Science

If Tucson was twice as hot as Miami, it certainly wouldn’t be 160 degrees Fahrenheit (71 degrees Celsius). But that’s not because 160 degrees is too hot; it’s not hot enough. The temperature that is “twice as hot” as 80 degrees Fahrenheit, believe it or not, is 621 degrees Fahrenheit! Here’s what’s going on. First … Read more

Everything is hot. That is, it contains some heat. And as a consequence, it has a temperature. Even an ice cube contains heat. “Hot” is strictly a relative term. Heat is the ultimate form of energy, the form into which all other forms ultimately degenerate. There is energy of motion (Techspeak: kinetic energy), there is … Read more

Your question may sound silly to those who haven’t heard about it before, but chomping on those little candies really does make flashes of light. It may not help you at all to know that the phenomenon is called triboluminescence, but there, I’ve said it and done my duty as a scientist. Life Savers, it … Read more

Mirrors are the best reflectors of light that human ingenuity has been able to devise. Notice, however, that the light is reflected only from the backing of the mirror, after passing through the front layer of transparent glass. What is there about the backing that makes it such a good reflector? It’s a thin, smooth … Read more

Well, what does “transparent” mean? It means that any light being reflected in our direction from an object outside a glass window, for example, can pass right through the glass unobstructed and come out the other side, where our eyes can deal with it. We therefore see the object through the window. That’s why people … Read more

A radiometer (also known as a light mill, light windmill, or roentgenometer) is generally supposed to illustrate that light has pressure. But they don’t. If a machine could be a con artist, this gadget would take the cake. You’ve seen them. They look like a light bulb on a stand. Inside the bulb, which has … Read more

The SPF numbers aren’t sun -filtering factors, they’re sun -protecting factors. SPF stands for “sun protection factor.” The numbers are not telling you how much radiation they block out, but how much time you can spend in the sun before your skin turns red, a condition doctors call erythema. And that’s quite another matter. With … Read more

Whenever a scientist has to explain something about light, he or she has the choice of explaining it on the basis of light waves or light particles (Techspeak: photons), because light behaves as if it were both or either a particle and/or a wave. Explaining refraction on the basis of light’s being a wave would … Read more

I’ll assume that you’re in the dining room, concerned about soup on your necktie, although you may have noticed this phenomenon in other rooms under different circumstances. We see an object because light is coming from that object and entering our eyes. The more light coming from the object, the brighter it appears. And of … Read more

Photographic film wasn’t as sensitive as it is today, so the exposures had to be longer and therefore further apart in time. The cameras shot only 16 pictures per second, rather than 24. In that longer amount of time between pictures, the people moved farther, so in a second’s worth of pictures they seem to … Read more

This is the only remaining artificiality in today’s remarkable, computer-driven movie effects, which can make anything imaginable look real, no matter how bizarre, except, ironically, an old-fashioned stagecoach wheel. You can also see the effect with automobile wheels, in those television commercials that show the cars speeding along an open road. If you watch carefully, … Read more

The distance from your eyes to the mirror is irrelevant. It’s the distance from your eyes to a given object that counts, just as it would when you look at it without the mirror. The light reflected from an object has to get to your eyes somehow, or else you wouldn’t see it. The light … Read more

This is one of those loaded questions that can drive you crazy because the question itself is misleading. It starts with a mistaken assertion and asks us to carry on our reasoning from that point. But you can’t pursue the road to truth if somebody starts you off in the wrong direction. A mirror does … Read more

Lightbulbs are very carefully engineered to last for a certain length of time. A suspicious person might be tempted to say that they are carefully engineered to burn out after a certain length of time. There is no reason that a lightbulb couldn’t be designed to last almost indefinitely. But you probably wouldn’t like it. … Read more

Halogen lightbulbs contain a gas called a halogen, which makes them brighter, whiter, more efficient and longer-lasting. And, of course, much more expensive. A halogen lamp is a variation on the standard incandescent, as opposed to fluorescent, lamp. An incandescent lamp contains a tungsten filament enclosed in a glass bulb filled with gas. An electric … Read more

