How do cloud chambers detect fast-moving particles?
You may have seen scientific photos of particles passing through cloud chambers, where they leave thin white trails. Scientists use these chambers to detect charged particles that come from radioactive elements, cyclotrons, and cosmic rays. How do cloud chambers work? Invented around 1900 by a physicist named Charles T. R. Wilson, a cloud chamber is a space filled with air and the vapor of some volatile (easy to evaporate) liquid. There is so much vapor in the air that it is almost ready to condense into floating droplets. When a charged particle comes zipping through the chamber, it rips electrons from the air molecules, producing charged atoms (ions). The floating ions attract molecules of the vapor, forming hundreds of microscopic droplets that clearly mark the trail of the particle as a thin, white streak. More about cloud chambers, including designs for home experiments  http://freeweb.pdq.net/headstrong/cloud.htm
Picture of Wilson's original cloud chamber  http://www.ioppublishing.com/Physics/Electron/Exhibition/section3/1911b.html
Charles T. R. Wilson

How were potato chips invented?
The humble potato chip is more popular in America than in any other part of the world. America's favorite snack food, it is a direct descendant of another popular potato snack, the french fry. How did it happen? According to the popular story, a dinner guest (rumored to have been wealthy railroad tycoon Cornelius Vanderbilt) was dining at Moon's Lake House in Saratoga Springs, New York in 1853. He sent his french fries back to the kitchen because they were too thick. The chef, a Native American named George Crum, was annoyed at the guest's complaint, so he responded by slicing the potatoes into extremely thin sections, which he fried in oil and salted. From that day forward, potato chips evolved into the many forms and varieties we have today including chips of many flavors, fat-free potato chips cooked in high-tech synthetic chemicals, and even artificially shaped chips pressed from potato pulp and sold in cardboard tubes. The story of potato chips http://www.ideafinder.com/facts/story/story007.htm http://www.dmgi.com/chips.html A blind
taste test of some popular brands
More Cool Facts about food

How are diamonds formed?
Natural diamonds are formed at least 150 kilometers deep in the Earth (93 miles) where the heat and pressure are great enough to squeeze carbon atoms together into the diamonds' tight crystal structure. How do they get to the surface? Almost all diamonds mined today are collected from "diamond pipes," deep channels of a kind of volcanic rock called kimberlite or blueground. These structures started as nearly vertical columns of magma that pushed their way up carrying diamonds formed much deeper, and solidified in place. The most well known kimberlite pipes are in South Africa. Most mined diamonds are of low quality, suitable for use in industrial abrasives. These are called "boart." The gem quality stones are only 15 to 20 percent of those mined. A diamond in its original kimberlite matrix
More about diamond mining in South Africa
More Cool Facts about diamonds

What is the highest point in Antarctica?
Antarctica's highest peak is Mt. Vinson, a pyramid-shaped mouontain 16,076 feet high (4897 meters). It's part of the Ellsworth Mountains, which overlook the huge Ronne Ice Shelf at the base of the Antarctic Peninsula. First climbed in 1966, Mt. Vinson's peak has been reached by fewer than 400 people. It is a place of utter desolation and dramatic beauty. From the top, one can look out across hundreds of miles of ice, to a horizon that is distinctly curved. Mt Vinson is about 600 miles (970 km) from the South Pole. Even during the summer, when the sun shines around the clock, conditions can be harsh and deadly. The average summer temperature is -20 degrees Fahrenheit (-29 C). Although conditions are usually cold and windless, high winds and snowfalls are always possible. Climbing Mt. Vinson: cybercast of a 1999 expedition http://mountainzone.com/climbing/antarctica/index.html More Cool Facts about mountains http://www.cool-fact.com/archive/1997/06/24.html http://www.cool-fact.com/archive/1997/11/06.html http://www.cool-fact.com/archive/1999/04/01.html

