What's the 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. More about leatherback turtles http://www.turtles.org/leatherd.htm http://www.nature.ca/notebooks/english/leathert.htm Another Cool Fact about a turtle http://www.cool-fact.com/archive/1997/09/04.html
What kind of robot can "see" by sonar?
"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. More about Rodolph http://www.yale.edu/opa/ybc/v26.n5.news.03.html More Cool Facts about robots http://www.cool-fact.com/archive/1998/03/20.html http://www.cool-fact.com/archive/1998/12/01.html http://www.cool-fact.com/archive/1998/12/22.html http://www.cool-fact.com/archive/1999/02/02.html
How much cosmic dust falls to Earth?
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. Cosmic dust is collected in the stratosphere by NASA http://www-curator.jsc.nasa.gov/curator/dust/dust.htm Another Cool Fact about things that fall from space http://www.cool-fact.com/archive/1997/03/20.html
What kind of crystals do not have a repeating structure?
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. Introduction to quasicrystals http://www.cmp.caltech.edu/~lifshitz/quasicrystals.html A more technical introduction http://www.nirim.go.jp/~weber/qc.html More Cool Facts about crystals http://www.cool-fact.com/archive/1998/01/05.html http://www.cool-fact.com/archive/1998/03/31.html http://www.cool-fact.com/archive/1998/07/30.html http://www.cool-fact.com/archive/1998/12/15.html
What fire has burned for 2,000 years?
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. Underground fires are a problem for miners, and an environmental risk http://www.penweb.org/issues/mining/tribrev/swfires.html http://www.penweb.org/issues/mining/tribrev/centralia.html http://www.itc.nl/~coalfire/
What cat lives in the snowy heights of the Himalayas?
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. More about snow leopards http://www.halcyon.com/mongolia/snowleopard.html http://www.wwf.org/species/snlep_fs.htm Today's Cool Word is leopard http://www.cool-word.com/archive/1999/04/14.html More Cool Facts about the Tibetan Plateau http://www.cool-fact.com/archive/1999/04/01.html http://www.cool-fact.com/archive/1997/11/06.html
Who created the first working 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. Baird's work was based on ideas of other creative inventors http://www.dfm.dircon.co.uk/tvhist1.htm Baird's mechanical TV was only the first of his many inventions http://www.digitalcentury.com/encyclo/update/baird.html http://www.cinemedia.net/SFCV-RMIT-Annex/rnaughton/BAIRD_HILLS.html
What is the most distant object that can be seen without a telescope?
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. If viewed with 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. Andromeda Galaxy is one of the most beautiful sights in the sky http://antwrp.gsfc.nasa.gov/apod/ap950724.html Two Cool Facts about the Milky Way Galaxy http://www.cool-fact.com/archive/1997/09/08.html http://www.cool-fact.com/archive/1999/01/12.htm
How can the ocean's temperature be measured with sound?
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. More about acoustic thermometry http://atocdb.ucsd.edu/Explorations_f98/Atoc.html Some people are concerned that ATOC may be troublesome to marine mammals http://www.voyagepub.com/stories/0996mar2.htm More Cool Facts about temperature http://www.cool-fact.com/archive/1997/10/30.html http://www.cool-fact.com/archive/1998/05/11.html
When was the first pottery made?
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. More about Jomon pottery and early Japanese history: http://www.rekihaku.ac.jp/e_zyoosetu/no1/ http://pages.nyu.edu/~sw4/jomon.html A quick tour of Japanese art history http://fmc.utm.edu/~dmcbeth/asiart/japan.htm
What kind of shrimp can break glass with its claws?
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. Underwater photographers can lose their lenses if they get too close http://home.mem.net/~zipper/mantis.htm http://www.divernet.com/biolog/manti297.htm
How does air temperature vary with altitude?
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. The structure of Earth's atmosphere http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/ATM_CHEM/atmospheric_structure.html As hot as it is, the thermosphere does not "feel" hot http://spider.ipac.caltech.edu/staff/waw/mad/mad14.html More Cool Facts about the Earth's atmosphere http://www.cool-fact.com/archive/1997/07/10.html
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What parts of your cells are "guest 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. Mitochondria are the "power houses" of human cells http://www.mdausa.org/publications/Quest/q55mitochondria.html More about the many different parts of cells, from a college course http://esg-www.mit.edu:8001/esgbio/cb/org/organelles.html
How can nature help humans deal with hazardous waste water?
