by Bob Berman
It’s clear that any and all energy can change forms. But energy can never be destroyed or used up. Scientists nowadays say that all energy falls into one of two categories—either kinetic energy (the energy of motion, including those scampering atoms that comprise heat) or potential energy (meaning money-in-the-bank future energy, such as the kind stored in a car parked on a hill, which can release its brakes anytime and glide down on the strength of its favorable position in a gravitational field).
The sun illustrates energy conversion beautifully. Technically it’s converting nuclear energy to electromagnetic energy. Put another way, it’s obeying Einstein by changing its mass to energy, as expressed in the famous equation E = mc². Before anyone figured this out (it was Arthur Eddington, in 1920), the sun’s prodigious light and heat were an utter mystery. Science had already calculated that a massive ball of coal with the sun’s weight—the mass of 333,000 Earths—would completely burn itself out in two thousand years. But the sun is obviously older than this, so it just couldn’t be burning in the usual sense.
It wasn’t. Instead the sun’s high internal heat means that its hydrogen atoms move furiously enough to smash together. When four of them combine, they create a single atom of helium. That’s the whole story.
It so happens that a helium atom weighs just a smidgen less than four hydrogen atoms, so there is a loss of mass in this fusion process. The mass is released as its energy equivalent. Using Einstein’s equation, the conversion of a single pencil eraser’s worth of mass to energy could light up all the electric bulbs in the United States for thirteen days. In the sun, the conversion involves four million tons of hydrogen per second. That has a bit more bulk than a pencil eraser, so the resulting energy output is staggering.
This is not some theoretical figure. If we had a giant scale and could weigh the sun, our nearest star, we’d find that it actually weighs four million tons less every second. We might get worried and say, “Whoa! Slow down!” But given that the sun has a total mass of two nonillion—that’s the number 2 followed by twenty-seven zeros—tons, its ongoing loss of mass is not noticeable. It’ll be billions of years before any serious consequences ensue.
The sun’s tiny fusion reactor, a small ball at its exact center, which has just one two-hundredth of the volume of the sun in its entirety, emits mostly gamma rays and X-rays as a by-product of that hydrogen-to-helium conversion. But the energy keeps getting absorbed and reemitted as it tries to squirm its way out. After as many as a million years, the original ultra-high-energy photons are now safely shifted down to a mix of visible light and infrared light with a small percentage of ultraviolet light thrown in. This final mixture—the sun’s rays—leaves the sun’s visible gaseous surface, the photosphere, at a speed of 186,282 miles per second, then takes a mere eight minutes to reach us and deliver that energy.
So our lives depend on the solar mass-to-energy conversion. The result is very nearly an equal mixture of invisible light and the rainbow colors. The sun’s blue light then gets scattered around by our planet’s atmosphere, giving us our blue sky. So when we look at the sun it seems yellowish—the result of its missing the blue that went into painting the daytime sky.
The sun’s fusion reactor, that unseen ball at its center, is more than the source of all life. The conversion of one form of energy to another is what the universe does, inside and outside our bodies, here on earth and in every cosmic village.
CHAPTER 9
No Soap
It’s a good thing we can’t see radio waves. They’d overwhelm us. They’re absolutely everywhere, bouncing off layers of the atmosphere above us and reflecting off hills and buildings. They pass through our bodies as if we were ghosts.
Being longer than visible light waves, they’re also wimpier. In fact radio waves are the weakest kind of light. But their impact on our world has been anything but weak. Once they were discovered, radio waves were rapidly integrated into our technologies—a process that continues today, well into the twenty-first century. This most harmless kind of invisible light is also the kind that has most changed our daily lives and continues to do so. But don’t imagine that radio waves are some kind of sound. Sound is merely a mechanical compression, usually of air, that sets our ear drums vibrating. By contrast, radio waves are a form of light whose waves are each much longer than those of the visible colors.