How does a scratch-n-sniff pad work?
Have you seen a scratch-n-sniff pad? You rub a hard object (like your fingernail) along the paper and somehow an aroma is released. You might also have seen perfume ads in magazines where you pull open a panel and the smell comes wafting out. How does this work? The secret is microencapsulation, a technology that is used in much more than just scratch-n-sniff pads. The idea is to enclose minute amounts of liquid, solid, or gas inside very tiny containers called microcapsules. When the containers are broken, the contents are released. In the case of scratch-n-sniff, your fingernail breaks the tiny capsules and the smell is released. Microcapsules are also used in detergents, drugs, and many other places where chemicals need to be released at controlled times. All about microencapsulation http://www.swri.edu/3pubs/ttoday/summer/microeng.htm Another Cool Fact about something aromatic http://www.cool-fact.com/archive/2000/03/06.html

How can cartilage-jawed fish crush hard clams?
Like all elasmobranchs (fish in the shark family), stingrays have no solid bones. Instead, they have skeletons of cartilage. So how can some stingrays manage to crush and consume hard clams, whose shells are much harder than their own bones? The secret is leverage and smart design. The clam-crushing rays have special three-layer cartilage, with an outer layer of tough, fibrous cartilage and a middle layer that is harder than the inner portion. There are also thin, hollow bracing struts that reinforce the jaws and add extra leverage. Because of the way the jaws are designed, they can crush objects that are harder than they are. Then the ray's sharp, hard teeth can further crush the shell fragments, releasing the meat inside. More about the clam-crushing stingrays http://helix.nature.com/nsu/000316/000316-2.html More Cool Facts about elasmobranchs http://www.cool-fact.com/archive/1997/08/01.html http://www.cool-fact.com/archive/1998/08/31.html http://www.cool-fact.com/archive/1999/11/05.html

What are the states of freeway traffic flow?
Although freeway traffic flow is very complex, science is beginning to reveal its dynamics. It turns out to have distinct states, like the gas, liquid, and solid states of matter. When traffic moves like a gas, the cars are far enough apart that each one can move freely without much affecting its neighbors. Drivers instinctively maintain large separations, and traffic flows at maximum speed. When things get a little busier, cars slot together into clusters that travel only a little slower than they do in the gas state. The clusters are like condensed droplets of liquid, and they are separated by intervals of gaseous traffic. If traffic gets even heavier, another transition happens. The traffic enters a thick, viscous state like honey or tar. If it gets much heavier you have gridlock, the solid state of traffic flow. Computers make the study of "traffodynamics" easier http://www.sciencenews.org/sn_arc99/7_3_99/bob1.htm The curious musings of a traffic psychologist http://www.aloha.net/~dyc/ch14.html More Cool Facts about transportation http://www.cool-fact.com/archive/1998/11/05.html http://www.cool-fact.com/archive/1999/12/07.html http://www.cool-fact.com/archive/2000/01/28.html

How does Teflon stick to pots and pans?
Teflon, or polytetraflouroethylene, (PTFE) is one of the most inert substances known. It's so inert that nothing sticks to it; to stick, it would have to react in some way. So how does it stick onto the surface of a frying pan? In early days, the Teflon was pressed onto the metal surface after the metal had been "roughed up" by abrasion and coated with a primer chemical with lots of microscopic cavities. The Teflon squeezed into the cavities and stuck to the pan by sheer mechanical strength. But those early frying pans didn't keep their coating very long, because Teflon is so inert that its long molecules slither like wet spaghetti, and it often came loose from the mechanical primer. Modern non-stick pans are made with a much more sophisticated process. Parts of the Teflon molecules at the bottom of the coating have different side chains that actually stick to the metal, while the upper ends of the molecules are pure Teflon. The layer sticks on the bottom, but not on top. More about how they make it stay stuck http://more.abcnews.go.com/sections/tech/Geek/geek990118.html Teflon is a registered trademark of DuPont Corporation http://www.dupont.com/teflon/ Teflon is a fluorocarbon. A Cool Fact about another fluorocarbon http://www.cool-fact.com/archive/1999/05/27.html

