What Einstein Told His Barber: More Scientific Answers to Everyday Questions - Robert L. Wolke (2000)

Chapter 7. Stuff and Things

Ours is a materialistic society.

We may talk about the birds, the bees, the trees, the moon and the stars, but what we surround ourselves with is an accumulation of goods—stuff and things that have been manufactured, sold, bought, used and ultimately thrown away. Even when trekking through the wilderness we must have a sleeping bag, a canteen, a knife and, customarily, some clothing. (Mosquitoes can be fierce.) Manufactured goods all.

Science resides within everything. Every artifact has perfectly good reasons, often unsuspected and fascinating reasons, for being precisely what it is and nothing else. I'm not talking about its invention or the technology of its manufacture. Invention and technology are not science; they are applications of science. I'm talking about the fundamental principles that endow each substance or object with its unique individuality as a stuff or a thing.

In this chapter we'll examine the materials and articles that we use daily, or almost daily—everything from soap to soda pop, erasers to explosives, rubber to radioactivity, airplanes to automobiles, aluminum foil to skateboards.

And then we'll end this book of answers by tackling the Most Fundamental Question in the World: Why do some things happen and other things not happen? Believe it or not, there is a general answer.

Extra! Shark Bites Airplane

Every time I get jittery about flying, someone tells me that the chances of being in a fatal airplane crash are much smaller than the chances of being attacked by a shark. What I don't understand is how a lot of shark attacks make my airplane any safer.

Congratulations. You've put your finger on the most flagrant example of figures that lie, with the possible exception of breast implants.

Let's take a look at some statistics.

From 1994 to 1997, the average number of shark attacks per year in U.S. waters was thirty-three. In the same four years, the average number of fatal airplane crashes was three. So you're eleven times less likely to be in a fatal crash than to be attacked by a shark, right?

Wrong. It is utterly meaningless to compare two such completely different sets of circumstances. Why on earth would anyone want to mention shark attacks and plane crashes in the same breath, except to push a predetermined point of view? Anyone who is comforted by such a fake argument is more likely to die of gullibility than from either a shark or an airplane.

But even if it were relevant to compare such totally unrelated sets of figures, they would still be meaningless without a lot of other information. Did the people who were killed in air crashes fly a lot more, or a lot less, than you do? If so, their odds were different from yours. And how many of America's 250 million citizens even went into the water? Did they do it in Florida, where most shark attacks occur, or in New York, where all the dangerous animals are in the zoos and subways?

What people fail to understand is that when you're in an airplane, your chances of dying in a crash are infinitely higher— not lower—than your chances of being attacked by a shark, because except for lawyers, there are no predatory beasts on airplanes. Worry about sharks when you're in the water; worry about airplanes when you're in the air. The only possible connection would be if your plane crashes into shark-infested waters, in which case your statistical ass is up for grabs.

But a legitimate question remains: How much should you worry about airplanes when you're in the air? What are the relevant statistics?

I feel safe when flying because of one statistic only, and it has nothing to do with the numbers of deaths by shark attacks, drowning, accidental falls, suicides, auto accidents or lightning strikes—numbers that are frequently quoted to assuage the fears of white-knuckled passengers, and all equally irrelevant. The one statistic that I keep quoting to myself has to do with my particular flight, the one I'm actually on. And the probability of any one flight ending in a fatal crash is about 1 in 2.5 million. That's plenty good enough for me.

Except when my flight gets bumpy, of course.

Here's the Rub

How does an eraser erase pencil marks?

It doesn't work like a chalkboard eraser, which wipes an accumulation of chalk off a smooth surface. Paper isn't that smooth and a pencil mark isn't all on the surface; most of it is embedded among the paper fibers.

If you look at a pencil mark under a microscope, you'll see that it's not continuous; it is made up of individual black particles, a few ten-thousandths of an inch (several thousandths of a millimeter) in size, clinging to the paper fibers and tangled among them. The eraser's job is to pluck out these tiny particles. It can do that because (a) it is flexible enough to reach down between the fibers and (b) it is just sticky enough to grab on to the black particles and pull them out.

But while the eraser is rubbing the paper, the paper's fibers are rubbing off pieces of the rubber, which is now the rubbee, so to speak. The rubbed-off shreds of rubber roll up their collected black particles into those pesky crumbs that you have to brush away. Under the microscope, those crumbs look like enchiladas rolled in coal dust, to coin a rather unappetizing simile.

The black particles are made of graphite, a shiny, black mineral form of carbon that breaks apart easily into flakes. In its pure form graphite is much too crumbly to make sharp, detailed lines, so it is mixed with clay as a hardener and wax as a binder, in order to make pencil “leads” which, it behooves me to point out, contain no lead at all.

Real lead is a soft, gray metal that will leave dark marks when rubbed on a smooth surface. It was used for writing until the mid–sixteenth century, when a Swiss naturalist named Conrad von Gesner (1516–1565) put some graphite into a wooden holder and made the first pencil. Up until that time, graphite was thought to be a form of lead, and with an astounding display of inertia we are still calling the black stuff in pencils “lead” more than four centuries later. Even Herr Gesner was apparently unable to prevent the German word for his pencil invention from becoming bleistift, which means “peg of lead.” And while we're at it, the English word “pencil” comes from the Latin penicillus, meaning a brush. And if you must know, penicillus is the diminutive of penis, meaning a tail. Don't blame me.

BAR BET

Lead pencils contain no lead.

So-called soft pencils, like the notorious No. 2s that we have all had to use on machine-scored tests, are not darker because the particles of graphite are any blacker. It's that more of them are deposited on the paper because of a higher ratio of soft graphite to hard clay in the pencil. The larger proportion of graphite allows more and bigger black particles to be scraped off onto the paper, which makes a broader and denser mark.

Graphite is a shiny mineral, and the dense marks that are left on the test sheets when we fill in the spaces with our No. 2 pencils reflect light. The sheets are run through a machine that scans them with light beams and searches for reflections. If light is reflected from the right places but not from the wrong ones, congratulations. You get a good grade.

And finally, did you ever wonder why rubber is called rubber? Because it's used to rub out pencil marks, of course.

In 1752, a member of the French Academy first suggested that coagulated caoutchouc, or latex, a gummy sap from certain South American trees that we turn into rubber, could be rubbed on lead marks to erase them. In 1770 the English chemist Joseph Priestley (1733–1804) was apparently so impressed that he named the substance “rubber,” and it stuck. Today the name makes little sense, because rubber automobile tires, gaskets and so on aren't used to rub anything. Even the name “graphite” makes little sense today, because it was derived from the Greek word graphein, meaning “to write,” and graphite has many other uses, in items ranging from lubricants to golf clubs.

