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These are the facts you could find on this page:
"Invisible" Jet, Ancient Plumbing, Ancient Rubber, Ancient Vending Machine, Asteroid Sizes, Atmosphere's Temperature, Best Hearing Animal, Blood Amoebas, Cellular ZIP Codes, Clocks With Hands, Constructed Wetlands, Coral Eater, Cosmic Dust, Dust from Africa, Early Code of Laws, Emperor Penguin, False Teeth, Faster than Light, Fire Loving Beetles, First Flies, First Planned Cities, First Punched Cards, First Television, First True Trees, Guests in your Cells, Half-brain Sleep, High-altitude Cat, Largest Highlands, Largest Turtle, Life without a Nucleus, Long Blood Vessels, Longest Burning Fire, Longest Neck, Martian Meteorites, Metal-tailed Wasp, Most Primitive Animal, Most Remote Island, Naked Eye Galaxy, No Tusk Elephants, Ocean's Temperature, Oil-spitting bird, Oldest Musical Score, Oldest Pottery, Opal Colors, Petrified Wood, Popping Joints, Powerful Light Microscope, Powerful Shrimp, Quasicrystals, Reverse Burning Wick, Salt Water Tree, Smallest Genome, Solar Sail, Sonar Robot, Speedy Particles, Star Systems, Stinging Nettle, Swimming Cat, Three Eyed Crustacean, Viewing Distant Planets

"Invisible" Jet
The B-2 bomber has a wing span of 172 feet (52 meters), yet its radar "signature" (apparent size on a radar screen) is as big as that of a bird. Not only that, but it makes very little sound and is difficult to see, from the ground or from the air.
The bomber's construction uses graphite composites, which trap radar waves inside the plane, and its outer surfaces contain no flat parts and no right angles, which would reflect radar.
The jet's hot exhaust is mixed with cool air before being released, foiling heat-seeking missiles. Its engines are also hidden deep inside the plane, where their noise is muffled by the structure of the aircraft. Even the plane's shape is designed to fool the eye, making it difficult to tell whether it's coming or going.
The result is an aircraft that is able to fly deep into enemy territory without detection.

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Ancient Plumbing
The palace of King Minos of Knossos in Crete featured a number of early plumbing innovations. The palace, built around 1700 BC, had tightly sealed terra cotta drain pipes, and a large underground sewer system that discharged into the river Kairatos.
Also at the palace were some of the earliest known bathtubs, made of painted terra cotta. Unlike today's tubs, these had no drains, and were filled and emptied by hand.
The palace was also home to the first known flushing toilet. It was a private chamber, walled off by gypsum panels. It was flushed by rainwater, or by cisterns poured by hand.

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Ancient Rubber
The ancient Mayans of Central America made rubber out of natural latex 3500 years before the modern process of vulcanization was invented. They played games with rubber balls and used rubber bands to attach axe heads to their handles.
The Mayans made latex, which is the sap of rubber trees (Castilla elastica), into flexible, durable rubber by mixing it with the juice of morning glory vines (Ipomoea alba). The mixture developed molecular cross-links that made the latex elastic, and removed substances that caused the rubber to turn brittle. The resulting rubber was black and bouncy, with a texture like a pencil eraser.
The Mayans used balls made out of this rubber to play a game called Ulama, something like a cross between tennis, basketball, and soccer. The game had deep religious significance.
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Ancient Vending Machine
You might think that coin operated vending machines were invented during the industrial revolution, but actually the first one was installed in ancient Greece around 215 BC.
Its inventor was a mechanical genius named Hero of Alexandria, who came up with a way to dispense holy water in return for one of the Greek coins used in those days. The heavy coin would drop onto a lever, causing a cork to be pulled out of a spigot just long enough to release a trickle of holy water.
Since then, vending machine technology has advanced quite a bit. Today's machines contain microprocessors that use sophisticated software to detect even the tiniest deviation from the expected weight and size of genuine coins.
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Asteroid Sizes
Asteroids are rocky or metallic bodies that orbit the sun, mostly between the orbits of Mars and Jupiter. There are probably more than a million of them. Most asteroids are smaller than a medium-size city, and the vast majority are just boulders or pebbles.
The largest asteroid is Ceres, which is at least 580 miles (930 kilometers) across. The mass of Ceres is just a bit more than 1/100 of the mass of the moon, and probably about one quarter of the mass of all the asteroids combined.
The second largest asteroid is Pallas, with less than half of the mass of Ceres. Vesta is the third largest, but is much brighter than Ceres or Pallas.
Are asteroids the smashed debris of an ancient planet, or are they uncombined leftovers of the time when the planets formed? Closer examination of more asteroids by upcoming robot missions may help answer the question.
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Atmosphere's Temperature
Moving away from the Earth's surface, air temperature decreases steadily to a low of around -63 degrees Celsius (-81 degrees Fahrenheit) at around 15-20 kilometers (9-12 miles). The temperature decreases because lower layers are warmed by contact with the ground, which absorbs much more solar energy than the air does.
Above that layer, the air warms to about 0 degrees C (32 degrees F), at 50 kilometers (31 miles). Air at that height is warmer because a layer of ozone molecules absorbs the sun's ultraviolet light.
