Electric Universe

by David Bodanis

  Suppose you snipped off the extra charge from your finger at that point, and left it hovering in position, that fraction of an inch from the metal railing. Since the field is strong here, it would send the charge shooting back to where you’d been. A “voltage” measures that pushing force, the difference in what potentially might happen.

  If the wire is in an area where the field’s not changing, there’s a curious safety. That is why a bird can safely sit on a high-voltage power line. When both its feet are on wires of the same voltage, there’s no difference between the pull that the associated force fields can give to the electrons in its body. Let the bird extend one foot to an aluminum ladder that’s touching the ground, however, and a sudden explosion of coq flambé will result.

  They drift along so slowly, barely at walking speed

  Individual electrons travel fast, but since they also bounce in all directions they make hardly any net progress forward. Only if a wire could be cut open and the electrons somehow released would we see their intrinsic speed, for many would be going fast enough to shoot straight out of the atmosphere and into outer space. What the force field from your wall socket does inside a wire is make sure that the majority of the high-speed crashes jostle forward in the same direction.

  Whenever you shake that charged-up finger

  We create and launch electromagnetic waves all the time. Comb your hair on a dry day and you tear a small number of electrons from your hair. They accumulate on the comb, and if you then wave the comb in a graceful andante, taking five seconds to swing the charged comb to the right, and another five seconds to swing it back to the start, you will have pumped out a wave whose front has a head start of ten seconds on its back. The wave travels at 186,000 miles each second, so in the ten seconds of this graceful comb-conducting you’ve created a soaring wave that stretches upward into outer space and is 1,860,000 miles long.

  Other launch devices are also to be found around the home. If you wash your dog on a dry day, and towel it vigorously, there’s likely to be a slight buildup of static charge on its tail. As the dog happily wags its tail, creating a complete back-and-forth cycle in just half a second, then it’s creating an electromagnetic wave that stretches 93,000 miles (i.e., half of 186,000) from head to end. This invisible hurtling wave will reach the moon in less than two seconds; it will reach the orbit of Saturn in a bit under an hour, and the canine-launched beacon will exit the solar system a few hours later, and keep on going.

  Just by jostling an electric charge

  If shaking any charged particle can send out these waves, why doesn’t the movement of electrons inside a computer send out similar waves? The answer is that it does: not very powerfully, and at highly variable frequencies, but it’s one of the reasons that airlines have stewardesses check that no one’s using a laptop at the delicate moments of takeoff and landing. The undulating fields that shoot out from laptops or other equipment this way—and especially the undulating fields from the active processors inside such devices—could fly the length of the plane and easily bounce off the wing, affecting the pilot’s controls.

  His name was Robert Watson Watt

  But not for long. To the distress of archivists everywhere, after Watt was knighted in 1942, he changed his last name, and became the double-barreled Watson-Watt. Frederic Lindemann engaged in yet another of these peculiarly British morphs; in his case, through the help of Winston Churchill, he became the impressively named Lord Cherwell during the war. For ease of reference, I’ve stuck to the earlier names throughout.

  Plutos were floating loose

  The electron gas model of metals stemmed from the work of Paul Drude, working at Leipzig in 1900. It was long out of date by the time Wilkins and Watson Watt used it, and they knew it was “wrong”—atoms aren’t little solar systems, and electrons aren’t little planets.

  But they could still use it, for Drude’s theory was not so much false as just incomplete. This happens a lot in physics. A larger domain is seen, in which the previous theory is realized to be a special case. But so long as you stay within the limits of the smaller domain, the archaic equations and vision that came from that domain will still accurately apply. Newton’s laws of motions, for example, are still good enough for our ordinary environment, even though they’re actually just a special case of Einstein’s far richer special theory of relativity. They give valid results, so long as one stays away from the realm of speeds approaching that of light. In a similar way, Mozart’s simple triads can be used by modern composers, even though Debussy and then, even more, the American jazz greats opened up a range of possible chords beyond what Mozart ever imagined.

  For the origins of Drude’s model in the kinetic theory of gases, see Walter Kaiser, “Electron Gas Theory of Metals: Free Electrons in Bulk Matter,” in Histories of the Electron: The Birth of Microphysics, edited by Jed Z. Buchwald and Andrew Warwick (Cambridge, MA: MIT, 2001), 255–303.

  By pumping up…radio waves…the enemy plane [could] become a flying transmission station

  Which is why mirrors work. Ordinary light is a wave much like those transmitted from Britain Chain Home radar towers, only with a shorter and more energetic wavelength. When a light beam made of these waves hits the metal coating at the back of a piece of glass, loose electrons there begin to shake.

  Like all jostled electric charges, those electrons start broadcasting out their own Faraday-style waves. If the metal backing of the glass is jagged and rough, the broadcasts fly out in all directions and we just see a dark blur. But if the back of the mirror is very smooth, the broadcasts lift off in stately flight patterns beside each other, carrying a close duplicate of the original image that flew in. Smile in a mirror, and multitudes of mini-radar broadcasts, lifting out from the ancient metal atoms back there, are what you see smiling back.