All of which shows that writing has always been of more importance to mankind than automobiles or golf, although in our present society you'd never know it.

Understanding Rubber Is a Snap

Why does rubber stretch?

If there is one statement that will make you a passionate believer in molecules, it's this: Rubber stretches because it is made of stretchy molecules. A rubber band stretches because each of its molecules, all by itself, is built like a miniature rubber band.

Rubber molecules are shaped like long, skinny worms, all coiled and curled up, but capable of being straightened out by appropriate tugs on their heads and tails. A piece of rubber is like a can of these worms, all tangled together.

But think: You couldn't straighten out a whole snarl of worms by grabbing a head and a tail at random and tugging them apart; they would just slide past one another (unless they belonged to the same unfortunate critter). The two would have to be tied to each other in some way, so that a tug on one worm would get transmitted to its neighbor, and then to its neighbor's neighbor, and so on.

What we need is a can of worms that are spot-welded to one another in various places: Siamese worms, joined at the hip in various locations along their lengths. (Okay, so worms don't have hips, but you get the point.)

That's what the molecules of rubber are really like. But not at first, when the latex sap drips out of the rubber tree and is congealed and pressed into a sticky glob. Its molecules aren't spot-welded together very much, and especially when warmed they can slide easily over one another and the stuff becomes soft and gooey. A ball made out of raw rubber would hit the floor with a dull thud. And don't even think of making tires.

Humans therefore have to come along and accomplish the spot-welding themselves. They use a simple process called vulcanizing: heating the rubber together with sulfur. The sulfur atoms form bridges, or cross-links, between the rubber molecules, which allow them to stretch out to a certain extent, but unremittingly urge them back to their initial positions. That's why treated rubber is elastic: The molecules will stretch, but the cross-links will always bring them back.

Vulcanization makes wimpy, sticky raw rubber tough enough to be used in tires. The process was discovered in 1839 by Charles Goodyear (1800–1860)—yes, that Good-year—who had been trying for ten years to find a way of making rubber tougher until he accidentally spilled some rubber mixed with sulfur onto a hot stove and it became tough and elastic. His discovery made him famous but not rich, and he died deep in debt.

That's the way the ball bounces.

TRY IT

Find a sturdy rubber band, at least a quarter of an inch (about half a centimeter) wide, and touch it briefly to your upper lip to test its temperature. Now stretch it quickly and while it's stretched, touch it again to your upper lip. It's warmer than it was.

What made it heat up?

When you stretched the rubber band, you put energy into it, didn't you? That energy warmed it up. The energy came from your muscles, and you'll have to eat a calorie or so of food to replenish it.

When a rubber band is stretched, its stretched-out molecules are in a more orderly arrangement—more lined up— than they were in its unstretched, jumbled-up state. As every-body knows from doing housework, orderliness can be achieved only by putting energy into the job. So the stretched-out molecules must contain more energy—they're hotter—than the relaxed, unstretched molecules.

I have just sneaked in on you one consequence of the Second Law of Thermodynamics. This law of nature expresses the relation between energy and entropy, the degree of disorderliness of an arrangement. That's dis orderliness: the degree of random, haphazard scrambling. The Second Law recognizes that Nature's natural tendencies are (a) for energy to decrease—things tend to slow down and cool down—and (b) for entropy or disorderliness to increase—things tend to randomize and scatter. If you want to counteract the tendency for higher disorderliness (higher entropy), you have to increase the energy of the arrangement. That's an inevitable fact of nature; everything that happens is a trade-off between energy and entropy.

Life in the Contact Patch

What makes my new set of tires so much noisier than the old ones, especially when I drive fast? Sometimes I can hardly hear the police siren behind me.

I'll ignore the implications of that last part.

One obvious factor is that your old tires may have been pretty smooth, and smoother tires will be quieter.

Tire noise depends on the tread pattern, the roughness of the road and the roundness of the tires. Really, tires can be out-of-round, and the high spots will thump on the road during every revolution. But assuming that your tires are more round than square and that you're on a relatively smooth highway (that is, you're not in the state of Pennsylvania), the real question is why rolling rubber should make any noise at all; you'd think there would be nothing quieter. And indeed, tire manufacturers put a lot of effort into making their products operate as quietly as possible. Here are some of the things they have to consider.

As you can guess from the complexity of the sound—it's hardly a pure musical tone—it comes from a combination of several factors that make the tires vibrate. When the walls of a tire vibrate, it makes the air inside and outside vibrate also, and that's exactly what sound is: vibrations of air.

The source of most of the vibrations is the “contact patch”—the constantly changing flattened area that is in contact with the road. As each segment of the tire comes around in turn, it slaps against the road and is flattened into the contact patch. That constant slapping makes noise. But your new tires aren't perfectly smooth (unless you're a race driver). They have crosswise tread grooves that divide them into separate blocks of rubber, and those blocks hit the road in a rat-a-tat-tat machine-gun sequence. More noise. Moreover, as each block of rubber reaches the back end of the contact patch it snaps back into shape, again making the air around it vibrate. Still more noise.

A less obvious source of noise involves the escape of compressed air. As the tire turns, a groove entering the contact patch can trap some air and compress it against the road. Then when the groove leaves the contact patch the trapped air is released to the rear with a sudden—if you'll excuse me—fart. Experiments have been done with porous road surfaces that can significantly reduce this source of noise by allowing the air to bleed off directly into the road.

All of these effects depend on the groove pattern in your tires and the characteristics of the road surface. And the faster you go, of course, the more times per second all of these noise-producing processes are taking place. Driving at slower speeds will not only reduce the noise coming from your tires but will completely eliminate that annoying siren.

X-Rated Windows

A dirty film always seems to build up on the inside of my car's windshield. I don't smoke or allow anybody to smoke in my car. What makes that film?

One good film deserves another, so I'll borrow my answer from a famous line in the 1967 movie The Graduate: “One word: ‘plastics.’” It's mainly the plastics in your car that produce the coating on your windshield.