Above the ozone layer is another cold layer, but then the temperature soars to over 2,000 degrees C (3632 degrees F) in the thermosphere, above about 130 kilometers (81 miles). It remains hot right out into interplanetary space.
Why is the thermosphere so hot? Because the very thin air at that height is stirred up by the solar wind, a constant sleet of high- energy particles flying out of the sun, and because the few remaining oxygen molecules absorb the sun's light.
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Best Hearing Animal
The best ears of all land animals are those of the barn owl. Even though its ears are not directly visible, it can pick up the faint sounds of a mouse walking across a log from hundreds of feet away. It can then home in on it and snatch it up in pitch darkness.
How does a barn owl hear so well? Its face, which is largely shaped by the feathers around its eyes, forms a parabolic dish shape that funnels the sound to its ears. The owl can open or close the dish by moving the feathers, to improve the reception or protect the ears from loud sounds.
Its ears are also placed asymmetrically, with one ear high up near the owl's forehead and the other lower down, about level with the bird's nostrils. This odd placement helps the bird locate the exact source of faint sounds.
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Blood Amoebas
Your body contains cells that look and act very much like amoebas. Certain kinds of leukocytes, or white blood cells, cling to the walls of arteries and veins, moving around by extending pseudopods and flowing along.
The most common white blood cells are called neutrophils. Trillions of them are created every day by the bone marrow and released into the blood. They are attracted to substances that are present at the sites of injury or infection. Once they arrive, they engulf bacteria, dead cells, and other debris.
The largest white blood cells are the macrophages, which specialize to clean up various tissues and organs. One kind of macrophage eats dead neutrophils.
There are many other kinds of white blood cells. All of them are part of the human immune system, which keeps the body free of infections.
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Cellular ZIP Codes
It's not enough for a living cell to manufacture protein molecules (the building blocks and active agents in every cell). It must also put the newly built proteins into the right places where they can do their jobs. How do new protein molecules get where they belong?
Many newly-made proteins bear molecular "tags" that are not part of the final molecule. These tags are special coded markers. Each marker directs the cell to carry the protein molecule to a specific place, much the same way that a ZIP code directs the Post Office to deliver envelopes to specific addresses. When the protein molecule arrives at its destination the tag is removed.
No one knows exactly how the molecules are carried within the cell, but biotechnology companies are already making use of the discovery by engineering plants to produce new proteins and deliver them to desired parts of their cells.
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Clocks With Hands
The first known mechanical clocks in Europe were built in the thirteenth century, but they did not have a circular dial or pointers to show the time. These primitive timekeepers had bells or other noisemakers that sounded approximately once every hour.
The first clocks with pointers (hands) were made in the fourteenth century. Those early dial clocks had only one hand, the hour hand. The idea of measuring time more accurately than that was ridiculous in those days, because the clocks were not accurate enough to make it worthwhile.
Although Jost Burgi invented the first clock with a minute hand in 1577, it was not until the invention of the pendulum-regulated clock in 1657 that a minute hand became practical, and second hands were not used until the eighteenth century.
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Constructed Wetlands
Instead of building expensive, difficult-to-maintain sewage treatment plants, some cities are now building "constructed wetlands" to treat their waste water.
Sewage and street runoff, both of which can carry high amounts of harmful chemicals as well as hazardous bacteria, are allowed to filter through artificially created swamplands, where the healthy, living ecosystem removes and detoxifies all the contaminants. By the time the water flows out of the wetlands, it is clean and pure, suitable for release into rivers, lakes, or the ocean.
The world has lost much of its wetlands ecosystems due to human activities. Now, in some places, wetlands are being recreated as an important part of the natural cycle, and a valuable resource for humans as well.
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Coral Eater
The parrotfish is a reef dweller that takes bites out of rock-hard corals, and pulverizes the stony material with its hard beak. It swallows the resulting mixture of coral sand, algae, and living coral polyps.
By breaking off chunks of coral, the parrotfish plays an important role in the coral reef ecosystem. It removes surface algae, which might otherwise completely swallow up the reef. The chewed-up coral sand passes through the fish and is released, to fall in drifts between the reefs. It slowly dissolves, and becomes available for use by growing corals.
Although the parrotfish chews up living corals, it is no threat to the coral reefs. However, overfishing of parrotfishes by humans is a threat. In some places, parrotfish are now protected from fishing, to preserve the ecological balance of the reefs.
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Cosmic Dust
Every year, about 33,000 tons (30 million kilograms) of dust falls into Earth's atmosphere and settles down to the surface of the planet. The largest of these particles would just barely be visible without a microscope, and most are far smaller.
Most of the dust comes from a belt called the zodiacal cloud, which is formed by evaporation from comets, colliding asteroids, and a few other sources. This diffuse band of dust is the cause of the "zodiacal light," a faint glow of reflected sunlight that can sometimes be seen just before dawn or after sunset, if the sky is very dark and clear.
A small amount of cosmic dust comes from outside the solar system. Although they are rare, particles of extra-solar dust are important to science because they reveal what conditions are like in interstellar space.
