How do advertisers make pictures big enough to put on billboards?

how do advertisers make pictures big enough to put on billboards

Billboard painters make pictures big enough to put on billboards, with brushes and oil paint. “We’re probably the fresco painters of the modern era. In the Renaissance, the Church had the money; now it’s the ad agencies. Our stuff isn’t as creative as other art, but it’s real craftsmanship that goes into these signs,” says … Read more

How do skating rinks keep the ice on the rink from melting?

how do skating rinks keep the ice on the rink from melting scaled

Skating rinks maintain their frozen surfaces even in warm air because the temperature beneath the ice is so cold that the ice is not affected significantly by moderate temperatures above it. Thus a burst of sunshine over an outdoor rink, which allows skaters to shed their sweaters, cannot succeed in melting the ice. In a … Read more

How does radiation therapy help cure cancer by damaging cells?

how does radiation therapy help cure cancer by damaging cells

Radiation works on cancer because it damages cells; by and large, normal cells recover from the bombardment better than malignant ones. “Radiation” in this case refers to ionizing radiation, a flow of energy that tends to split the molecule it strikes into ions, or particles with an electrical charge. For example, when a water molecule … Read more

Where does dry ice come from and How is dry ice made?

where does dry ice come from and how is dry ice made

This strange substance, ice so cold it burns, is an excellent refrigerant, of course, and also a useful source for the ghoulish vapors in vampire and mystery movies. Dry ice is actually composed of carbon dioxide, which at normal temperatures sublimes, or becomes a gas. The carbon dioxide is stored and shipped as a liquid … Read more

How does the bank transfer money from your checking account to someone else’s account?

how does the bank transfer money from your checking account to someone elses account

When people wrote checks in England as early as 1762, the banks hired delivery clerks to run back and forth between banks to collect the money. To expedite matters, banks developed clearinghouses, organizations in the bank’s locality through which checks were exchanged and net balances settled. Woodrow Wilson organized this system on a nationwide basis … Read more

How do molecular biologists splice genes using enzymes?

how do molecular biologists splice genes using enzymes

Gene splicing, a truly revolutionary feat of molecular biologists in recent years, has the potential to make new life forms from different organisms and to synthesize cheaply the scarce substances needed to cure disease. Among those is the potent antiviral protein interferon, which may at last cure the common cold and may provide effective treatment … Read more

How does a thermostat keep the temperature constant by sensing if it’s too cold or too hot?

how does a thermostat keep the temperature constant by sensing if its too cold or too hot

Thermostat means, literally, “heat constant.” Temperature changes have a great effect on matter, including the matter human beings are made of; being too hot or cold can do the body great damage. A thermostat keeps the temperature of a house constant by using the response of matter to temperature change to throw switches in a … Read more

How did newspapers and magazines transmit pictures by telephone in the 1980s?

how did newspapers and magazines transmit pictures by telephone in the 1980s

The transmission of photographs over telephone wires was extremely useful, especially for newspapers and magazines which required photographs instantly, and it is not as complicated as one might think. First, a positive photographic image is illuminated with a small light. The whiter the image, the greater the reflection; darker images reflect less light. A photocell … Read more

How are mirrors made and Where do mirrors come from?

how are mirrors made and where do mirrors come from scaled

Whether out of curiosity, vanity, or a motive as yet unexplored, people throughout the ages have wanted to see their own reflection. As early as 2500 B.C. the Egyptians had mirrors of highly polished metal, usually of bronze, occasionally of silver or gold. The first commercial glass mirrors were made in Venice in 1564; these … Read more

How do camels go without food and water for days in the desert?

how do camels go without food and water for days in the desert

The notion that camels can go without water completely is a myth, nor do they use their extraordinary humps as storage tanks for water. The fact is, camels are able to make long, burdened treks across blazing deserts where oases are few and far between because of their uncommonly economical use of water. They are … Read more

How does the U.S. Geological Survey measure the elevation of a city or mountain?

