Many years ago, long before I was born, a particular stream of light burst away from the sun, the result of a nuclear explosion. There’s nothing particularly unusual about this—the sun itself is ongoing nuclear explosion that has been exploding for four and a half billion of years. But I was moved to consider this particular stream last year when I sat down at my laptop and opened an email from my dad. At that moment I was hit with an overwhelming feeling of recognition and amazement. When I think back of all that went into making that feeling possible, I feel amazed all over again.
Like all the light coming from the sun, this particular stream consisted of photons emitted when hydrogen atoms fused together to create helium.(1) This stream of photons left the sun traveling at the usual photon speed of 670 million miles per hour—the speed of light. Yet even at this incredible speed it took them about eight minutes to cover the distance between the sun and the Earth. They didn’t know it, but they were headed for California, and about to hit a barrier.
About the time that light began it’s journey, a little boy was climbing on a pony outside his house in Fillmore, a little town surrounded by Orange groves an hour north of Los Angeles. On that particular afternoon, a photographer was going house to house with the pony offering to take pictures of children.
When the light finally arrived, it hit that boy on the horse. These were very real but very gentle “hits”—it would take trillions of them to have the weight of a feather. Many of these photons were absorbed by the clothes he was wearing, the skin of his face, or the tree behind him. But some of them, depending on their wavelength and surface that they hit, bounced off and continued. And of those photons that bounced, a few of them ended on a particular path through that hot summer air that took them into a piece of glass. This glass bent their course ever so slightly, aiming them at a small rectangle of cellulose film coated with a layer of silver salts. Specks of the film turned dark as the the photons interacted with these salts; salts laid on the film by a process perfected by Eastman Kodak.
Some days later another stream of light would be shown through the film and projected onto a piece of special paper, with the dark spots blocking some of that light. In the end, this paper with patterns of light and dark in just the right places was given to my father’s family. In exchange his mother gave the photographer several green pieces of paper bearing the words “Legal Tender.” She then wrapped the print in a book, along with others, and kept it in the house.
Decades passed, and sometime in 2005 in the mountains of Colorado that particular print was pulled out of the book and placed on a glass plate, just like others my father had pulled out in the previous month. As a motor hummed, bright light from a moving fluorescent bulb below showered millions of photons upward to the print. In an echo of that process many years before, some photons were absorbed and some were reflected. And some of the reflected photons ended up on a course to hit a “Charge-Coupled Device.” In this device the movement of these light photons was converted to movements of electrons. All of those photons in that particular pattern of dark and light were transformed into a pattern of current running across silicon wafers, and eventually through wires in a USB plug and into a computer. The pattern of light was now a pattern of electricity, was now a pattern of bits.
Inside the computer, this pattern of bits was then processed and transformed into a new pattern, one with far fewer bits. Much of this bit-reduction was done by throwing away those bits representing patterns which the camera perceived clearly, but which a human eye could not. This particular bit-reducing procedure was invented in 1992, by the “Joint Photographic Experts Group.” Today it is simply called JPEG.
Inside the computer, this reduced pattern of bits was then pushed out onto a small metal arm hovering above a magnetic disk spinning over five thousand times a second. The the electrons of those bits perched at the tip of this arm caused some of the small magnets in the disk to change direction. The pattern of electricity was now a pattern of magnetism, spinning on a hard disk in my dad’s laptop.
Sometime the next day, at after a mouse click from my father, that small metal arm went to the same spot on the disk and the process went in reverse: the pattern of magnetic spots went back into patterns of electricity. But this time, this electricity set off on a long journey. It left via an ethernet cord, where it went to a router. From there it went to a DSL modem which shifted the pattern onto the telephone wires of my father’s house. This pattern of electricity moved quickly, almost at the same speed that the photons left the sun, crossing the mountainous terrain of northern Colorado on wires hanging from poles 20 feet above the ground. At some point they went underground, and eventually reached a computer belonging to Google’s Gmail service. There is no way of knowing where this computer was, but it probably was not at Google headquarters in California.It is more likely that it landed at one of Google’s huge data centers spread throughout the United States, mostly in places chosen for access to cheap electricity to power.
The very first bits to reach Google represented four letters, spelling out “HELO.” This is the first step in “Simple Mail Transfer Protocol,” which we know as simply “email.” Then came the rest of the bits, containing that special pattern.