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Dust from Africa
Because of the strong, persistent trade winds that blow across the equatorial Atlantic Ocean, each year millions of tons of reddish-brown dust from Africa settle over Florida, sometimes forming a thin coating on cars and other surfaces. These fine dust particles make it hard for some Florida cities to meet federal clean air standards.
The dust is swept up from the Sahara Desert during dust storms. It can rise as high as 15,000 feet (4,600 meters) before it gets carried out to sea.
While the clouds of dust cross the Atlantic Ocean, most of the large particles fall out and sink into the water. But the smallest remain aloft, sometimes causing hazy skies and health problems for Floridians.
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Early Code of Laws
One of the oldest known legal systems was the Code of Hammurabi, who was the King of Babylon around 2500 BC. It was a written record of the "Sumerian Family Laws," a system of socially agreed rules and penalties that had been in common practice for hundreds of years before Hammurabi's time.
The Code described and regulated three classes of people: the amelu (patricians, nobility, and professionals), the muskinu (free commoners), and the ardu (slaves, mostly). There was a strict system of justice, with different rules for the different classes.
Hammurabi's code is a complete legal document, containing 282 specific rules. Unlike today's legal documents, it is preceded and followed by extensive invocations of the gods and recitations of the greatness of Hammurabi.

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Emperor Penguin
Emperor penguins brood their eggs by holding them on their feet. The single egg is protected from the Antarctic cold by a fold of loose skin called the brood patch.
Unlike other penguins, emperors brood their young during the cold, dark winter months. The female lays one egg, passes it to the male, then travels out to sea, where she feeds for about nine weeks. Meanwhile, the male stands still and does not eat, weathering temperatures as low as -65 degrees Fahrenheit (-54 degrees Centigrade).
When the female returns, she takes over, receiving the just-hatched chick from the hungry male, who goes out to sea. While he is gone, the chick is fed and raised by the mother penguin. By the time the sea-ice begins to break up, the penguin chick is ready to fend for itself.
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False Teeth
The Etruscans in Italy were the first people known to build and use false teeth. As early as 700 BC they were constructing ivory or bone teeth, secured with bridgework made out of gold, good enough to eat with. Such sophisticated work was not seen again until the 1800s.
In the 1700s false teeth were secured to any remaining original teeth or held in place by spring-loaded mechanisms. The latter sometimes resulted in embarrassing accidents, as sets of teeth might suddenly pop out, springing into the air. Such cumbersome dentures had to be removed during eating, since they were not designed for chewing.
Today crowns (false teeth cemented to existing teeth) and dentures are far more comfortable and practical. It is even possible to implant artificial teeth directly into the jaw.
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Faster than Light
Very radioactive elements are surrounded by a deep, blue glow when they are submerged in water. The glow, which is called Cerenkov radiation, is produced by high-energy, electrically charged particles moving faster than light.
Isn't faster than light travel impossible? The speed of light in a vacuum is an ultimate limit, but when light travels through a dense medium like water, it slows down. If a matter particle travels fast enough in such a medium, it can leave light photons behind.
Such a particle trails a "wake" of light as it penetrates the medium. The wake is similar to the shock wave that follows an airplane moving faster than sound. The faster the particle travels, the sharper (brighter) the wake becomes, and the smaller the average wavelength of light in the wake.
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Fire Loving Beetles
Most creatures flee in panic from forest fires, but one kind of beetle deliberately flies toward them. The beetle is called Melanophila, in the family Buprestidae. Its name means "lover of blackness" because it seeks charred wood.
These beetles lay their eggs on burnt wood that has recently been killed by a forest fire. They can detect fires from as far away as 20 kilometers (12 miles) by using special infrared sensillae (sensory organs) on their thorax (mid-section). They are especially attracted by the wavelengths of infrared light that correspond to the temperature of burning wood.
There are other insects that can detect infrared light, such as bloodsucking bugs that seek warm-blooded hosts. But only Melanophila is known to seek out fire.
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First Flies
The first true flies were Tanyderid crane flies that flew 225 million years ago. They looked something like today's mosquitoes, and their larvae lived in swamp mud or wet sand.
Crane flies appeared during the Triassic Period, when the first large dinosaurs were alive. Since then, the true flies (members of the order Diptera) have evolved into over 100,000 different species, on every continent. Flies are the most widespread insects on the planet.
Today, the most primitive crane flies are quite rare, but other kinds of crane flies that evolved more recently are more common. Maybe you have seen them attracted to lights at night, like huge mosquitoes with extremely long legs.
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First Planned Cities
The first system of planned public works was invented and described by the Greek Hippodamus, who redesigned his own city, Miletus, after it was destroyed by the Persians.
Hippodamus divided his cities into three sections, for religious, administrative, and commercial uses. He believed that city design was an art, and that mathematical laws of balance and proportion were important.
Hippodamus invented the concept of "city blocks." Streets were laid out in regular grids for efficiency. His cities had systems to deliver water and dispose of sewage and garbage.
New Greek cities took on his distinctive look, and existing cities were redesigned and rebuilt. Later, the Romans embraced and extended his ideas in their own ambitious public works projects.
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First Punched Cards
The first punched data cards were invented before there were any computers in the world. They were used in the Jacquard Loom, a weaving machine invented in 1801 by Joseph-Marie Jacquard.