What is a sonic boom?
Sonic booms are not often heard these days in most inhabited parts of the world. That's because they can be somewhat destructive, not to mention annoying. They are caused by aircraft that travel faster than the speed of sound. The sonic boom is a shock wave that forms when the aircraft's speed outstrips the ability of air molecules to get out of the way. It's a moving pressure wave that starts at the nose, wingtips, and other forward-projecting parts of the aircraft and forms a cone trailing back from the plane and expanding up, down, and out to the sides. When that cone-shaped pressure field passes across a point on the ground, a sonic boom is heard. Since the pressure wave of a moderate sonic boom can be enough to break windows, non-military aircraft are no longer allowed to travel faster than sound near inhabited areas. More about sonic booms http://www.pbs.org/wgbh/nova/barrier/boom/ http://www.abovetopsecret.com/sonicboom.html Sometimes a large meteor causes a sonic boom http://www.cnn.com/TECH/space/9907/08/new.zeland.meteor/ More Cool Facts about sound http://www.cool-fact.com/archive/1997/09/16.html http://www.cool-fact.com/archive/1998/07/07.html http://www.cool-fact.com/archive/1999/05/20.html

Where are the largest flowing ice streams on Earth?
The greatest glaciers of the Northern Hemisphere are puny trickles next to the vast ice rivers that flow off the Siple Coast into the Ross Ice Shelf of West Antarctica. The five giant ice streams there are up to fifty kilometers wide (31 miles), 1000 meters deep (3280 feet) and hundreds of kilometers long. Huge ice sheets that hardly flow at all surround these vast streams. While the surrounding ice sheet moves maybe a meter per month, the ice streams can move at more than a meter per day. Why do they move so fast? The secret is what's underneath. While most of the West Antarctic Ice Sheet sits on solid rock, the Siple Coast ice rivers rest on a thick layer of wet, warm, slippery mud. The heat comes up from the Earth itself, melting the bottom layer of the ice, and the movement of the ice grinds the bedrock into fine mud. Many giant ice streams were discovered by radar mapping surveys http://explorezone.space.com/archives/99_10/19_antarctic_map.htm The Siple Coast ice streams http://www.newscientist.com/ns/19990417/greatriver.html A scientific paper about the ice streams http://www.agu.org/GRL/articles/98GL52327/GL063P01.html

How do modern freezers remain frost-free?
If you own an old refrigerator you may need to defrost the freezer from time to time, a difficult task possibly requiring a lot of scraping and hot water. How do modern freezers stay free of accumulated ice? Ice condenses in the freezer because cold air can't hold as much water vapor as warm air. In an older freezer frost forms on everything every time warm, moist air enters from outside. In a more modern freezer the air is circulated by a fan and the frost forms mostly on the coldest surface, which is the cooling coils in the back. You might think that the coils would quickly be surrounded by solid ice, and they would, if not for the defrost function. Every so often a heating element warms up the air around the coils just long enough to melt the frost. The water trickles down the back of the freezer to a tray near the floor where it evaporates. More about the auto-defrost function http://www.phoenix.net/~draplinc/defrost.html Auto-defrost uses energy. Here are ways to save energy http://www.ladwp.com/resserv/coninfo/refrig/ecs2.htm http://www.energydepot.com/Jackson/library/refrfrez.htm More Cool Facts about household technology http://www.cool-fact.com/archive/1997/03/24.html http://www.cool-fact.com/archive/1999/04/15.html http://www.cool-fact.com/archive/1999/05/25.html

What color is pure water?
You might think that absolutely pure water would be perfectly clear and utterly transparent, but it's actually blue. The blue color of the water in the oceans (and not the blue of the sky) is the reason why Earth is mostly blue as seen from space. Pure water absorbs some of the light that passes through it. It absorbs red light more than yellow, yellow more than green, and green more than blue. Only the deepest blue light can travel very far through water, so a large mass of water takes on a deep blue color. The blueness of water is easily visible in a swimming pool lined with white concrete. It's even visible in a white porcelain bathtub. But the bluest water of all is the clear tropical ocean far from land, where the sea is much bluer than the sky. The color of the ocean is strongly affected by plankton and impurities http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/OCDST/what_is_ocean_color.html http://www.oceansonline.com/rainbows.htm More Cool Facts about water http://www.cool-fact.com/archive/1997/07/11.html http://www.cool-fact.com/archive/1998/06/08.html http://www.cool-fact.com/archive/1999/01/19.html