The brilliant Heinrich Hertz is justly credited for first discovering radio waves and demonstrating how they work. But he couldn’t have done it without the genius groundwork of two men who came before him.
The first player in this particular tale is Michael Faraday, born in England in 1791 in what was then Surrey and is now the London borough of Southwark. He received minimal formal education, and in his youth he showed no sign that he would become one of the most influential scientists in history. A century later, Albert Einstein kept only three pictures on the wall of his study to serve as inspiration. They were portraits of Isaac Newton, Michael Faraday, and James Clerk Maxwell—who, oddly enough, is the other main character in our radio story.
During his seven-year apprenticeship to a bookbinder, Faraday came across a single volume that changed his life: Isaac Watts’s The Improvement of the Mind. Now largely forgotten, it was an early self-help book that contained a list of sixteen general rules for the improvement of knowledge. It also contained an overview of books and reading, a guide for study and meditation, tips on improving one’s memory, and other suggestions for the betterment of the self. Faraday happened to read it just as he was developing a fascination with science, particularly the then-mysterious field of electricity, and he embraced the book’s principles and suggestions.
The next critical turn in Faraday’s life came as he completed his bookbinding apprenticeship, at the age of twenty. Like today’s youth, who sometimes feel a bit adrift after obtaining their undergraduate degrees, Faraday still wasn’t sure what he wanted to do in life, so he checked out the science lectures being given in his neighborhood. He was particularly drawn to talks by the famous chemist Humphry Davy, of the Royal Society. Faraday was so enraptured by everything he heard from Davy that he eventually sent his idol a three-hundred-page book of the notes he made from Davy’s lectures. Anyone would have been flattered by such a gift, and Davy immediately responded with a grateful and kind reply. The following year, when Davy damaged his eyesight in a lab accident involving the highly unstable compound nitrogen trichloride, he sent word to Faraday, offering him a job as his assistant, which the latter immediately accepted.
Thus began a series of fortuitous events that was to change the course of science. Soon one of the assistants at London’s Royal Institution—like the Royal Society, an organization devoted to scientific research—was fired, and the task of finding a replacement was handed to Davy. By then he was so impressed with Faraday’s genius and initiative that in March of 1813 he appointed Faraday the organization’s chemical assistant. Later that spring, the understandably NCl3-shy Davy started letting Faraday prepare the nitrogen trichloride samples. It was a prudent step, but it still proved to be no insurance against lab disasters. Sure enough, both men managed to get injured in yet another explosion of this dangerous compound.
Even so, their relationship thrived. In late 1813, Davy planned to begin a one-and-a-half-year professional tour of Europe, and he asked Faraday to accompany him as his assistant. Unfortunately, Davy’s valet resigned just before the tour began, so Faraday was asked to assume that menial role as well. One hopes that Davy was respectful to his colleague during this time, but it can’t have been easy for Faraday. English society was extremely class-oriented in the early nineteenth century, and Davy’s wife, Jane Apreece, never treated Faraday as a peer. She sent him to eat with the servants, and even when there was plenty of room in the coach, Jane insisted that he ride outside, no matter how hard it was raining. Faraday became so disheartened that he came very close to abandoning the whole thing, returning to England, and switching from science back to bookbindi
ng. But he stuck it out, which is how he got introduced to many of Europe’s top-notch scientists, their keen minds, and their groundbreaking ideas.
When he returned to England, Faraday began researching the magnetism that shifted compass needles in the vicinity of wires carrying electricity. He found that simply moving a magnet through a loop of wire produces an electric current. Alternatively, he could create a current by moving a loop of coiled copper around a stationary magnet. His experiments showed that a changing magnetic field produces an electrical field—a relationship mathematically articulated three decades later by James Clerk Maxwell, who called it Faraday’s law. Perhaps the most amazing of Faraday’s revelations was the concept of an electromagnetic field, its unseen curving lines extending into empty space. This spooky and original idea—a force field penetrating the unoccupied area around electrical wires—was initially rejected by other scientists. Still, Faraday’s notion of fields emanating from objects that have electrical and magnetic charges, as well as the implication that electricity and magnetism are inextricably linked as a single entity, proved to be spot-on. He showed that magnetism can affect light (although never measurably altering its path) and suggested that light, too, is a manifestation of magnetism and electricity.
