Electric Universe

by David Bodanis

  As a result, we now can detect such small numbers of electrons that we are able to see and hear things that in the past would have been utterly imperceptible. And we can use our control over those electrons—our understanding of how to make them teleport forward or seemingly halt—to bring their immense powers of speed and agility into our world. The door behind which the ancient electrical force existed has been opened one notch wider. This is Turing’s legacy.

  Consider the way GPS navigation works. Hundreds of miles above our heads, electrons are being led back and forth within the transmitters of GPS satellites. The shimmering force field that stretches from those electrons starts to wobble each time the electrons move, and that faint wobble continues, free-floating, all the way down to us on Earth. It’s a GPS location signal, being sent on its way.

  The wave that reaches the ground is invisible and inaudible to us: no one could peer at the orbiting satellites and see this wave coming; no one could cock his head and hear it.

  Our eardrum is composed of atoms that have an immense number of electrons around them. The invisible rolling wave from a GPS satellite would be lost in all their jostling and shuddering. Even if the wave hit an old-fashioned TV antenna, it would have little effect; those metal rods, as placed on 1950s rooftops, still need a lot of electrons—perhaps several trillion—to be walloped forward in unison if there’s going to be a noticeable response. That’s better than our ears can do, but still involves more electrons than a satellite wave can produce.

  Yet when that faint wobbling from space reaches our GPS receiver, something different happens—something made possible by the Bell engineers who showed how to access and control the quantum world. The incoming wave, feeble as it is, nudges forward a very small number of electrons, but those few electrons are guided to one of the special ore veins. The silicon they touch transforms; it’s no longer a puritanical, disapproving, don’t-even-think-of-letting-anything-get-across-me substance. Instead, its own electrons spring forth, stimulated by the tiny flicker of incoming electric current. Its inner cavities are no longer gloomy and blocked, but switch on and easily transmit a clear signal. The distant satellite has been heard.

  Almost instantly the incoming ripple from space dies down; the ore vein inside the receiver shuts off. But then, a billionth of a second later, another ripple that’s been floating down from the satellite arrives. The ore vein sparks into action again. After a mere few hundred billion repetitions or so, the distinctive identifying signal for that satellite is received.

  A wavering bipedal human is likely to be scanning this GPS device to “hear” a satellite hundreds of miles up in space, and so navigate her way to a new office building. She can then go on to use other devices for a Web search to examine, ever so easily, a few billion information sources scattered in silicon and metal memories within millions of computers worldwide. This too would have been inconceivable in earlier times, for even though there was a system of storing great amounts of information—the world’s great libraries—it took trained archivists months to go through even one small part of those records.

  That was because traditional information was stored by means of ink marks that have soaked into the thin slabs of modified wood pulp we call paper. But ink is big. Atoms are small. The archivists who looked through stored books, or even just the microfilm indexes for those books, were clumsily looking at immense solid lakes of electrons and other submicroscopic particles—for that is what written or typed letters, stretching for their great height of a quarter-inch or more, actually were.

  Web searches are faster. Hit a key on a laptop or handheld browser, and long-stretching tunnels of electrons, in wires underneath our keyboards, are ready to begin the hunt. Our fast finger-pecks are ungainly, ponderously slow thumps to them, so there’s plenty of time. (Every key on an ordinary laptop is sampled dozens of times each second, with electrons constantly reporting “No hit, No hit” to the computer’s central processor, until, wondrously, one of the keys does slowly lower itself as we type.)

  Great numbers of transistors in our computer and connected ones quickly reconfigure themselves to allow the desired request for Web information to pass, their ore veins instantly transforming into efficient conduits, then back into inert barriers, once the request has gone through.

  Millions of Web pages begin to be scanned—some as summary indexes coded within a search engine’s central computers, others at far-flung machines located all across the globe. Soon the request is making force fields shift the ancient yet powerfully charged electrons back and forth in thousands and then millions of pages, as the desired phrases being hunted for are compared with what’s in storage. Decisions are made, and funneled through more transistor rocks, till finally the results start pouring back into our computers. The emissaries are reporting and a final set of signals is led to our screens. From their bizarre quantum flights, the answer we sought now glows into life.

  It can all take place in the time we reach a hand toward a waiting cup of coffee. For centuries humans lived separated from the flurrying, fast inner world of electrons. But we no longer do.

  The story of electricity still isn’t over. We know that electrons can bounce along inside a wire; that insight led to telegraphs and telephones and lightbulbs and motors. A whirling, long-hidden force pushes those electrons along within the wires, and when shaken hard enough, the force can even vibrate as a wave that flies free from those wires. The result was radio, radar, and ultimately their miniaturized use in our cell phones. Quantum theorists found that electrons could teleport in great, precarious leaps, and even be forced to remain in seemingly immovable states of low energy; the result was switches contained subvisibly within solid rock, whence the computers transforming our lives. But beyond our technology, there’s one event even more central to our lives where these electric charges so many billions of years old are crucially active.

  PART V

  THE BRAIN AND BEYOND

  The metal atoms that exploded from distant stars were not alone when they landed on Earth, back in the era billions of years ago when our solar system was new. Floating along with them in deep space had been carbon and oxygen and many other elements.