You can buy the common, 48-inch shop-light tube in home centers for a couple of dollars, whereas a small, thin fluorescent tube for under the kitchen cabinet might cost up to five times that amount. The answer is that the four-footers, used by the thousands in schools, factories and office buildings, vastly outsell the smaller, … Read more

Fluorescent lights were invented for one purpose: to confuse you. I’m glad to see that they’re doing their job. When an ordinary incandescent lightbulb burns out you can just screw in a new one with the help of a certain number of friends, depending on your vocation or ethnicity. But when a fluorescent light burns … Read more

Because they think of color differently. Scientists describe objectively what Nature provides. They therefore think of color as a fundamental characteristic of light itself. To a scientist, light of different colors is radiation of different wavelengths. Artists, on the other hand, create their own interpretations of Nature. They therefore tend to think of color subjectively, … Read more

A black surface is one whose molecules are absorbing all visible wavelengths of the light that is falling upon it, and reflecting virtually none of it back. So black isn’t really a color, because we define a color in terms of the specific combination of light wavelengths that reflect back into our eyes. But, of … Read more

First, we have to look at what “white” is. You’ve heard people say dozens of times that white light is the presence of all colors. But other people tell you that white isn’t a color at all, that it’s the absence of color. You use bleach to remove all color from your laundry and make … Read more

You mean those plastic rods full of liquid chemicals that are made by Omniglow and other companies and are sold at street fairs, festivals and concerts and that start glowing with green, yellow or blue light when you bend them, and that gradually lose their light after an hour or so? Never heard of them. … Read more

It’s the same fluorescence phenomenon as the Day-Glo colors. Most laundry detergents contain “brighteners” that absorb ultraviolet radiation from daylight and re-emit the energy as a bluish light that makes the shirt look “whiter and brighter.” Moreover, the blue cancels out any yellowish cast. When stimulated by an ultraviolet lamp, which is even richer in … Read more

In a Day-Glo colored object there’s a chemical that takes invisible ultraviolet radiation out of the daylight and converts it into visible light of the same color as the object. Thus, the object is not only reflecting its normal amount of colored light, but is actively emitting some light of the same color, which makes … Read more

This is purely an exercise in “What if?” Automobiles, of course, aren’t built sleek enough or strong enough to exceed the speed of sound or to withstand the physical stresses of the sound barrier. But it’s fun to think about. The answer is simple: Yes. Or, I could have posed a different question that would … Read more

It’s as if the lake magnifies the sound somehow, isn’t it? But it isn’t actually magnifying the sound, as a microphone and amplifying system would do; it’s just that more of the sound is being funneled toward your ears. Sound consists of vibrations of the air. The guy on the other side of the lake … Read more

Astronauts are not weightless in orbit. There’s a completely different reason why astronauts can do all those silly tricks for the cameras, such as performing somersaults in midair or sitting upside down on absolutely nothing, looking more witless than weightless. Earth’s gravitational attraction, like all gravitational attraction, reaches out indefinitely; it keeps getting weaker and … Read more

It can be done to wow the crowd at an air show, but it wouldn’t work for a commuter flight to Schenectady because, although it’s theoretically possible, passenger planes aren’t built to stand the stress. (Nor are the passengers.) A conventional airplane’s wings are curved or humped on top, and that produces lift for reasons … Read more

Even though I know something about how airplane flight works (and you will too, soon), it never ceases to amaze me. I remember landing after a transatlantic flight in a Boeing 747 and being directed by the crew to deplane directly onto the ground and into a waiting bus, instead of through one of those … Read more

Whether we realize it or not, we judge the motion of an airplane in the sky by its relation to common things on the ground, such as trees, telephone poles and houses. That’s the only way motion can be detected: in relation to something else. There’s no such thing as absolute motion; it’s all relative … Read more

Silver bullets serve mostly as a calling card, but they do have a very slight advantage over lead. Ordinary bullets are made of lead because lead is so heavy, or dense. And it’s cheap. We want a bullet to be as heavy as possible because we want it to have as much damage-causing energy as … Read more