Remember how your car smelled when it was brand-new? It smelled brand-new. A new car's smell is a potpourri of the many volatile chemicals used in its manufacture, from paint and cement solvents to chemicals used in treating rubber, plastics and fabrics and, if you're affluent, that “rich Corinthian leather” on the seats. In fact, every substance in the world is continually evaporating some of its molecules into the air to a greater or lesser degree. (Techspeak: Every substance has a certain vapor pressure.) We smell a substance when some of its evaporated molecules reach the olfactory nerve cells in our noses. And those that don't wind up in our noses might land anywhere else in the car.

Most of these volatile substances evaporate completely and dissipate long before you've paid off the loan, and when that happens your car no longer smells new. But other substances, smelling less noticeably of new debt, are released more slowly over a long period of time.

Plastics, in particular, are the biggest long-term emitters of chemicals: mainly plasticizers, which are waxy chemicals that give them flexibility. When your car is out in the sun, the intense radiation beating down through the windshield—modern automobiles have almost horizontal windshields for streamlining—hits the plastic dashboard cover and drives out plasticizer vapors, which then condense on the slightly cooler glass. The resulting, sticky film of waxy plasticizer then collects dust particles that blow in through the air ducts around the windshield, whereupon you may either clean it or buy a new car.

Wrinkle, Wrinkle, Little Bar

Why do my clothes get so wrinkled, and how do pressing and ironing get the wrinkles out?

Your clothes get wrinkled because you insist on putting them on a warm, moist, moving body. If you were cold, dry and motionless, you'd have no problem. No clothing problems, anyway.

It's heat and moisture that put the wrinkles in, and it's heat and moisture that are going to get them out. Dry, cold pressing, even with tons of pressure, will accomplish little; you need both the heat and the moisture that did the original damage.

It's hard to make generalizations about wrinkling and ironing, because there are so many different kinds of fibers that our clothes are made of these days. There are the synthetic (man-made) fibers, including nylon and a variety of polyesters and acrylics with various trade names. The synthetics are all chemicals known as polymers: materials that are made up of huge molecules, each of which consists of thousands of identical, smaller molecules, all strung together into enormously long (for a molecule) chains. Many of these synthetic fibers are sensitive to heat. That is, when heated they bend and when they cool they retain the bend. If that is done to a garment at the factory, it will keep its shape.

On the other hand, there are the natural fibers taken from plants, animals and insects, including cotton from the cotton plant, linen from flax, wool from various animals and silk from worms. I'll concentrate on one of the oldest and most wrinkle-prone of all the fibers: cotton. As far as wrinkling is concerned, it's one bad actor.

Cotton fibers are filaments of cellulose, a natural polymer that occurs in plant cells. (To split hairs, so to speak, a fiber is a single unit of cotton that is at least a hundred times as long as it is wide, while a filament is an extra-long fiber, a strand is made up of many filaments and a thread is made of many twisted-together filaments. I knew you'd want to know.)

A cotton fiber acts somewhat like a long, thin bar of metal, in that when bent slightly it will spring back to its original shape, but it can be bent only so far before it will stay bent. The amount of bending it can stand before retaining the crimp depends on the temperature. There is a certain temperature below which it will spring back and above which it will stay bent. For dry cotton, this so-called transition temperature is about 120 degrees Fahrenheit (49 degrees Celsius).

So far, you're lucky, because your body temperature is only around 99 degrees Fahrenheit (37 degrees Celsius), well below the crimping temperature.

But then there's the effect of moisture. Water, in the form of perspiration, for example, can lower the transition temperature of cotton down to around 70 degrees Fahrenheit (21 degrees Celsius). And whether you know it or not, you are always perspiring. You don't usually notice it because the perspiration evaporates from your skin as fast as it is produced—unless, of course, the air is very humid, in which case it doesn't evaporate and you say that you are “sweating.”

So now if you actually have the audacity to sit on your pants or skirt, or to stress your other apparel by sharply bending your warm, moist limbs, the fibers can be bent into new, crooked shapes. Then when you stand up, your perspiration evaporates and the fibers cool down below their transition temperature and stay in those new shapes. Your clothes are wrinkled and you are rumpled.

How do you get the fibers back to their original, straight shapes? Just give them heat and moisture again, to get them above the transition temperature while you hold the fabric in its original flat shape with the sole plate of a steam iron. The steam lowers the transition temperature way below the temperature of the iron, so the original, straight shapes can reform.

An easy way to think of all this is that heat and moisture “melt” the structure of the fibers, and when they cool their shapes “freeze,” whether those shapes happen to be straight or crooked.

In the laundry, always try to remove your clothes from the dryer while they are still warm and slightly damp. In that condition you can lay them out flat and they'll cool into that flat shape. Or you can hang them up and let gravity pull them flat. But if you leave them in the dryer too long after it stops, the clothes will cool down in their jumbled positions and the wrinkles will be set.

NITPICKER'S CORNER

Why is there a certain temperature above which cotton begins to wrinkle?

Cotton is made of cellulose, a natural polymer whose molecules consist of thousands of sugar (glucose) molecules, joined together into long chains. Cotton fibers are bundles of these cellulose molecules, all lying alongside one another in the direction of the fiber.

Here and there, the cellulose molecules are weakly bonded to one another sideways by so-called hydrogen bonds, which tie them together like a loose bundle of sticks. The trick is to keep them that way, because if those weak bonds are broken and reformed while the fibers are bent, they will stay bent.

Hydrogen bonds can be broken by a combination of heat, which makes the molecules jiggle, and water, which swells the fibers by getting between the molecules. Water lowers the transition temperature because when the fibers are swollen the molecules are farther apart and easier to separate. That's why a steam iron works so much better than a dry one.

Ollie Oop!

I've seen kids do things on skateboards that seem to defy the laws of physics. As they jump over an obstacle the board rises with them, even though it's not attached in any way to their feet. How can that be?

What you're describing is a maneuver called an ollie, named after its inventor, Allen Ollie Gelfand. Gelfand was one of a number of southern California surfers in the late 1950s who just couldn't wait for good surf to come up and decided to surf the sidewalks. That's what started the skateboard craze.

An ollie is a jump into the air without the loss of one's skateboard. It does indeed look as if the board simply follows the feet, as if in a magician's levitation trick, and a good skateboarder does it so fast that you don't see how it's done. It depends on the fact that a skateboard isn't just a flat board on wheels—it has a bent-up tail at the rear end, and that's the secret to how it gets launched upward.

DON'T TRY IT

Learning to do tricks on skateboards takes lots of practice, not to mention antiseptics, bandages and splints. The following description may sound logical but is not intended to be a lesson.

Here's how a skateboarder does an ollie.