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. More about constructed wetlands http://www.usouthal.edu/usa/civileng/wetlands.htm http://ag.arizona.edu/AZWATER/arroyo/094wet.html http://www.waterrecycling.com/constwetlands.htm
How can spacecraft sail on sunlight?
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. More about solar sail spacecraft http://www.ugcs.caltech.edu/~diedrich/solarsails/ http://www.ec-lille.fr/~u3p/ More Cool Facts about new space propulsion systems http://www.cool-fact.com/archive/1999/02/12.html http://www.cool-fact.com/archive/1998/12/08.html
What kind of insect flies toward forest fires?
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. Melanophila also attacks trees that have been weakened by disease http://www.forestry.ubc.ca/fetch21/FRST308/lab7/melanophila_drummondi/flathead.html
What kind of tree lives with its roots in salt water?
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. Florida's mangrove forests are a great biological treasure http://www.floridaplants.com/horticulture/mangrove.htm
What sort of laws were there in the earliest cities?
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. More about Hammurabi and his laws http://www.yale.edu/lawweb/avalon/hammenu.htm http://members.xoom.com/PMartin/hammurabicodeoflaw.htm
What kind of motorboat has no propeller?
Instead of a propeller, the penguin flipper boat uses a pair of paddles at the back that look and move like the flippers of a penguin. The twelve-foot boat, invented by James Czarnowski, is called "Proteus." The penguin flipper boat uses 17% less power than an equivalent propeller-driven boat, and produces far less turbulence and noise. It might be good for use in nature preserves, where propellers might cause too much disturbance of the ecosystem. For inspiration Czarnowski watched the penguins swimming underwater at Boston's New England Aquarium. He mapped out the way they moved their flippers, and designed a mechanical system to mimic it, moving the paddles side to side while turning them at the same time. More about the penguin boat http://web.mit.edu/towtank/www/flapfoil/index.html Cool Facts about penguins http://www.cool-fact.com/archive/1997/08/22.html http://www.cool-fact.com/archive/1997/11/14.html http://www.cool-fact.com/archive/1999/03/31.html
What are the conditions at the center of the sun?
The temperature at the sun's core is thought to be about 15 million degrees C (27 million degrees F), by far the hottest temperature in the solar system. The material there is plasma, a gas of electrons and atomic nuclei, compressed to about ten times the density of lead. The sun's nuclear fusion reactions only happen in the innermost core, where the pressure and temperature are high enough to fuse hydrogen into helium. The energy generated there starts out as high energy gamma rays and x-rays, not as visible light. The energy released by fusion makes its way out from the core through several layers, colliding with the dense plasma all the way. It takes about a million years for each photon (energy "particle") to reach the surface of the sun. By that time the energy has been divided and down- shifted by collisions, until it's mostly visible light. More about the sun's interior http://wwwssl.msfc.nasa.gov/ssl/pad/solar/interior.htm More Cool Facts about the sun http://www.cool-fact.com/archive/1997/11/19.html http://www.cool-fact.com/archive/1998/09/24.html
What kind of insect walks on the ocean?
The only insects known to live directly on the surface of the open ocean are the sea skaters (genus Halobates), close relatives of the water striders that walk on the surfaces of ponds and streams. Like the water striders, sea skaters have waxy hairs on their feet that repel water, allowing them to stand on the surface tension. They are delicate insects with long legs and highly coordinated reflexes, enabling them to move around with great precision on the surface of the waves. Sea skaters are predators, able to sense the presence of small swimming creatures just under the surface and spear them with their sharp mouthparts. They also eat insects that fall onto the water surface. Of course, they are themselves prey to any fish that is fast enough to snatch them. Water striders and sea skaters are "true bugs" in the family Gerridae http://www.insect-world.com/main/gerromorpha.html http://www.cnr.berkeley.edu/explore/Taxa/Heteroptera/Gerridae/FamilyGerridaePage.htm
What animal has the largest eyes?
The eyes of the giant squid (Architeuthis dux) can be up to 25 centimeters (ten inches) across, about the size of a volleyball. Those large, sensitive eyes are useful in the dark waters where the giant squid lives, 200-700 meters (660-2,300 feet) below the surface of the ocean. Giant squids are among the world's most mysterious megafauna (large animals). So far, no live specimen has been captured. They live in deep oceans all around the world, along with at least ten other species of very large squid. Like other cephalopods such as octopi, giant squids have complex, well-developed brains. They are ferocious predators, but they are also pursued and eaten by large cetaceans such as sperm whales, some of which show the obvious scars of giant squid sucker disks. An expedition in search of the giant squid http://partners.si.edu/squiddev/Default.html The American Museum of Natural History has just acquired a new specimen: http://www.amnh.org/science/biodiversity/giant_squid/ More Cool Facts about squids http://www.cool-fact.com/archive/1997/05/20.html http://www.cool-fact.com/archive/1997/06/26.html http://www.cool-fact.com/archive/1998/11/19.html
What mineral can contain 46 different elements?