how does the u s geological survey measure the elevation of a city or mountain

In addition to the networks of highways, railroads, and telephone wires that connect the farthest sections of the country, another, less visible system exists by which elevations of towns, cities, mountains, and lakes have been determined. Points of reference are marked by thousands of bench marks from coast to coast, the work of state surveys, … Read more

How do astronomers measure the size of the universe?

how do astronomers measure the size of the universe

There are two answers to this question, depending on the definition of “the universe.” One answer is that the universe is infinite, that it consists of simply everything: all matter, dust, planets, stars, energy, time, and space. Nothing could lie beyond the boundaries of “everything”; so, by simple semantics, we know the universe is infinite. … Read more

How does a vending machine know that the coin you inserted is the correct value and not a slug?

how does a vending machine know that the coin you inserted is the correct value and not a slug scaled

Vending machines are equipped with a coin testing device that not only measures the diameter and thickness of your coin, but checks its weight, alloy composition, and magnetic properties. The coin enters a slot, which has been carefully measured to accommodate the required coin or coins, and rolls down a chute to two hook shaped … Read more

How do Astronomers know that the universe is expanding by studying light waves?

how do astronomers know that the universe is expanding by studying light waves

The universe is blowing up. Earth is but a particle of debris hurtling through space from an awesome explosion that took place 20 billion years ago, which generated temperatures of trillions of degrees, and marked the Beginning. Ever since the “Big Bang”, stars, planets, gases, and intergalactic dust have been moving away from one another … Read more

How do flavor chemists create artificial flavors for food that taste just like the real thing?

how do flavor chemists create artificial flavors for food that taste just like the real thing

This question is debatable. Ripe bananas, for instance, have more than 150 taste components; it is highly unlikely, therefore, that a synthetic banana flavor could really duplicate the ripe banana flavor. Furthermore, the cheap synthetic flavors that consumers have been fed in recent years have made them so accustomed to an artificial taste that often … Read more

How do Ballistics Experts trace bullets to specific guns?

how do ballistics experts trace bullets to specific guns

The hunt for New York’s infamous “Son of Sam” killer ended when ballistics experts at the city’s Police Academy Crime Laboratory examined the .44 caliber Charter Arms “Bulldog” revolver they had turned up in the car of suspect David Berkowitz. The bullets found in the bodies of the victims had all been fired from that … Read more

Who Made the First Microwave Oven and When?

who made the first microwave oven and when

In 1945 Edison General Electric introduced the first microwave oven for popular consumption. Since then the commercial and domestic use of these ovens has been steadily increasing, largely because of the speed with which they cook food. Microwave ovens cook food by friction: the oven emits short radio waves (microwaves range from 1 millimeter to … Read more

How does a hovercraft hover across the water?

how does a hovercraft hover across the water

When a hovercraft moves across water, it is literally floating on air, for a high pressure air cushion is maintained beneath the hull that provides lift and allows even large vessels to whiz along at high speeds. First developed in 1959, air cushion vehicles (AVCs) are sometimes amphibious, capable of traveling both on land and … Read more

How do neon signs glow and What does the word neon mean in Greek?

how do neon signs glow and what does the word neon mean in greek

Neon is a colorless, odorless, inert gas, first discovered in 1898 by the British physical chemists Sir William Ramsay and Morris W. Travers, who named the gas after the Greek word meaning “new.” About that time physicists were experimenting with generating radiation by striking an arc between electrodes in an evacuated tube containing only small … Read more

How do tape manufacturers roll up a roll of Scotch tape?

how do tape manufacturers roll up a roll of scotch tape

If you ever pull out more Scotch tape than you need, you might as well forget trying to save it by rolling it back onto the roll. It’ll twist and stick to itself, your fingers, and the dispenser, and if it does actually get back on the roll it’s bound to be crooked and overlap … Read more

How does a Polaroid picture develop in broad daylight?