The cards were carried in linked chains, and they controlled the weaving pattern by influencing the position of the needles. Small sensing pins detected the presence or absence of holes in the cards, and determined whether or not a needle would pick up a thread.
On seeing Jacquard's punched card system, the mathematician Charles Babbage was inspired to use the same principles to design a mechanical calculating machine, the forerunner of modern computers.
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First Television
The first television was created by John Logie Baird, a Scottish engineer. In 1924 he built a working, mechanically-scanned television out of cardboard, scrap wood, needles and string, among other materials.
Baird was a driven inventor and researcher. For years he battled ill health, poor funding, and inadequate technology. Among his greatest challenges were amplification of the tiny electrical signals from the camera's photocells and the problem of synchronizing the signals so that a recognizable image could be produced.
His first working prototype was called the "Televisor." It was a rickety assembly glued together with sealing wax, but it worked. With it, he was able to transmit the profile of a Maltese cross several yards away, to a receiver where the image was displayed.
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First True Trees
Imagine a tree shaped like a modern pine tree, but with leaves like a fern. That's something like Archaeopteris, the first true trees. These primitive but very successful plants formed extensive forests in the late Devonian Period, 370 million years ago when simple amphibians were crawling onto land.
A mature Archaeopteris was about 20 meters tall (65 feet). It had a straight, woody trunk with horizontal branches. The lowest branches were deciduous, meaning they died and fell off like those of some of today's pine trees. Unlike today's trees, Archaeopteris reproduced by shedding spores into the wind.
What made Archaeopteris so successful? It was apparently the first plant to solve the problem of supporting large branches with cross-braced woody tissues and dove-tail joints. Cross-sections of its trunks show annual growth rings just like today's trees.
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Guests in your Cells
Inside of most non-bacterial cells, there are self-reproducing parts that perform vital functions. These small parts were originally free-living cells, but they took up residence inside of other cells millions of years ago. Almost every cell in your body contains these "guest cells."
In animal and plant cells, there are tiny compartments called mitochondria that break down sugar molecules, and make the sugar's energy available to the rest of the cell. Most plant cells also harbor chloroplasts, which contain the molecular machinery to build sugar molecules, using the sun's light for energy.
Both kinds of organelles (sub-parts of a cell) reproduce themselves by copying their DNA molecules and dividing in two, just like bacteria. Like bacteria, they make their own proteins and feed on molecules from their environment (the inside of the host cell).
The arrangement has proved to be a great success, both for the host cells, which receive valuable services, and for the internal guests, which are fed and sheltered from the outer world.
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Half-brain Sleep
Many kinds of birds sleep with only one half of their brain at a time, keeping one eye open and one eye closed. They alternate which half of their brain is awake and which half is asleep.
A recent study suggests that the reason is simple: the birds are literally keeping an eye out for predators. Birds that are on the edge of the flock are much more likely to sleep this way, and the eye that is open usually faces out into the area surrounding the flock. That way predators cannot approach without being seen.
Birds are not the only animals that sleep this way. Dolphins and other sea-mammals sleep with only half their brains, but for a different reason: they need to remember to swim to the surface to get a breath of air.
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High-altitude Cat
The highest mountains in the world are habitat to the beautiful snow leopards (Panthera uncia). They live in the steep, rugged heights of the Tibetan Plateau, at altitudes up to 18,000 feet (5500 meters). There may be as many as 6,000 snow leopards remaining in the wild.
Snow leopards are strong, graceful animals, with luxurious, soft fur. Their pelt shows the typical leopard spots, shaped like rosettes or pawprints, on a white or light gray background with a slight yellowish tinge. In winter, the coat is much lighter, sometimes nearly white.
These big cats are well-adapted to their mountain habitat. They are expert jumpers and climbers, able to leap as far as 50 feet (15 meters) and land accurately on a small ledge or rock. Their long, densely furred tails help them balance.
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Largest Highlands
The Tibetan Plateau of Asia includes over two million square kilometers (780,000 square miles) of land, with an average elevation of over 5000 meters (16,400 feet), making it the largest uplifted area on Earth. It is surrounded by some of the highest, most deeply eroded mountain ranges on the planet.
14 million years ago, the plateau was even higher. It was formed about 50 million years ago by the collision of what is now India with the Eurasian continent. That slow, powerful collision pushed up the Himalayas, and lifted the Tibetan Plateau. Even today, India still moves north about five centimeters (two inches) each year.
The elevation of the plateau caused massive changes in the planetary climate, including the annual monsoon pattern, which brings seasonal floods and droughts to southeast Asia.
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Largest Turtle
The largest living species of turtle is the ocean-going leatherback. Individuals of this species can be over 2 meters (6.5 feet) long, and weigh hundreds of kilograms. The largest one ever recorded was a male weighing 916 kilograms (2,020 pounds). They can dive deeper than any other turtles.
Unlike other sea turtles, the leatherback does not have hard, bony plates on its back. Instead, it has a flexible, leathery surface. Another unique leatherback feature is their body temperature, which can be several degrees warmer than the water, giving them a distinct advantage in colder climates.
