light and shade are used to draw attention to the subjects light falls upon, and to give a three dimensionality to forms. But while we focus on the lit objects first in paintings, it is the shadows that beckon. They call on our curiosity and imagination to fill in the recesses of the world. 

Famous cinematographer Conrad Hall says that “manipulating shadows and tonality is like writing music or a poem.” In his 1960’s cult classic television show The Outer Limits, shadows are so ubiquitous and impactful on the noir mood and setting, they are like a central character in of themselves.

Recently, I came across an article on the Society of Physics Students’ site about a performance by the modern dance group Pilobolus called “Shadowland.” It was a special viewing of the show for young students, proceeded by a presentation on the science of shadows by Kutztown University’s Society of Physics Students (KUSPS). 

I’m avidly fascinated by the integration of art, science, and imagination as a means of learning, so I was more than a little excited to learn about the inspired merging of science, shadows, storytelling, and dance. 

The KUSPS shadows presentation explored both the science of light and shadows, since shadows, of course, can’t exist without light. “After the workshop,” they noted, “the audience was able to appreciate Shadowland in a new light.” Which made me wonder…in what way can a deeper understanding of the science of shadows impact our appreciation of the art and poetry of shadows. And inversely, how does the art and poetry of shadows impact our understanding or appreciation of the science of shadows? 

And so, I decided to delve in to the science of shadows — and its counterpart light — in hopes of obtaining a keener or even altered understanding of the shadows that I find so compelling in art. 

The Science of Light

Let’s begin by exploring the science of light, the basics at least. What is perhaps most amazing about light is that it’s both a particle and a wave. Historically, before Einstein’s discoveries about light, at least, the world around us could be classified as a particle — this thing, we could hold in our hand (theoretically) — or a wave, an amorphous phenomenon moving past us. There were and are different mathematical formulas that are used to describe their properties. A particle still had movement, it would move in a straight line, until hitting something would send it into an alternate trajectory, but this movement was so infinitesimally small, we wouldn’t notice it. 

Light was believed to be solely a wave, for the most part, up until the late 1800s, when theoretical physicist Max Planck, and later Albert Einstein, proposed that light is emitted in little chunks — packets of energy they called photons — which travel in waves. And this has since proven to be true. 

What’s even more fascinating is that since this discovery of light’s dual properties, it’s been found that the same is true of other matter in the world, such as antimatter.

Where, however, do photons come from? Light photons always come from a source, such as the sun, or a lightbulb. When matter is heated up or gains energy, the excess energy is released in part as light. The sun creates energy through nuclear fusion, a process beyond the scope of this post, but we can say that the sun creates light energy, particles called photons, which travels in waves to the earth. As far as we know, light photons have no mass and do not decay as they travel, unless they are absorbed, scattered, or reflected. Thus, they continue to travel at the speed of light, bringing the light of the stars to us from a billion years past. 

There is light we can see, also called white light, and light we cannot see, such as infrared, ultraviolet light, gamma rays, and x-rays. Altogether, visible and invisible light make up the electromagnetic spectrum. Different colors, or types, of light, travel at different frequencies, or wavelengths, as the image below demonstrates. Light with a longer wavelength or lower frequency, such as red, has less energy. Light with a shorter wavelength or higher frequency, such as violet, has more energy. 

Philip Ronan, via wikimedia

Light that is the reddest red, beyond the red that we can see, is called infrared light. Light that is more violet than the violet we can see, is called ultraviolet light. There are some insects that can see ultraviolet light, such as honeybees and monarch butterflies. I wonder, do these insects also see shadows of ultraviolet light, that we cannot see? 

All of this brings us to the movement and behavior of light. When we see colors what we’re actually seeing is the light reflecting off that object. A plant is green because the plant absorbs all the other colors, and reflects green light.