As he approaches an obstacle that he wants to jump over, the skateboarder places one foot in the middle of the board and the other one at the tip of the tail. He then stomps hard on the tail with his rear foot, which makes the tail hit the ground and the front end of the board (the nose) flip up like the opposite end of a seesaw. Simultaneously—and timing is critical—he jumps upward, hopefully high enough to clear the obstacle. As he becomes airborne, the board's nose will still be pressing upward against his front foot with momentum that it received from the tail-stomp. He quickly slides his front foot forward to push the board's nose down level with the tail. He is now in midair on a level skateboard, sailing—again hopefully—with enough forward momentum to clear the far end of the obstacle (which, of course, requires that he had enough forward speed when he began the jump). Finally, as gravity begins to win out, he and the board fall together, with his feet still in contact with the board.

The important thing for the skateboarder to realize is that he can go no higher than he could by jumping straight up from a standing position. The amount of vertical travel he achieves is completely independent of any forward travel, because gravity doesn't know or care about any motion parallel to Earth's surface; it cares only about how far he is from Earth's center and whether it can pull him down any closer.

So if a skateboarder wants to sail over a picnic table, he must first make sure that he can jump straight up and onto the table before he tries it with a skateboard under him. And the board does add to the height that he must jump in order for it to clear the table along with him.

Note that the skateboarder and his board received their upward flight energies from two different sources: he from his leg-powered jump and the board from the tail-kick he gave it, which shot the nose into the air. (In fact, even without anyone on it, a skateboard on the ground would leap into the air when its bent-up tail is stomped on.) There's nothing magic, then, about the fact that board and rider go upward together, in spite of not being fastened to each other. An expert olliemeister allows no crack of light to show between his feet and the board, so it really does look as if they're glued together.

Once a person masters the ollie and is released from the hospital, he can use it as the basis for any number of other skateboarders' tricks, all of which seem to involve life in midair. What tricks? How about a nollie, grind, heelflip, kick-flip, ollieflip, pop shov-it, shov-it kick flip, casper, melloncollie, McTwist, tailslide, wheelslide, lipslide, indygrab or wallride? Many of these tricks are performed not on the street but in skateparks with artificial slopes, walls and slides in which competitions are held.

TRY IT

To see how a skateboard will fly upward from a stomp on its tail, place a spoon on the table, hollow side up. The turned-up bowl is like the turned-up tail of the skateboard. Now tap the end of the bowl sharply with a finger, as the skate-boarder would stomp on his board's tail. The spoon goes flying upward, handle first, in a seesaw effect and then continues to flip end-over-end. If it were a skateboard, the rider's front foot would be holding down the handle end, shifting its momentum backward to the bowl end, which would then rise to the level of the handle.

I'll stick to golf.

Soda … POP!

Why does the champagne gush out all over the place when I open the bottle? That stuff's expensive, and I hate to waste it.

You mean you actually want to drink it? Judging by what we see on television, you'd think that the major role of champagne in American culture is to hose down Super Bowl winners in locker rooms. Somewhat younger children do the same thing with soda pop, making sure to shake the bottle well before moving the thumb partially aside on the top in order to aim better…. Well, you know the rest. (DO NOT TRY THIS AT HOME!)

If I said that shaking a bottle of champagne, beer or pop raises the gas pressure inside, ninety-nine out of a hundred people, even chemists and physicists, would agree. But it's not true. When you shake an unopened bottle or can of carbonated beverage the pressure inside does not change.

It certainly does seem as if the pressure is increased by shaking, and it's easy to dream up smug theories as to why that should be. But I won't muddy the waters by quoting those theories here, because they've turned out to be all wet.

Then why does the liquid squirt out with so much force when you open a shaken bottle? It's only because shaking makes it easier for gas to escape from the liquid, and in its eagerness to escape when the bottle is opened it carries some liquid along with it.

It was two chemists named David W. Deamer and Benjamin K. Selinger at the Australian National University in Canberra who in 1988 settled the question in the simplest possible way: by measuring the gas pressure inside a bottle of pop before and after shaking it. They adapted a standard pressure gauge, not too different from a tire gauge, so that it could be screwed onto the top of a soda bottle.

Their results (which would have been the same if they had splurged and used champagne): If an unopened bottle has been standing quietly at room temperature for a day or so and is then shaken, the pressure of carbon dioxide gas in the head space (the space above the liquid) does not change.

The reason is that the gas pressure is determined by only two things: (a) the temperature and (b) how much carbon dioxide can dissolve in the liquid at that temperature (Techspeak: the solubility of the gas in the liquid). There is only so much carbon dioxide gas in the bottle; some of it is dissolved in the liquid and some of it is loose in the head space. When an unopened bottle of soda has remained at the same temperature for some time, the amount of gas dissolved in the liquid—and more important, the amount of gas that is not dissolved in the liquid—settles down to whatever the appropriate proportions are for that particular temperature. (Techspeak: The system comes to equilibrium.) You can't change those proportions by doing anything short of changing the temperature or adding more carbon dioxide.

(If you put the bottle in the fridge for twenty-four hours or so, more of the gas will dissolve in the liquid, because gases dissolve to a greater extent in colder liquids. There will then be less gas in the head space, and the pressure will be less. That's why you get less of an outburst of gas when opening a cold bottle than when opening a warm one.)

The point is that shaking alone can't change the pressure because it doesn't change the temperature or in any other way change the amount of force or energy that is available inside the bottle. So never fear that manhandling your beer, soda or champagne on the way home from the store will make the bottles explode. On the other hand, make sure not to let the bottles heat up in the trunk of your car, because the higher temperature will indeed raise the pressure of the gas.

Now we can take a more educated look at what causes the explosive emission when we open a recently shaken bottle. It is caused by an increase in the amount of gas that is set loose—not by heating, but by the mechanical “outing” of some dissolved carbon dioxide from the liquid when the bottle is opened.

Here's how.

First of all, a bunch of dissolved carbon dioxide molecules can't just decide to gather together in one spot and form a bubble. They need something to gather upon—a microscopic speck of dust or even a microscopic irregularity on the surface of the container. These congregation spots are called nucleation sites, because they serve as the nuclei, or cores, of the bubbles. Once a small gang of carbon dioxide molecules has gathered at a nucleation site and formed the beginnings of a bubble, it is easier for more carbon dioxide molecules to join up, and the bubble grows. The bigger the bubble gets, the easier it is for even more molecules to find it and the faster it grows.