Leatherbacks are gentle creatures that like to eat jellyfish and other soft-bodied prey. Like many kinds of marine turtles, they are endangered by human fishing activities, and their critical seashore nesting places are also threatened by development and pollution.
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Life without a Nucleus
Most living cells contain a nucleus, a semi-enclosed compartment where the cell's DNA (genetic material) is stored, but bacteria just have a single, looped DNA molecule, tangled into a mass called the nucleoid.
Bacteria are the simplest life forms on Earth, and the most ancient. There are no sub-compartments inside bacterial cells, just a rich, syrupy liquid, thick with enzymes and other organic molecules.
Bacteria prosper by growing and dividing as fast as possible. Because they are small and simple, they can be fast and hardy. If the environment is good, the population of some bacteria can double in 20 minutes.
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Long Blood Vessels
If you could stretch out all of a human's blood vessels, they would be more than long enough to go around the world twice. There are over 62,000 miles (99,780 kilometers) of veins, arteries, and capillaries inside of each of us.
The thickest are as thick as a forefinger, while the thinnest, which are called capillaries, are as thin as a hair. By far the largest part of the total length is the length of the capillaries.
Arteries (which carry blood away from the heart) and veins (which carry blood back to the heart) are not just simple tubes. Their walls are lined with muscles that squeeze the blood inside, providing part of the blood pressure (the rest is provided by the heart).
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Longest Burning Fire
The oldest known continuously burning fire is an underground coal fire in New South Wales, Australia. This fire apparently started over 2,000 years ago when lightning struck a large coal seam at a point where it reached the surface of the earth. Today the fire is more than 500 feet (152 meters) underground, and is still slowly eating away at the coal
There are also long-burning coal fires in the eastern USA and in China. These fires were started by lightning or by accidents in coal mines. Some towns have been evacuated because of the danger of collapse as the underground coal seams slowly burn away.
Underground coal fires are almost impossible to put out. They burn very slowly, using up the scant oxygen in the depths, but not going out because they stay very hot. Despite their slow burn rates, underground coal fires are so extensive that they are estimated to produce 2-3% of the world's carbon dioxide output.
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Longest Neck
The longest known neck was that of the dinosaur Mamenchisaurus. Its neck could be as long as 15 meters (49 feet), seven and a half times as long as a giraffe's neck. The whole dinosaur could be as long as 26 meters (85 feet) and might weigh as much as ten metric tons.
Mamenchisaurus necks contained 19 vertebrae, more than any other known dinosaur. A giraffe's neck contains only seven vertebrae.
Memenchisaurus was related to the Diplodocus, another huge dinosaur. Both were herbivores that used their long necks to get at vegetation without having to move their bodies very much. Mamenchisaurus lived during the late Jurassic Period, about 140 million years ago.
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Martian Meteorites
Analysis of the chemical composition of some meteorites suggests that they may be pieces of the planet Mars. They were probably thrown into space during large asteroid impacts on Mars, and may have spent millions of years in orbit before falling onto the Earth.
In 1996, tiny fossil-like structures, smaller than bacteria, were discovered inside one of these Mars rocks. There is debate about whether these cylindrical capsules were once living cells.
Is there life on Mars? The presence on Earth of Martian meteorites may have given us a rare, close-up look at Martian chemistry, but we still have no certain answers about Martian life forms.
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Metal-tailed Wasp
Female parasitic ichneumon [ik-NOO-mun] wasps have egg-laying organs (ovipositors) that are reinforced with ionized manganese or zinc. They need the strength of the metal because they must bore through solid, dry wood to deposit their eggs.
When an ichneumon wasp detects that there is a beetle grub making its characteristic chewing vibrations deep within a dead tree limb, she uses her hard, sharp ovipositor to dig into the wood, sometimes as deep as three inches (7.5 cm). When she reaches the chamber where the beetle grub lives, she drops the egg.
Later, the wasp larva (having consumed the beetle grub) chews its way out through the wood using metal-reinforced jaws.
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Most Primitive Animal
In the animal kingdom, the most primitive multicellular forms are the sponges, members of the phylum Porifera. These animals have been around since just before the Cambrian Period, more than 500 million years ago. Today there are about 5,000 known species of sponges.
Sponges do not possess any distinct organs, but instead have cells of various types responsible for bodily functions. This porous mesh of cells, like a living filter, is designed to trap tiny, floating life forms. It does not move, but pulls water through itself, filtering out microscopic life forms, which its cells engulf.
The simplest sponges can spontaneously reconstruct themselves after being torn apart into individual cells. The cells move together and build a body much like the old one, but with the individual cells in different places.
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Most Remote Island
The volcanic island group of Tristan da Cunha is 1,180 miles (1,900 km) from the nearest neighbor, the island of St. Helena. It is in the South Atlantic Ocean between the southern tips of Africa and South America. There are five islands in the Tristan da Cunha archipelago, but only the main island of Tristan is inhabited.
The islands are surrounded by deep waters on all sides. Tristan's highest point is a volcano that erupted in 1961. Below the volcano is a small but fertile shelf of land, where potatoes and other crops can be grown. Around the rest of the island, high cliffs face the sea.