Where's the best place on Earth to find meteorites?
Meteors fall into Earth's atmosphere over every spot on the planet. However, there is one place that's far better than anywhere else to find the meteorites that make it all the way to the ground. That place is a windswept field of ice near the edge of the East Antarctic Ice Sheet. There, near the Allan Hills (which are actually the tips of huge mountains buried in the ice) one can find hundreds of meteorites lying around on the surface of the ice. There are tons of them. How did they get there? Meteorites fall into the snow all across Antarctica, then sink down until they hit a layer of solid ice. That ice flows slowly across the continent, to certain places where ice-buried mountains push it up. The upthrust ice evaporates in the dry Antarctic wind, leaving the meteorites exposed. More about Antarctic Meteorites and the people who hunt for them http://wwwdsa.uqac.uquebec.ca/~mhiggins/MIAC/antarc.htm http://www-curator.jsc.nasa.gov/curator/antmet/antmet.htm http://www.cwru.edu/affil/ansmet/ NASA has a robot that searches for Antarctic meteorites http://www.frc.ri.cmu.edu/projects/meteorobot/

Where were maps deliberately published with errors?
In the old Soviet Union, maps were often made with deliberat errors. Towns, rivers, and roads were placed incorrectly, and entire towns would be missing in some versions. Moscow street maps were especially inaccurate. The false maps were part of a plan to prevent foreigners and even the Soviet citizens from knowing the details of the geography of the Soviet Union. It was thought that this would increase security, but actually it made the whole country less efficient. The false maps were part of a much broader concept called Maskirovka, a word that has meanings relating to misdirection, camouflage, misinformation, and diversion. According to some experts, the Maskirovka philosophy is still very much a part of Russian strategy, and influences many parts of the society. Maskirovska deeply influenced Soviet military strategy http://www.airpower.maxwell.af.mil/airchronicles/apj/apj88/smith.html The first world map was inaccurate for different reasons http://features.LearningKingdom.com/fact/archive/1999/01/26.html

What kind of fax machine makes 3-dimensional objects?
A normal fax machine receives a coded message over the phone and translates it into a pattern of black and white dots on a page of paper. But there's a kind of fax machine that builds a three- dimensional object instead of a picture on paper. Charles Hull invented the process, called stereolithography or solid imaging, in 1984. More than just a 3-D fax machine, it's a whole new way of making things. Descriptions of objects are stored as computer data files, which can be given physical form in a solid imaging machine. A solid imaging machine creates an object by scanning a light beam across the surface of a liquid. The liquid solidifies wherever the light touches it. The newly created solid is lowered slightly, and another scan adds another layer of solid material. An object of almost any shape can be created. More about stereolithography http://www.aaroflex.com/stereo.htm http://www.caip.rutgers.edu/~kbhiggin/VDF/SLA.html Description and diagram of a solid imaging machine http://www.cs.hut.fi/~ado/rp/subsection3_6_1.html Why is it so important? http://reality.sculptors.com/stereolithography.html

Why do some kinds of sloths need to bask in the sun?
Sloths are among the slowest-moving mammals in the world. Part of the reason for this slowness is their diet: lots of green leaves. Green leaves are not a very energy-rich diet, and they can be quite difficult to digest. All sloths have intestinal bacteria that help them break down the leaves they eat. Even so, it can take up to 100 hours to digest a full meal. Some kinds of sloth have developed a habit that helps further: they bask in the sun, warming themselves up so the bacteria can do a better job on the leaves. If a sun-loving sloth is not able to find a sunny place, the bacteria can't do a good enough job on the leaves it eats, and the poor animal may starve to death even while eating plenty of food. Sloths on Barro Colorado Island, Panama http://www.csam.montclair.edu/ceterms/mammals/sloths.html Why do three-toed sloths have green hair? http://features.LearningKingdom.com/fact/archive/1997/06/10.html

