Zoom

by Bob Berman

  Paper “catches” easily. Its famous ignition temperature inspired the title of the 1953 Ray Bradbury novel, Fahrenheit 451, in which “firemen” went about burning books. Catchy, but in reality, different types and thicknesses of paper have distinct ignition points that vary from 424 degrees to 475 degrees. Real science is often less succinct than its fictionalized analogues. (Bradbury, who died in 2012, knew this, of course. He also knew that the title Somewhere Between 424 and 475 Fahrenheit would not have been as memorable.)

  Coal ignites reluctantly, with a very high ignition point of 842 degrees. Kerosene is much more eager to go, at 444 degrees. Gasoline will ignite at 495 degrees, alcohol at 689, and hydrogen at 752. But there are nuances, especially with flammable liquids. When atomized as a spray, home heating oil burns brilliantly. But a two-foot-deep pool of it that has leaked into a basement is unlikely to ignite even if a lit match is tossed into it. Similarly, you can squirt Pam cooking spray into any candle flame and it’ll instantly whoosh as a brilliant blaze. But even if heated to its self-ignition point of 644 degrees Fahrenheit, cooking oil may not burn unless it’s atomized, which envelops it with needed oxygen. That temperature is slightly higher than what’s normally achieved in an oven, which is why oils aren’t frighteningly ablaze whenever you check on a baking eggplant Parmesan.

  Eerily enough, cool molecules can sometimes move faster and faster on their own until before you know it your house has burned to the ground. No spark or flame is needed. This spontaneous combustion begins when something with a relatively low ignition temperature, such as rags, straw, or even wheat flour, remains in contact with moisture and air. These substances supply oxygen and allow bacterial growth that encourages fermentation. This in turn generates heat, as anyone with a compost pile or a stack of rotting hay can confirm. If the heat is confined and unable to dissipate (e.g., if oily rags are crammed in a pail or buried in a pile of hay, which is a good thermal insulator on its own), the temperature rises, eventually exceeding the ignition point. The result is a thermal runaway.

  Pyrophoric substances are those whose molecules can explosively increase their speed with very little provocation. They’re wound up and raring to go. They burst into flame at room temperature or less. Sodium is a famous example. Its autoignition temperature is exceeded almost everywhere in everyday life, and it will undergo a violent reaction when in contact with water or even moisture.

  There have been grain elevator fires in which no culprit spark triggered the explosion. Items as seemingly innocuous as corn have blown up when moisture was allowed to accumulate. Among the substances most susceptible to spontaneous combustion are pistachio nuts. You can’t make this stuff up.

  The point is, it’s all motion. Heat is motion. Atoms’ motion is heat. When you run a fever you might complain that your temperature is 102. But you could just as well tell the doctor, “I feel awful. My body’s molecules are moving three miles per hour faster than normal.”

  Then he’d hand you some aspirin, saying, “Here. This will slow them down.”

  You can also get a rough idea of atomic speed and temperature by a substance’s color when heated. It’s wonderfully simple. It doesn’t matter what it is. Cast iron, copper, the tungsten in lightbulbs—when a noncombustible object starts glowing, the color of that light is an accurate guide to its temperature.

  TRANSLATING GLOW COLOR INTO TEMPERATURE

  If a substance glows a dull red, just barely visible in the dark, it’s 752°F.

  A red heat visible in subdued lighting means 885°.

  If the red can be seen in daylight, it’s 975°.

  If it’s visible as red in direct sunlight, it’s 1,077°.

  If it’s cherry red, it’s 1,650°.

  Orange indicates 2,012°.

  Yellow means 2,370°.

  White indicates a temperature of 2,730° or higher.