Tristan was discovered in 1506 by a Portuguese explorer named Tristao d'Acunha, but he was not able to land there. Permanent settlement began in 1810. Fewer than three hundred people live there today, farming potatoes and catching "crawdads" (rock lobsters) in the waters around the island.
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Naked Eye Galaxy
The nearest major galaxy outside of our own Milky Way Galaxy is the Andromeda Galaxy, which is 2.5 million light years away. Andromeda Galaxy is the most distant object that can be seen without a telescope.
Andromeda Galaxy is so faint that it can only be seen on the darkest of nights, when the air is very clear. It is a dim smudge of light in the northern sky, about as wide as the full moon. With the help of a good telescope, Andromeda can be seen as a beautiful spiral, tilted at about a 60 degree angle. It contains hundreds of billions of stars, but from this great distance they merge into a soft fuzz.
When you look at Andromeda Galaxy, you are seeing light that has been traveling across empty space for more than two million years. You are seeing Andromeda Galaxy as it was before the first humans walked on the planet Earth.
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No Tusk Elephants
Ivory poachers in Africa have provided a dramatic demonstration of how evolution works. By killing only those elephants that bear large, valuable tusks, they have allowed elephants with smaller tusks or none at all to multiply.
A survey conducted in Uganda's Queen Elizabeth National Park found that up to 30 percent of the elephants had no tusks, up from one percent in the 1930s, and many of the rest had greatly reduced tusks. The same trend is happening all over Africa, as a result of selective culling by poachers.
Elephants use their tusks to help them tear apart vegetation, dig in the ground for important dietary minerals, and to help them compete for mates. Without tusks, they are forced to rely on other sources for food and minerals, and their mating process must change.
Researchers believe that the elephant population is on the rise again after years of severe poaching.
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Ocean's Temperature
Sound travels faster in warm water than in cold water. By measuring the time it takes for sound to travel a known distance through the ocean, the average temperature of the water can be calculated with great accuracy. The technique is called acoustic thermometry of ocean climate (ATOC).
It takes sound about an hour to travel through 5,000 miles (8050 km) of ocean. On the way, it is continually refocused by the structure of warm and cold layers of water at different depths, so that the signal remains strong.
In a recent experiment, high-intensity, low-frequency sounds (fewer than 100 cycles per second) were generated at Pioneer Seamount in the Pacific Ocean, 939 meters (3081 feet) deep. Later, the sound was picked up by microphones at Hawaii, Christmas Island, and New Zealand.
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Oil-spitting bird
It is best to keep well clear of the nests of the fulmar, a seabird that is capable of spitting a foul-smelling, yellowish oil at nest intruders. The oil comes from the bird's stomach. The bird can send the oil as far as 1.5 meters (5 feet) with great accuracy.
Fulmars are related to albatrosses and petrels, in the order Procellariiformes. Most birds in this group produce stomach oil and feed it to their young, but only the fulmar spits it at intruders.
Even when they are not spitting oil, fulmars and their close relatives are malodorous creatures. Every part of the bird emits a strong, musky odor, even the eggs. Giant petrel egg shells that have been in a museum for 100 years still smell.
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Oldest Musical Score
In Ugarit (modern Ras Shamra) in Syria, an ancient tablet was discovered in the 1950s dating back to 1400 BC. The oldest known musical score, it takes the form of interval names and number signs, and even has lyrics. The text is identified as a hymn to the moon goddess Nikkal.
There is some controversy among ancient musicologists over the proper interpretation of the notes, but all agree that it is a genuine musical score. The markings were made in cuneiform (wedge-shaped symbols) in the Hurrian language, and there is an exact correspondence between the syllables of the text and the musical notes.
The find was especially interesting because it overturned conventional views of ancient music, showing that the diatonic (7-note) scale and musical harmony were in use more than a thousand years earlier than was thought.
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Oldest Pottery
The oldest known pottery (vessels and other objects made out of fired clay) was made in Japan about 12,700 years ago, at the beginning of the Jomon period of Japanese history.
Jomon means "marked with a rope," a reference to the distinctive surface patterns of some Jomon pottery. Braided rope was wrapped around the objects before they were fired, or rope-like strands of clay were added for a decorative trim.
The red-brown, unglazed pottery from this time was fired in only the most primitive ways, sometimes just an open fire. Although the methods were primitive, some Jomon pottery was very ornate, with highly sculptured rims and elaborate, detailed patterns.
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Opal Colors
Opal is one of the few gemstones that is not a crystal. Although it's made of silica (silicon dioxide), the same compound as quartz and agate, the molecules are not arranged in crystalline order.
Opal is made of millions of extremely tiny spheres of silica molecules, loosely packed together, with water molecules between them. The water content can be as high as 10%.
The colors come from the interaction between light and the silica spheres. If the spheres are almost the same size, they tend to pack into semi-regular patterns that diffract light, the same way a peacock's feather does. Each opal shows its own unique colored display.
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Petrified Wood
Petrified wood is wood that has turned to stone. Usually it is millions of years old. Often it shows beautiful colors that were not present in the original wood. How does wood turn to stone?
When wood dies it begins decaying immediately. To become petrified it must be quickly covered by a layer of volcanic ash, mud, or other material that excludes oxygen, thus preventing it from decaying.