  The less revealing label “Radio Direction Finding”

  “When Rowe and I sat down to devise a label for the system…we said to ourselves “Let’s think up something that doesn’t merely conceal the truth but positively suggests the false….We agreed on the initials “R.D.F.” [for radio direction finding]….” Watson Watt, The Pulse of Radar, 123.

  It’s possible he and Rowe could have chosen a worse code name, but it would have taken some doing. When they came up with the cover name, they were pretty sure their oscilloscopes would never be good enough to get a clear bearing on an airplane’s direction. Soon after they selected it, though, improved technology meant that British stations did begin to achieve accurate direction findings. Their secret label had became a blaringly informative clue.

  The Würzburg radar…poured out waves of a bare ten inches

  A close descendant of the Würzburgs sits in our kitchens today, for when the wave generated by a radar transmitter is just a little bit shorter—two or three inches is ideal—that radar beam will cause any water molecules it hits to vibrate. A few postwar researchers thought this process might be useful for curing tire rubber, but other markets beckoned. Waves of three inches in length are known as microwaves—and so the microwave oven was born.

  Since the oven is still basically a radar transmitter, any loose electrons it hits get tugged back and forth with such power that they can fly loose and even start sparking. This is why putting metals—which are laden with extra electrons—inside the machines is not recommended.

  No one else there dared to speak in his support

  Why did so many officers go along with Harris? Partly it was because precision bombing hadn’t worked; in late 1941, for example, only one fifth of all sorties managed to place bombs within seventy-five square miles of the target. Partly it was the great momentum of having created all those bomber squadrons, and airplane factories, and trained aircrew—for who could justify not trying to use them just a little bit more? Left unspoken were the memories of the World War I trenches, which Harris had flown over, and the strong feeling that any aerial attack was better than sending British troops into land battle on the continent of Europe a
gain.

  When those arguments missed—and what exasperated the Royal Navy and other branches of the British armed services so much—is that resources that went into bombing could not be used for anything else. A vast amount of Britain’s wartime GNP went into Bomber Command, and so was not available for extra destroyers, artillery, transport aircraft, and everything else.

  Some of the ground controllers in such circumstances yelled…“Break off…”

  The recording is from attacks on Essen the following night. No transcripts or recordings of ground radar staff survive from the Hamburg night. See David Pritchard, The Radar War (Wellingborough, Northamptonshire, England: P. Stephens, 1989), 213.

  “They were on their hands and knees, screaming”

  German civilians weren’t done with terror once the bombers left. After a similar giant raid on the city of Cologne, also led by Harris, the Nazi government made all surviviors sign the following pledge: “I am aware that one individual alone can form no comprehensive idea of the events in Cologne. One usually exaggerates one’s own experiences and the judgment of those who have been bombed is impaired. I am therefore aware that reports of individual suffering can only do harm, and I will keep silence. I know what the consequences of breaking this undertaking will be.” From Dresden: Tuesday 13 February 1945, by Frederick Taylor (London: Bloomsbury, 2004), p. 128.

  The world…with teleporting jumps

  The term “teleporting” is frequently used in describing the quantum realm. But it does suggest that the objects so described have a continuous identity before and after their “leaps”—and a central tenet of quantum mechanics is that such identifications are inherently impossible at the level we’re discussing.

  The concepts can be confusing even to specialists, and the reading guide keyed to this section might give some solace to the perplexed.

  An exclusion zone seemed to operate

  This is Pauli’s Exclusion Principle, and the effect is not so much on linear speed as on the overall energy that the electrons possess. For the strange thing about electrons is that two electrons can’t have the same energy, just as two people can’t occupy the same point in space. If one electron does already occupy a particular energy state, it can actually stop another electron from moving up into it—much like blocking a particular rung on a ladder.

  Pauli’s principle is immensely powerful, for atoms are almost entirely hollow, and without this restriction on the way electrons can overlap, we’d be in trouble. Even when you just hit your fingertips to the table in a vainly time-wasting drum roll, the great empty spaces in the atoms of your finger would travel right through the great empty space in the atoms of the table if it weren’t for the Pauli principle.

  Your feet would start sinking through the floor, just as your posterior would tumble through the chair. There might be a brief moment of reappearance—as your body fell into the airspace of any room below—but when you reached the floor of that room, you’d simply sift through again, a process that would be continued to distressingly great depths in the planet below.

  That’s why our whole life is, safely, spent hovering. We hover over the floor when we walk, and we hover over a chair when we sit. Even a dedicated couch potato, slumped as slothfully as possible on the sofa before a television, is also being propped up in the air by the wonders of quantum mechanics: his body kept floating by the resistance of his electrons to sharing too many energy states with those of the couch.

  Charles P. Enz’s No Time to be Brief: A Scientific Biography of Wolfgang Pauli (Oxford, England: Oxford University Press, 2002) is excellent for background on Pauli. For more on the associated topic of the virtual electrons that “shoot up” from electrons and help preserve our separations, see Richard Feynman, QED: The Strange Theory of Light and Matter (Princeton, NJ: Princeton University Press, 1985); for Pauli’s at times maddening role in the formative years of QED, along with Enz, see Silvan Schweber, QED and the Men Who Made It (Princeton, NJ: Princeton University Press, 1994).