A spinning bullet flies farther and truer than it would without the spin. And if your favorite sport is football rather than shooting, just about everything I’m going to say about spinning bullets also goes for spiraling passes. The fact that a spinning bullet or football goes farther may sound strange, because you’d think that … Read more

Quite dangerous. As we’ll see, physics tells us that when it hits the ground the bullet will have the same velocity it had when it left the muzzle of the pistol, which can be 700 to 800 miles per hour (1,100 to 1,300 kilometers per hour). But that ignores air resistance. More realistically, the bullet’s … Read more

That’s precisely why they’re smooth. Regular tires waste a lot of their potential road-grabbing surface by having grooves, which act like gullies to channel out rain and mud. But racing cars usually compete in good weather, so the rain-and-mud grooves aren’t necessary. They’re just wasted space that can better be used to add more road-grabbing … Read more

It has been rubbed off, and no, that’s not why they call it rubber, onto the road, whence it was scattered in the form of fine dust into that vast, complex everywhere that we call the environment. Some of it was then washed off the road and into sewers by rain, or else it was … Read more

Ho hum. I don’t know how many times this question has flashed into the minds of worrywarts in elevators, or how many times it has been asked of every friendly neighborhood physicist. It is easy to answer in one word (No), but thinking about it does raise a whole bunch of fun questions. First, here’s … Read more

No, but it sure would create a windfall for Chinese podiatrists. I suppose that everybody picks on China when they ask this question because China is the most populous country on Earth, containing 2.5 billion potentially sore feet. There are really two questions here, aside from the question of why people who ask this question … Read more

Ramps and loops on freeways enhance the traffic flow, from construction companies to politicians’ campaign chests. Sorry. They allow us to make left turns without getting killed by oncoming traffic. It’s a matter of simple geometry. When freeways and superhighways began to be built, engineers had to figure out how to allow traffic to make … Read more

There’s no such thing as a dumb question. Actually, yours 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 figured it all out in the late nineteenth century. The answer is that everywhere in nature … Read more

If by recycling you mean transforming something into a more useful form. We do it all the time. Power plants transform water, coal, or nuclear energy into electricity. In our kitchen toasters we transform electrical energy into heat energy. In our automobile engines we transform chemical energy into motion (kinetic energy). The different forms of … Read more

Those ladders of fuzzy black dashes used as evidence in court are just a way of making DNA visible to jurors and other ardent scholars of biochemical science certain things that are too small to see, even with a microscope. They’re the end result of a number of laboratory manipulations that never get explained in … Read more

Everything is made of particles: atoms and molecules. But it’s not simply that some particles are lighter than others, although that’s a big part of it. It’s also that some particles are packed more tightly together than others. Lead is denser than, i.e., heavier than the same volume of, water, mostly because lead atoms are … Read more

Yes, there is a much simpler way, and it’s a shame they don’t teach it in school. Once those complicated formulas with all their parentheses and 32s got into a textbook somewhere, they seem to have taken on a life of their own. Here’s the simple method: To convert a Celsius temperature to Fahrenheit, just … Read more

Among all the nations of the world, only four great powers, Brunei, Myanmar (Burma), Yemen, and the United States of America, have not yet adopted the metric system of measurement. Is it possible that the rest of the world is onto something that has thus far eluded these four? Let’s see how our creaky and … Read more

Suppose that the Rockettes came on stage one at a time and did solos. You would agree that the intended effect would be lost, would you not? But that’s exactly how school science curricula are designed: the chemistry and physics teachers do solo acts on separate stages, and there’s no course in school called Putting … Read more

Pedestrians in the vicinity of Chicago’s 1454-foot Sears Tower need not fear. Hatted or not, they are in little danger from purely scientific experiments such as yours. (We won’t deign to discuss water balloons.) What you undoubtedly have in mind is the acceleration due to gravity, the fact that a falling object will fall faster … Read more