Faraday even built the first crude motors using the interplay of wires and magnets. His was the first power generator, and his discoveries form the basis of all the electric motors that dominate modern technology and our everyday lives. Beyond the gasoline-powered engine, every automobile also uses more than a dozen electric motors that owe their origins to Faraday: the electric starter, the power windows and doors, the push-button seat adjustments, the windshield wipers and washers—all of them are electric. Their increasing use starting in the 1990s resulted from the development of ever-more-powerful magnets based on rare earth elements, such as neodymium, europium, and yttrium, which provide a high level of torque in small spaces. An iPhone, for example, uses eight rare earth elements.
Faraday lived into his mid-seventies, honored, world renowned, but always remarkably humble. He twice refused when he was asked to be president of the Royal Society. When the queen offered to knight him, he turned down the chance to be Lord Faraday: he believed it was against the spirit of the Bible to pursue riches and worldly rewards. He preferred, he said, “to remain plain Mr. Faraday to the end.” And he declined on ethical grounds when the British government requested his advice on the production of chemical weapons for use in the Crimean War.
Faraday died in 1867. Two years earlier, a Scottish physicist expressed Faraday’s observations in mathematical terms, proving that Faraday was right. Well off, educated, and brilliant, James Clerk Maxwell displayed an intense curiosity about nature even as a young child. According to his biographer Basil Mahon, when Maxwell was as young as three years old “everything that moved, shone, or made a noise drew the question: ‘what’s the go o’ that?’” Maxwell’s father, in an 1834 letter to his sister-in-law Jane Cay, describes the boy’s innate sense of inquisitiveness: “He has great work with doors, locks, keys, etc., and ‘show me how it doos’ is never out of his mouth. He also investigates the hidden course of streams and bell-wires, the way the water gets from the pond through the wall.”
His curiosity never ebbed. Maxwell spent his life solving such seemingly intractable problems as the nature of Saturn’s rings. (He mathematically showed why they could be neither a single solid structure nor a liquid nor a gas but must instead be composed of innumerable separate tiny rocks—moonlets.) He essentially established the basis for color photography with his scheme for creating negatives that would reproduce individual primary colors. But it was his lengthy 1861 paper, On Physical Lines of Force, that set the stage for his most important work: four differential equations, forever after called Maxwell’s equations, that mathematically explained electromagnetism, showing that oscillating electrical and magnetic fields travel through space as waves and move at the speed of light. Maxwell’s equations also showed that radio waves should exist. This logical unification of magnetism, electrical fields, and light is what inspired Heinrich Hertz’s search for, and discovery of, the existence of radio waves exactly twenty-one years later. Who can say what else Maxwell might have discovered had he not succumbed to abdominal cancer at the age of forty-eight?
Heinrich Hertz, born in 1857 in Hamburg into a prosperous family, was fascinated by Faraday’s experiments and Maxwell’s mathematical conclusions about them and methodically set out to see if he could demonstrate the existence of these putative electromagnetic waves. Like Maxwell, Hertz would die young—the result of a failed operation for an infection—at age thirty-six. His life was short, but his work affected nearly every life that came after his own.
Hertz’s groundbreaking 1886 experiment involved the first ever “spark gap transmitter,” which used wires to carry current but left a gap in the circuit so that one could observe the current as it leaped across empty space. These energies were neither infrared nor ultraviolet nor visible. They were something else—yet they had the power to create a visible electrical “snap” through empty air.