Later that day I was sitting on my couch in New York City. It was a tiny apartment in a crumbling century-old building. Two hundred square feet wasn’t much, but it had a magnificent view of the Empire State Building. The bits of data from the Google server—in the same pattern that was on my dad’s computer—zoomed across the country, crossed the Hudson river onto Manhattan, zipped under the city streets, climbed a perilously hanging wire outside my building, and finally passed through a DSL modem and into my laptop.
Another stream of photons, the last one in this long journey, was flying away from a bright fluorescent light in the back of my laptop. The photons rushed forward—again at that incredible speed. But barely a millimeter later some were blocked by small liquid crystals, rotated into blocking position by electric signals. The crystals were laid out in a grid 15 inches diagonal: 1024 across by 768 down, with three crystals at each point, precisely positioned behind vertical bits of color. Millions of tiny stained-glass windows of red, green, and blue. This pattern of blocking and non-blocking crystals was carefully orchestrated by my laptop to match that received pattern of bits, then piped through the flexible hinge and into the Liquid Crystal Display, or LCD.
The unblocked photos streamed through the color and out of the laptop, crossing a few inches through the air of my apartment before falling on my face. Some tiny percent of them fell on my eye, continuing first through a small plastic contact lens, then through the transparent cornea, on past the brown-colored iris (Which looks green in the right light!), and a few millimeters further their course was ever-so-slightly adjusted by my eye’s lens, pulled into focus by tiny muscles. (My lens is already not as flexible as it used to be. Perhaps in ten years they both will need help from reading glasses?)
On the backside of my eye, the light passed through a thin layer of blood(2), and then into the retina at the back of my eyeball. The blood was there to sustain a layer three special cells; cells tuned exactly to the frequencies of red, green, and blue. (I have to thank my mom for the third variety of cell. My dad, being colorblind, has only two of them.). These cells converted the light into a pattern of small electrical pulses of neurons, each pulse like the firing of a tiny gun. Like a moving highly choreographed wild-west shootout; a train headed to the space between my ears.
This pattern, which had travelled so long and so far, was now in my own body. Small chemical-electrical patterns of my nerves echoed the pattern of scattered light from that sun explosion so many years and eight minutes before.
Once in the brain, different aspects of the image stimulated different parts. Low-level areas in the visual cortex, in the back of my head, responded to edges between dark and light, or that long straight section. Later areas, fed by earlier ones, responded to recognized objects. A horse, a fence, a tree! Half a dog! In the parahippocampal cortex, close to the exact center of my head, the stimulus from the eyes was compared and integrated with my stored memories. And so many memories! Meanwhile, still less than a second after the photons hit my eye, this pattern of neuron firing reached the Fusiform Facial Area. It began firing wildly because it recognized these impulses as having a special sort of pattern: a human face.
Some of these neurons along the visual part of my brain have what are called “mu-opioid” receptors. In fact, these receptors become more numerous in areas handling the more complex patterns. When these receptors were found there in the 1980’s it was a bit of a surprise, since they had previously been found only in brain areas correlated with feelings of pleasure. After all, it is these exactly these receptors which can be tricked into action by smoking Opium.
Activation of even a few would have been enough to draw the attention of my eyes. A level of “pleasure” so low as to be unconscious. But like a secret handshake that gets you into the deepest chambers, this particular pattern passed through almost every visual area of my brain, triggering these mu-opioid receptors all along the way. This gave rise to a now-conscious good feeling. Further neuron firing in a brain area called the Amygdala somehow connected this with my emotions, causing me to smile.(3)
Somehow I feel a glow of recognition. Somehow a flood of memories is summoned. Somehow I feel a connection between myself and my father. Somehow I feel like I should write him back, and start to think of what I should say.
“Somehow,” yes. But how? It’s here that the trail goes cold, at the boundary between processes and brain-parts I know about, and the mysterious thing I call “me.”
But what a trail it is!
From “me” to my brain. From my eyes to the brain. From the laptop to my eyes. From Google to my laptop. From a house in Colorado to Google. From the photo to his computer. From the film to the photo. From my father’s face to the film. And from the sun to a young boy, sitting on a pony in California.
(1) Okay, to say it was made of photons is not strictly correct, as any modern physicist will tell you how Newton was wrong, and how light is both particles (aka photons) and simultaneously a wave.
(2) If you look at a clear blue sky and defocus your eyes a bit, you can actually see your white blood cells as they pass over. Interestingly, other species have different eyes of “better” design, where blood flows from the back.
(3) For people with the rare disease Capgras, this connection between emotions and vision doesn’t work, leading them to percieve people as imposters. See here.