If conditions are right, the organic part of the wood dissolves slowly, and at the same time minerals replace the organic matter, duplicating its structure exactly. The mineral replacement can be silica, calcite, pyrite, or marcasite.
The colors are caused by impurities in the replacing mineral. The most common impurity is iron, which causes red, orange, or yellow colors. Manganese or copper can cause blue, black, or green colors.
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Popping Joints
Do a deep knee bend, and it's very likely you'll hear popping sounds coming from your knee joints. There are also popping sounds when you "crack your knuckles." What causes the popping sounds? Actually, there are two kinds of sounds.
The joints in your fingers are enclosed in capsules that contain a lubricating fluid. When the joint is moved near the end of its range, gas that is dissolved in the joint fluid suddenly comes out of solution, forming a small bubble and making the popping noise. The joint can't be "popped" again until the gas redissolves.
The knee-bending sounds are most likely made by tendons (fibers that connect muscles and bones) that snap into new positions when the joint moves under stress. This kind of popping noise can be repeated many times, because the tendons shift back and forth as the joint moves.
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Powerful Light Microscope
The light microscope that can see the smallest details is the laser scanning confocal microscope (LSCM). It's a sophisticated combination of a laser, a computer, and advanced optics.
The LSCM eliminates one of the biggest sources of optical "noise" in ordinary microscopes: light from parts of the image that are not in focus. Instead of creating the whole image all at once, a confocal microscope aims a tiny spot of light at the subject, scanning it like the beam of electrons used in a scanning electron microscope.
The result is an image that shows much smaller details than traditional light microscope images. There are other devices, like electron microscopes, which achieve much greater magnification than the LSCM. Nevertheless, LSCM images sometimes show information that is impossible to see with any other microscope.
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Powerful Shrimp
The predatory mantis shrimp catches its prey by stunning it with a sudden chop from its claws. The striking force is so great that some kinds of mantis shrimp can't be kept in ordinary aquariums, because they easily break the glass with their powerful claws.
The claws of the mantis shrimp are among the fastest-moving animal parts known. The force of impact can be almost as large as a bullet fired from a gun. Divers call mantis shrimp "thumb splitters," and there are divers who have lost fingers or thumbs to the shrimp's ferocious chop.
Mantis shrimp are voracious predators. If they are kept in a community tank with fish, all the fish will eventually be eaten by the shrimp.
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Almost all known crystals are solids formed by a repeating "unit cells": three dimensional patterns of atoms or molecules. But there's a kind of crystal that does not have repeating unit cells.
A quasicrystal is a solid made out of identical unit cells that form a non-periodic (non-repeating) pattern. Although the patterns of unit cells do not repeat, the quasicrystal still shows regular faces. Most quasicrystals show icosahedral (five-fold) symmetry, which is never seen in ordinary crystals. The first quasicrystals were discovered in 1982, and now many kinds are known.
Quasicrystals are examples of "Penrose tesselations," patterns made from identical shapes that cannot be assembled into a repeating arrangement. They are named after Roger Penrose, a mathematician who discovered the first nonperiodic patterns.
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Reverse Burning Wick
If you watch candles you might sometimes notice small extensions that grow out of the end of the wick. They are made out of amorphous carbon, a very fine powdery form of the element, and they are unbelievably fragile. Big ones can reach all the way out to the inside edge of the flame. The biggest ones are often shaped like a horn, with a flat surface facing out. The outer edges often glow red.
These extensions of the wick can temporarily increase its length by as much as three millimeters (1/10 inch). They form because the space just inside the flame is a reducing zone. Instead of oxidizing and burning, the vaporized carbon in that zone condenses onto any solid object, including the wick itself. If conditions are steady the horn-shaped growths can appear spontaneously.
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Salt Water Tree
Mangrove trees are specially adapted to live at the shores of salt water lagoons with their roots actually submerged in the salt water. They grow in tropical regions around the world. Mangroves are also called "walking trees" because of the tall, stilt-like "prop roots" that keep their branches and leaves up high, out of the water.
Salt water is challenging for flowering plants, because it interferes with the plant's ability to stay crisp and firm. Some kinds of mangroves shed extra salt by forcing it out through their leaves. Others prevent the salt from entering their roots, so they pull only fresh water into their branches and leaves.
The mangrove forest is a fascinating, unique ecosystem. The tree's roots provide shelter and attachment points for a wide variety of marine creatures, and many kinds of birds live among the branches.
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Smallest Genome
A bacterium of the genus Mycoplasma has the smallest number of genes of any known self-reproducing organism. (Some viruses have fewer genes, but they need to use another cell's DNA machinery to reproduce.)
Mycoplasma's DNA was recently sequenced (spelled out in detail). It contains only about 470 genes, meaning that Mycoplasma can make at most only 470 different kinds of proteins within its cells. Most bacteria can make thousands of kinds of proteins, and human cells can make hundreds of thousands.
Because Mycoplasma is a parasite, it can steal many important substances from its host, so it doesn't need to make the proteins that the host uses to make those substances. Over millions of years, the genes that code for those proteins have disappeared from its DNA.