What is the oldest board game in the world?
The oldest board game still played today is Go, a game with only a few very simple rules but such complex strategy that many players dedicate their entire lives to its mastery. The game is played on a plain grid of black lines, where two players alternate placing black and white "stones" on the intersections, simultaneously trying to capture one another's stones, avoid capture of their own stones, and surround territory. The aesthetics of the game are as important as the game itself. The best boards are thick, solid pieces of yellow hardwood; the best stones are made from slate and clamshells; the stones are kept in elegant wooden bowls. Although most people play with much less expensive boards and stones, it is possible to spend many thousands of dollars on a nice Go set. A good introduction to the game http://www.well.com/user/mmcadams/gointro.html More Go resources http://www.cwi.nl/people/jansteen/go/go.html

What asteroid is shaped like a bone?
An asteroid called 216 Kleopatra that orbits between Mars and Jupiter has been imaged by radar, creating a detailed model of its shape. It is shaped like a giant dog bone as big as New Jersey. Because of its optical color and because it reflects radar waves very well, astronomers believe that 216 Kleopatra is made mostly out of metals like nickel or iron. Large parts of it are composed of loose, metal-rich rubble, although there may be larger solid chunks in the center. How did 216 Kleopatra get to be so strangely shaped? It may have been sculpted by one or more tremendous collisions billions of years ago. With two lobes connected by a thin neck, 216 Kleopatra is the most unusually shaped object found in the Solar System so far. A computer image of 216 Kleopatra's shape http://antwrp.gsfc.nasa.gov/apod/ap000510.html Early images revealed hints of Kleopatra's strange shape http://sc6.sc.eso.org/~fmarchis/Science/Kleopatra/ More Cool Facts about asteroids http://features.LearningKingdom.com/fact/archive/1998/06/01.html http://features.LearningKingdom.com/fact/archive/1998/08/04.html http://features.LearningKingdom.com/fact/archive/1999/03/25.html

What's the active ingredient in catnip?
Something about catnip (Nepeta cataria) is very appealing for cats. Crush a few leaves of this herb in the mint family, and many cats will rub their faces on it, roll around on it, and dig their claws into it. Why do they do this? Like many predatory mammals, cats are very sensitive to smells. Humans, who do not generally share this kind of deep olfactory experience, may not fully understand what it is like for a kitty to smell catnip. For years, catnip's effects were mysterious. Then the active ingredient was discovered, a complex molecule called nepetalactone. Researchers suspect that nepetalactone resembles some of the molecules cats respond to during the hunt. Maybe it smells like "super prey," triggering an extreme response. However it smells, catnip is harmless fun for your pet. More about catnip and your pet http://www.thevet.com/catnipresp.htm More about nepetalactone (and more catnip links) http://chemistry.about.com/education/chemistry/library/weekly/aa083099a.htm What's the only cat that always lives in the desert? http://features.LearningKingdom.com/fact/archive/1998/04/08.html

What kind of glowing cloud floats sixty miles high?
When an unusually large meteor of a certain kind streaks into Earth's atmosphere, it might leave behind a glowing trail that can last several minutes before it dissipates. These "glowworms" shine mysteriously by their own light as high-altitude winds slowly tear them apart. Scientists who want to study the glowing trails are forced to wait for a meteor of the right kind. Fortunately, the annual Leonid meteor shower often includes such meteors, and in 1998 and 1999 laser beams from the ground probed several of the glowing trails. No one knows why some meteor trails glow for several minutes. The light may come from the recombination of atoms with electrons ripped away by the energy of the passing fireball, or possibly from chemical reactions within the cloud of vapor. A Leonid glowworm being probed by a laser beam http://antwrp.gsfc.nasa.gov/apod/ap000428.html One Leonid glowworm was called "Puff Daddy" http://www.de.afrl.af.mil/PA/RELEASES/1999/99-78.html More glowworm trails http://www.sor.plk.af.mil/Leonids.htm How fast do meteors move? http://features.LearningKingdom.com/fact/archive/1998/03/11.html