Now when you shake a closed bottle of pop, you're making millions of tiny bubbles of gas from the head space that become trapped in the liquid. There, they serve as millions of nucleation sites upon which millions of brand-new bubbles can grow. If the bottle is then left to stand for a long time, the new baby bubbles will be reabsorbed and all the contents will return to normal, in which condition it is no longer a threat.

But those new nucleation sites and their newly hatched bubbles don't disappear very quickly; they remain for some time in a recently shaken bottle, just waiting for some unsuspecting soul to come along and open it. When he does, and the pressure in the head space suddenly drops to atmospheric pressure, the millions of baby bubbles are free to grow, and the bigger they get the faster they grow. The large volume of released gas erupts abruptly into a gigantic blurp that carries liquid out of the bottle.

BAR BET

Shaking a bottle or can of beer or soda pop does not increase the pressure inside.

Oh, the champagne? Same thing. The best way to handle it is to leave it undisturbed in the refrigerator long enough for it to “come to equilibrium”—at least twenty-four hours. Then be careful not to either warm or agitate it before or during opening. After removing the wire twist, ease the cork upward with your thumbs. All of the champagne will stay in the bottle and the cork won't become a lethal missile.

Diet Coke Loses Weight

My buddy claims that he can tell a can of diet Coke from a can of Classic (regular) Coke without opening them or reading the labels. Can he?

Probably. It isn't difficult, and it works with Pepsi too. It's based on the fact that a can of the diet drink is slightly lighter than a can of the regular drink.

Regular Coca-Cola is sweetened with sugar (sucrose) or corn sweeteners, which are other sugars, usually fructose, maltose and/or glucose. Diet Coke, on the other hand, is sweetened with aspartame, an artificial sweetener. Gram for gram, aspartame is 150 to 200 times sweeter than sucrose, so only a tiny amount of it is needed to produce the same sweetness as in the sugared product. While the amount of sugar in the regular drink is 2 or 3 percent, there are only a few hundredths of a percent of aspartame in the diet drink. Therefore, a can of the diet drink is very slightly lighter in weight.

Your buddy can't tell the difference just by hefting the two cans. But if he fills a sink with water and places the unopened cans in it, the diet can will float higher in the water than the regular can, which might even sink.

BAR BET

I can tell a can of diet Coke from a can of regular Coke without opening them or reading their labels.

Sour Power

In a novelty catalog I saw a “fruit-powered clock.” You stick two wires into an orange or lemon, and it runs a small digital clock on “the natural energy found inside a fresh fruit or vegetable.” What's the scoop?

“Natural energy” is a favorite buzz-phrase of hucksters and kooks pushing everything from arthritis cures to communication with the dead. There seems to be this idea that “natural energy” is everywhere, to be plucked out of the air by such magic trinkets as copper bracelets (for arthritis) or by those crystal amulets that you wear around your neck or fondle in your pocket to ward off what supposedly less sophisticated societies would call “evil spirits.” If any of these things provided one-thousandth of the energy that their boosters expend in peddling them, we'd never have to burn coal or petroleum again.

As far as fruits and vegetables are concerned, their only “natural energy” is in the form of the calories that you get by eating them—the energy that you gain when you metabolize, or “burn,” the food, just as you can release energy by burning a piece of coal. Eating coal, however, doesn't work because our bodies have no mechanism for digesting and metabolizing it—that is, for extracting its chemical energy.

Oranges and lemons contain precious little food energy, as you might guess from the fact that they don't burn worth a damn (except for the oils in the rind). Even if you could convert all its nutritional energy into electricity instead of muscle power, the fifteen calories in a lemon would keep a 7½-watt night-light burning for only about two hours.

Other than that, the only way to get useful energy out of a lemon would be to drop it from a tall building.

Does the fruit clock actually work? Amazingly, it does. It will run for weeks or months with its wires thrust into a fruit or vegetable—almost any fruit or vegetable. “Potato-powered” clocks are quite popular, presumably because there's nothing quite so dumb and lifeless as a potato, and getting energy out of it appeals to people's sense of the ridiculous.

Here's how the veggie clocks work.

The wires that you thrust into the fruit are made of two different metals, usually copper and zinc. Together with the fruit juices in between, these two metals make a genuine electric battery (more properly called a voltaic cell, but we'll call it what everybody else does). All it takes to make a battery is two different metals with some sort of electricity-conducting liquid in between.

You know that an electric current is a flow of electrons going from one place to another—through a wire, through a lightbulb, through a motor or in this case through an electronic digital clock. The question is, How do you entice electrons into traveling from one place to another so they can run a clock along the way?

A battery induces electrons to travel because it contains two different kinds of atoms that hold on to their electrons with different degrees of tightness. For example, copper atoms hug their electrons more tightly than zinc atoms do. So if you give zinc's electrons a chance, they'll leave home and migrate to the copper, where they feel more wanted.

Clever humans that we are, we offer the electrons only one route from the zinc to the copper: through our digital clock. If they want to get to the copper, they'll simply have to force their way through our clock, operating it as they go.

Then why is the fruit or vegetable necessary? The juice inside it is what chemists call an electrolyte: a liquid that conducts electricity. It completes the circuit of electrons, restoring them and their charges to the zinc, which would otherwise quickly become so depleted of electrons that the whole process would stop.

So where does the “natural energy” actually come from? It's inherent in the constitution of the zinc and copper atoms—in their natural difference of electron-holding powers.

A battery is so easy to make that at least one may have been built by the Parthians, a people who lived two thousand years ago in what is now Iraq. In 1938 a German archaeologist described a small clay jar from that period, then in the National Museum in Baghdad. The jar contained an iron rod inside a copper cylinder; one needed only to fill it with fruit juice (or wine) for it to have enough kick to power an ancient Parthian digital wristwatch.

Okay, so nobody really knows what it was used for. If indeed it was a battery.

If it wasn't a hoax.

If …

You Didn't Ask, but …

Why does the “Two-Potato Clock” need two potatoes?

For the same reason that your flashlight needs two batteries.

A set of zinc and copper metals will move electrons with only so much oomph. That's because there's only a certain amount of difference between the electron-holding powers of zinc and copper. But if you need more electron-moving force—to light a bulb, for example—you can connect a second set of zinc and copper metals after the first, giving twice as much kick to the electrons.

The technical word for electron kick is voltage: the force with which the electrons are made to move. The zinc-copper combination makes about 1 volt of kick. If a particular clock needs 2 volts to run, you'll need two potato batteries connected together.