Reflection — Light travels in a straight path (albeit in a wave pattern), hence the phrase, ray of light. Reflection is when light waves bounce off an object, back into the same medium through which they traveled (such as air). If the object is smooth, the light will reflect back at the same angle it hit the surface with — this is called specular reflection. If the surface is rough, the light will reflect back in many different directions — this is called diffuse reflection. All objects that don’t create their own light must reflect light to be seen. So, nearly everything we see is made up of different wavelengths of reflected light. 


Refraction — As we know, light travels in a straight path. But when light passes through a transparent material, such as water, gas, or a prism, the speed of the light waves change, causing them to bend, or refract. This separates the light into its various wavelengths — red, orange, yellow, green, blue, indigo, violet — causing a rainbow to appear. Lenses in tools such as telescopes, microscopes, and glasses use refraction to help us see things.


Diffraction — Another behavior of light waves is called diffraction. When the lightwaves hit a barrier and bend around it, or bend as they pass through an opening that is approximately the same size as or smaller than the lightwaves, this is diffraction. The light waves spread out as they pass by the barrier, or through the opening, and can produce a rainbow. 


When the lightwaves bend, they also may overlap and interfere with one another, creating a diffracting pattern. (This is especially clear when there is more than one opening, as seen in the double-slit model below, but it can occur with a single opening as well.) When the top of one wave combines with the top of another wave, they’ll create a bigger, brighter wave of light. This is called constructive interference. When the top and bottom of a wave combine, they’ll cancel each other out, creating a dark area. This is called destructive interference. 

Double Slit Diffraction

Imagine sunlight traveling through the spaces between clouds. You see a combination of bright light streaming down, and long dark bands streaming down as well — this is a diffraction pattern. 

Sun over Lake HāweaOtago, New Zealand, by Michal Klajban, via wikimedia

The Science of Shadows

And so as we start to better understand the behavior of light, we can better understand its relationship with darkness, as well. Which brings us to shadows. 

What is a shadow? Shadows, as we know, are created when light is blocked. Shadows are proof that light travels in straight lines. When an object gets in the way of the lightwaves, it creates a shadow behind the object. 

When the object in front of the lightwaves lets almost all of the light through, creating a shadow that’s barely visible, it’s called a transparent object. 

When some, but not all of the light can pass through the object, the object is called translucent.

When the object is solid, not letting any light pass through, and creating a very dark shadow, it’s called opaque. 

Now let’s imagine the possible interplay between these various phenomenon. It’s a semi-overcast day with a combination of light and dark clouds in the sky, creating a series of transparent and nearly opaque shadows on the ground. Light is diffracting in the space between clouds, creating a diffracting pattern of light and dark bands streaming from the sky. 

Within the clouds, light waves hit a drop of water, refracting when they first hit the droplet, traveling inside the droplet then reflecting off the other side, then refracting once again as it leaves the droplet, creating a rainbow effect. 

It’s been shown that when lightwaves leaves water, a small portion of the light will also diffract, again, potentially creating a rainbow.

Photo by Diego F. Parra on

The interweaving of shadow and light, and the different forms of light, for that matter, takes the form of a delicate, intimate dance. As yin and yang are opposing but interconnected, complementary forces in nature, so, too, are light and shadow a similar duality of energies, governed by the laws of physics. Light is energy itself, the movement of photons at varying frequencies, whereas shadows denote an absence of energy, a calm sanctuary or respite from life, and yes, a kind of ghostly echo of light, or a kind of death. 

Although, what’s also interesting to me is that the shadows created by the diffraction pattern — if they can technically be called shadows — are created by the movement of light itself, its own waves canceling each other out as a result of their dissonant patterns, and thereby eradicating the energy of light. 

The Parts of a Shadow

What happens when we take a closer look at shadows? The shadow is made up of two parts: the umbra and the penumbra. The umbra — Latin for “shade” or “shadow” — is the darkest part of the shadow, where the light source is completely blocked by the object creating the shadow. The penumbra — Latin for “almost shadow” or “to hang on the shadow” — is the lighter area on the sides of the shadow that appears when there’s a larger or extended light source, such as the sun, creating an area that’s only partially blocked by the light. 