  When those elements landed on the still-boiling Earth, only some of them fell deep beneath the surface. Many of the rest remained closer to the top, becoming part of landmasses and oceans, seafloors and swamps. Although they weren’t metals, an electric field was leaking out of them as well, produced from the charged electrons and nuclei of which they were made.

  Most of these nonmetals remained inert, stuck dully in their mountains and clays, but a few of them began to do something peculiar. The stretching electric field from their electrons made them writhe and twist and pull into strange configurations.

  The sun over the new planet was hot. Energy was absorbed. The contorted clusters of atoms twisted some more, causing others around them to contort as well. Most of the shapes fell apart, but a few of the configurations created others so similar that they had duplicated themselves.

  Life—built out of electric charges—had begun.

  11

  Wet Electricity

  PLYMOUTH, ENGLAND, 1947

  Electric forces weren’t just important in assembling the first life, but are everywhere on our planet and in the body even today, active in the most mundane of activities. Just switching on a television or a computer, for example, means that from each glowing pixel on the screen, fresh electromagnetic waves are sent rippling outward at 670 million miles per hour. An awesome sequence of events quickly unfolds.

  The watcher’s eyes are likely to swivel forward in a sequence of stately turns as the screen’s pixel glows: each quarter-ounce mass of eyeball tugged by six flat muscles, in a glissando slide within the slippery fat lining the orbital cavity. The eye blinks, the widened pupils are in position, and the incoming electromagnetic waves roar in.

  Ripping through the thin layer of the cornea, they decelerate slightly, with their outermost edge
s forming a nearly flat plane as they travel inward, carrying the as-yet-undetected signal from the screen deep into the waiting human.

  The waves continue through the liquid of the aqueous humor and on to the gaping hole of the pupil. The human may have squinted to avoid the glare, but human reflexes work at the rate of slow thousandths of a second and are no match for these racing intruders. The pupil is crossed without obstruction.

  The stiff lens just below focuses the incoming waves even more, sending them into the inland sea of the jellylike vitreous humor deeper down in the eye. A very few of the incoming electric waves explode against the organic molecules in their way, but most simply whirl through those soft biological barriers and continue straight down, piercing the innermost wrapping of the eyeball, till they reach the end-point of their journey: the fragile, stalklike projection from the living brain known as the retina. And deep inside there, in the dark, barely slowed from their original 670 million mph, the waves splatter into the ancient, moist blood vessels and cell membranes, and something unexpected happens.

  An electric current switches on.

  Its existence seems odd, for the inside of the body is sloshing wet. We’ve seen electricity in telegraphs, telephones, lightbulbs, electric motors, radios, radars, and computers of every sort. But here too? Water and electricity are not supposed to mix. James Bond, famously, could terminate villains by tossing radios (electric) into their bathtubs (wet). Yet these tiny circuits in our eye sockets duplicate the operation of the most refined electrical receivers, despite being composed not of insulated copper wire, or even of cleverly modified silicon, but just of ordinary proteins, fatty cholesterol—and lots and lots of water.

  Our entire body operates by electricity. Gnarled living electrical cables extend into the depths of our brains; intense electric and magnetic force fields stretch into our cells, flinging food or neurotransmitters across microscopic barrier membranes; even our DNA is controlled by potent electrical forces.

  The result is that researchers today have created yet another new form of technology, a liquid technology, in which miniature puddles can be loaded with electrical particles that swarm into the inner recesses of our body. Anesthetics float down to electrical pumps in our nerve cells, numbing us so that surgery is endurable; Prozac latches on to electrical receiving units in our brain, keeping our sorrows in check; the electrically charged molecules that emerge from a Viagra pill operate on nerve firings elsewhere, making our pleasures rise. It’s all part of the great shift in the frontiers of current science—from physics to biology; from the physical world outside, to the body and thoughts within.

  This is so unexpected—what are live electrical circuits doing embedded in our bodies and brains?—that electricity’s role in the body wasn’t even imagined till recent times. Early Greek and Islamic investigators noticed a few electric effects, as we saw, such as the way the fur in pelts stands on end when you rub it, so long as the air is dry. Anatomists of the Renaissance and later found hollow white tubes running through the body and recognized that these were nerves. But they too assumed the nerves were run by a divine power or, in lieu of that, by miniature pulleys or perhaps hydraulic fluids, not by electric sparks.

  What began to change this was the inability of most scientists, however independent they imagined themselves, to ignore the fashions of the society around them. Pumps were an exciting, rapidly improving technology in 1600s England and Italy, so when William Harvey was investigating the circulation of blood, it was natural for him to think of the heart as resembling a pump. Newton’s followers naturally thought of the universe as a clockwork, because accurate clocks were a compelling fresh technology in the late seventeenth century.

