How to Destroy the Universe (9 page)

You are at your most vulnerable when you're out in the open. Your main concern is to stay low—literally. Lightning takes the path of least resistance, traveling through the shortest distance of air possible, which is why it always strikes the highest point above ground. Sheltering from the rain under the only tree for miles around is a very bad idea (the same applies to standing near telegraph poles and metal fences). Not only do you
risk severe burns should the tree be struck, but there is also the danger that you will get electrocuted directly thanks to a phenomenon called “side flash.” This is where the current from the lightning bolt passes directly into the ground and spreads horizontally outward. The electric charge this creates in the ground diminishes rapidly with distance. However, you may still receive a fatal surge of current through your body if you are standing close enough to where the lightning struck.

Standing in a dense forest of trees all more or less the same height is fine. But if your friends insist on sheltering under a lone tree, you could remind them that getting wet will actually boost their survival chances. This is because of a phenomenon called external flashover, where the current passes over the victim's body rather than through it—thus reducing the risk to the heart, brain and other organs. External flashover happens because water is an extremely good conductor, with a much lower electrical resistance than the human body.

The best advice in open country is to crouch down (keeping as low to the ground as possible), on the balls of your feet (minimizing your contact area with the ground), and with your feet close together (to lessen the risk from side flash). Some experts even recommend putting your hands over your ears and shutting your eyes (hearing and vision injuries are common among
lightning strike victims). And should you feel the hairs stand up on your neck—a strong sign that a strike is imminent—hold your breath (some victims sustain internal burns from inhaling the superheated air). Oh, and make sure you and your friends all keep your distance while you're crouching—lightning can hop between people standing up to 6 m (20 ft) apart. Even once a storm seems to have passed, don't be lured into a false sense of security—charge remains in the air and lightning can still strike for up to half an hour afterward.

It seems incredible that a human being can stand in the path of such a powerhouse of natural energy and survive. And yet 90 percent of lightning strike victims do. Injuries can be severe and debilitating—including burns, amputations and psychological trauma—but fatalities are not the norm. Statistically, men are more than four times more likely to be struck than women (maybe because men are more likely to be out in a storm in the first place). The average lifetime odds of being struck by lightning are about 1 in 3,000. For poor old Don Frick, it can be little consolation to know that by getting struck twice in the course of his life so far, he's managed to overcome odds of around 9 million to 1.

• Starfish Prime

• Induction

• Maxwell's equations

• How an EMP works

• E-bombs

There are few things that can match the devastation caused by the heat and explosive force of a nuclear weapon. But in the 1960s, the true power of what, up until then, had been considered a mere side-effect of a nuclear blast became apparent. Called an electromagnetic pulse, it has the power to destroy electrical equipment thousands of kilometers from the site of the explosion. With our reliance today on electronic communication, a well-placed electromagnetic pulse could bring an entire continent to a standstill.

On July 9, 1962, the American military carried out a nuclear test with a difference. They detonated a 1.4 megaton nuclear bomb in space, 400 km (250 miles)
above the Pacific Ocean. The purpose of the test, called Starfish Prime, was to find out the effects of letting off nuclear weapons at high altitude. But with Starfish Prime they got more than they bargained for.

The bomb went off at just after midnight local time. Almost instantly, streetlights started to go out in Hawaii nearly 1,500 km (900 miles) away. Burglar alarms were triggered and telephone networks were thrown into disarray. Hawaii had been hit by what's called an electromagnetic pulse (EMP). The effect had been known about since the first nuclear tests in 1945. Enrico Fermi—one of the scientists involved in the Manhattan Project to develop the American atomic bomb—had predicted that there would be an EMP from a nuclear explosion. As a result, all the electrical equipment involved in the early tests was shielded. But no one had anticipated the magnitude or the range of the effect as revealed by the Starfish Prime high-altitude test. With the impact of the EMP that hit Hawaii, scientists realized that this was not just a by-product of nuclear explosions—it was a powerful effect that could be weaponized with devastating effects.

EMP is caused by the intense electric and magnetic fields that are given out by nuclear explosions. The fields induce voltages in any electrically conducting
materials that they pass through. If the field is strong enough, the voltage generated can be sufficiently high to overload circuits and wreck electrical equipment. When Enrico Fermi predicted this effect, he drew upon a theory that had been established 80 years earlier by Scottish physicist James Clerk Maxwell. Maxwell's theory drew together two phenomena in physics that had previously been believed to be distinct from one another: electricity and magnetism. Electricity is the force that makes electrical charges move to create an electric current. Electrical charges can be positive or negative and tend to flow toward areas where the charge is opposite—negatively charged electrons will flow away from the negative terminal of a battery and toward the positive terminal. Magnetism, on the other hand, is the force that makes compass needles move. Permanent magnets—of the sort that you might stick to your fridge—are made from types of metal with a property called ferromagnetism. This means that they are particularly susceptible to the effects of magnetic fields and, if left in one for long enough, become magnetized themselves. Permanent magnets have two oppositely magnetized poles, labeled north and south. Like electric charge, opposite poles attract and like poles repel.

By the early 1800s, it was becoming clear that these two concepts weren't as unrelated as physicists had believed. For example, it had been noticed that a
current can be generated in a wire that's moving through a magnetic field. Conversely, when a current flows through a wire a magnetic field is produced around the wire. This phenomenon is known as induction. The laws governing how it works were formulated by British physicist Michael Faraday and the American Joseph Henry in 1831. Induction plays a central role in the operation of dynamos, which use an arrangement of magnets to turn rotational motion—for example, produced by a wind turbine—into electricity; and electric motors, which use an electrical current to turn a magnetized axle, so generating motion. The interplay between the electric field, the magnetic field and motion in each case were given by Fleming's rules, named after British scientist John Ambrose Fleming.