Magnets are attracted only to other magnets. A piece of iron contains billions of tiny magnets, but copper and aluminum don’t. The only thing that the pole of a magnet will attract is the opposite pole of another magnet. It’s exactly the same as with electric charges: The only thing that a positive electric charge … Read more

All atomic nuclei are made up of particles called nucleons. A big nucleus like uranium’s is a conglomeration of more than a couple of hundred of these particles, all crowded together into an incredibly tiny space. That’s such a large number of objects to hold together that the nucleus’s average grip on each one is … Read more

Uranium doesn’t burn like in a combustion, a chemical reaction with the oxygen in the air. But the uranium atoms do get used up. Coal, oil, and uranium contain energy. Actually, every substance contains a certain amount of energy. It is inherent in the unique arrangement of its atoms and how they are held together. … Read more

Frankly, E = mc2 doesn’t mean a hell of a lot. But that’s not to say that it isn’t one of the most momentous realizations ever to dawn upon the human mind. Although it has to do with things that are happening right under our noses every day, they are much too small to notice except … Read more

Twenty degrees, eh? Well, let’s just see about that. (We’ll assume that we’re dealing with Fahrenheit cucumbers, rather than Celsius.) If cucumbers are always twenty degrees cooler than their surroundings, let’s put a cucumber into a barrel with a whole bunch of other cucumbers and wait to see what happens. Will they fight it out, … Read more

Superman could probably see through lead with his X-ray vision if he really tried. It’s just that his inventors, Jerry Siegel and Joe Shuster, told him that he can see through anything but lead, and like any good cartoon character, he faithfully obeys his creators. Siegel and Shuster’s idea seems to have been that X-rays … Read more

Strictly speaking, infrared radiation is neither light nor heat. It’s not light because we can’t see it, and it’s not heat because it contains no substance that is capable of being hot. I like to call it “heat in transit.” We’ll see why. Infrared radiation is nothing more than a certain segment of the broad … Read more

If you listen with a linguist’s ear, you’ll find that the ice in your drink isn’t actually popping, which implies a certain hollowness. But it certainly does snap and, on occasion, crackle. First, the snap. When you plunge a cold ice cube into a warmer liquid, the water warms up parts of the ice cube, … Read more

As we were saying, water is a champion heat absorber, without getting very hot in the process. When you put a flame; to something that’s wet, the water soaks up the heat like a sponge, preventing the object itself from ever getting hot! enough to ignite. This one will astound you. Put a little water … Read more

Before we get any further, note well: Water must never be used on an electrical fire or on an oil or grease fire. Reasons: Water conducts electricity and can lead it elsewhere, perhaps to your very own feet. And because water won’t mix with oil or grease, it just scrambles it around and spreads the … Read more

Solid ice itself isn’t slippery. There’s a thin film of liquid water on its surface that the skaters are sliding on. Solids in general aren’t slippery because their surface molecules are tied tightly together and can’t roll around like ball bearings. The molecules of liquids, on the other hand, are free to move around, so … Read more

As we delve into how the boiling temperature of water depends on the weather, uncover the fascinating dynamics that influence how and when water boils, providing a nuanced understanding of this common yet intricate phenomenon. The weather has only a small effect on the boiling temperature of water. When people go around saying that water … Read more

When it’s boiling, water in New York is a little hotter than water in Mexico City. And hotter water will get an egg to a given state of doneness in a shorter time. A little thought will show that the biggest difference between New York and Mexico City, apart from the relative difficulty of finding … Read more

“Water seeks its own level” is a catch phrase that was probably uttered by a Greek philosopher two thousand years ago, and people have been parroting it ever since. In plain language, it means that water will lie flat whenever it can. If a body of water, anywhere from a bucket to a bathtub to … Read more

Generally, yes. But water is an exception. As trivial as this question may sound, the answer is of life-and-death importance. If ice didn’t float on water, we might not even be here to wonder why. Let’s see what would happen if ice sank in liquid water. In prehistoric times, whenever the weather got cold enough … Read more

