How does a boomerang return to the person who threw it? asks Rajendra Singh, of Jaipur, India.
Baseballs don’t. Footballs don’t. Even frisbees don’t. But boomerangs do–come back, that is.
If boomerangs were a new toy on the market–just invented–there would probably be a boomerang craze going on. Everyone would rush out and stand in long lines to be the first on the block to have one.
But in fact, boomerangs are very old. People were playing with the come-back toys thousands of years ago.
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What causes quicksand, and where is it found? asks Edward McClarty, of San Francisco.
Unless you’re on Gilligan’s Island, roiling pits of dangerous quicksand aren’t found around every bend in the trail. There are a lot of myths about quicksand, among them:
Quicksand sucks you down like a vacuum cleaner. In fact, quicksand doesn’t pull you down any more than a swimming pool does. Quicksand is more buoyant than water, so it’s actually easier to float in quicksand than in a swimming pool.
Quicksand is a bottomless pit. Most patches of quicksand are a few inches to a few feet deep.
Quicksand is always made of sand. In addition to sand, clay, swamps, and silt can all become what scientists call “quick.”
By now you might have guessed that what we call “quicksand” is more of a phenomenon than a thing. The phenomenon is “quickness,” the way water flowing through sand, clay, or other material lifts and separates its small grains.
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Where do bugs like flies go when the weather gets cold, so they can appear like magic when it gets warm again? asks Jonathan Conway, of Syosset, NY.
Unfortunately, many insects don’t survive the freezing cold of winter. Others, however, have come up with clever schemes to hang on until spring.
For example, cluster flies sometimes hide out in the nooks and crannies of a warm house or barn over the winter, venturing out to fly around only on milder winter afternoons.
Mosquitoes, like bears, hibernate through the winter cold. Adult mosquitoes look for dark, damp, hiding places–like your basement–to spend their winter vacation. In spring, the females slowly become active, flying around looking for food (fresh blood). Once they’ve had their blood meal, they’re ready to lay eggs, and hatch a new crop to plague us during the summer.
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How come you can still see a star that disappeared many years ago? asks Rebecca Herskovits, a student in Yeshiva Har Torah, Bayside, NY.
Human beings are fascinated with the idea of a time machine–a way to shake off the bonds of the present and travel into the past or the future. No one has ever made a time machine, and scientists say it may be impossible–the very nature of the universe may prevent such “travel.”
But the sheer size of the universe means that light carries information from the distant past into our present, showing us what the cosmos looked like long, long ago and far, far away. When we look into the night sky–or even at our own Sun–we are seeing the past, not the present.
Here’s how it works. Light, the speediest thing we know of, zips along at 186,000 miles a second in the vacuum of space. Light leaves the surface of a star or planet, travels a great distance, and finally enters our eyes. We see the star or planet as it was–not as it is.
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How do cats see in the dark? asks Fenny Samuel, a student in Kerala, India.
Domestic cats evolved to do much of their hunting at night. Nowadays, that may mean locating the bowl of cat chow in a dark kitchen (and your cat could as easily do that by smell). But in a power failure, while you are still groping for candles, your cat might be strolling through the living room–without crashing into the coffee table.
In your eyes or your cat’s, the pupil reacts to changing light by changing size. The pupil gets bigger to let more light in, tinier in bright sunlight. Behind the pupil, a rubbery membrane called the lens focuses the light as it passes through. Continuing on through the eye’s inner chamber, the light strikes a screen called the retina. The retina’s nerve cells, called rods and cones, send signals to the brain through the optic nerve, and the brain registers an image.
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How can birds sit on electrical wires and not get electrocuted? asks Jonathan Sanchez, a student in Lynbrook, NY.
High above the ground, electrical and telephone poles and their connecting wires must seem made for birds, like artificial trees with limbs that stretch on forever. Sometimes a hundred birds will be stretched out along a wire, in a kind of high-tension convention.
How come a bird on a wire doesn’t get shocked? When the bird perches on a live wire, her body becomes charged–for the moment, it’s at the same voltage as the wire. But no current flows into her body. A body is a poor conductor compared to copper wire, so there’s no reason for electrons to take a detour through the bird. More importantly, electrons current flow from a region of high voltage to one of low voltage. The drifting current, in effect, ignores the bird.
But if a bird (or a power line worker) accidentally touches an electrical “ground” while in contact with the high-voltage wire, she completes an electrical circuit. A ground is a region of approximately zero voltage. The earth, and anything touching it that can conduct current, is the ground.
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