  In the early 1800s, many people had seen demonstrations of simple batteries and wires. The twenty-year-old Mary Shelley, sharing ghost stories one stormy night with friends near Geneva, had naturally thought of Dr. Frankenstein as using electricity to give his monster life. In the 1840s, telegraph lines were being built, carrying messages using fast-surging electricity. As the main western European cities were linked one after another, it was almost impossible to believe that the long nerves that carried messages inside our bodies didn’t somehow surge with electricity as well. When German researchers managed to measure it clearly in the 1850s, they found that electricity didn’t travel through living nerve cells at the millions of miles per hour that it traveled in telegraph wires. Instead something seemed different within the body, for the speed was only 100 miles per hour—just a few times faster than an arm moves in a fast jab.

  In one sense that was satisfying, for it would be hard to understand how fragile human tissue could hold together if there really were signals rushing inside us at a million miles an hour. But it also was confusing, for the chemistry of that era still couldn’t explain it. Eyelids are tugged down by muscles. Anatomists can easily find those muscles. But there are no little muscles acting as booster units to keep our numerous nerve signals going. And if our nerves were like telegraphs, where were the batteries and what, exactly, was inside the cables? There are no long strands of copper wire or any other metal inside our bodies.

  The solution the researchers were looking for—the explanation of how electricity can exist even when surrounded by water—appeared only when they stopped focusing on the machinery of the era. Telegraphs work by bouncing electrons around, but electrons, of course, are just one part of the atoms from which they come. Telegraphs and lightbulbs and even computers have to rely on those small, vulnerable electrons. But our electrical technologies are a mere two centuries old. Evolution on Earth has been operating for billions of years, and long ago yielded another approach for conducting electricity, using not just tiny electrons but entire atoms.

  The trick is to find atoms that have a greater-than-usual amount of electrical force leaking out. Normally we’re taught that doesn’t happen, for there’s as much negative charge in electrons orbiting an atom as there is positive charge in the nucleus at the atom’s center. The result is that the whole atom is in a state of equipoise. That’s why it’s electrically neutral, and why even the great Newton sometimes thought of atoms as boring, simple spheres.

  Yet in quite a few atoms, such as those of the common metal sodium, it’s easy to tug off a single outermost electron. Our planet and bodies are loaded with these amputees. That’s most convenient, for this galumphy giant is ideal at pushing other electrical charges along. It has one more positive charge in its own center than it has negative charges in its remaining electrons, and so it beams out a strong positive electrical force field. Also, this big, atom-sized sodium chunk—lacking one of the orbiting electrons that ordinary sodium has—can survive in places where tiny electrons cannot. It’s impervious to churning water or reactive oxygen; atom-sized ions like it can spend millions of years loose in the atmosphere, pummeled by wind and rain and electrical storms, or buried deep inside mountains, crushed under miles of rock.

  Individual electrons couldn’t survive for long in the warm, sloshing water of a living body, but these giant reshaped fragments do fine. Any atom that has a different number of electrons than it normally starts with is called an ion, from the Greek for “traveler.” The snipped-down sodium atom is called a sodium ion.

  This is what our bodies use to carry the currents Helmholtz measured. But how? Nerves are smaller than early anatomists thought they were; the white hollow tubes that Renaissance dissectors found are actually just conduits for the real nerves, which are much finer, almost like hollow threads, miniaturized far below ordinary vision. The narrowest part of all is the axon, the long-stretching part of a nerve cell along which signals shoot. They’re so small that even with modern microscopes it’s hard to see clearly inside most axons.

  Luckily for science, different nerves send signals at different speeds. If a nerve is very slender, the signal goes fairly slowly. If the nerve is wider, the signal goes faster. This meant that twentieth-century physiologists who wanted to improve on what the first Ge
rman researchers had begun simply had to find creatures that needed ultrafast nerve signals for their attacks and escapes, since that meant the creatures would likely have wide, plump nerves. The physiologists would also need pretty long creatures, since lengthy nerves would be easier to pull out. The logic’s great, until one thinks what it means: hunting for huge, fast, living animals. Frogs would seem too small, bears could be too slow, but giant squid or, in lieu of that, ordinary squid—which need fast signals for their jet-propelled strikes—are ideal.

  First, of course, one had to find one’s squid. Alan Hodgkin, a gentle young English Quaker, had some difficulties when he returned to Plymouth, England, in the summer of 1939, after a stint in the United States. He went out on trawlers, he scoured the fish markets, but where were the squid? In chatty letters to his mother, he tried to be positive, but then, despondent, he couldn’t help bringing up “the almost complete lack of squid.” Yet by the end of July his luck had turned. He went away for a week’s vacation to Scotland, having asked local fisherman to keep on hunting, and they came through: “On my return, found a large supply of squid waiting for me.”

  The squid nerves that he and his even younger colleague Andrew Huxley pulled out dwarfed anything from more-common creatures. These nerves were so big—almost as wide as a crisp pencil line—that they could stick a thin glass needle right down the middle of each one. (The squid was dead, but the nerves were “alive,” in the sense that for several hours they still worked even without a host.) The nineteenth-century researchers could only measure along the length of a nerve, not see what was happening within. Hodgkin and Huxley, though, could now measure the electricity inside the nerve and compare it with the outside.

  At first their experiments failed because the hollow needle scraped against the membrane. But Huxley was good with his hands, and eventually, with the help of some miniature mirrors to see upcoming bends, they could steer the needle without scratching the fragile, still-living nerve.