What is the "green flash" of the sun?
You may have heard stories about the "green flash" that can sometimes be seen as the Sun sets, if conditions are just right. Is it real, or just a myth? As the Sun descends toward the horizon, its color changes from yellow- white at noon to deep shades of orange and red, because the blue and green colors are scattered by the air. But there's still some green light in the mixture, and that is the key to the green flash. If the air is very clear, there's a point when the topmost rays of the Sun's light can shine brilliant emerald green. This green flash, which lasts only a few seconds, happens when the Sun's light is split into its component colors, the same way that a prism creates a rainbow. The shortest wavelengths (green at sunset) appear at the top of the Sun just as it drops below the horizon. Photographs of the Sun showing green flashes: http://www.isc.tamu.edu/~astro/research/sandiego.html http://antwrp.gsfc.nasa.gov/apod/ap000507.html More about the green flash http://stardate.utexas.edu/radio/sd_search.taf?f=detail&id=19980711 http://mintaka.sdsu.edu/GF/ How hot is the core of the Sun? http://features.LearningKingdom.com/fact/archive/1999/05/04.html What are sunspots? http://features.LearningKingdom.com/fact/archive/1998/09/24.html

Where is the world's largest airport?
You might think that the world's largest airport would be near one of the world's largest cities. Actually, the largest airport in the world (measured by total land area) is Saudi Arabia's King Khalid International Airport, which covers 87 square miles (225 square km). Located near Saudi Arabia's capitol, Riyadh, it was opened in 1983 and like Riyadh it is surrounded by hundreds of miles of empty desert. When it was first opened, King Khalid Airport (air traffic code: RUH) had the capacity to handle 7.5 million passengers a year. Projections then claimed that by the year 2000 that capacity would be doubled. It is one of the most modern airports in the Middle East, with a high-tech industrial park nearby that specializes in the aviation industry. What Saudi Arabia says about the airport http://www.saudinf.com/main/a8124.htm Basic facts about Saudi Arabia http://www.us-saudi-business.org/basic.htm A guide to the world's airports http://www.d-l-s.freeserve.co.uk/aircraft_and_airports.htm

How many "primary smells" are there?
Our subtle senses of color and taste are the result of various combinations of a small number of "primary" senses. There are the sweet, sour, bitter, salty, and umami of taste, and the red, green, and blue of color. Are there "primary smells" too? The sense of smell is far more complex than taste, but it too has primary senses. There are a lot more of them: several hundred, according to recent studies. Smell receptor cells come in many varieties, each of which responds to a small group of similar molecules. When you smell the complex aroma of baking cookies or the subtle tang of seaweed decaying on the beach, your brain is recognizing a very complicated message composed of hundreds of distinct signals. Change just a few of those signals by a tiny amount, and you might realize that the cookies are beginning to burn. How smell works http://www.sfn.org/briefings/smell.html A school project on smell (for teachers and students): http://faculty.washington.edu/chudler/chems.html A very smelly fruit http://features.LearningKingdom.com/fact/archive/2000/03/06.html The five primary tastes, including umami http://features.LearningKingdom.com/fact/archive/1999/01/04.html

Who invented the singing telegram?
A Western Union executive named George P. Oslin invented the singing telegram in the depths of the Great Depression. It was on July 28, 1933 that he asked an operator named Lucille Lipps to deliver a singing message to the great vocal star, Rudy Vallee. It was Rudy's birthday. Oslin, who was public relations director for Western Union, was criticized for making a laughingstock of the company. But as the US emerged from the depression, singing telegrams became more popular. Today in the age of email and long-distance telephone calls, singing telegrams are falling into obscurity. The only ones available from Western Union now are those sung to the tune of "Happy Birthday to You" -- the same song sung by Lucille Lipps in 1933. More about George Oslin and singing telegrams http://www.wps.com/dead-media/notes/14/147.html Oslin wrote a book called "The Story Of Telecommunications" http://amacord.com/telecom/ The history of Western Union http://members.tripod.com/morse_telegraph_club/comphis.htm How were messages sent before the electric telegraph was invented? http://features.LearningKingdom.com/fact/archive/2000/02/21.html

