Scientofy

Recently, some banks in the United States have moved away from magstripes. Instead, they're issuing cards containing tiny microchips that are activated with a personal identification number (PIN). These microchip cards, already popular in Europe, store the same type of information that a credit card does. When the card is inserted into a reader, two electrical contacts create a current that transfers the information through a point-of-sale system for verification and processing. The readers for these cards are expensive, but the security and universality advantages of these cards make them worthwhile.

Did you know that the dark stripe on the back of your credit card called a magnetic stripe. or magstripe is actually a type of magnet? It consists of hundreds of tiny magnetic particles contained in a film of plastic. Magstripes have three tracks that contain varying amounts and types of information in specific formats based on established banking standards. The first track contains proprietary information relevant to the card issuer and often you, the cardholder. The second track is primarily used by financial institutions and contains account information, among other things. Most credit cards only use the first two tracks, as there are no standards governing how the third track should be used. Although credit and debit cards are ubiquitous today and integral to Internet commerce, they have only been around since 1950 when Diners Club was issued as the first general credit card that could be used with multiple merchants.

A metal detector works something like sonar. The base of the wand-like apparatus of the A metal detector contains a coil that emits an electromagnetic field into the ground. Metallic objects, such as coins or rings, respond to this electromagnetic field by emitting their own fields. The coil detects this and transmits this signal to the control box at the top of the wand. The result is a signal-usually a series of beeps letting the person operating the metal detector know that something has been found. Obviously. unwanted objects, such as nails or random pieces of steel, are detected as well.

Metal detectors and dogs can both detect mines, but both methods have their disadvantages: false positives and physical limitations, respectively. The solution is a system that detects a very specific component of a landmine its chemical signature. One prototype of such a system employs a chemically treated film that's applied to the ground and then viewed through ultraviolet light. If the chemical signature is not present, the film remains fluorescent. If an explosive is present, however, a dark circle forms around the area on the film. Another exploratory method uses microwaves and remote- vibration sensing.

What do cows standing in a field, a flock of migrating birds, and bacteria have in common? They all have an unerring sense of where true north (also called magnetic north) lies. How they do this is still a mystery, but scientists believe it may have something to do with a built-in compass the creatures possess. A recent study on a certain kind of bacteria discovered that the organisms have small particles of magnetite (iron oxide) inside them, and this may very well be responsible for their ability to find north. The particles in these bacteria line up with earth's magnetic field. Scientists have also found these magnetic particles near the brains of bees, birds, and trout.

Compasses expanded our ability to navigate and therefore explore our world without losing our sense of direction. Before the invention of these simple devices. voyagers had to use the stars and nearby land- marks to navigate their journeys. The ancient Chinese were the first to employ water-based compasses magnetic needles floated in bowls of water, The needles were magnetized by stroking them with a lodestone, a naturally magnetized piece of the mineral magnetite. At first, the needles were used in fortune-telling boards before being put to a more practical (and reliable) use. A compass works by sensing the magnetic field that is produced by Earth's core. which contains iron. But consider this: Earth's magnetic field is weak on the surface, which makes sense, given that it's spread out across the entire surface of the planet. In order for the magnetic field to have any effect on the compass at all, the compass must be light and have an almost frictionless bearing.

The magnets that we're most familiar with are made of iron or ceramic. However, magnets made from rare earth alloys combine different elements to produce what is called a permanent magnet-and these are super strong. Two of the most common alloys are samarium cobalt and neodymium iron boron. Because the iron in the magnets can rust, they're often coated with gold plate, nickel, zinc, copper, or some combination of those. How does a rare earth magnet compare to a traditional magnet? Well, a neodymium iron boron magnet is approximately ten times stronger than the little horseshoe-shaped magnet used in basic science classes. Magnets are. used in everything from computer hard drives to self-powered flash- lights to wind turbine generators.

During an earthquake the majority of injuries and deaths occur to people who are trapped in can withstand earthquakes is vitally important. But is it possible Yes! (Buildings that date back to the sixth century are still standing despite the fact that they're located in earthquake-prone areas. such as the Hagia Sophia in Istanbul Turkey). In order for a structure to resist the massive power of an earth- quake, it has to withstand the lateral or side-to-side motions earthquakes produce: the vertical motions are accounted for because buildings, by their very design, already counteract the effect of gravity. The ideal earthquake- resistant building is one that is symmetrical in shape, with little ornamentation, such as cornices or buttresses. SAFER BUILDINGS. The Tokyo Skytree tower wi Tokys Japan, shown here in the feal sops of comarction, was derged with numerous earthquake-netta festures that could break off during a tremor. A diaphragm, a middle tier of softer material that allows the building to wobble without breaking, provides side-to-side flexibility. Cross-bracing helps too by providing vertical stability and shear walls (walls made up of braced panels) provide lateral stability. Some structures even have frames in which the joints provide stability, yet allow the columns and beams to bend in response to an earthquake's force In addition, some buildings are attached to their found on a system of cylinders or springs. Lead-rubber bearings are a favorite choice for designers. A lead core makes the bearing stiff and strong in the vertical direction: alternating layers of rubber and steel bands provide strength horizontally. A damping system of gel-like pads connected to a heavy weight on top of the building can also help absorb the force of the earthquake.

