How Come?

How do dogs smell things we can’t? asks Olivia Minogue, a student in Sayville, NY.

Sniff sniff sniff. You can actually see a dog’s nose hard at work, picking up a scent wafting through the air, following the invisible trail a rabbit left in the yard, or investigating your pants leg for evidence of a secret meeting with a cat.

No one knows for sure how much more scent-sensitive dogs are than humans: A thousand times? Ten thousand? But what is known is that a dog’s nose has many more odor receptors, and an olfactory (smell) center that takes up much more room in the brain.

Human beings have about 5 million odor receptors, while dogs, depending on the breed, may have more than 220 million. The small human nose devotes only a postage stamp-sized area to odor receptors. The average dog nose has a mucous-y scent receptor area which, if spread out, would cover a Kleenex tissue. A dog’s nose—moist on the outside, as well as the inside—acts as a magnet to scent molecules in the air and on the ground.

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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 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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Which came first, the chicken or the egg? asks Jessica Bolz, a student in Melville, NY.Chicken or egg? Like a hall of mirrors at the carnival, each attempt at an answer just leads to another question. If the chicken came first, then didn’t it hatch from an egg? And if the egg came first, wasn’t it laid by a chicken? It’s one of those questions that seem unanswerable.

Scientists agree on where chickens came from: In a sense, human beings invented them, just like they invented cows and pigs and other domesticated animals on Old MacDonald’s Farm.

If chickens were interested in tracing their family trees, they would need to bone up on some DNA research done in Japan. Every chicken that ever lived can trace its ancestors, say researchers, to a particular subspecies of Red Jungle Fowl in Thailand.

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Why do elephants have trunks? asks J. Navarrete, a student in Woodside, NY.Imagine life with a trunk: Sniff a friend’s sandwich, then grab it with your nose. Reach for something on a high shelf without standing on a chair. Swim across a pool underwater, using your long nose as a snorkel.

There are no bones in an elephant’s trunk, making it as supple as a garden hose. A trunk has more than 40,000 muscles and tendons, and its tip is covered with nerve endings. In addition, there are one or two “fingers” on the tip to grasp small objects. Like a monkey’s tail, a trunk is “prehensile,” and can be wrapped like a rope around an object such as a branch. Unlike a monkey’s trail, an elephant’s trunk can weigh 400 lb. and measure 7 feet long.

All of this makes a trunk flexible (it can hoist a log), strong (the log can weigh more than 300 lb.) and precise (it can pick up a penny lying flat on the floor).

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