  Upon attaining the color white, you may well have trespassed beyond the object’s melting point. In any case, white is the end of the line. In theory, an even hotter substance would glow blue—just as blue stars are the hottest in the universe—but by then all earthly materials would have melted if not boiled into gas.6 Finding a substance that would remain solid when white hot was what created so many headaches for Edison as he struggled to perfect his electric light. He finally found tungsten, the element with the second-highest melting point, which stays solid until it’s a whopping 6,170 degrees Fahrenheit. This was vital: a thin lightbulb filament is asked to remain at an amazingly high 4,500 degrees for hours or even days at a time; that’s about twice as hot as melting steel. (Carbon has a slightly higher melting point but is too brittle to be practical as a filament.) The incandescent bulb’s fantastic heat would ultimately prove its own undoing: it is now being replaced by LEDs or fluorescents or banned outright. The complaint is that incandescent bulbs utilize most of their electricity for the production of heat rather than light.

  Aluminum melts at a mere 1,220 degrees Fahrenheit. For copper it’s 1,976; for gold, 1,945. Unlike common steel, which melts at 2,500 degrees or so, these metals turn liquid at lower temperatures than their glow-white point. That’s why you’ll never see a white-hot aluminum ingot, just as you never see a red-hot chunk of solid tin or lead, which melt before they can glow in any way.

  As for their atoms’ speeds, the main motion in a solid is a very small amplitude vibration around its equilibrium position. These vibrations grow larger and more frantic with increasing temperature until the melting point frees them. But only atoms in gases break the sound barrier.

  Unbeknownst to Eadweard Muybridge, ultrafast rhythms that rule virtually every aspect of our lives are not rare phenoms, nor could they ever be captured by his or anyone else’s camera, then or now.

  These astonishing discoveries began in the late nineteenth century, when physicists started finding strange small-scale vibrations. Probably the coolest and most useful example is the piezoelectric effect, discovered by the Curie brothers, Jacques and Pierre, in 1880. They found that many kinds of crystal (they liked to work with quartz) naturally vibrate tens of thousands of times a second if a little electricity is applied to them. And it works the opposite way, too. If a crystal is compressed or distorted or struck so that it vibrates, it briefly produces electricity. It’s a two-way street.

  A flood of technology arose from this. Breakthroughs occurring between 1921 and 1927, mostly at Bell Labs, resulted in the creation of a superaccurate clock that relied on those quartz vibrations. Vacuum tubes and other bulky components confined the early devices to laboratories, where they kept America’s official time to a new level of precision on behalf of the National Bureau of Standards (now the National Institute of Standards and Technology) for thirty years, until atomic clocks took over in the 1960s.

  Cheap semiconductor technology enabled manufacturers to mass-produce quartz watches beginning in 1969, when they replaced mechanical spring watches and made it possible for everyone to have a personal timepiece accurate within one second per month. Your watch’s quartz crystal is shaped to naturally vibrate 32,768 times a second. This is, conveniently, a power of two (it’s two multiplied by itself fifteen times over), which lets digital circuitry easily convert it into whole seconds.

  Pulsating crystals are now in every home. For example, you may own one of those barbecue grill lighters—the ones with an annoyingly hard trigger. Pulling the trigger strikes a crystal, which piezoelectrically creates a momentary high voltage, thus producing a quick spark. No battery is ever needed. Indeed, gas stoves now use vibrating crystals to create the spark that ignites the gas. If you hear repeated “snaps” whenever you turn it on, that’s what’s happening.

  Thirty-two thousand vibrations a second may seem fast. But it turns out it’s not just crystals that undulate. Absolutely everything vibrates. The molecules that make up every substance around us display complex atomic harmonic oscillations.

  We may imagine that a simple common compound such as water, made of two hydrogen atoms bond
ed electrically to an oxygen atom, has a rigid structure. Not so. The atoms stretch away from each other a bit and then snap back as if on a rubber band. At the same time they twist around and then return to shape. They also rock back and forth like a metronome. Each of these repetitive atom motions—twisting, stretching, rocking, bending, and wagging—has its own precise period that is somewhere between one trillion and one hundred trillion times per second. You’d think this shaking would dampen out and stop. It never does.

  Meanwhile, light itself consists of waves of magnetism and electricity whose pulsation rates depend on the color. Green light’s waves, for example, pulse 550 trillion times per second. These vibrations are not just extraordinarily regular. They have in-your-face consequences.