Magnetism T 'he power to attract or repel is all in a magnet's atoms. Electrons and protons are always in motion. Because any moving charge generates a magnetic field, each electron and proton has one. Usu- ally these fields are haphazard, but in materials such as iron, they tend to line up within specific regions called domains. When ferrous (iron- containing) rock is molten, all the domains align with Earth's own magnetic field; this is how natural magnets are formed.

Tidal Power Generator The power produced by tides as they move in and out can be used to generate power, as the ancient Romans were well aware. Similar to a hydroelectric dam, a barrier is erected across a tidal basin. As the tide rises, water enters the basin, where it spins turbines and generates power. There are some environmental impacts that need to be addressed, such as silt buildup and reduced tidal flow, but the potential these generators provide as a clean source of energy is amazing, with an estimated 80 percent efficiency. The technology is expensive to implement, though. France is the only country currently using it on a large scale (one plant in France can provide power to 240,000 homes), and the hope is that more countries will follow. There's one requirement there must be an increase of at least 16 feet between low tide and high tide in order for a tidal power generator to work.

TIDES The ebb and flow of the tides may be something T we take for granted, but without gravity, the tides wouldn't exist. In a 24-hour period. there are two high tides and two low tides. These occur every day although the times vary due to something called slack the period of time in between tides when water is still How long this slack period lasts depends on the moon's gravitational pull. Even though the moon's gravitational pull is only one ten-millionth that of Earth's, it combines with Earth's centrifugal force to create tides. (The sun also has an effect on tides, but it's not nearly as strong as the moon's effect) The strength of the moon's effect on tides is based on the moon's phase (whether it's a full moon or a new moon) and distances between Earth the sun, and the moon in their orbits Tides are at their maximum when Earth, the sun, and the moon are aligned. The Bay of Fundy in Nova Scotia boasts the highest tides in the world, with a range of 44.6 feet between high tide and low tide.

SUSPENSION BRIDGE When you think of bridges, you might picture a classic suspension bridge, such as the Brook- lyn Bridge in New York or the Golden Gate Bridge in San Francisco. One look at the slender, graceful design of these structures can make you wonder how they stay up, much less support traffic. Suspension bridges date back to the fifteenth century and comprise a deck, towers (called abutments) at either end, and a network of cables that form a parabolic curve (a parabola is a curve where any point is at an equal distance from a fixed point and a fixed straight line). A main cable runs horizontally from tower to tower, and vertical cables run off the main cable, supporting the weight of the deck and transferring it to the towers. The main cable is actually anchored beyond the abutments, to prevent the bridge structure from giving in to the force of compression. The weight of the bridge itself (called dead weight) pulls inward on the towers; however, the cables counteract this with an equal force. In other words, compression from the bridge's deck and tension from the cables are balanced. Because of their design, suspension bridges have many advantages over other kinds of bridges. For one thing, they can span great distances. The longest suspension bridge in the world is the Akashi-Kaikyo Bridge in Japan, covering an impressive 12,831 feet. However, suspension bridges have disadvantages, too, which engineers must take into consideration. For example, if the main cable is made of chain links or just one strand of cable, and a link in the chain breaks or the cable snaps, the bridge loses its tension and comes down. Also, if the deck of the bridge is too thin, it can lose its stability in heavy winds and shake itself to pieces, which is what happened to the Tacoma Narrows Bridge in 1940.

The most interesting and important-aspect of Tan an elevator isn't even in it. It's the counterweight that makes it all possible. The counterweight hangs opposite the pulley system and balances the weight of the car in which the passengers ride, plus an additional 40 to 45 percent of the car's weight. An electric motor with a braking system drives an arrangement of cables and pulleys. In some ways, the design of the traditional elevator is actually inefficient; these days, hydraulic systems have replaced the old pulleys. At times, the counterweight is heavier than the car it's lifting such as when the car has no passengers in it. This arrangement creates excess energy, which dissipates as heat. Recent designs are revamping elevators to harness the power of gravity and divert this energy to a building's electrical grid.