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Solar Sail
For years spacecraft designers have been toying with the idea of using sunlight the way a sailboat uses the wind. Now NASA and other organizations are funding development projects for solar sail spacecraft.
A solar sail spacecraft uses the small but steady pressure of light against a huge, very thin reflective membrane. It can use the sun's light, or it might use the light of a powerful laser aimed at it from Earth. By angling the sail it can control its path across the solar system.
Light pushes on the solar sail by changing the movement of electrons in the surface. The best solar sails are mirrors that bounce the light right back the way it came. Solar sails won't be as fast as traditional spacecraft, but their sunlight energy source is free and perpetual.
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Sonar Robot
"Rodolph" (short for "robotic dolphin") is a specialized robot that can "see" detailed images using sonar. Its sonar vision is so precise that it can tell whether a coin is showing heads or tails.
The robot has electrostatic transducers that emit and receive sound waves. The receivers are mounted in movable "ears" that swivel to aim at the object being examined. The ears and emitter are mounted on a movable arm, so that the whole robot can aim in different directions. The robot's inventor, Yale professor Roman Kuc, says the next step is to give the robot a mobile body so that it can explore its environment.
Sonar vision is simpler in some ways than vision by light. Sonar images are three-dimensional, which might make them good for uses such as security devices, like a device to recognize people by the exact shape of their face.
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Speedy Particles
The fastest known matter particles are ultra-high energy cosmic rays. These are mostly atomic nuclei of various elements, which come zipping down into the Earth's atmosphere at nearly the speed of light.
Cosmic ray energies are measured in electron volts. One electron volt is the amount of energy that an electron gains when it moves across an electric field of one volt. The fastest cosmic rays can carry more than 100,000,000,000,000,000,000 (one hundred quintillion) electron volts of energy.
How much energy is that? Pick up a rock about the size of your fist, and throw it as hard as you can. This gives the rock roughly the same energy as a single cosmic ray particle
When such a super-particle crashes into the atmosphere, it explodes into an "air shower" of thousands of less energetic particles. The air shower can be detected from the ground by the faint light it emits.
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Star Systems
Most stars belong to double (binary) or multiple systems, in which two, three, or even more stars orbit around each other. Orbital periods range from hours to centuries, depending on the masses of the stars and distances between them.
The closest-orbiting binaries are called contact binaries. In these very fast-orbiting pairs, the two stars actually touch. Each member of a contact binary system is shaped like a pear, with the small end touching the other star. They may actually exchange mass at the point of contact.
There are many multiple star systems with four, five, or even more members. Clusters of stars exist, numbering in the tens or hundreds, and there are also much larger "globular clusters," which can contain hundreds of thousands of stars.
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Stinging Nettle
If you've ever brushed up against a stinging nettle plant (Urtica dioica), you know how painful the resulting welts can be. How does the nettle inflict such pain from such light contact?
Many kinds of plants have leaves or stems that are covered with thousands of tiny, sharp hairs, but those of the stinging nettle are more than just sharp. They are like tiny hypodermic syringes, pressure-loaded with a caustic solution of formic acid.
When one of the nettle's tiny needles pushes against you, it pops a tiny burst of formic acid into your skin where it quickly invades delicate cells, causing them to swell up painfully. Age-old remedies are to quickly slather the painful zone with cool mud, or to rub with the juice of dock, mint, or the nettle itself.
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Swimming Cat
Although most cats can swim if they are forced to, they generally avoid water. But tigers love the water, and are able to swim for several miles.
Throughout most of their range, tigers face extinction. But there is one place where their numbers are increasing: the swampy mangrove forests of the Sunderbans in West Bengal, India. There, the water-loving cats use the braided streams and river channels as highways, expertly navigating through the maze of mangrove thickets. Humans who hunt in the Sunderbans must remain constantly alert for marauding tigers that attack from the water -- the great predators sometimes kill people.
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Three Eyed Crustacean
The aquatic crustacean Triops (the name means "three eyes") in the subclass Branchiopoda has three eyes. It has two ordinary compound eyes, and between them a third simple eye. This is the nauplius eye, which is retained from the larval stage. Triops are also known as phyllopods or tadpole shrimp.
Triops is a very ancient life form. Fossils have been found from the Permian Period, more than 250 million years ago. In those days, primitive reptiles and amphibians walked on land, but the dinosaurs had not yet evolved.
Triops can be a pest in rice paddies, where the finger-size creatures dig in the mud. They have a shell-like cover over the front of the body, as many as 71 pairs of legs, and a forked tail.
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Viewing Distant Planets
It's about as easy to see a planet around another star as it is to see a candle flame next to a searchlight from many miles away. The star's light drowns out the planet, and the planet is lost in the glare.
By a method called nulling interferometry, astronomers can optically remove most of the light of the star, leaving the planet's light undimmed. In infrared light, in which planets are relatively bright, a planet might be visible.
The method works by using two mirrors to create one image. One mirror is adjusted so the light travels very slightly farther to make the image. Light waves from the star are canceled out, but light from the planet gets through.
Several observatories are beginning to explore the idea, and a space- based nulling interferometer is under design. If there are planets like Earth out there, we may soon be able to see some of them.

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