The Canon (19 page)

Of course, you don't want unregulated electrons cruising in your home—exposed bundles of wires that, if touched, will divert some of their sizzle in your direction. The metal conduits of a common cord come wrapped in layers of insulation, a material with a comfortably large ohm, such as rubber or plastic, where the atoms clutch their electrons tightly and have no desire or patience for the passage of wayfaring particles. Electrons may gather readily on the surface of a balloon, but the rubber resists their transdermal penetration—as does the rubber or similar insular material wrapped around an electric wire.

But what does it mean to talk about a flow of electrons, or an electric current? It means that energetic charged particles are being directed along a pathway, such as a length of wire, usually toward a target, where they will be expected to do some work. Not all or even most of these excited electrons will traverse the entire length of the conducting corridor. Some may flow all the way through; the majority will jostle an atom en route, loosening an orbiting electron and pushing it forward, then moving into the vacancy itself. The important point here is that a large stream of trillions of electrons is either getting a push from behind or a pull from up ahead, and is excited, anxious, driven.

Now, electrons are always on the move, no matter what. As they cloud around an atom, they refuse to stop. The electrons in a discarded fragment of copper wire are jiggling about continuously, hopping from one metallic atom to its neighbor, rearing back at any sign of other electrons, with the territorial indignation of cats. Yet these are ordinary electron motions, powerful enough to fulfill the edicts of their atoms, but not enough to do more, not enough to flip a switch or turn a gear. If the electrons are to take on any organized, extracurricular activities, they must feel inspired. They must be animated. They must eat.

Electrons have mass—an exceedingly small amount of mass, but mass nonetheless. Electrons, then, are a form of matter. They are condensed fragments of the cosmos that need some reason to get out of bed in the morning and off the couch in the evening. They are not self-motivated. That is to say, they are not a form of energy, or at least not of useful energy.

The vast splintered vale of our universe, as far as we know, is stocked with two basic offerings, two categorical insults to His Lowly Holiness of Absolute Nothingness that might otherwise have held sway: matter and energy. For all the comparative emptiness out there and in here, we still have our amulets of somethingness. We still have matter and energy. True, Albert Einstein famously demonstrated that matter and energy are two ends of the same lucky horseshoe, and that matter is, in the words of the science writer Timothy Ferris, "frozen energy." From tiny quantities of mass we can extract enormous plumes of energy, as the nuclear bombs that destroyed Hiroshima and Nagasaki proved all too darkly. Our sun, too, shines by transforming its core tissue into the pure energy of light and heat; but because it can squeeze so much radiance
from so little solar mass, it has shone for 5 billion years and will burn for at least 5 billion more.

Nevertheless, in our workaday world, matter and energy, like the four fundamental forces of nature, behave according to distinct operating manuals, and are proud of their specialized talents. Matter is indispensable to the making of all things—planets, the Crab Nebula, 350,000 species of beetles, four members of the Beatles. Matter comprises the hundred-odd elements in any number of mixes, matches, solids, liquids, or gases. But mass can do nothing of interest without energy. The formal definition of energy is "the capacity to do work," which sounds drearily nagging. Have you finished your algebra yet? OK, then, time to practice piano! Better to think of energy as the opposite of parental or pedantic. Think of energy as romantic. Think of it as a lover, or the idea of a lover, as the spark that makes matter matter. You want to turn on a light. You want electrons to surge through your circuits. They will not move of their own accord. You must excite them. You must supply a source of energy, which will stimulate the electrons in the circuits and send them streaming and screaming to do your bidding.

