Q&A, 2001

A. Absolutely. Even if your dog caught you climbing out of a bathtub filled with perfume and mud, it would recognize you without a hitch, says Naomie Poran, who studies the science of smell at the University of North Carolina. A dog's smelling ability is so powerful and refined that it can sort through thousands of odors and zero in on the owners' special scent—or on any scent the dog is especially interested in, Poran says.

But what if 1) you look different than usual, and 2) your dog sees you but can't pick up your scent—say if you're coated with mud and separated from your dog by a pane of glass? Then your dog wont recognize you so easily, Poran told me. She's noticed that if her two dogs, Tessa, an English setter, and Oz, a border collie, look out the window and see her wearing something out of the ordinary, they react to her as if she's a stranger (grrrr). "Usually I wear slacks, so when I have on a dress, they get confused." That's because a dog's vision isn't very keen—nowhere near as sharp as most humans'.

But a dog's sense of smell is much better than ours. "The neat thing about dogs is that their sense of smell is about 300 times more sensitive than humans'," I was told by Marie Suthers-McCabe, who teaches about human-pet interactions at Virginia Polytechnic Institute. Her own dog, a black Labrador retriever named Star, amazes her with its sniffing ability. "Star is blind and partially deaf, but she follows me around the backyard without any problems. She gets around great using just her sense of smell," she told me.

This was Rosanne's first answer for the Q&A column. She usually answers questions about animals, the human body, and anything funny or gross, while Robert tackles "straighter" questions about things that aren't alive. Sometimes they do switch topics just for fun, however.

Q. Why do you sleep, and what makes you go to sleep?

—K.C. and Kaitlyn

I asked Craig Heller, a biology professor at Stanford University who spends most of his waking hours studying sleep. He told me that you sleep so your brain can recover from all the work it does while you're awake. "Most of your body can get rest by just relaxing. But the brain can't really rest except through sleep," Heller said. When you sleep, he explained, your brain is shut off from the outside world. That allows it to be a lot less active than when you're awake. And you are a lot less active, too— paralyzed, in fact. That's a good thing, because otherwise you'd respond to the weird signals your brain fires off during the night. "You'd try to act out your dreams. That could get you in a lot of trouble," Heller said.

While you sleep, chemical reactions refresh your brain. What these reactions are is one of the big questions sleep biologists are trying to answer. As for what puts you to sleep, scientists think that it's a chemical called adenosine, which your brain makes when it is active. Adenosine builds up in your brain cells all day long. When enough of it has accumulated, it acts like a sleeping potion and makes you conk out.

—Rosanne

Q. Who wrote the first book, before any other book was written?

—Andy P.

I sent your question to two experts on ancient writing: Professors Eric Leichty, of the University of Pennsylvania, and Piotr Michalowski, of the University of Michigan. The earliest books we know about, they said, were written by people called the Sumerians, who lived in what is now Iraq. The Sumerians wrote on clay tablets or on wooden writing boards covered with wax. They used a kind of writing that we call cuneiform, which they invented around 3400 B.C.—about a hundred years before Egyptians started writing hieroglyphs.

Cuneiform

Because the Sumerians almost never signed or dated their tablets, no one knows which of their early books came first or who wrote what. The first author whose name we know was Enheduana, a daughter of a Sumerian king. Enheduana is best known today for long poems she wrote around 3250 B.C. praising a goddess called Inanna. (Sample: "My Queen! All enemy lands bow down at the sound of your roar! / Under your fearsome radiance, your terrible glare and storm, the people / Turned their steps toward you in mute dread." Grrl power goes way back.)

—Robert

Q. Why does chocolate make people feel good?

—Jessie G., age 14

One reason, of course, is that it tastes good. But some scientists think that chocolate's appeal goes beyond simple yumminess. One of them is Emmanuelle di Tomaso at Massachusetts General Hospital, who has studied how some of the chemicals in chocolate affect the brain. Chocolate contains at least two chemicals that help improve your mood, as well as caffeine, which perks you up. Though she doesn't have proof yet, di Tomaso thinks chocolate contains enough of these chemicals to make people feel better than they did before they ate it. "As a result of eating chocolate, people will feel a little bit better—just a little bit, though, not jumping for joy or anything like that," said di Tomaso.

—Rosanne

I e-mailed your question to Harry Ferguson, an astronomer at the Space Telescope Science Institute in Baltimore, Maryland. Astronomers can't count all the stars in the universe, he explained. Instead, they count the stars in small parts of the universe and use that information to figure out how many there must be all together. "We estimate that the universe contains about 100 billion galaxies, and the typical galaxy has roughly 10 billion stars, so that makes 1000 billion billion stars total in the universe," Ferguson told me. That's a one with 21 zeroes after it—1,000,000,000,000,000,000,000—or, as scientists write it for short, 10²¹ stars.

Scientists can tell what stars are made of by studying their light, the way they vibrate, and the chemicals that make up other objects in space, such as meteors and the Earth. It turns out that the sun and most other stars are about 77 percent hydrogen, 21 percent helium, and only 2 percent other elements.

March 2001

September 2001

October 2001