Mineralogists at the Canadian Museum of Nature and the University of Copenhagen were surprised when they began analyzing specimens of eudialyte, a mineral that is an important source of the rare, expensive metal zirconium. After finding inconsistencies in x-ray diffraction patterns, which are often used to study the crystal structures of minerals, they conducted further studies that revealed as many as 46 different chemical elements could be part of eudialyte's crystal structure. Eudialyte's unusually complex structure includes many places where rare elements might be incorporated. Understanding that structure might make the refining of zirconium and other rare elements more practical. As a result of this study, several new varieties of eudialyte have been discovered. More about eudialyte, including a picture of its crystal structure http://www.nature.ca/English/treasures/trsite/trmineral/tr2/tr2.html More Cool Facts about minerals http://www.cool-fact.com/archive/1998/04/09.html http://www.cool-fact.com/archive/1998/07/17.html http://www.cool-fact.com/archive/1998/07/30.html http://www.cool-fact.com/archive/1999/03/01.html
What kind of life forms live inside glass shells?
Diatoms (Bacillariophyta) are tiny, floating, one-celled life forms that build intricate shells out of silicon dioxide, the compound found in glass, sand, and rock crystal. Their minute shells are beautiful structures with very tiny details, and there are thousands of varieties. The shell of a diatom has two halves called frustules. One of the frustules is slightly larger than the other, and they fit together tightly. Most diatom frustules are decorated with hundreds of tiny holes, grooves, or bumps, arranged in regular patterns. Diatoms have been around for hundreds of millions of years. They are very important to Earth's ecology, producing about a quarter of all the free oxygen in the atmosphere. Although they may seem like plants, they have recently been assigned to a new kingdom, the Chromista, along with some other related life forms. More about diatoms http://botany.miningco.com/library/weekly/aa082697.htm http://www.comet.net/gek/phytoc.htm http://www.microscopy-uk.org.uk/mag/art97b/diatom.html The Chromista includes some strangely diverse life forms http://www.ucmp.berkeley.edu/chromista/chromista.html
What's the deepest known cave?
Lechuguilla Cave, near Carlsbad, New Mexico, goes down at least 1,571 feet (479 meters), making it the deepest known cave on Earth. It is only partially explored, but already more than 97 miles (156 kilometers) of passages have been mapped. The immense maze of rooms and passages that forms the Lechuguilla system was discovered in 1986. A group of spelunkers (cave explorers) decided to investigate a desert pit called Misery Hole. When they reached the bottom, they dug down and found a chamber from which a howling wind emerged, a sign of a large cave system. Unlike most limestone caves that were formed by water dissolving the rock from above, Lechuguilla was formed by hydrogen sulfide gas coming up from underneath. The gas was released from an underground oil pocket because of geological shifts. Take a tour of Lechuguilla http://www.extremescience.com/LechuguillaCave.htm More Cool Facts about caves http://www.cool-fact.com/archive/1997/07/29.html http://www.cool-fact.com/archive/1997/08/18.html http://www.cool-fact.com/archive/1997/08/20.html http://www.cool-fact.com/archive/1997/08/28.html http://www.cool-fact.com/archive/1998/09/03.html
What new kinds of planets are being discovered?
Astronomers are finding more and more planets orbiting stars outside the solar system. Many of these "extrasolar planets" are quite strange. One group is the "hot Jupiters." These are super-giant planets several times the size of Jupiter, in very close orbits around their stars. Some of them are in orbits much smaller than Mercury's orbit around our Sun. There are also planets that have very eccentric orbits, swinging in close to their star and then coasting out very far away. There are many other odd planets, including at least two that orbit around neutron stars. As more strange, new planets are discovered, astronomers are scrambling to come up with explanations for how they came to be. Existing theories of solar system formation simply do not cover such oddities. There are many new theories. More about extrasolar planets http://astron.berkeley.edu/~gmarcy/sciam.html Another Cool Fact about extrasolar planets http://www.cool-fact.com/archive/1998/09/16.html Cool Facts about neutron stars http://www.cool-fact.com/archive/1998/02/05.html http://www.cool-fact.com/archive/1998/06/04.html http://www.cool-fact.com/archive/1998/08/25.html
What great sea evaporated and was refilled?