In thinking about energy, forget for a moment the upsetting image of large oil rigs being constructed in the world's few remaining wildernesses, where the heavy machinery may scar the landscape and disrupt the ecosystem long after having extracted the bare semester's worth of fossil fuels that lie underneath. Consider happier ways to get energy. You can eat a bowlful of cherries, offering your body a source of complex carbohydrates that it can break down into smaller pieces, thus releasing the so-called chemical energy that had held the carbohydrate chains together. You can set up a windmill that exploits the moving currents of air to turn a blade that turns a crank that powers a pump that generates an electric current. Or you can hoist the rigs of your sailboat and let the mechanical might of the wind carry you from one leisure-time activity to the next. You and your lover can snuggle in front of a fireplace and warm yourselves with the "heat energy" generated by the combustion of a selection of seasoned hardwood logs, perhaps kindled by crumpled pieces of newspaper or the old love letters of unfaithful partners past. If you see a cockroach too large and revolting to fit comfortably beneath the sole of your tennis shoe, you can kill it with the "gravitational energy" supplied by the release of a brick from your hand onto the floor.

All of these disparate forms of energy that we describe as chemical, mechanical, heat, gravitational, or hysterical are variations on two mega-categories of energy: stored energy, which is more grandly known
as potential energy; and moving, or kinetic, energy. A ripe cherry holds potential energy in its carbohydrate bonds. As those bonds are systematically pried apart by metabolic enzymes in your cells, some of the fruit's potential energy is converted into kinetic energy that you can then use to go shopping for more cherries. A frozen lake in the mountains is a reservoir of potential energy that, when the ice thaws in spring and starts burbling downward, becomes kinetic energy of considerable scenic value. A lit match translates the potential energy of timber into the kinetic energy of hot, dancing flames. Lift a brick, and you essentially inject it with potential energy. Drop the brick, and potential energy quickly expresses itself as a kinetic whop on the greasy auburn exoskeleton of an unfortunate
Periplaneta americana.

The energy that we call electric energy also has its potential and kinetic guises. Electrons and protons are, as a fundamental feature of our atomic world, drawn irresistibly toward each other. Separate them, and the electromagnetic force will hound them to find some way to rectify the imbalance. Move toward a proton! Fill that hole! What do you think you are, a neutron? The electromagnetic force also urges particles of the same charge to keep a certain distance from others of their kind. Push two like charges unnaturally close together, and they will feel hemmed in, keyed up, anxious to spring away. The electric power on which we are so dependent takes advantage of these particulate impulses in numerous ways. We have batteries in which one set of chemical reactions generates a buildup of excess electrons on one end, while a different set of chemical reactions yields a preponderance of positively charged atoms, or ions, on the other end. Give the opposing charges a chance to mingle, and the resulting burst of energy just may light up the room.

For the electric current to flow, however, it needs a path, a circuit, a conductor, just as the excess electrons you picked up from the carpet required the bridge of your finger on doorknob or on nose of pet in order to reach more positive pastures. A length of metal wire linking the battery's negative and positive poles provides that path. The excess electrons at one end feel the tug of positive ions over yonder, and a concomitant repulsion from the other negative yokels around them. They begin jostling atoms in the wire, which shed some of their outer electrons, which in turn thump the atoms a little farther along, and like a row of clattering dominoes the charge is propelled forward. The potential energy of the battery's chemicals is reinterpreted as the kinetic energy of jostling atoms and electrons, which can be tapped to run a motor or heat the filament of an incandescent bulb until it radiates light, wondrous light, compliant Tyger burning bright.

The electric current that streams from your wall sockets courtesy of your local utility also relies on a pushing and pulling of electric charges along compliant channels. The initial sequestering of positive and negative charges is not easy. It takes work to keep protons from electrons, and work requires energy. A fruit tree needs the sun's radiant bounty to blossom, and a power plant needs one source of energy to spawn the handy electric kind its customers demand. Most power plants in the United States burn coal, gradually converting the substantial sums of potential energy banked in these fossilized briquettes of ancient forests into a river of charged particles tumbling forward in a furious crusade to meet their match. And one of the ways that the transformation from charcoal to sparkle unfolds is through the second half of the force in charge of charge: magnetism.

As Michael Faraday and James Clerk Maxwell determined more than a century ago, the electric force and the magnetic force are intimately, mathematically related. Both physicists were brilliant pioneers in the quest to unify the fundamental forces of nature, an industry that keeps thousands of theoreticians gainfully employed to this day. For his effort, Faraday was awarded not one but two standard units of measurement—the farad and the faraday. As for Maxwell, we honor him each time we utter the compressed term he coined: electromagnetism.