When you see the shadows of trees and leaves on the ground, it is the penumbra that softens the edges of the shadows, and helps to create a beautiful, gradient depth and near-shimmering effect. 

Photo by Pixabay on

A less common definition of umbra is ghost, phantom, or spectral image, and penumbra has been used to suggest a shroud, or even foreboding. Per Merriam Webster, “a penumbra of despair fell over the doomed city.” Given what we know of the umbra and penumbra, I can see the logic in these definitions. Umbra is the darkest shadow, and most clearly outlines the form it’s shadowing. When we see the umbra of our own likeness, we are inclined to think of it as our doppelganger. It might very well walk away from us at any moment. The penumbra, on the other hand, is less clearly defined; half light, half darkness, it has more of the quality of a shroud or a blanket. It imparts the feeling of a shadow.

Our Adaptation to Shadows

Perhaps another perspective on shadows is the one that the physiological makeup of our eyes permit us to see. While photoreceptors in our eyes called cones allow us to see the full spectrum of color and spatial acuity, the photoreceptors called rods function at very low levels of light and enable us to see various shades of gray at night. So, like a night animal adapted to navigating in the dark, we can leverage our rods to see the shadows of the night. 

Once on a night tour of the woods offered by the Portland Audubon Society, our group was instructed to walk the wooded path without flashlights, to allow our rods time to adjust to the dim light of the night. And in doing so we experienced the dark objects enshrouded by night coming slowly into focus, making it easier with each step to see and experience the wild, shadowy world surrounding us. 

The Colors of Shadows

What perhaps surprising about shadows is that they are not always dark. Again, our eyes have light receptors in them called cones, which allow us to see colors. We have three different cones, each one sensitive to a wide, but different range of wavelengths — one is most sensitive to red wavelengths, one blue wavelengths, and one green wavelengths. These are considered the primary colors of light (yes, green instead of yellow), and adding them together in different ways creates new colors. We are able to see millions of colors based on how these three types of cones in our retina respond to lightwaves. 

So, if you do an experiment, as the Exploration did for students, and shine a red, green, and blue light onto a white surface, you can create different colors, and different colored shadows. Shining all three lights together creates white light, which is how your eyes perceive all three colors together. If you block the blue light with your hand, you’ll see a yellow, hand-shaped shadow, created by the combination of red and green. Block the red light, and you’ll see a cyan shadow, created by the combination of blue and green. Block the green light, and you’ll see a magenta shadow, thanks to the combination of red and blue. 

What color are the shadows we see day to day? Well, that depends on factors such as the light source, the transparency of an object, and the possible reflection off of nearby objects. If light shines through a colored, transparent object, that color may be projected in the partial shadow. If the source of the light is colored, it may color the shadow. Many artists will paint outdoor shadows in hues of blue, because, when an object blocks the yellow light, the surrounding blue light from the sky colors the shadows. And if light is reflected off of a nearby object, such as the color of a glass or a vase causing the shadow, this hue may appear in the shadow, as well. 

Photo by PhotoMIX Company on

So, sometimes shadows — those ghostly phantoms — do take on the colors of life itself. Sometimes, we look in their depths and see life brewing within, whether in the orange-hued shadow of a dancer dancing in the spotlight, or in the sea blue shadow of a cobalt blue glass resting on the cafe table. We vaguely note the jeweled shadow of the glass stretching across the table in time with the sun, as the afternoon wanes, and cafe patrons come and go. 

We commonly think of shadows that appear in the light — on the sidewalks as we walk outdoors on a sunny day, for example. But there is another perspective: that of looking for the light within the shadows and the darkness. Indeed, physiologically, as mentioned earlier, our eyes have adapted to this skill, as the rods in our eyes adjust to the darkness of the night, making out at first willowy outlines, then more concrete shapes, then the hint of color. Is it any wonder then, that on a level that’s more internal, perhaps more poetic, that we are moved to search the darkness and the shadows for signs of life, for connection, for meaning, for light?