There Are No Smoke Alarms in Hell

While changing the battery in my smoke alarm I decided to read the fine print on the label. It says that it contains radioactive material: americium-241. What does radioactivity have to do with detecting smoke?

What you have is an ionization-type smoke detector. It detects smoke by the fact that smoke interferes with air's ability to conduct a tiny electric current.

Under ordinary conditions, air doesn't conduct electricity at all; it's an excellent insulator. That's because the nitrogen and oxygen molecules in the air have no electric charge of their own, nor do they contain any loose electrons that could carry charge from one place to another, as metals do. If that weren't the case, electricity from those high-tension power lines overhead would zap right through the air to the ground, passing through anything—including us—in its way.

Air molecules—nitrogen, oxygen and a few others—don't have any net electric charge because the atoms of which they are made contain equal numbers of positive and negative charges that cancel each other out. The positive charges reside in the atoms' nuclei and the negative charges are in the form of electrons orbiting around the nuclei. But radioactivity can make air into an electrical conductor by knocking electrons out of the molecules, leaving them with some uncanceled positive charge. These electron-shy, charged molecules are called ions, and we say that the radioactivity has ionized the air. Because ionized air contains electrically charged molecules, it will conduct electricity.

How does radioactivity ionize the air?

The nuclei of radioactive atoms are unstable, and they spontaneously disintegrate by shooting out some of the particles of which they are made at speeds close to the speed of light. The nuclei of americium-241 choose to shoot out alpha

particles, which compared with other radioactively emitted particles are as a baseball is to a BB. A hefty alpha particle can do a lot of damage to an atom that it hits, so it is very good at ionizing air molecules.

A tiny amount of americium-241 is packaged inside your smoke detector and its alpha particles keep a small region of air around it continually ionized. The battery provides a very small electric current that flows through that air. But when some smoke particles get into that air, the ions can collide with them and lose their charge. Less charge in the air means that less current can flow. A circuit detects this drop in current and triggers an ear-piercing alarm.

The amount of radioactive americium-241 in a smoke alarm is extremely small: usually nine-tenths of a microcurie, which corresponds to a quarter of a microgram. Even though that quarter of a microgram is emitting more than 30,000 alpha particles every second, they're nothing to worry about, because alpha particles are such weaklings at penetrating matter that they can be stopped by a sheet of paper. No alpha-particle radiation whatsoever gets out of the smoke alarm box.

NITPICKER'S CORNER

Whenever an atom of americium-241 (or any radioactive material) disintegrates, it is no longer the same kind of atom and doesn't have the same radioactive properties. So as time goes by, the remaining radioactive atoms decrease in number and so, therefore, does the amount of radiation they emit. In the case of americium-241, its number of atoms decreases by half every 433 years. (Techspeak: Its half-life is 433 years.) So 433 years from now, the americium-241 in your smoke alarm will be emitting only about 15,000 alpha particles per second. But don't throw it away yet, because after another 433 years it will still be working fairly well while emitting only 7,500 alpha particles per second. I'd advise you to replace it around 433 years after that, however, because by the year 3300 the electric current will be getting pretty weak and the alarm might go off even without any smoke. And those alarms, you know, can make enough noise to wake the dead.

Of course, if by then you're where I expect to be, smoke alarms aren't permitted because they'd be going off all the time.

Fertilizer Grow Boom!

Newspaper accounts of terrorist bombings have said that a chemical fertilizer was used as an explosive. How can a single chemical have such Jekyll and Hyde uses?

It's one of those coincidences that aren't really accidental when you dig a little deeper. As we'll see, the good-guy and bad-guy properties both stem from the fact that nitrogen gas is made up of molecules that strongly resist being torn apart.

First, the fertilizer role.

Every gardener knows that nitrogen is one of the three main elements that fertilizers provide, along with phosphorus and potassium. Nitrogen is extremely abundant; it makes up about 78 percent of the air we breathe. Its molecules consist of pairs of nitrogen atoms bound together into two-atom molecules, which chemists symbolize as N2.

Those two nitrogen atoms are tied together so tightly that plants can't split them apart to get their nitrogen fixes. They need the help of lightning, which undeniably has enough power to do the job as it cracks through the air. Also, there are certain so-called nitrogen-fixing bacteria and algae that can split nitrogen molecules, but they haven't told us exactly how they do it.

We humans must resort to our powerful chemical technology in order to convert those nitrogen molecules into more plant-usable forms, such as ammonium compounds or nitrate compounds. The fertilizer ammonium nitrate contains nitrogen atoms in both of these forms, which makes it a doubly potent fertilizer.

Now what if the two separated nitrogen atoms in ammonium nitrate were suddenly given the chance to pair up again into strong molecules of nitrogen gas? They would grab that opportunity eagerly. After all, if nitrogen atoms love one another so much that when paired up they strongly resist being split apart, wouldn't they want to break out of the ammonium nitrate to reestablish their tight pairings and become nitrogen gas again? They would do that with such eagerness that they would literally explode out of the ammonium nitrate to rejoin each other and fly away into the air in blissful gaseous freedom.

I have just described an explosion: anytime a solid turns into a gas with great suddenness. The wave of released gases, which are expanding rapidly because of the heat that is also being released, is the pressure that does all the damage.

In the case of ammonium nitrate, which contains oxygen and hydrogen atoms as well as nitrogen, it's not just the nitrogen atoms that combine suddenly into tight gas molecules. Oxygen and water molecules are almost as tightly held together as nitrogen molecules are, so the oxygen atoms pair up into oxygen gas (O2), while the hydrogen and oxygen atoms join up to form water vapor (H2O). If given the chance, then, solid ammonium nitrate will suddenly break up and turn into an enormous volume of gases: nitrogen, oxygen and water vapor.

All it takes for ammonium nitrate to decompose violently in this way is heat: enough to reach a temperature of at least 570 degrees Fahrenheit (300 degrees Celsius). Even at temperatures as low as 340 degrees Fahrenheit (170 degrees Celsius), ammonium nitrate can explode, turning somewhat less violently into nitrous oxide gas and water vapor.

Keep your powder dry, certainly. But also keep your fertilizer cool.

Foiled Again

Why is one side of my aluminum foil shinier than the other?

It's because of a time- and space-saving shortcut that's used in the final stage of the manufacturing process.

Aluminum, like all metals, is malleable; that is, it will squish when enough pressure is applied. That's in distinction to most other solid materials, which will crack under pressure. So metals can be rolled out into extremely thin sheets.