What year was missing ten days in October?
In 1582 Pope Gregory decreed that October's dates would skip from the fourth to the fifteenth, dropping ten days. The reason for this seemingly strange act had to do with the calendar system that was in use at the time. Unlike our current system, the old Julian calendar had a leap year every four years without exception. Because a year is really a fraction shorter than 365.25 days, tiny errors began to accumulate. By the time of Pope Gregory's decree, the calendar was adjusted by ten days compared to Earth's solar year. When he issued his decree, Gregory also fixed the leap year rule, so that leap years do not occur on century years (divisible by 100), unless the year is also divisible by 400. There is one other exception: years divisible by 4000 are not leap years. For example, 1900 was not a leap year, but 2000 is one. More about calendar adjustments and leap years http://www.digtl.com/leapyr.htm A suggestion for an even more accurate system http://www.greenheart.com/billh/leapyear.html What clock measures time in thousands of years? http://features.LearningKingdom.com/fact/archive/1998/12/18.html What's the most accurate clock in the world? http://features.LearningKingdom.com/fact/archive/2000/02/02.html

How do forest workers in Bengal protect against tigers?
The mangrove forests of the Sunderbans in West Bengal, India are home to deadly Bengal tigers, which are easily able to kill a human. Yet hunters, woodcutters, and honey gatherers often enter these swampy forests. How do they protect themselves? Each person who enters the Sunderbans wears a rubber mask of a human face on the back of his or her head. The belief is that the tiger will only attack its prey from behind. If it can see your face, it will not attack. The masks, issued by the government, are part of a larger program that includes the placement of electrified human dummies and the construction of freshwater ponds to keep the tigers out of the rivers, where people are often attacked. The Sunderbans is one of the few places where the tiger population is growing http://www.csmonitor.com/durable/1998/02/25/intl/intl.1.html More about Bengal tigers http://the-planet.net/co/animal/Btiger.html A reptilian tiger-equivalent that lived 260 million years ago http://features.LearningKingdom.com/fact/archive/1999/02/10.html

When was money first used?
If money is a physical object traded as standard tokens of value, then the first money was being used by 9,000 BC in the middle east and Africa, where cattle and measures of grain were exchanged as standard units for other items like food, raw materials, land, or wives. Among the first objects specially created as value tokens were coils of cast silver "ring money" that were used in Mesopotamia as early as 2,500 BC. These bits of silver were weighed in shekels, the world's first standard units of measure. The first coins were circulated in Lydia in 687 BC, according to Herodotus. Although the Chinese may have used paper money for a short time in the same century, the first western use of paper money was not until the 18th century, by the French. How did the invention of money change civilization? http://www.discover.com/oct_issue/cradle.html Coins and money systems in ancient Greece and Rome http://www.columbia.edu/~rcc20/romans/money.html Mesopotamia's standard units of weight and measure http://features.LearningKingdom.com/fact/archive/1999/01/29.html

What kind of zoo keeps its animals in liquid nitrogen?
All around the world, zoos are busy creating frozen collections of tissue samples from hundreds of species of life, including animals, plants, and other life forms. These "frozen zoos" could be vital resources in the future if any of these species become extinct. With the current rate of species extinction between 1,000 and 10,000 times the natural "background" level and still increasing, it is critical that we preserve the genetic information of as many life forms as possible. While we do not yet have the ability to create cloned animals or plants from many of the samples, it seems likely that in the future we will. If we can get past the immediate crisis, then the frozen zoos may provide the DNA we will need to reconstruct many of the missing species and perhaps rebuild some of the vanished ecosystems. Betsy Dresser is one scientist who is building a frozen zoo http://future.newsday.com/4/fmon0412.htm http://www.usnews.com/usnews/issue/000103/dresser.htm http://www.the-scientist.library.upenn.edu/yr1991/may/eisner_p1_910527.html Zoos have changed a lot since the first menageries http://features.LearningKingdom.com/fact/archive/2000/05/11.html