  And in 1920s England…at its private schools

  “The great thing about a [private] school education,” Turing said, “is that afterwards, however miserable you are, you know it can never be quite so bad again.” (What Americans call private school, the British call public school.) The quote is in Andrew Hodges, Alan Turing: The Enigma (London: Vintage, 1993).

  What he needed…were the new insights in physics

  Until then, Turing and all other researchers had to make do with the intermediary technology of vacuum tubes (the “valves” of British terminology). These were basically miniaturized lightbulbs, with added wires or metallic meshes inside that attracted the electrons flying up from a heated filament and accelerated them upward. This was good for making weak signals stronger, but vacuum tubes were miserable devices to work with.

  Cold filaments don’t boil out many electrons, so there was a long wait while the tubes heated up (which is why old electric devices needed “warming up”). The glass around the hot filaments had to be airtight, which meant the tubes regularly overheated; the tiny filaments also cracked. Anyone using large numbers of vacuum tubes knew to keep equally large boxes of spares handy. As John Pierce—who later coined the label transistor—put it, “Nature abhors a vacuum tube.”

  The British government’s codebreaking group

  Actually a “cipher-breaking” group. A code is a direct-substitution system, where one word is used to stand for another, as with a child’s code in which, for example, the words national embarrassment are substituted wherever the word shrub has been written. A cipher involves more-complex substitutions of the components, ranging from Julius Caesar’s early efforts, where each letter of the Latin alphabet was replaced by a letter three places later in the alphabet, to far more intricate ones, where complex intermeshing gears produce the substitutions. For simplicity I follow the informal usage, where the term code is used to cover both types.

  There’s a nice twist here. Without radio, there wouldn’t have been Bletchley Park, for before radio, military messages were sent directly to their intended targets, and outsiders couldn’t listen in simply by setting up a big antenna. But without Bletchley Park, when would there have been computers? Such are the unexpected ways in which electricity fed its own further development—radio begetting codebreaking centers, and those centers helping beget computers.

  The machine was more than a calculator

  The first Colossus in 1943 could quickly test a possible solution against an encoded text, but then had to be reset by hand. An improved version was soon built at Bletchley—wartime pressures concentrated the minds of procurement directors wonderfully—and this one could change the target decodings it was considering without being reset from outside. But although this meant there now existed machines that could automatically make choices, it still wasn’t fully programmable, nor could it store programs.

  Turing was only marginally involved with its construction, but Colossus was initiated in great part by Max Newman, who’d been one of his lecturers at Cambridge, and Turing was kept informed of its workings.

  A new technology being perfected in America

  Although the transistor technology came from America, the logical switching it would follow built on work of the mid-nineteenth-century English mathematician George Boole, who took it upon himself to codify every logical thought that could possibly exist. Such an obsession would not be considered too odd in certain polite English circles even today, but what’s curious is that he succeeded.

  Boole wrote down his results as simple equations, which is where his connection with computers comes in. For if any two true statements are combined, then the result is also true, and he’d write that as T+T=T. If a true and a false statement are combined, then the result is false—he’d write that as T+F=F.

  It seems a bizarre, elaborately obvious arithmetic, of the sort only Lewis Carroll would appreciate, and it became even more bizarre when Boole wrote “1” for “True” and “0” for “Fa
lse.” In that system, the previous equations become 1+1=1 and 1+0=0. This is binary code.

  Logicians liked this, the ordinary world ignored it, but by 1937 Claude Shannon had realized that relay switches controlled by electromagnets could actually carry out these equations Boole had proposed so long before. The transistors created a decade later could do it even better, for a solitary signal coming into a switched-off transistor won’t be enough to get a current moving; at most that signal will jolt the silicon into its active, current-carrying state so that a second signal can now pass through without hindrance. In other words, it takes two signals coming into such a transistor to get one signal going out. But if the number “1” is taken to represent a signal, this is just saying that inside a transistor, 1+1=1. If the absence of a signal is written as “0,” then a transistor will also operate to ensure that 1+0=0.

  What had happened was wonderful. Boole had looked inside the human mind and pulled out his odd-looking equations about how truths and falsehoods operate. Transistors can imitate those equations, but this time inside solid rock. Thus did one obscure nineteenth-century mathematician pave the way for our inner thoughts to be accurately copied inside silicon grains. For Boole’s original work, see George Boole, An Investigation of the Laws of Thought (London: Dover Publications, 1995). For more on Shannon, see the chapter “Understanding Information, Bit by Bit,” in It Must Be Beautiful: Great Equations of Modern Science, edited by Graham Farmelo (London and New York: Granta Books, 2002).

  Intruder atoms such as phosphorus

  What Bardeen and Brattain actually found when they inserted the phosphorus into their semiconductors in late 1947 was that instead of making negative charges race forward, they apparently were making positive charges race backward.