Metals are malleable because their atoms are held together by a moveable sea of commonly owned electrons, rather than by rigid bonding forces between the electrons of one atom and the electrons of the next, as is the case in most other solids. In effect, then, it doesn't matter much where a metal's atoms are with respect to one another, and they are therefore free to be pushed around within the electron sea.

In the aluminum foil factory they roll sheets of aluminum through pairs of steel rollers that get progressively closer together, which squeezes the aluminum down to progressively thinner sheets. Household aluminum foil is less than a thousandth of an inch (two-hundredths of a millimeter) thick.

To save space in the final rolling, they feed a sandwich of two sheets at a time through the rollers. The top and bottom surfaces are in contact with the polished steel rollers and come out nice and shiny. But the inner surfaces of the sandwich are pressed against each other—aluminum against aluminum. Because aluminum is so much softer than steel, these surfaces press into each other somewhat, leaving a rougher, duller surface when they're separated. It makes no difference whatsoever in how you're able to use the foil.

And by the way: I hope you're not one of those people who sometimes call it “tinfoil.” A foil is a very thin sheet of metal—any metal. Aluminum foil is a thin sheet of (surprise!) aluminum metal and tinfoil is a thin sheet of an entirely different metal: tin. Tin is a rather heavy, nontoxic metal whose foils were used as food and medicine wrappers before aluminum became cheap and widely available. But habits die hard, and many people still call aluminum foil tinfoil.

Someone should also let it be known that “tin cans” aren't tin, either. A “tin can” used to be a steel can lined with relatively noncorroding tin on the inside. But these days the linings of steel and aluminum cans aren't even tin; they're plastic or enameled coatings.

Avast, Ye Slob … uh, Swabs!

While sailing on a friend's boat, I didn't want to use up fresh drinking water, so I tried to wash my shirt in seawater. But I couldn't get any lather at all. Why doesn't soap work in salt water?

It's one of life's little ironies. Sailors do hard, often dirty work, yet with all that water around they can't bathe or wash their clothes with soap. Not with ordinary soap, anyway. There is a special soap called “sailors' soap” that works in salt water. But first let's see why the ordinary stuff doesn't.

It will not surprise you to learn that seawater contains a lot of salt—sodium chloride. Averaged over the world's oceans, every quart (liter) of seawater contains more than half a tablespoon (10 grams) of sodium chloride. It's the sodium that messes up the soap, because soap must dissolve in water before it can do its job and it won't dissolve well in water that contains a lot of sodium.

Soap molecules are made of sodium atoms attached to long tails of what are known as fatty acids. The way soap works is that its fatty tail grabs on to the oily or greasy part of the dirt, while its sodium end drags it into the water. But if there are already too many sodium atoms in the water, the entry of still more of them in the form of soap molecules is inhibited. (In Techspeak, chemists refer to this situation as the common ion effect, because the sodium atoms, which are common to both the salt and the soap, are actually present as ions, or electrically charged atoms.)

This means that a sodium-containing soap won't dissolve enough in salt water to do its job of dragging sticky oil off the sailor and into the water, where it can be rinsed away.

But soaps don't have to be made with sodium. Potassium is a very close chemical relative of sodium's, and it too can combine with long fatty acid tails to make soap molecules. Compared with sodium, there is very little potassium in sea-water, so potassium soaps aren't inhibited from dissolving. So-called “sailors' soap” is a potassium-based soap.

From Dust to Dust

Housecleaning is a never-ending round of dusting, dusting, dusting. If I stopped dusting, would my house eventually fill up floor to ceiling with dust?

You think you've got trouble? In China there are 2-million-year-old accumulations of dust (called loess by geologists) that are more than 1,000 feet (300 meters) thick. But it's not due to sloppy housekeeping. The dust has been swept up by winds from the Gobi Desert. In certain locations where the winds die down, they drop their loads of dust particles. The resulting huge dust piles became compressed from their own weight over the years, and some of them have actually been hollowed out into cave dwellings.

But never fear. At the rate at which the dust has accumulated in the Chinese loess cliffs, you could stop dusting in your house for a hundred years and still have a layer that is no more than an inch (2 centimeters) thick.

Unless you live near the Gobi Desert, you may be wondering where all the dust in your house comes from.

The dust in our atmosphere has many sources. Winds blow over dry earth, such as plowed fields, dirt roads and deserts. Plants give off pollen and other particulate matter. Forest fires and volcanos can spew dust and smoke particles high into the upper atmosphere, where they may blow around for years before settling. There is less dust over the oceans than over land, but still there are tiny bits of dried salt spray and even ash particles falling from meteorites that burn up in the atmosphere.

And, you're thinking, it all winds up on your bookshelves, right? Well, we're not done yet. Let's take a close look at the household dust that you generate yourself.

Notice that dust settles only on horizontal surfaces such as sills, shelves and the top edges of picture frames. (Forgot about those, didn't you?) Therefore, the stuff must be falling out of the air under the influence of gravity. That means that the particles of dust must be bigger than a certain size; if they were any smaller, the constant, agitated motion of the air molecules would keep them permanently suspended. That's the case with cigarette smoke, for example—the individual particles are so small that the bombardment of air molecules keeps them from falling. On the other hand, if dust particles were too big they wouldn't have been wafted into the air in the first place, later to come to rest upon that ugly china fig-urine that Aunt Sophie gave you.

But it's not all a matter of particle size. A relatively big tuft of lint from your clothing will float on the air because of its feathery shape, and this too will eventually find a landing pad someplace where you'd rather not have it. Those dust bunnies that take refuge in the windless climate under your bed are made up largely of fibers from clothing and other fabrics, often tangled together with fallen human or pet hairs and flakes of skin. (I never said this would be pretty.)

Everything that moves inside your house has the potential for sending out microscopic bits that are worn off and carried into the air. When a high-traffic area on your carpet wears out, where do you think all those carpet fibers went? Mote by mote, they wound up scattered around the house, to be dealt with on cleaning day.

Which brings up the question of how effective dusting really is. It depends a lot on how you do it. A dry dust cloth might just redistribute the dust, moving it perhaps from the shelf to the floor, demonstrating “to dust shall it return” in the literal, rather than the biblical, sense. Rubbing with a dust cloth can actually be counterproductive, because it can produce an electrostatic charge on the dust particles. Once charged, they can adhere tenaciously to any nearby object, so they will simply have been transferred from one object to another.