ELLIPTICAL ORBITS OF PLANETS Why do planets have an elliptical, instead of a circular orbit? In a word, gravity. That the orbits of planets were elliptical (in the shape of an ellipse, or oval) was first proposed by Johannes Kepler in his the laws of planetary motion. It wasn't until Newton developed his law of universal gravitation, though, that we understood why. An elliptical orbit is the result of a complicated tug of war between the gravitational pull of different celestial bodies, like the sun and the planet. The bigger the celestial body, the more pull it exerts anomaller objects around it. One massive body, acting alone, might create a circular orbit. But if there's more than one massive object, as in our solar system, each rotating object will have an elliptical orbit. In addition, the farther away from the sun a planet is, the less it feels the sun's gravitational pull. Some planets have a more complicated orbit than others, which was partially explained by Einstein, who later refined Newton's explanation, adding the effect of the curvature of space-time. An object, like the sun, has mass, and this mass essentially deforms space-time, causing it to curve. The work of Kepler, Newton, and Einstein helped us understand the complex mathematics involved in planetary orbits. And the orbit of a planet can change. All celestial bodies including the sun-are moving so, as the gravitational pull changes, the orbits change, becoming more or less elliptical in response to the changes in velocity and mass.

ESCALATOR A n escalator is basically a conveyor belt with steps. It has two wheels at each end that drive a set of chains in a pulley-like fashion. The steps also have two sets of wheels that move along their own inner tracks and are positioned in such a way that each step is always level which is especially important when someone is getting on or off a moving escalator: Obviously, gravity is exerting a constant force on you; however, the force the escalator exerts as it moves you up or down perfectly counteracts gravity. keeping you in place on the step. This conveyor-belt technology-the same that has moved coal, sand, and grain for years is also used in another kind of people mover. The moving sidewalk complete with handrails and other safety devices is a horizontal version of the escalator.

BULLET TRAJECTORY the path a bullet follows as it leaves a gun is called its trajectory But a bullet doesn't rise, or arc, as it leaves a gun. Instead, it immediately begins to drop because of the effects of gravity (and the loss of the gun barrel's support); it also slows down due to ar resistance. So how does a person shooting a gun manage to hit a target? Even though the bullet doesn't travel in an arc, the shooter still has an arc to take into account. Skilled shooters often aim at a point slightly above the target while holding the barrel perfectly straight (although less-experienced shooters hold the barrel slightly raised and aim a little low). This point can be calculated and is, in the case of high-tech military artillery but nobody takes the time to do that on a shooting range. This skill comes with practice and a little trial and error.

PARABOLIC CURVE If you want to understand what a parabolic curve is just throw a baseball The are the ball travels as leaves your hand and fly back to the ground takes the shape of a parabola, or high arch because of grainy. We can calculate the trajectory of we know two things a foxed point the focus your hand or the point where the ball makes contact with a bat) and a fixed line (the directrix-the distance the ball travels) Any point on the trajectory is an equal distance from the focus and the directrix. Why is this important? Well, besides letting us calculate just how far a home run was actually hit, parabolic curves have important implications in everything from suspension bridges to car headlights to satellite dishes Many constructed arches resemble parabolic curves, but they are not true parabolas because mathematically their points are not at an equal distance from a directrix and focus The Arc de Triumph in Paris is just one example of an arch that is not a true parabolic curve even though it appears to be one

When we think of gravity, we tend to think of Sir Isaac Newton sitting under an apple tree: an apple falls on his head, and the idea of gravity is born. The story probably didn't ha happen quite that way, but Newton did observe falling objects, and he did wonder what mysterious force drew them to the ground and why some items seemed to fall faster than others. Newton's law of universal gravitation, published in 1687, holds that everything in the universe exerts a pull on other objects (called attraction), and the pull increases with mass and proximity.

In the 1980s scientists discovered that certain ceramics become superconducting at unexpectedly high temperatures—a leap forward that could make this ultra-efficient technology far more practical. Ordinary superconductors work only in the extreme cold achieved by applying liquid helium, which is costly to produce. They're used in such sophisticated and expensive technologies as medical magnetic resonance imaging (MRI) but will never be a sensible way to transmit power to home or run electronics. The newer super conductors do their thing at temperature as high as - 211 degrees Fahrenheit. That's still ultracold, but it's achievable using liquid nitrogen, which is cheaply derived from liquid air. Of course, the field's holy grail is the material that could eliminate resistance at room temperature—for now, only a dream.