But what is magnetism, and why do you have too much of it on your refrigerator door? How are electricity and magnetism related? They are both, it turns out, very good at fieldwork. They generate fields of their own—magnetic fields and electric fields—and the field of one force can affect the behavior of the other force. To talk about a "field" is another way of saying, action at a distance, or, the pluck doesn't stop here. The earth has a gravitational field, a tugging of other bodies toward itself, which progressively weakens the farther from Earth you manage to fly. Similarly, a charged particle like an electron or a proton has an electric field around it, a personal sphere of influence that projects into space and that either repels or attracts other charged particles. As with a gravitational field, an electric field gets feebler the farther from its source you roam. And, as anybody who has ever played with a couple of bar magnets or with Thomas the Tank Engine trains knows, magnets have distinct fields, too, regions of force that radiate outward from each end of the magnet and either repel or suck closer the ends of the other bar. From whence this rigid animal's magnetism? Whether it is a bar magnet, a classic horseshoe magnet painted silver and red, a lodestone at the natural history museum, or the bendable black backing that keeps your veterinarian's business card on perpetual display, the items
we call magnets have the unusual property of spin synchronization. As electrons float around an atom, they also spin on their axes, although "spin" in the curiouser context of Quantum Corner is not exactly like a spinning disco ball or planet; for one thing, it takes an electron two complete rotations to get back to where it started from. Nevertheless, electrons cloud around the nucleus and gyrate on their toes, each producing a tiny magnetic field as it spins. Some may be spinning in one direction, some in another, the end result being that in most atoms, the magnetic effects of these motions cancel each other out. In some metals, though, like iron, cobalt, and nickel, the electron spins can become synchronized, either temporarily or permanently, amplifying those little magnetic fields into one big one. Now you have a magnet, an object that, among other properties, generates a magnetic field, attracts iron and steel, and is keenly responsive to electricity.

Send an electric current through a wire and, depending on which direction its electrons are flowing in, the current can demagnetize a magnet, remagnetize a demagnetized magnet, or turn a nonmagnetic metal temporarily magnetic. The flowing electrons of the electric current affect the distribution of the atoms in the magnet or magnet aspirant, aligning atoms of similar spin and thus magnetizing the material in some cases, or jumbling up clockwise and counterclockwise spinners and demagnetizing the substance in others.

The wheelings and dealings are mutual, and a magnet can set an electric current coursing along a wire with cardiovascular verve. If a copper wire is spun quickly around a magnet, the magnetic field will jostle the electrons in the copper and start them dancing from shell to shell, atom to atom. Add a positive incentive to one end of the wire, and the electron surge will flow fiercely toward it. Power plants often create electric currents by spinning large copper coils inside giant magnets at very high speeds, the rotation driven by a coal-powered turbine engine. The domino wave of hyperexcited electrons in the coil is then transmitted along a lengthy grid of power lines, some of them tucked underground, others fastened onto high-tension towers that loom phantasmically over the highway, like a procession of giant Michelin Men with arms of aluminum lace.

When you flip on your home computer, you divert some of the electric current rowing merrily along the wires in that utility pole outside your place of residence, directing it through the distribution line that feeds your household wiring and allowing it to stimulate the electrons in the computer cord. The kinetic energy pumped into the cord can then be assigned to a task, like activating a tiny motor in the computer's
hard drive. Or it can re-separate the positive and negative charges in your computer's battery pack: the business we call "charging" the battery, again to the annoyance of electro-purists, who observe that no new charges are added, but rather the existing ones yanked apart and sufficiently segregated so their eventual reunion will have some oomph. With a comfortable supply of potential energy in your battery and at your disposal, you won't weep should a great static stutter in the sky knock a tree onto your utility pole. The lights may wink off but, lo, the computer still beams, and you can work, work, work in the dark.