how does a polaroid picture develop in broad daylight

Each frame in a pack of Polaroid film is a self contained unit that serves as film, darkroom, and finished print. It works its sorcery in the seventeen chemical layers crammed with great precision under the surface of a square image area less than .002 inch thick. Migrating among these layers are the dyes that … Read more

How does the Motion Picture Association of America rate movies?

how does the motion picture association of america rate movies

Movie ratings are determined by a board of seven, six members and a chairman, within the Classification and Rating Administration (CARA), under the auspices of the Motion Picture Association of America (MPAA). The six board members are full time, paid employees based in Hollywood, where they watch movies nearly all day long. “The members are … Read more

How do corn producers get corn off the cob and into the can?

how do corn producers get corn off the cob and into the can

When truckloads of freshly picked corn arrive at a processing plant, the ears are dumped onto a conveyor belt that transports them to a husking machine. Rotating rollers with fluted surfaces strip the foliage and stalk from the randomly fed corn and send it on for inspection. Immature or diseased corn is removed by hand; … Read more

How do turbine generators generate electricity using different sources of power?

how do turbine generators generate electricity using different sources of power scaled

A simple combination of motion and magnetism underlies the creation of electricity by turbine generators. In the mid nineteenth century scientists found that an electric conductor passed near a magnet and through its magnetic field picks up an electric current. In generators today, the magnet is a huge electromagnet bolted to the shaft of a … Read more

How do they select donors at a sperm bank and Why was I rejected?

how do they select donors at a sperm bank and why was i rejected scaled

In the late 1950’s and throughout the 1960’s, new knowledge was acquired and new methods developed for the storage and preservation of human sperm. The 1970’s saw the natural consequence: the advent of sperm banks and sperm as a salable commodity. Today there are nearly a dozen sperm banks scattered across the country, and the … Read more

How does a Xerox machine make copies of a document instantly?

how does a xerox machine make copies of a document instantly

A Xerox machine seems a miraculous thing: it makes a clear, permanent copy of a document on ordinary paper in about 5 seconds and the copy is sometimes easier to read than the original. Like many modern inventions, the Xerox copier should not be possible under the classical laws of physics laid down by Isaac … Read more

How do time release capsules release medication gradually and evenly?

how do time release capsules release medication gradually and evenly

In the late 1940’s Don MacDonnell of Smith Kline & French, a pharmaceutical company, went into his local grocery store and lighted upon a jar of “petites”, tiny candy beads used for decorating pastry. Scientists at the time were searching for a form of medication that would release slowly, and the candy provided MacDonnell with … Read more

How do mountain climbers scale sheer rock walls using specific techniques?

how do mountain climbers scale sheer rock walls using specific techniques

Tools help, as do various specific techniques, but rock climbers depend mostly on sound judgment, careful analysis, and astonishing nerve. The physical mechanics of rock climbing involve not only the feet, knees, hands, arms, and body. Pressure of the body against the rock, for example, lends support. If a very steep rock affords no hand … Read more

How does a metal detector at the airport use induced magnetism to detect metal?

how does a metal detector at the airport use induced magnetism to detect metal

The people at Infinetics, Inc., the manufacturer of “Friskem” detectors, which comprise over 90 percent of the worldwide market for airport metal detectors, are fearful of releasing any secrets about how their detectors operate. According to the management (who seem to assume guilt on the part of the questioner until proof of innocence is established), … Read more

How does The New York Times determine its best seller list?

how does the new york times determine its best seller list

As anyone can read in the back of The New York Times Book Review each Sunday, the best seller lists reflect the sales of books in 1,400 bookstores across the country. Each week those stores submit sales figures of the most popular titles, and this information is fed into a computer, which comes up with … Read more

How does truth serum work and Where did truth serums come from?

how does truth serum work and where did truth serums come from

The plain fact is truth serum doesn’t work, at least not well or consistently enough to be accepted by our legal system as a reliable means of extracting the truth from unwilling subjects. Most courts of law do not admit information produced by drug analysis as legal evidence. The catchy phrase truth serum appears to … Read more

