Archive for the ‘nature’ Category
How does dry ice go from gas to solid without becoming a liquid? asks Deidre Hocevar, a student in Brookville, NY.
Dry ice is frozen carbon dioxide, the gas that make soda pop bubbly. Like other substances, carbon dioxide (CO2) can also be a liquid or a solid. At normal air pressure, water is a liquid at room temperature, turning to a gas (steam) when heated to 212 degrees F and into a solid (ice) when its temperature drops to 32 F. But to at 32 F, carbon dioxide remains a floaty gas. A block of dry ice has a temperature of about -109 F.
Dry ice gets its name from its peculiar behavior: Instead of melting into a puddle on the floor, it disappears into a cloud of gas. The scientific term for this process is “sublimation.”
But carbon dioxide can and does exist in liquid form. To turn carbon dioxide into a liquid requires a big squeeze–at room temperature, a pressure of about 30 atmospheres. Many fire extinguishers contain liquid carbon dioxide, held under just such high pressure. And in 2006, scientists discovered a shallow lake of carbon dioxide hidden under the floor of the East China Sea.
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Why does the moon change color in the fall? asks Alex Dickinson, a student in Holtsville, NY.
It just wouldn’t be fall without a huge Halloween moon glowing orange at the horizon, rising above a spooky landscape of black tree limbs and piled-up leaves.
We call the moons of autumn harvest moons, but the official Harvest Moon rose on September 26th. The Harvest Moon is the full moon closest to the autumnal equinox, which fell on September 23rd this year. The Hravest Moon was probably named by farmers. Long before there were huge, gas-powered harvesters with blinding headlights, there was the bright fall moon, lighting the fields as the work of crop-gathering stretched into the night.
The romantic image of the autumn moon even inspired a famous song: “Shine On Harvest Moon,” written more than 100 years ago, remained popular for much of the 20th century. (For a clip of comedic actors Laurel and Hardy performing the song, visit
www.hamienet.com/midi12542_Shine-on-Harvest-Moon.html. )
The moon is a rocky gray-and-brown ball, lit up by brilliant sunlight. But the color we on Earth see depends on where the moon is located in the sky. No matter what the time of year, as the moon first peeks over the horizon, it may appear yellow, orange, or nearly red. Gradually, as the Earth turns eastward and the moon rises higher in the sky, the color pales to white.
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Why are hurricanes named after people, and in a certain order? ask Melissa Vallance and Kelli Day, students in Holtsville, NY.
While a tornado would have skipped to the next county and disappeared before you could call it “Ralph,” hurricanes take their sweet time building up their winds, moving towards coastlines and back out to sea at a stately pace. So it’s important to identify these big storms for pilots, ships, and people living in a hurricane’s path.
In the U.S. before the 1950s, hurricanes were identified by latitude and longitude, a system that became confusing when there was more than one tropical cyclone brewing at a time. In the early 50s, the U.S. decided to name storms using the Army/Navy phonetic alphabet, devised for World War II military communications: Able, Baker, Charlie, etc. So in 1952, the news reported on Hurricane Dog, Hurricane Easy, and Hurricane Fox. (If the tropical storm season had been busier, coast-dwellers might have been threatened by Hurricanes How, Item, Love, Sugar, Uncle, X-ray, and Zebra.)
Human beings have a long history of personifying nature (as in Thor, the Norse god of thunder), so using human names for big storms makes sense. Hurricanes that hit the West Indies in the 19th and early 20th centuries were named after saints. And in the 1940s, weather forecasters often gave hurricanes women’s names, like World War 2 fliers naming their fighter planes.
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Why does a penny at the bottom of a glass of water sometimes look like it’s floating on the surface? asks a reader.
Tricks of light and water are all around us. Gaze at a goldfish through the curved wall of its bowl: The fish looks both bigger and at a different depth than it appears when we look down through the open top. And if the fish decides to hang out on the bottom of the bowl, you may see a fishy mirage, floating on the surface.
And then there’s the drinking-straw-in-the-glass illusion. Put a straight straw in a glass of water, and voila: Instant bendy straw. The fact that a straw appears bent or broken is caused by something that really is bent: light.
Light moving from thin air into solid glass slows (and the light wave bends) as it passes into this denser material. It bends again when it travels out of glass and into water. Reflecting off objects underwater, the light travels back through the water and glass, re-emerging in the open air. At each junction, it has bent a bit more. By the time it reaches your eyes, the light is seriously off course. So the part of an object that is submerged in water, like a drinking straw, appears to have moved seriously out of place.
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Why do things made of rubber bounce? asks Khiana Lowe, a student at Long Island Lutheran Middle and High School in Brookville, NY.
If you’ve ever tried dribbling a wooden ball, or attempted to shoot a piece of string across the room, you know there’s something different about rubber. Rubber, whether natural or manmade, is very elastic. An elastic material is one that can be stretched to several times its own length without breaking – and then snap back to its original size.
Bouncy is just another word for highly elastic. And rubber is very, very bouncy. Natural rubber is made of long, flexible chains of carbon atoms, connected here and there to hydrogen atoms, coiled up into a tangled mass. In plastic, another material whose molecules are arranged in long chains, the chains are rigid. But rubber’s chains can twist and flex. When a piece of rubber stretches, the molecular chains uncoil; when the rubber is released, the chains retract, curling back into place.
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Why do leaves change color in the fall? asks Patricia Brown, of New York City.
Autumn’s cool days are trimmed with deep blue skies and golden light, and brilliant leaves of yellow, orange and red. Leaves changing color in the fall are a tree’s way of preparing for long winter, rather like we put up storm windows and pull warm clothes and blankets out of storage.
In summer, the leaves on trees like pin oaks and sugar maples are green because they are chock-full of the green pigment chlorophyll.
Trees need sunlight to produce chlorophyll. In turn, chlorophyll uses sunlight’s energy to split water (H2O) into hydrogen and oxygen. Meanwhile, leaves also absorb carbon dioxide gas from the air. The end products of leaf chemistry: carbohydrates (homemade plant food for the tree), and oxygen, released into the air (the gas we need to breathe). The whole process is called photosynthesis.
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