Shadows of Poetry

And so, I return to the original question I posed: Does having an understanding of the science of shadows impact our appreciation of the art and poetry of shadows. To explore this, I decided to look at how shadows impart meaning and feeling in a few well-known poems, beginning with William Wordsworth’s “The Ruined Cottage.”

In this poem, a friend of the narrator, whom he happen upon while hiking in the woods, tells the story of Margaret, an unreservedly good-hearted soul who suffers the loss of love, and eventually, after much torment, the loss of life. It’s a tale that asks us, what are we to make of this life, and this world, where so much irrational and undeserved suffering occurs? 

It is in nature, that the friend find’s comfort. Nature, which almost cruelly and carelessly assimilates the remnants of Margaret’s life — her long abandoned cottage — back into its ken, through its “calm oblivious tendencies.” Nature is dismantling the ruined cottage’s broken wall, its bowl fragment, and its overgrown well, but at the same time, it’s caught those things up into the continuity of life. 

And what, exactly, does nature offer us? Well, for one thing, diffraction. Read the introductory lines of the poem below: 

The Ruined Cottage
by William Wordsworth

Along the south the uplands feebly glared
Through a pale steam, and all the norther downs
In clearer air ascending shewed far off
Their surfaces with shadows dappled o’er
Of deep embattled clouds: far as the sight 
Could reach those many shadows lay in spots
Determined and unmoved, with steady beams
Of clear and pleasant sunshine interposed; 
Pleasant to him who on the soft cool moss
Extends his careless limbs beside the root
Of some huge oak whose aged branches make
A twilight of their own, a dewy shade 
Where the wren warbles while the dreaming man, 
Half-conscious of that soothing melody, 
With side-long eye looks out upon the scene, 
By those impending branches made more soft, 
More soft and distant. Other lot was mine. 
Across a bare wide Common I had toiled
With languid feet which by the slippery ground
Were baffled still, and when I stretched myself
On the brown earth my limbs from very heat
Could find no rest nor my weak arm disperse
The insect host which gather round my face 
And joined their murmurs to the tedious noise
Of seeds bursting gorse that crackled round.
I rose and turned towards a group of trees
Which midway in that level stood alone,
And thither come at length, beneath a shade 
Of cloistering elms that sprang from the same root
I found a ruined house, four naked walls
That stared upon each other. I look round
And near the door I saw an aged Man,
Alone, and stretched upon the cottage bench; 
An iron-pointed staff lay at his side. 
With instantaneous joy I recognized
That pride of nature and of lowly life, 
The venerable Armytage, a friend
As dear to me as is the setting sun. 

Has diffraction ever been described more beautifully?

In clearer air ascending shewed far off
Their surfaces with shadows dappled o’er
Of deep embattled clouds: far as the sight 
Could reach those many shadows lay in spots
Determined and unmoved, with steady beams
Of clear and pleasant sunshine interposed;

The shadows “lay in spots / Determined and unmoved,” much as nature itself appears unmoved by Margaret’s disappearing legacy. But already what we know of diffraction brings this into question. On one hand, diffraction signifies the destruction of light waves, of light energy, as the tops and bottoms of lightwaves combine and essentially cancel each other out, resulting in shadows. But even this action reflects a kind of movement, and energy. 

And at the same time, “steady beams / Of clear and pleasant sunshine interposed”. Just as diffraction creates shadows through “destructive interference”, it also results in “constructive interference,” as the tops of congruous lightwaves combine, and create a stronger, brighter waves of light. Amidst the cool shadows streams a feeling of hazy, enveloping warmth and hope.

And then there is the beauty of the shadows and sunshine combined, for is not the site of the diffraction of light among the clouds a site to behold?