  To give one example, an automobile parked in sunlight heats up because the pulsation rate of the infrared waves that are inside it coincidentally match the atomic vibration rate of the car’s glass. This creates a chaotic boundary, blocking the heat from escaping through the windows the way light does. Instead, light gets in, but the heat it creates can’t get back out. It makes the car’s interior very uncomfortable when you step inside. People have been arrested for leaving pets and children in such parked cars. The charges probably didn’t specify that the suspects “ignored the lethal perils of ultrafast vibrations,” but that’s what it amounts to.

  As another example, consider the chrome that adorns motorcycles and makes the exposed metal parts of cars look so shiny. This happens because the outer electrons of the element chromium absorb and then reradiate the photons of light that hit them. But the light doesn’t get too much farther. That metal’s inner electrons are held so tightly in their orbits that they have too little flexibility to vibrate and give off light. The end result is that sunlight striking chrome and most other metals isn’t fully absorbed, nor does the light pass through. It’s neither transparent nor dull but something else: gleamy.

  So we’re immersed in more than mere animation. Nature doesn’t just go wild with countless pulsations producing powerful everyday experiences. It also never tires of repeating itself within time frames of the tiniest fractions of a second—or in milliseconds, whole seconds, minutes, years, centuries, millennia, you name it. Ours is a shimmering, vibrating universe on multiple levels. These patterns, which interact with each other, influence everything—even if we’re unaware of virtually all of them.

  CHAPTER 15: Barriers of Light and Sound

  A Thirty-Century Quest That Began with Thunder

  As fast as it can go, the speed of light, you know

  Twelve million miles a minute…

  —ERIC IDLE AND TREVOR JONES, “THE GALAXY SONG” (1983)

  The sound barrier. The speed of light.

  These classic entities created endless mind torture for Homo bewilderus. We who are utterly dependent on sight and sound learned early on that nature performs its symphonies prestissimo. Even the people most associated with sight and sound gained renown, such as the sound-barrier-breaking Chuck Yeager and light’s maestro Albert Einstein, who symbolized its speed with a lowercase c in his famous E = mc2 equation.

  The head-scratching began far before those twentieth-century celebrities captured the limelight. It may have all started with thunderstorms. Here is nature’s only exhibition of simultaneous brilliant light and deafening sound. It always attracts attention. As in the days of Aristotle, a lightning bolt can be temporarily blinding. A thunderclap can rattle dishes. The birds outside grow ominously silent.

  These days, at least, we regard thunderstorms scientifically. When the flash comes we think “electricity” and console ourselves with the fact that fewer than one hundred Americans a year are killed by lightning. Odds are it won’t be you. If you are female rather than male (men are struck five times more often), live in any state except Florida (the most lightning-prone state by far), and neither fish nor play golf (the most lightning-attracting activities), you can maybe even let yourself enjoy the violence.1

  Back when the Parthenon was built, when there were fewer lightning-prone golf courses, thunderstorms were always exhibitions of—you knew this was coming—godly power. The word thunder comes from the name of the old Norse god Thor, the hammer-wielding deity who also gave us the word Thursday.

  Yet he scarcely had a monopoly. The Bible makes many references to lightning being dispensed by Jehovah. The first occurs in Exodus 9:23: “And Moses stretched forth his rod toward heaven: and the Lord sent thunder and hail, and the fire ran along upon the ground.”

  This intimidating amusement was also a specialty of a wide pantheon of Roman and Greek deities. The ultimate thunder hurlers were the German god Donar and the Greek god Zeus, whom the Romans called Jupiter. When you traveled east, if you’d managed to evade the wrath of the European gods, you’d instead get smitten by the Slavic god Perkunis and then the Indian god Indra.

  The lightning bolt itself was often depicted as a spear. In Roman times, whatever it hit was considered sacred. Sometimes, where melted glassy sand marked a strike, the place was so revered it was fenced off. The authorities didn’t quite charge admission, but people killed by lightning were conveniently buried right in that consecrated place rather than carted off to a burial ground. In African and South American cultures, the mythical giant thunderbird was often fingered as the cause of storms.