This controversy has been raging ever since the early seventeenth century, when Sir Francis Bacon became a charter member of the Betcha-the-hot-water-freezes-first camp. The only appropriate answer to this puzzle is, “It depends.” It depends on precisely how the freezing is being carried out. Freezing water may sound like the simplest of happenings, but there … Read more

No, all liquids are not wet. Even water is not always wet. It depends on who or what is the “wet-ee.” Make this inquiry of a linguist, however, and you’ll be told that it is a foolish question. The word wet is so intimately related to the word water in the roots of our language … Read more

In the strength of its inward-directed surface-tension force, water is the champion of all liquids. Its surface tension is so strong that water resists being stretched outward at all, even into the three-dimensional shape of smallest surface area: a sphere. Water knows that it can have an even smaller amount of surface area by simply … Read more

Let’s put it this way: You’d be pretty surprised if they were square, wouldn’t you? That’s because all of our experience since we were babies tells us that Mother Nature prefers smoothness. There just aren’t many natural objects that have! sharp points or jangling angles. The major exception is certain mineral crystals, which occur in … Read more

Fortunately, it isn’t necessary to answer that question, because divers, and fish,  don’t get the bends (more accurately known as decompression sickness) from staying down too long. Divers get the bends by coming up too fast, but fish can indeed get the bends from other causes. When the water pressure on a diver’s body is … Read more

Of course, it can always swish its tail and swim to wherever it wants to go, but that’s just a temporary solution. What it would really like to do is adapt its body to the pressure of the new depth, so that it can maintain its neutral buoyancy and rest there without constantly having to … Read more

In order to be at home suspended in seawater, in precisely neutral buoyancy without sinking or rising, a fish, or any other object, must have exactly the same overall density as the water. That is, it must weigh exactly the same as an equal volume of seawater. If it weighs more, it will sink to … Read more

If you doubt that the water exerts an upward pressure, try to submerge a balloon in the bathtub. You’ll feel a substantial upward push that resists your downward push. When we lowered the Admiral Nimitz into our giant bathtub, the water level rose; it got deeper. As every diver knows, deeper water means higher pressure. … Read more

Very simply. They change their amount of internal air space, thereby changing their density. You want to dive? You let water into your ballast tanks. You want to surface? You blow the water out with compressed air. It gets a bit tricky in reality, though, because the density of seawater actually varies a bit, depending … Read more

The pat answer to the everyday puzzle of why things float invariably goes like this: “According to Archimedes’ principle, a body immersed in a fluid is buoyed up by a force equal to the weight of the fluid displaced. And that’s why things float.” Perfectly correct, of course, but just about as illuminating as a … Read more

The answer is, “It does and it doesn’t.” Maybe that’s why people go around simply parroting the prefabricated, though hardly enlightening, answer, that “evaporation is a cooling process.” We notice that our sweat glands are exuding a liquid water containing a little salt and urea, onto our skin only at certain times, such as (a) … Read more

The cooling effect on your skin has little to do with the evaporation of perspiration, in case that’s what you were thinking. That effect peters out as soon as there is enough wind so that all the perspiration has already evaporated. A strong wind cools us because the moving stream of air molecules carries off … Read more

No, that would knock the sponsor’s neon signs off the sides, and that would never do because today’s blimps are nothing but flying billboards. Instead, they use a clever system of swapping helium and air back and forth. The blimp is, as you’ve noted, essentially a big rubber bag full of helium. The contraption floats … Read more

Antigravity? We don’t use that word. Science fiction is two shelves over to the left. Surprisingly, there is no upward-pushing force. It’s just that there is less downward-pulling force on the helium than there is on the air that surrounds it because helium gas is lighter than an equal volume of air. Gravity pulls less … Read more

The colors are actually glowing atoms, stimulated by electricity. It’s pretty much the same as making the colors in fireworks: Stimulate atoms with energy, and they’ll quickly get rid of the excess energy by emitting light of their own characteristic colors. There are a couple of differences (fortunately) between fireworks and neon signs. In neon … Read more