Looking forward, there is more to the shadows than diffraction: 

Pleasant to him who on the soft cool moss
Extends his careless limbs beside the root
Of some huge oak whose aged branches make
A twilight of their own, a dewy shade 
Where the wren warbles while the dreaming man, 
Half-conscious of that soothing melody, 
With side-long eye looks out upon the scene, 
By those impending branches made more soft, 
More soft and distant. Other lot was mine.

What of the “dewy shade” and “those impending branches made more soft”? I am likely imposing what I now know of shadow science upon the unsuspecting poem. But, for me, the softened shade conjures the presence of the shadow’s penumbra, the “almost shade” that is generated by an extended light source, such as the sun. 

By its very nature of existing between two worlds, an existence between pure light and darkness where possibilities lurk, it is the realm of the dreaming man, where creativity and the warble’s song calms the soul. 

And in this place, where the ruined cottage resides, the narrator’s ruffled spirits are uplifted when he happens upon a friend as dear to him as the setting sun.

With instantaneous joy I recognized
That pride of nature and of lowly life, 
The venerable Armytage, a friend
As dear to me as is the setting sun. 

The setting sun is a time of day when shadows themselves grow long, and the horizon glows in multi-hued colors. (This phenomenon is in of itself the result of the sun being farther away from us in the evening. Because the blue and violet wavelengths are shorter, they are easily scattered by the particles in the atmosphere, and don’t stand a chance of reaching us. The larger red and orange wavelengths, however, are not as easily scattered by the particles, and they’re able to travel through the atmosphere. Hence the wonderful, beloved warm-colored sunsets.) The sunset is a beautiful ending, a kiss good-night and a time of closure, before one enters darkness, and perchance dreams. And it is also the eve of a new beginning. 

Was Wordsworth thinking of diffraction and penumbras when he wrote this poem? Probably not. But he surely felt them. He was moved by them, as we are moved by these phenomena when we experience them. Have we not all been moved by the magic of dappling shadows, light streaming amongst the shadows, and a beautiful sunset. Is it not our own storied experience with these phenomena that enables the narrator’s surroundings, experience, and feelings to resonate with us, and ring true? 

The lights and shadows feel magical and I would argue they are, in a way, but it is also the science behind them that enables these phenomena to not only occur, but reoccur consistently, so that humankind can share these experience, providing us with a language — nature’s language — that we can all understand. 


There is but one mention of a shadow in John Keat’s poem “On Seeing the Elgin Marbles,” the “shadow of a magnitude,” which follows the image of the sun — a dichotomy in a poem filled with dichotomies.  

On Seeing the Elgin Marble
by John Keats

My spirit is too weak—mortality
   Weighs heavily on me like unwilling sleep,
   And each imagined pinnacle and steep
Of godlike hardship tells me I must die
Like a sick eagle looking at the sky.
   Yet ’tis a gentle luxury to weep
   That I have not the cloudy winds to keep
Fresh for the opening of the morning’s eye.
Such dim-conceived glories of the brain
   Bring round the heart an indescribable feud; 
So do these wonders a most dizzy pain, 
   That mingles Grecian grandeur with the rude
Wasting of old time—with a billowy main—
   A sun—a shadow of a magnitude.

A study of the seemingly timeless nature of artwork, we see the narrator contrasting his own mortality to the lasting Grecian grandeur of the Elgin marble statues, “of godlike hardship” that tell him he “must die.” But on further reading, we see that these statues are subject to the “rude wasting of old time,” and are thus ephemeral in comparison to forces of nature — the “billowy main” (the sea), and the sun itself. 

And what of the sun? The powerful life-force, perhaps even evocative of the sunlit Grecian lands where creativity and artistic mastery flourished? It is compared to “a shadow of a magnitude.” It is this very comparison that brings us back to science, the yin and yang relationship of light and dark. As this shadow follows the sun in the poem, so do shadows follow the sun across the earth, lengthening as the day grows long, as our planet spins around the giant orb. It’s evocative of time itself and given its magnitude, it’s also evocative of the entire natural order of the world, in contrast to which even the most permanent-seeming artwork is subject to decay. 