  During the classical Greek period, when science and observation flourished, the importance of vision and hearing generated widespread speculation about how sounds and images might go from point A to point B. And while the hypothesizing is certainly not over, the basic, baffling, early puzzles have now metamorphosed into a continuing modern fountain of gee-whiz science.2

  The century during which much of the Old Testament was penned witnessed the first nonreligious ideas about visual and auditory fury, proposed by the Greek thinker Thales (ca. 620–546 BCE) and his followers Anaximander (ca. 611–547 BCE) and Anaximenes (ca. 585–528 BCE). The three get merit points for stepping away from the Zeus-hurling-spears business, even if their conclusions were wrong. They each wrote that thunder is wind smashing through clouds, a process they believed kindled the flame of lightning. Thus thunder came first, a conclusion embraced, curiously, for the next two thousand years.

  Not that there weren’t any dissenters. Anaxagoras (ca. 499–427 BCE) said that fire somehow flashed first, only to be doused by the clouds’ rain. Thunder, he believed, was the sound of the lightning being violently extinguished.

  Aristotle, his brain crammed with intricate beliefs about everything, entered the fray in his ca. 334 BCE collection of essays called Meteorologica. There he sided with Thales. He wrote that thunder is the sound of trapped air in clouds slamming into other clouds, and added, “Lightning is produced after the impact and so later than thunder, but it appears to us to precede it because we see the flash before we hear the noise.”

  It wasn’t entirely malarkey. Here was the very first known statement that light moves faster than sound. This may seem like a groundbreaking notion, one more bit of evidence that Aristotle belonged in an accelerated classroom. In actuality, determining the relative speeds of sound and light never required a genius IQ. Echoes within great halls and canyons had always suggested that sound was a slowpoke.

  The colliding-clouds explanation for thunderstorms remained popular for century after century. Around the middle of the first century BCE, the Roman poet Lucretius, in his On the Nature of Things, wrote of thunder:

  The winds are battling. For never a sound there comes

  From out the serene regions of the sky;

  But wheresoever in a host more dense

  The clouds foregather, thence more often comes

  A crash with mighty rumbling.

  Why didn’t the 100 percent more correct lightning-first idea catch on? Probably because in that pre-gunpowder era it would have been a unique event, totally without precedent.3 A light never caused a sound, especially in the heavens. The sun and moon are of course silent. So are common ex
ploding meteors and fireballs. The aurora is mute as well. Even in the biological realm of fireflies and phosphorescent marine creatures, the glows unfold in silence.

  Meanwhile, some of the early Greeks went beyond storms to probe the very nature of sound. Pythagoras (ca. 570–495 BCE) wondered why some combinations of musical notes sounded more lovely than others. He made a startling discovery. Experimenting with vibrating strings of various lengths, he found that when they had whole-number ratios to each other the resultant combination was always pleasant and harmonious. For example, if a plucked string produces the musical note A, a string twice as long will also create an A, but an octave lower, corresponding to a numerical ratio of 2:1. The notes in between are produced by plucking strings that have string-length ratios such as 8:5, 3:2, 4:3, and so on. Later, Aristotle correctly wrote that sound is nothing more than the expansion and contraction of air produced by air’s proximity to pulsating or oscillating objects, such as strings, rustling leaves, vocal cords, and the vibrating bronze of a bell.

  And that’s where things stood, with no further acoustic progress as century bells tolled and tolled again. Sound remained a mysterious subject right into the dawn of the scientific revolution. In the early 1600s, Shakespeare had King Lear ask (in act 3, scene 4): “What is the cause of thunder?” and there was no answer. At around that same time, in 1637, René Descartes—who wrote cogently about optics and vision and sound propagation—nonetheless maintained that colliding clouds create thunder, wrongly echoing the Greeks two thousand years earlier.

  But things were starting to change. We celebrated Galileo in our exploration of gravity and falling bodies, but the great man’s observations about sound were spot-on, too. Early in the seventeenth century he wrote, “Waves are produced by the vibrations of a sonorous body, which spread through the air, bringing to the tympanum of the ear a stimulus which the mind interprets as sound.”