They add chemicals to the explosive mixtures that emit specific colors of light when subjected to heat. You could throw some of these same chemicals into your fireplace if you thought that a green fire, for example, might be more romantic. When you throw an atom into a fire, it can pick up some of … Read more

It’s a nice idea, because snowflakes certainly do have beautifully complex shapes, with spikes, lacy edges, and all the rest. But interlocking hooks and loops are a bit too much to expect. Besides, they’re much too fragile and brittle; when you pack them together they suffer a crushing experience. The answer lies in the fact … Read more

Just pumping a spray of water into the air wouldn’t work very well, except perhaps in extremely cold weather. And by the way, the machines don’t produce actual snowflakes; they make tiny beads of ice, each one around ten thousandths of an inch in diameter. The simple spraying of water wouldn’t work because when water … Read more

It really does get warmer when the snow begins to fall. Think of it this way: In order to melt a lot of ice or snow, you have to add heat to it. So when a lot of water freezes into ice or snow, which is the reverse process, that same amount of heat has … Read more

Freeze dried coffee is made by the sublimation of ice. Freeze-dried coffee differs from ordinary instant coffee in an important way. To make either kind of fast-beverage powder, they first brew two-thousand-pound batches of incredibly strong coffee. If they are making instant coffee, they then quick-dry this thick brew by dropping it down through a … Read more

The snow in winter isn’t melting if it’s below freezing; it is actually going straight off into the air as water vapor, without having to melt into liquid water first. We might be tempted to say that the snow is evaporating, but scientists prefer to reserve the word “evaporation” for liquids only. So when a … Read more

The Greenhouse Effect is the effect of infrared radiation-trapping by the Earth’s atmosphere, which can raise the average temperature at the surface of the entire globe, just as the trapping of infrared radiation within a greenhouse raises the temperature inside. The overall temperature of the Earth’s surface, averaged over all seasons and climates, depends on … Read more

Greenhouses, sometimes called hothouses or glasshouses, are always naturally warmer, without any artificial heating. But believe it or not, the main reason is not what everybody refers to as “the greenhouse effect.” A greenhouse is just a closed, glass container for plants. The glass lets in sunlight, which the plants need for growth, while keeping … Read more

You can tell the temperature by counting the chirps crickets make. All cold-blooded animals perform their functions faster at higher temperatures. Just compare how fast the ants run around in cool and hot weather. Crickets are no exception. They chirp at a rate that is geared directly to the temperature. To understand their message, all … Read more

It’s all a matter of how big the water droplets are. That’s what clouds are: collections of tiny droplets of water. The droplets are so small that under the continual bombardment of air molecules they are kept suspended in the air and do not settle out by gravity, until it rains, of course. The droplets … Read more

First of all, please don’t call air pressure “barometric pressure.” The air around us has a temperature that is measured by a thermometer, a humidity that is measured by a hygrometer, and a pressure that is measured by a barometer. Television weather reporters wouldn’t dream of talking about the air’s “thermometric temperature” or its “hygroscopic … Read more

It’s very simple. The molecules in air are so far apart that we’re actually looking through empty space. To notice anything at all, we would have to be able to see the individual molecules, but air molecules are about a thousand times smaller than anything we can observe, even with a microscope. We’re talking about … Read more

Those copper roofs on old churches and city halls have been out in the weather longer than a borrowed lawn mower, all those years that have passed since people could afford to cover roofs with that durable and beautiful red metal. Today copper is too expensive to use to shelter even the heads of politicians … Read more

While the temperature “in the shade” is a fairly reproducible figure, the temperature “in the sun” depends too much on whose temperature you’re talking about. Different objects, including different people in differed clothing, will experience different temperatures in the sun because they will absorb different amounts of different portions of the sunlight’s spectrum. Light-colored clothing, … Read more

Right on. When it is winter on the part of the Earth where you live (northern or southern hemisphere), your hemisphere is leaning away from the sun a bit. That is, the axis of the Earth wobbles, so that during winter in the northern hemisphere the North Pole is farther from the sun than the … Read more