How does the IRS decide which taxpayers to audit?

how does the irs decide which taxpayers to audit scaled

Visions of auditors and interminable interrogations may rattle your nerves as you mail in your tax return each year, wondering whether an inscrutable Big Brother will select you as the lucky host to an IRS agent. There is no surefire answer to the question of who will be audited, but you can be aware of … Read more

How do scientists count populations of animals on earth?

how do scientists count populations of animals on earth scaled

Humans are the only beasts who use telephones or permanent addresses, or fill out census forms. How are the other animals counted? How can anyone tell that the timber wolf and the California condor are rare and “endangered”? How do we know how many robins chirp every spring? The task of taking a census of … Read more

How is a subway built under a city using the cut and cover method?

how is a subway built under a city using the cut and cover method

The first step is to chart the subway precisely, taking note of all underground utilities, existing subways, foundations, and soil and rock conditions. If the route happens to coincide with the path of a street, or if it lies beneath clear areas above ground, a “cut and cover” method of digging trenches at the surface … Read more

How does a submarine dive and resurface using ballast tanks?

how does a submarine dive and resurface using ballast tanks scaled

Submarines dive and resurface simply as a result of changes in the amount of weight on board. It’s essential, then, that the captain keep careful track of the number of crew members and the amount of food, batteries, torpedoes, and so on. When the submarine’s weight is equal to the weight of water it displaces, … Read more

How do bees know how to build honeycombs in their hives so perfectly?

how do bees know how to build honeycombs in their hives so perfectly

Bees know how to build honeycombs in their hives by accident, that’s the biological answer to the question. The dazzling geometric perfection of the honeycomb, with its perfectly flat surfaces made of straight rows of elegant hexagons, compact, yet capacious enough inside to support a population of 80,000, is the product of blind instinct, the … Read more

How are Pencils Made and How do they Put Lead Into a Pencil?

How are Pencils Made and How do they Put Lead Into a Pencil?

You might think that lead gets into a pencil by being inserted into a hole drilled the length of a cylindrical piece of wood, for if you look closely at a pencil, it certainly appears that the wood is all one piece. “That’s the sign of a good pencil,” says a salesman for the Joseph … Read more

How did publishers and editors write the 15th Edition of the Encyclopaedia Britannica ?

how did publishers and editors write the 15th edition of the encyclopaedia britannica

The accumulation of knowledge that went into the making of the fifteenth edition of the Encyclopaedia Britannica is astounding, for the ambitious publishers and editors of this edition actually started from scratch, a feat to give even the most knowledgeable scholar reason for misgivings. The first Encyclopaedia Britannica, published in 1771 and comprising only 2,659 … Read more

How do street lights turn on automatically when it gets dark?

how do street lights turn on automatically when it gets dark

The magic lies in a little metal box with a glass top perched high up on the pole of one light in a given area. Inside is a highly sensitive photoelectric cell which reacts to the absence of light. When it gets dark, the cell automatically closes the circuits, allowing electricity to run through and … Read more

How do meteorologists predict the path of storms and hurricanes?

how do meteorologists predict the path of storms and hurricanes

In order to safeguard against unforeseen destruction by hurricane winds and floods, the National Weather Service, after detecting a storm, tries to predict its course. Forecasting, in actual practice, is very technical, but it rests on several methods that may be described broadly. According to a theory of persistence, forecasters assume a storm will persist … Read more

How does a steel ship float if it is heavier than water?

how does a steel ship float if it is heavier than water

Archimedes’ principle states that a body immersed or partially immersed in water loses an amount of weight that is equal to the weight of the fluid it displaces. Whether or not an object can float depends on the density (weight ÷ volume) of both the object and the water. If the density of the object … Read more

How do homing pigeons find their way home and navigate in flight?