A dust cloth with a downy nap that traps the dust particles is one good idea. Another is to use one of those commercial dusting sprays. They contain an oil that not only makes the dust particles stick to the cloth, but coats them with a thin insulating layer so they can't adhere electrostatically to nearby objects.

For a surprising glimpse of how much dust there actually is in the air, look up at the beam of light coming from the projector the next time you go to the movies. The reason you can see the beam at all is that the light is being scattered sideways by ordinarily invisible dust particles that are approximately the same size as the light's wavelength.

To Go, or Not to Go? That Is the Question

This may be a stupid question, but what makes things happen or not happen? I mean, water will flow downhill, but not up. Sugar will dissolve in my coffee, but if I put in too much I can't undissolve it. I can burn a match, but I can't unburn it. Is there some cosmic rule that determines what can happen and what can't? 3

There's no such thing as a stupid question. You have asked what is perhaps the most profound question in all of science. Nevertheless, it does have a fairly simple answer ever since a genius by the name of Josiah Willard Gibbs (1839–1903) figured it all out in the late nineteenth century.

The answer is that everywhere in Nature there is a balance between two fundamental qualities: energy, which you probably know something about, and entropy, which you probably don't (but soon will). It is this balance alone that determines whether or not something can happen.

Certain physical and chemical things can happen all by themselves, but they can't happen in the opposite direction unless they get some outside help. For example, we could make water go uphill by hauling it or pumping it up. And if we really wanted to, we could get that sugar back out of the coffee by evaporating the water and then chemically separating the sugar from the coffee solids. Unburning a match is quite a bit tougher, but given enough time and equipment, a small army of chemists could probably reconstruct the match out of all the ash, smoke and gases.

The point is that in each of these cases a good deal of meddling—energy input from outside—is required. Left entirely to herself, Mother Nature allows many things to happen spontaneously, all by themselves. But other things will never happen spontaneously, even if we wait, hands-off, until doomsday. Nature's grand bottom line is that if the balance between energy and entropy is proper, it will happen; if it isn't, it won't.

Let's take energy first. Then we'll explain entropy.

In general, everything will try to decrease its energy if it can. At a waterfall, the water gets rid of its pent-up gravitational energy by falling down into a pool. (We can make that cast-off energy turn a waterwheel for us on the way down, if we like.) But once the water gets down to the pool, it is “energy-dead,” at least gravitationally speaking; it can't get back up to the top.

A lot of chemical reactions will happen for a similar reason: The chemicals are getting rid of their stored-up chemical energy by spontaneously transforming themselves into different chemicals that have less chemical energy. (The burning match is one example.) But they can't get back up to their original energy conditions by themselves.

Thus, other things being equal, Nature's inclination is that everything will lower its energy if it can. That's rule number one.

But decreasing energy is only half the story of what makes things happen. The other half is increasing entropy. Entropy is just a fancy word for disorder, or randomness, the chaotic, irregular arrangement of things. At the scrimmage, football players are lined up in an orderly arrangement—they are not disorderly, and they therefore have low entropy. After the play, however, they may be scattered all over the field in a very disorderly, higher-entropy arrangement. It's the same for the individual particles that make up all substances: the atoms and molecules. At any given time, they can be either in an orderly arrangement, or in a highly disordered jumble, or in any kind of arrangement in between. That is, they can have various amounts of entropy, from low to high.

Other things (namely, energy) being equal, Nature's inclination is that everything tends to become more and more disorderly—that is, everything will increase its entropy if it can. That's rule number two. There can be an “unnatural” increase in energy as long as there is a more-than-compensating increase in entropy. Or, there can be an “unnatural” decrease in entropy as long as there is a more-than-compensating decrease in energy. Got it?

So the question of whether or not a happening can occur in Nature spontaneously—without any interference from outside—is purely a question of balance between the energy and entropy rules.

The waterfall? That happens because there is a big drop in (gravitational) energy; there is virtually no entropy difference between the water molecules at the top and those at the bottom. It's an energy-driven process.

The sugar in the coffee? It dissolves primarily because there's a big entropy increase; sugar molecules swimming around in coffee are much more disorderly than when they were tied neatly together in the sugar crystals. Meanwhile, there is virtually no energy difference between the solid sugar and the dissolved sugar. (The coffee doesn't get hotter or colder when the sugar dissolves, does it?) It's an entropy-driven process.

The burning match? Obviously, there's a big energy decrease, a sudden exodus of energy. The stored-up chemical energy in the match head is released as a burst of heat and light. But there is also a huge entropy increase; the billowing flame, smoke and gases are much more disorderly than the compact match head was. So this reaction is doubly blessed by Nature's rules, being driven by both energy and entropy. That's why it proceeds with such gusto the instant you supply the initiating scratch.

What if we have a process in which one of the quantities, energy or entropy, goes the “wrong way”? Well, the process can still occur if the other quantity is going the “right way” strongly enough to overcome it. That is, energy can increase as long as there is a big enough entropy increase to counterbalance it; and entropy can decrease as long as there is a big enough energy decrease to counterbalance it.

What J. Willard Gibbs did was to devise an equation for this energy-entropy balance. If the Gibbs equation shows that after counteracting any “wrong-way” entropy changes there is still some energy left over, that energy (Techspeak: the free energy) can be used to make things happen and the process in question will take place automatically. If, on the other hand, the amount of available (“free”) energy is inadequate to counteract any “wrong-way” entropy changes, the process will not and cannot take place unless some additional energy is obtained from outside.

By adding enough energy, then, we can always overpower nature's entropy rule that everything tends toward disorderliness.

Here's an example. There are about 10 million tons—60 trillion dollars' worth—of dissolved gold distributed throughout Earth's oceans, just sitting there for the taking. With enough effort we could collect it all, atom by atom. But the atoms are dispersed through 336 million cubic miles (1.4 billion cubic kilometers) of ocean in a completely chaotic arrangement that has extraordinarily high entropy. The energy that we would have to expend in order to reduce its entropy by collecting it all in one place would cost enormously more than the value of the gold.

In a fit of fervor over the laws of mechanics, Archimedes (287–212 B.C.) is reputed to have said, “Give me a lever long enough and a place to stand, and I will move the world.” If he had known about entropy and apple pie, he might have added, “Give me enough energy and I'll put this chaotic world into apple-pie order.”

3 This question is so fundamental to the way in which the universe works that I'm repeating the answer, slightly modified, that I gave in What Einstein Didn't Know: Scientific Answers to Everyday Questions (Dell 1999). All other questions and answers in the present book are new.