Given the poem’s focus on art, is the narrator wondering to what end is art — often born on pain, struggle, and self-sacrifice — created, when it is merely ephemeral? As shadows, themselves, at the day’s end, are ephemeral, and ebbing into pure darkness, they appear to be a reminder of our own inescapable immortality.


When it comes to our own shadow, we are entranced. Shadows are the inspiration for any number of stories, especially children’s books, where they serve as our surrogates, the braver, wiser, more adventurous and scintillating selves we wish to be. 

In “Smoot, A Rebellious Shadow,” by Michelle Cuevas, illustrated by Sydney Smith, the story is told from the perspective of the shadow. The shadow longs to embark on his own adventure, and when he does, he becomes an inspiration to the boy who dismissed his shadow in the first place. In “Hortense and the Shadow,” written and illustrated by Natalia and Lauren O’Hara, Hortense’s shadow teaches her what it is to be brave. My own children’s favorite shadow book when they were young was “Shadow,” by Suzy Lee, in which all the shadows of the attic come to life through the imagination of one little girl. Going further back in time, there is Hans Christian Anderson’s much darker fairy tale, “Shadow,” in which the protagonist’s shadow was a nefarious force, but nonetheless an intriguing one.

Part of the shadow’s lure is the extent it’s connected to us, and by the same token, the extent that it’s separate from us. When we look at our own shadows, they move as we move, they are an echo of our own selves, and yet they are elusive to us, in some ways more closely tied to the natural realm than they are to our own beings. And in some ways, technically speaking, this is true. We may feel that we are the creators of our shadows, but they rely just as much, if not more, on the light source for their existence. And other factors, such as the distance and angle of the light source, and the nature of the surface the shadow appears upon, all have a role in the creation of our shadow. They do not belong exclusively to us. Ultimately, our shadows are poised to take flight into their own imaginary world, and how we long to follow them there. 

To a certain extent, we long to know our shadow as we long to know the mystery of our own selves. In this sense, shadows lure us into the land of the imagination. In literature, it is not the exact replication of our world, of our days, our hours, our image, that we instinctively respond to, but the imaginative and metaphoric representation of our world, the echo of our world that resonates with us, and strikes a chord that’s true.

We are limited in our self-understanding, after all. We are but skin and bones and a flutter of feelings, and evolving memories. The shadows that move so assuredly in the light seem to offer understanding, if we could only speak to them.

The Limitless Shadow

Shadows, at the end of the day, are simple. Shadows are created by blocking light. When a solid object gets in the way of light, it stops light from traveling through it, and we get a shadow. We all know this. But when looked at from another angle, shadows are not quite so simple. They are a window into light, which is endlessly complicated. Shadows are proof, for example, that light rays travel in straight lines. And shadows beg the question, what lurks in the darkness? Not just metaphorically speaking, but technically speaking, as well. Shadows block light, and therefore energy, but how much energy? Can we measure how much energy, how much movement, is in a shadow, and its resulting impact on life? 

Shade, a kind of shadow, not only offers us respite from the sun, it directly influences living things. Plants have adapted to growing in shade. Shady plants have adapted broader leaves to catch more sunlight for photosynthesis, for example. And many shade plants will leaf out in early spring, before the trees above them leaf out, to catch more sunlight. Animals, such as humans, have adapted physiological structures and mechanisms in our eyes so that we can see — at least to a slight degree — in the shadows and the darkness. 

Shadows play a significant role in the larger dynamic of life. Life forms have evolved to live in it and to benefit from it. And as we continue to evolve, shade may be, to a small extent, a harbinger of what’s to come. We don’t fully understand the impact of shade on plants and life. I certainly don’t fully understand how shade blocks different spectrums of light, nor can I predict how life will continue to adapt to shade and light in the future. I will never be able to clearly see what lies in the shadows and dark.

And so, as much as the science of shadows offers us insight into light and life, it also offers us mystery, it emboldens our imagination, and that is part of its lure.