how do homing pigeons find their way home and navigate in flight

Scientists have long been baffled by the uncanny ability of these small one pound birds to make precise point to point flights over great distances and to hold their course whether the skies be overcast or clear. The answer to how pigeons home would undoubtedly provide a clue to the related mystery of how birds … Read more

How does an artificial pacemaker help a weak or damaged heart pump blood?

how does an artificial pacemaker help a weak or damaged heart pump blood scaled

Artificial pacemakers are able to correct low cardiac output primarily because of the remarkable qualities of the heart itself. Ever since the experiments of the prominent Italian physician Luigi Galvani in the eighteenth century, men have known about the ability of muscle to respond to electrical stimulation. The fibers of the myocardium (the middle muscular … Read more

How do doctors determine a baby’s gender before birth?

how do doctors determine a babys gender before birth

Cells present in the amniotic fluid within the fetal sac are largely of fetal origin, and they contain the secret of a baby’s sex. In the procedure called amniocentesis, a sample of this fluid is examined and the baby’s sex revealed. Because of a minimal but nevertheless real risk to the health of the fetus … Read more

How do NASA and the USDA predict future crop yields using weather satellites?

how do nasa and the usda predict future crop yields using weather satellites

Global crop forecasting, still very much in the experimental stage, is a massive undertaking that calls on the research facilities and technologies of such organizations as the National Aeronautics and Space Administration (NASA), the United States Department of Agriculture (USDA), and the National Oceanic and Atmospheric Administration (NOAA). There is no magical system by which … Read more

How does the Nobel Foundation pick Nobel Prize winners?

how does the nobel foundation pick nobel prize winners

Alfred Bernhard Nobel was a shy, reclusive man with a fondness for English poetry, and a passion for explosives. Even after killing his youngest brother and four other men in his experiments with nitroglycerin, he persisted: he invented dynamite, the detonating cap, and later blasting gelatin, an even more powerful explosive. Not a very peaceful … Read more

How does a high speed elevator take you 60 floors in 30 seconds?

how does a high speed elevator take you 60 floors in 30 seconds

When an elevator lifts you almost instantaneously to the 60th floor, you feel you must be traveling at a tremendous speed. Actually, the elevator rises 800 feet in 30 seconds, or only 18 miles an hour. Compared with the slow hydraulic elevators used in buildings of five stories and less, however, this speed is indeed … Read more

How do window cleaners wash the windows of the World Trade Center?

how do window cleaners wash the windows of the world trade center

During the spring, summer, and fall, the windows of the World Trade Center from the 9th to the 106th floor are always being washed. The winter season is prohibitive because of heavy winds and freezing temperatures. A huge automatic window washer for each tower, resembling a crane, is operated by one man standing on the … Read more

How do baseball teams measure the speed of a fastball?

how do baseball teams measure the speed of a fastball

The game is tied, the crowd hushed with anticipation, as “Goose” Gossage winds up for one of his famous fastballs. The batter swings, misses, strike three, the inning is over and Howard Cosell tells us Gossage’s deadly pitch went 98 miles an hour. How does he know? Just as the police use radar to trap … Read more

How is instant coffee made and Where does instant coffee come from?

how is instant coffee made and where does instant coffee come from

Whether you agree with the ads that freeze dried instant coffee packs in more flavor, or stand by the powdered brand you’ve been using for years, the manufacturing process for both is similar, at least until the final step. When coffee arrives at a factory that will turn it into instant, it already looks like … Read more

How do cigarette companies remove and reduce tar from cigarettes?

how do cigarette companies remove and reduce tar from cigarettes scaled

Cigarette companies keep talking about reducing the “tar” in their latest brands, as though it were a single ingredient, easily removed for better health, easily replaced for more taste. Actually, “tar” is not tar at all but a combination of some 2,000 to 10,000 elements, including alkaloids, ammonia, carbon dioxide, carbon monoxide, and hydrogen cyanide, … Read more