Millions of years ago, the land at what is now the Straits of Gibraltar rose up, blocking off the connection between the Mediterranean Sea and the Atlantic Ocean. Slowly the sun did its work, and the Mediterranean Sea evaporated, leaving behind vast layers of salt and a few shallow salt lakes. Geological changes continued at their slow pace. One day about five million years ago, the Atlantic Ocean finally burst through again, and a torrent of seawater began refilling the basin. Centuries later, the Mediterranean Sea was full again. A very similar event happened around 5650 BC at the mouth of what is now the Black Sea. Once a freshwater lake, that body of water is now much larger, containing salt water that flooded in through the Bosporus. Some historians relate the Black Sea deluge to Noah's Flood http://www.sciam.com/1999/0299issue/0299wonders.html The fascinating history of the Rock of Gibraltar http://www.nexus-pt.com/news/esc2port/gibhis.htm More Cool Facts about oceans and seas http://www.cool-fact.com/archive/1997/03/16.html http://www.cool-fact.com/archive/1997/07/11.html http://www.cool-fact.com/archive/1998/10/08.html http://www.cool-fact.com/archive/1998/10/20.html http://www.cool-fact.com/archive/1998/10/28.html
What kind of rocket has a spinning motor and lands like a helicopter?
The Roton Rotary Rocket not only has blades at the top, like the blades of a helicopter, it also has a rocket motor at the bottom that spins. It's a design for a fully reusable, manned, Earth-to-orbit spacecraft that only uses one stage. The spinning rocket motor is more efficient than an ordinary rocket because no complicated, heavy fuel pumps are needed. The spin of the rocket motor causes the fuel to flow out toward the nozzles, where it mixes and burns. On re-entry, the helicopter-like blades at the top are deployed. At first they spin passively, slowing down the craft as it enters the atmosphere. But later, small rockets at the tips of the blades are ignited, and the rotary rocket becomes able to hover and make a delicately controlled soft landing, tail first. The Roton Rocket is expected to fly in 2000 http://www.rotaryrocket.com/ More about new designs for reusable spacecraft http://www.discovery.com/stories/science/entrepreneurs/rockets.html More Cool Facts about new kinds of spacecraft http://www.cool-fact.com/archive/1998/12/08.html http://www.cool-fact.com/archive/1999/02/12.html
What kind of bird can untie knots?
Ravens and their smaller cousins, crows, are among the smartest birds. Not only can they untie knots, they can also unzip zippers and unfasten velcro. Ravens have a highly sophisticated language with hundreds of distinct sounds. They are highly social birds, who mate for life and play complex games with each other. Ravens are the largest perching birds. They can have up to a four- foot (1.2 meter) wingspan, and they are powerful fliers with tremendous endurance. They live all around the northern hemisphere, from tropical jungles to the snowy wastes of the high Arctic. Their high intelligence and endurance give them the ability to adapt to many conditions and eat a wide variety of foods. For years ravens were thought of as pests in the United States. They were seen as thieves of eggs and small barnyard animals, and shot on sight. Their numbers declined steadily until recently, but now they are recovering across the western and northern states, learning to coexist with the humans who were once their main enemy. Crows and ravens have an enthusiastic following among humans http://www.shades-of-night.com/aviary/ http://www.well.com/user/crow/corvids.html Another Cool Fact about ravens http://www.cool-fact.com/archive/1997/03/02.html
What are the most accurate clocks?
The most accurate clocks in the world are atomic clocks, which use the vibrations of atoms to keep track of the time. They are so accurate that they would gain or lose only one second in three million years. Most clocks use mechanical or electronic oscillators (vibrators) to count out a fixed number of "ticks" per second. The oscillators are not all exactly the same, so ordinary clocks must be periodically reset. Atomic clocks use the absolutely stable vibrations of atoms (usually cesium atoms). Since every atom of the same type vibrates exactly the same number of times each second, atomic clocks are extremely accurate. The largest error in the best atomic clocks comes from slight variations in how the atoms are moving as their vibrations are measured. New atomic clocks will slow the atoms down almost to a stop, making them up to 10,000 times more accurate than today's models. More about atomic clocks http://www.nextstep.com/stepback/cycle10/123/atomic.html http://iptsg.epfl.ch/aps/mar96/vpr/J5.02.html More Cool Facts about clocks and time http://www.cool-fact.com/archive/1998/09/25.html http://www.cool-fact.com/archive/1998/12/18.html http://www.cool-fact.com/archive/1998/01/28.html http://www.cool-fact.com/archive/1999/01/12.html
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