It was starting to seem like electricity and magnetism were just different aspects of the same underlying phenomenon. Maxwell, along with his colleagues, provided the solid theoretical basis to back up this hunch by pulling all these emerging ideas about electric and magnetic fields together into a unified theory. In the 1860s, he carried out research that led to four equations, which summarized how electric charge, electric current, electric fields and magnetic fields are all interwoven with one another. The theory became
known as electromagnetism, and the four equations will forever bear the name of the man who pioneered them: Maxwell's equations.

One of the most ground-breaking concepts to drop out of the equations is that light is an electromagnetic wave. It's made up of waves of both electricity and magnetism vibrating at right angles to one another. The resulting “electromagnetic radiation” forms a spectrum depending on frequency with light sat roughly in the middle, at a frequency of around a million billion Hertz (where 1 Hertz, Hz, is one wave cycle per second). Below light in the spectrum are lower-frequency radio waves and infrared radiation, while above it are ultraviolet light, X-rays and, at the far end, high-frequency gamma rays. The frequency of an electromagnetic wave is directly linked to its energy and so radio waves have relatively low energy, while at the opposite end of the spectrum gamma rays are highly energetic—so much so they are hazardous to living things, and are classified as harmful radiation alongside alpha and beta particles (see
How to turn lead into gold
).

In 1897, Irish physicist Joseph Larmor used Maxwell's equations to prove another interesting fact. If you accelerate an electric charge, it gives off electromagnetic radiation. This is how a radio transmitter works. Passing a time-varying current through an antenna
causes electrons in the antenna to vibrate in response to the time-varying signal. Let's say the current is the sound of someone's voice, which has been turned into an electrical signal using a microphone. The current makes the charged electrons vibrate and emit electromagnetic radiation—radio waves—and the time-varying signal in the current is imprinted into the radiation's waveform.

The waves can then be picked up by a radio receiver. Electrons in the receiver antenna are made to vibrate in synch with the waveform of the arriving radio waves. This sets up a time-varying current in the antenna (identical to the one in the transmitter antenna just seconds before) and this carries the signal to an amplifier, which cranks it up enough to drive a loud speaker through which the original voice message can then be heard.

The EMP from a nuclear explosion is a kind of intense electromagnetic wave. Any conductor that it meets—such as the circuitry in an electrical device—acts like an antenna and absorbs some of the wave, which in turn sets up an electric current. If the current is strong enough it will overload the electrical circuit, burning out components and rendering it useless. Back in the 1940s, '50s and '60s the kind of circuits used in electrical
devices were less sensitive and better able to withstand EMPs. But modern-day circuits, such as those inside computers, use tiny electrical currents inside semiconductor devices such as microchips. These circuits are easily fried by the massive currents induced by an EMP—which is why EMP weapons can have such a devastating effect on the digital infrastructure that civilization today relies on.

The EMP generated in a nuclear blast is divided into three components—called E1, E2 and E3. E1 is caused by gamma rays. These rays have so much energy that they knock negatively charged electron particles from atoms in the air that they collide with. These electrons streaming through the air set up a massive electric current. The current is accelerated by Earth's natural magnetic field, and these accelerated charges emit a pulse of electromagnetic radiation. E1 is the quickest and most destructive kind of EMP from a nuclear detonation. It generates high voltages that can wreck computer equipment, and cannot be blocked by standard surge protectors. E2 is caused by scattered gamma rays from the blast, which then collide with electrons created during the formation of the E1 pulse, accelerating them and releasing another EM wave. It's similar to the EMP generated by a lightning strike and so is easier to guard against. Finally, the E3 pulse is brought about by the disturbance to Earth's magnetic field caused by the explosion. This is similar to the
electrical effects that are generated by solar storms. It can last for anything up to a few hundred seconds after the explosion and sets up currents in power lines that can damage transformers and electricity distribution networks. EMP effects can be reduced by shielding sensitive systems. However, a recent report for the US Congress into the vulnerability of the US to EMP attack stated that it was impossible to protect both military and civilian electronic systems against the most powerful types of EMP weapon.

It doesn't necessarily take a nuclear explosion to create an electromagnetic pulse. Following the invasion of Iraq in 2003, there was speculation that US missiles and war planes equipped with non-nuclear EMP weapons had been deployed. This came after Baghdad suffered power cuts during raids, even though generators and distribution systems appeared physically intact. Scientists have known how to make non-nuclear EMP devices for over half a century. They work using a conventional explosive charge to compress a magnetic field to high intensity. A current is passed through a coil of wire, which—through induction—then generates a magnetic field through its center. Inside the coil is a hollow metal tube surrounded by a layer of high-explosive. The shock wave unleashed as the explosive detonates compresses the metal tube and the magnetic
field inside it, generating an intense burst of electromagnetic radiation. Fields hundreds of times more powerful than the huge magnets used inside medical scanners (and tens of thousands of times greater than the field of a fridge magnet) have been generated using this method.

E-bombs like this could be mounted in the nose cone of a cruise missile or in a bomb dropped from an aircraft. It would deliver a localized but intense electromagnetic pulse, enough to disable communication systems, radar stations and vehicle electronics, and even penetrate inside shielded underground bunkers. Military pundits also speculate that EMP grenades may have been developed, to be used by infantry soldiers to knock out enemy electrical systems on the battlefield. In an age when almost every aspect of our lives relies on communications, computers and other delicate electronic systems, electromagnetic pulse weapons have the potential to destroy civilization without toppling a single building or claiming a single life.