The complexity of simplicity
Posted in Technology on May 7th, 2010Note: Feel free to correct my science, or to expand on points that I’ve glossed over.
A neuron fires. An imbalance in electrical charge and concentration of particles moves through a tunnel of molecules like a ripple in a puddle. Reaching the end, it triggers the release of chemical signals which traverse a small gap and set off the process again in the next neuron. Millions of times this occurs, transferring the signal down the brain stem, through the arm and hand, finally reaching a group of cells in the finger.
Those cells then carry out a chemical reaction with simple sugars and oxygen that are passing by in the bloodstream. Oxygen which was freed from carbon dioxide by a ray of sunlight hitting the leaf of a plant, transferring its energy to chemical form. The sugars originated from a different plant, thousands of miles away. A blade of grass, eaten by a cow and digested with energy obtained from previously eaten food, a chain tracing back to the energy it obtained from its mother in the womb, and eventually to a bacteria somewhere in the sea near the dawn of life, absorbing a ray from a much younger sun. All of this to create part of a hamburger consumed by the finger’s owner earlier in the day. 500 calories it had, all of them originating in the nuclear furnace of a nearby star and traveling to the burger via separate paths.
Just a few molecules worth of the stored energy is needed to change the shape of the muscle from long to short, in unison with other cells creating enough force to move the bones and flesh of the finger. Down it goes, sending feedback all the while to the brain via sensory neurons, letting it know when to stop pressing and release.
A key has been struck, momentarily allowing electrons to flow from one metal contact to another, triggering another wave of imbalanced particles which charges the electric field inside of a nearby transistor. Another flow of electricity is set loose. Again and again this happens, the transistors translating the electrical impulses into logical abstractions. Current races around the silicon chip inside the keyboard, being converted to a language which can be transmitted down the wire to the connected computer.
Inside the computer, another chip receives this signal and signals the Central Processing Unit. For a nanosecond, the computer stops the calculation being performed to register the keypress. A series of instructions which were loaded when the computer was turned on guides the signal to a storage place for recent keystrokes. Another program soon comes along and asks for the contents of that space, and is informed that a lower case “h” has been pressed. At this particular moment, this means that the “h” should be added to another storage place in the computer’s memory, and displayed on screen in the input box of a webpage.
A program running inside the webpage is informed that the contents of the box have changed. It then asks the browser to retrieve as set of suggestions from a computer hundreds of miles away. The browser can’t do this by itself, so it asks another program, which runs a set of instructions that send a message to a card responsible for handling network traffic. This card sends and electrical signal down the wire connected to it, which is connected to another device on the other side. This device has circuitry of its own which handles reading the signal and sending it back out on another cable. This is repeated over and over. At each point, including the origin, the energy required for all of these transfers is acquired from an electrical outlet, hooked up to a huge power grid, in turn controlled by more computers and humans who have eaten hamburgers.
At some point in the chain, the signal is converted from electricity to light, and races down a fiber of glass at the fastest speed in the universe. At the other end it is picked up by a light-sensitive transistor and converted back to electricity again. A computer receives the query eventually and looks at the stored compilation of what other users have been searching for over the last few years. It finds the answer stored in the magnetic configuration of a disk spinning 120 times per second. A signal is sent back out via its network card, back across the hundreds of relay points. The network card on the receiving end tells the CPU that data is available, which lets the operating system know. The operating system determines the correct program to send the information to. The browser tells the program running inside the webpage that it got a response, which then asks the browser to display it below the search box.
The browser does some calculations and sends a message back down the chain to the graphics card, which changes the signal that it has been sending to the monitor. Tiny lights inside the monitor switch on and off. Photons travel to the eye of the finger’s owner and set off a chemical reaction that eventually reaches the brain, setting off a cascade of neurons firing, translating the sight into language and higher level thought. The information is processed and another motor neuron fires.
End note: It amazes me how much complexity goes into this simple action, and I haven’t even given the most detailed description possible. I’d love to see this expanded even more by people who know more about other fields. I like this action as an example because it bridges the gap between biology and technology, and describes an interaction between entities close to the pinnacle of both.