Do you feel like a fraud when your kids ask why the grass is green? (Because it contains chlorophyll-ring a bell?-a green pigment plants use to make their food.) Behold this parental compendium of uncommon knowledge, which explains a few mysteries of the universe.
By Julia Edelstein
What Causes Hiccups?
Hiccups usually occur when the stomach rubs against and irritates the diaphragm, a muscle at the bottom of the rib cage. An irritated diaphragm pulls back fast, forcing air sharply into the lungs, says Norman H. Edelman, M.D., the chief medical officer for the American Lung Association. When the air hits your voice box, you hiccup. This happens repeatedly until the irritation stops.
Why is Yawning Contagious?
Two Italian scientists studied this puzzling phenomenon just last year: They believe that contagious yawning shows empathy. (When you yawn after your mom does, maybe you're saying, "I hear you. I'm sleepy, too.") In fact, we're more likely to "catch" a yawn from a close friend or a family member than from an acquaintance or a stranger.
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Do Frogs Have Warts?
No. The bumps and the lumps you see on the skin of some amphibians (usually toads) are glands filled with foul-tasting poison, which protects them from hungry predators, says David Mizejewski, a naturalist at the National Wildlife Federation, in Reston, Virginia. By the way, frogs are hopping mad that they've been unfairly blamed for causing warts. Warts actually come from viruses and can be transferred only from human to human. Toadally gross.
Why Doesn't Gum Stick to My Teeth?
You know how you tend to slip on wet floors? The same thing happens to your gum when it touches your teeth, which are wet with saliva. Also, when you chew, you produce extra saliva, which makes the inside of your mouth even more moist, says Irwin Smigel, D.D.S., the president of the American Society for Dental Aesthetics.
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Why Does My Stomach Make Noise When I'm Hungry?
According to the Mayo Clinic, when you haven't eaten for a while, your brain sends a message to your stomach to get ready for some grub. That signal jump-starts the grumbling, rumbling release of acids and other digestive juices. Just the sight or the smell of food can trigger the sounds, too.
Why Can't I Tickle Myself?
When somebody tickles you and you squirm and scream, you're responding more to the surprise than to the sensation, says Ellen Marmur, M.D., the vice chair of cosmetic and dermatologic surgery at Mount Sinai Medical Center, in New York City. Since our brains can predict our own movements, we're less sensitive to them. But we're very sensitive to unexpected touches, which is why we flail around when the Tickle Monster comes calling. Scientists believe the response might date back to our cave-dwelling ancestors, who needed to be on the alert for the skittering of bugs and rodents.
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Do Fish Sleep?
Sort of. It's hard to catch some shut-eye when you can't shut your eyes. But according to the experts at the Mystic Aquarium, in Mystic, Connecticut, most fish do enter a resting period during which their metabolism slows. Some just drift aimlessly, while others nestle in coral or sand so they won't be disturbed. Even as they snooze, however, fish remain alert to potential danger, and the smallest ripple will rouse them instantly-no alarm clock necessary.
Why Do Feet Smell?
They're covered in tons of bacteria-and when bacteria excrete waste (or, in kid terms, poop), it really stinks, says Jane Andersen, M.D., a podiatrist in Chapel Hill, North Carolina. Why the feet in particular? Bacteria thrive in wet places, and our tootsies (which have a startling 250,000 sweat glands apiece) are among the body's dampest spots.
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