It's not really sweat that cools you down on a hot day, it's the evaporation of sweat. For surface liquid molecules to leave into the air as gas, they must overcome the force that binds them together. In the process, they use of energy in the form of heat, drawing this heat from the liquid surface. The water that remains—the perspiration left on your skin, that is—is cooler. Why is it you can sweat away sultry afternoon without feeling relief? The thick, saturated air has little room to receive escaping liquid particles, so they stay put. You're wet, but not cool. In very hot climes, it is common on a sweltering day to consume hot liquids, such as soup or tea. The reason is to facilitate perspiration, which when it evaporates makes you feel cooler.

The word cold describe something that is not a quality in itself but rather an absence of something: heat. Heat is energy, and energy drives motion. The whole universe is made up of molecules dancing with the energy of heat. It's a raw, random motion. The faster the molecules move, the warmer the substance they make up. Even a jug of ice water harbors so much molecular motion that if you gently place a drop of ink on the surface, it will diffuse evenly throughout. In theory, absolute zero is a point where all motion—and hence all heat— ceases to exist. Quantum physics says that absence of motion is impossible. Absolute zero is about -273 degrees Celsius (- 460 degrees Fahrenheit) .

Chilled to extraordinary cold temperatures—colder than - 321 degrees fahrenheit—certain metals conduct electricity with absolutely no resistance. The current can flow undiminished in a loop forever, entropy seemingly vanquished in 100% efficiency. An electrical current consistd of electrons streaming through a medium towards a positive charge. There are snags along the way. The conductive medium is like a lattice of atoms that may have irregularities and that vibrates with the energy of heat. What's more, the atoms in a lattice, having given up loose electrons to the stream, are now positivey charged and attract the electrons tumbling past. Akin to the friction that stops a sliding object, these snags result in loss of electrical energy. Resistance typically diminishes as the conductive material's temperature drops. But super conductivity is different; when susceptable materials reach a critical cold threshold, reresistance abruptly vanishes. To rush toward their destination with utmost efficiency, the streaming electrons organise themselves into pairs. As one electron passes near the positively charged atoms of the lattice, the atoms bend inward toward the electron, temporarily increasing the positive charge around it. This creates a weak attraction between the electron and the one just behind it, and they are drawn together through the lattice. Locked together, the electron simply ride roughshod over the lattice, losing no energy. Because heat energy readily breaks them apart, such unusual pairings of electrons form only at critical cold threshold—the tipping point for superconductivity.

Before widespread adoption of the clothes dryer in the 20th century, people hung out their laundered clothes to dry, exposing as much surface area as possible to Sun and wind. The electricity-powered household appliance merely accelerates these natural aids to evaporation. A tumbler keeps the clothes moving rather than in a heap, providing maximal exposure of surface-water molecules and facilitating their escape from the wet fabric as gas. The machine promotes this escape by applying heat with a wire element and fan; this get some molecules moving. Another important element is the vent that removes humid air from the tumbler. When the air is full of water vapour, it becomes dense and heavy, in effect pressing against the liquid molecules attempting to escape their liquid bonds. Evaporation declines. The vent keeps the water evaporating until all the clothes are dry.

When a layer of air may lies over a city like Los Angeles, it can trap thick, pollutant-rich air near the ground, a form of pollution we call smog. In the usual course of things, the sun warms Earth, and that warm air expands and rises. It cools as it rises, losing about 3.5 degrees Fahrenheit with every thousand feet of elevation. But certain condition can disrupt this order. Land warms up in the sun much faster than water and becomes less dense. So in the Los Angeles Basin, for example, cool sea breezes sweeping inland easily wedge themselves beneath this warmer air. At the same time, air warmed on the high deserts around the city is lifted up against mountains ringing from city and slides in on top of the cooler air over Los Angeles. This warm inversion layer, ad it's called, acts like a lead, blocking the vertical circulation of air—and trapping pollutants from the welter of fossil fuel-burning vehicles.

The extraordinary high specific heat of water—it warms slowly—stands in contrast to the quite low specific heat of soil, especially dry soil, which warms up fast on a clear day. Along a coastline, of course, this temperature difference means a pressure difference: cool, dense, high-pressure air over the water and warm, low-pressure air over land. A pressure gradient sets the air in motion. A sea breeze pushes inland. Water's high specific heat also means that, once warm, it is slow to cool. Wind sometimes blow offshore at night, as the land loses daytime heat faster than the water. This is why it really is cooler at the shore.