High-voltage sparks like these are accompanied by unseen radio-wave emissions. (Kevin Smith, www.lessmiths.com)
Hertz calculated that each of these mysterious waves was around thirteen feet from crest to crest, roughly the length of a subcompact car. He also measured the electrical-field intensity, polarity, and reflection of the waves from solid surfaces, particularly metal ones. To him these waves appeared to be a form of electromagnetic radiation that perfectly obeyed the Maxwell equations.
Remember the two basic properties of electromagnetic waves mentioned in chapter 1? Wavelength is the distance from one peak of a wave’s electrical field to the next peak. The frequency is the number of these waves that pass you every second. Maxwell had shown that those two basic properties are intimately related and inversely proportional. Meaning that if a wave is huge—say, the distance light travels in one second, or 186,000 miles from crest to crest—then just a single one will pass by per second. But if a wave’s length is one thousand times shorter—in this case 186 miles from crest to crest—then its frequency will be one thousand times faster. In that case, one thousand such waves would pass you per second. Conclusion: wavelength (in miles) times frequency always equals 186,282—the distance in miles that light travels in a second. Bottom line: the shorter the wavelength, the faster the waves must pulse. Moreover, the shorter the wave and the faster its frequency, the more energy it has.
Read the preceding paragraph one more time so that it is absolutely clear, and you will have grasped the most important properties of all light, visible and invisible.
The world soon honored Heinrich Hertz by naming the unit designating a wave’s frequency the hertz. A wave that pulses 700 times a second is said to vibrate at 700 hertz. If it pulses 700,000 times a second, we use the prefix kilo (meaning “one thousand”) and say it has a frequency of 700 kilohertz, or 700 kHz.
If you have an old AM radio, the kind with numbers on the dial, take a glance at it. The station frequencies are listed in kilohertz, or thousands of pulses per second. If your favorite AM station is at 710 on the dial, it means that 710,000 of its waves zoom through you and your radio each second.
In the FM band, waves are much shorter and thus pulse much faster. FM frequencies are expressed in megahertz, or millions of pulses per second. If your favorite FM station is 90.1 on the dial, then around 90 million waves pass by per second.
An AM station of 1,000 (kilohertz) would be identical to an FM frequency of 1 megahertz, because a thousand thousands are a million. Turns out, a 1,000 kHz wave has a length of 299.8 meters, or 984 feet. That’s around a fifth of a mile, or four city blocks. This 984-foot distance from one wave crest to the next happens to be one-millionth the distance light travels in one second, so one million of these waves must zoom past you per second. In short, roughly speaking, electromagnetism with a thousand-foot wavelength has a frequency of a million h
ertz. That’s the story for a radio frequency of 1 mHz, or 1,000 kHz. I hope you’re taking notes on all this.
If we instead consider a wave one hundred times smaller, meaning ten feet from crest to crest, its frequency must be one hundred times faster, or 100 megahertz. A hundred million of these ten-foot waves pass by per second.
This frequency—100 megahertz—happens to be commonplace in the FM broadcasting universe, so it’s worth visualizing. Picture a series of waves, each ten feet across. Now picture 100 million of them flashing past you, and through you, every second. Good luck.
Hertz’s groundbreaking work, “Researches on the Propagation of Electric Action with Finite Velocity Through Space,” announced his discovery of this new form of electromagnetic radiation—radio waves. But he saw no practical benefit to them whatsoever; he seemed satisfied to have proved their existence, and his inquiry ended there. His students soon got wind of all the attention the discovery was bringing to their professor. They’d ask him what it meant, and he’d say, “It’s of no use whatsoever.… this is just an experiment that proves Maestro Maxwell was right—we just have these mysterious electromagnetic waves that we cannot see with the naked eye. But they are there.”
On another occasion, a noted physicist asked him what technological value these waves had. His reply was short:
“Nothing, I guess.”
But others knew better. It may have required two decades between the time Maxwell laid out the mathematical reality of electromagnetic waves based on Faraday’s findings and Hertz’s proof that they really exist. But it took a mere eyeblink for enterprising inventors to put them to use.
CHAPTER 10
Turning On and Tuning In