Where was the first geothermal electricity generated?
In 1904, the world's first geothermal electric generator went into operation at Italy's Larderello Hot Springs. Using pressurized steam from underground, the original plant was able to generate about 250 kilowatts, barely enough to run one modern home. Electricity was not the first use of the hot springs at Larderello. Hot water was used in 1777,and starting in 1790 brine from the springs was processed to extract boric acid and other compounds of boron. Today, Larderello has 300 wells as deep as 700 meters (2300 feet), which yield ultra-hot water at 235 degrees Celsius (455 F) and a pressure of 30 atmospheres. The site now produces 300-400 megawatts of power. More about geothermal energy and how it is used http://geothermal.marin.org/pwrheat.html http://wwwphys.murdoch.edu.au/acre/refiles/geo/text.html Another place where geothermal energy is important http://features.LearningKingdom.com/fact/archive/1997/05/02.html Why do we use alternating current (AC) electricity? http://features.LearningKingdom.com/fact/archive/1999/10/14.html

How loud are a bat's echolocation calls?
Although we can't hear the sounds a bat makes as it flies around in the dark because they are too high-pitched, they are still sounds and instruments can measure their loudness. The loudest bats are those that usually fly in wide-open spaces. These include the common brown bat, which can be seen on summer evenings in temperate regions, flying above the treetops. These are "shouters" whose calls are sometimes as loud as a household smoke alarm (about 110 decibels). Even at that intensity, their ultrasonic calls fade out at about 50 feet because air does not carry ultrasound very well. Quieter bats are those that fly in tighter spaces like between the trees in a forest. These "whispering" bats have calls measuring about 60 decibels, the loudness of human conversation. A bat's sense of echolocation can be almost as accurate as our vision http://www.batcon.org/seedark.html More than a million bats visit Austin, Texas every year http://features.LearningKingdom.com/fact/archive/1998/01/08.html

What's the world's most precious spice?
The golden-orange spice called saffron is the most expensive spice in the world. Although it can sell for as much as $8 per gram, it is available for as little as $36 for an ounce ($1.29 per gram) if you know where to look. Why is it so expensive? It is produced from one tiny part (the stigma) of the flowers of a certain kind of purple crocus that blooms only once each year in the fall. The yield per acre is very small, since it takes thousands of flowers to make a handful of spice. The bright red stigmas must be removed from the flowers in the early morning, when they are still fresh. Saffron is a versatile spice that can be used in many ways, ranging from the traditional rice dishes to sweet baked goods. There's even potent saffron liquor from northern Greece. One person's love affair with saffron http://www.saffroninfo.com/harvest3.html What is saffron? (from a merchant) http://www.saffron.com/what.html

Why do moths have ears?
In the course of evolution, hearing ability has arisen several times in moths. Some moths have special membranes near the base of their wings, while others have sound detecting organs on their legs, heads, or bodies. The first hearing moths appeared about 50 million years ago, right around the time bats first began using echolocation. This is no coincidence. Moth ears are especially sensitive to the ultrasonic sounds bats emit, and their behavior helps them escape the agile predators. When a flying moth hears the sharp squeak of an approaching bat, it responds by suddenly veering off in an unpredictable direction. It might dive straight down, scoot sideways, or suddenly spin in a loop. To catch the moth, the bat has to react very quickly. The fascinating "evolutionary arms race" between bats and moths: http://galliform.bhs.mq.edu.au/psy_105/neuroethology.html A spider that specializes in catching moths http://features.LearningKingdom.com/fact/archive/1998/07/29.html A moth that has been domesticated http://features.LearningKingdom.com/fact/archive/2000/05/22.html



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