It seemed impossible to answer. And that is why David Feldman was interested. Why do women open their mouths while putting on mascara? Friends didn't know. Neither did the ladies at the makeup counters at department stores. Then he got a tip to call a New York plastic surgeon.
"He said, 'When I give patients an eyelid job, I have them open their mouths as wide as possible because it stretches the skin,' " Feldman says. "Women do this for a completely logical reason, even though they don't know it."
Mr. Feldman didn't stop there. Next he moved on to find out why dogs have wet noses, why flyswatters have holes, and if penguins have knees. The answers to these questions and many more are now in 10 books, including "Do Elephants Jump?" (HarperCollins, $19.95), due to be released Friday.
"I think everybody thinks about these things, but normal people let them go by," says Feldman, a middle-aged man with a charming habit of smiling after nearly every sentence.
Indeed, Feldman rarely lets anything curious slip by.
Walking down a grocery aisle, he can't help wondering why frosted and unfrosted cornflakes have the same amount of calories; at a diner, he'll question why it is so difficult to open a package of crackers. For months he'll ponder if elephants can jump.
His curiosity isn't "on" all the time, he admits. "To be honest," Feldman says, "I turn it off when I don't have to" be looking for ideas to fill books. "But I can't help it. I've always been curious."
Feldman's hyperactive curiosity began as a child, he says, when he started wondering why some television shows and rock bands were more popular than others.
"He always liked to ask a million questions," says Phil Feldman, David's brother. "I remember being annoyed. You'd think you'd answered the question, then he'd take it a level deeper."
Feldman went on to study popular culture at Grinnell College in Iowa, and later took a job in TV programming at NBC.
His career plans changed, however, one day at a Manhattan grocery store. Perusing the aisles for a low-calorie cereal, Feldman discovered that Kellogg's Sugar Frosted Flakes and Kellogg's Corn Flakes both had 110 calories per ounce. Later he went to a diner and watched a man struggle to open a package of saltine crackers.
"If we can put a man on the moon," Feldman says, "why can't they make a cracker package you can open with your hands?" That's when the word "imponderable" popped into his head, he says.
Feldman began writing down his "imponderables" (the word means "something that cannot be answered conclusively") in a notebook. To answer them, he'd start at the New York Public Library. There he'd consult the Encyclopedia of Associations and the Thomas Register of American Manufacturers.
The multivolume Thomas Register is "gigantic, like this big," Feldman says, stretching his arms wide. "Let's say you have a question about pencils.... You go to the Thomas Register, and it'll give you a list of every pencilmaker in the country."
Feldman is often skeptical of the first answers he receives from the companies, associations, and professionals he contacts. In trying to answer the imponderable of why dogs have wet noses, for example, he was told by several veterinarians that it was because dogs don't have sweat glands.
Feldman says that sounded too simple. So he contacted two canine respiratory specialists. They told him they were not entirely certain of the answer, either.
"The higher you go," Feldman says, "often they're not as sure. One thing kids need to know is: Don't assume it's right, even if it's in a book."
Most of the time, Feldman says his sources respond kindly to his inquiries. They are usually in small industries and do not regularly get calls from writers.
"I often say, 'Have you heard of Ann Landers?' " referring to the late advice columnist. " 'You know how she helps people with their problems? I help them with their meaningless problems.' "
Sometimes, the people he calls seem confused. To find out why some barbecues are circular and others rectangular, he called a well-known maker of round grills. "That's confidential information," he was told. Later he received a letter from the company's lawyer. That struck Feldman as "downright weird."
Feldman says he receives thousands of letters and e-mails from people asking him to solve their imponderables. If he knows the answer, he says he writes back. If he doesn't, the letters go into a database of thousands of questions he draws on for his books.
Craig Kirkland of New Haven, Conn., first wrote to Feldman 13 years ago after reading an "Imponderables" book in high school. Feldman replied with a hand-written note. Later, one of Mr. Kirkland's imponderables (Why is decaffeinated coffee served in orange-rimmed coffee pots?) appeared in Feldman's "When Did Wild Poodles Roam the Earth?" (1992).
"What I particularly liked was Dave's style," Kirkland says. "Dave is able to present his information while also instilling it with a great deal of humor."
Among the other imponderables Feldman has solved: Why are certain parts of our bodies more ticklish than others? Why do doughnuts have holes? and Why do fire stations have Dalmatians?
It can take months of research to solve an imponderable, Feldman says. Calling people and discussing the answers is his favorite part of the process. When he gets conflicting answers, he either writes what he has or tosses the question back into a database of unsolved questions.
"I have to judge ... how much I trust the expertness of someone who is answering," Feldman says. "Sometimes it's really easy." But the imponderables that are toughest to answer are the most satisfying, he says.
David Feldman says he looks for questions that have to do with everyday life, but that most people don't have the time or determination to figure out. Here is a sample of Feldman's best imponderables:
Why don't we see baby pigeons?
Pigeons' nests are perched on building ledges that are difficult to see. Once the young pigeons are old enough to fly down to the street, they are already full-size.
When do fish sleep?
Fish don't have eyelids. When it gets dark, they slow down and might appear to be sleeping. But they dart away as soon as they feel the vibrations from the approach of a potential predator.
How do they keep raisins from falling to the bottom of cereal boxes?
Raisins are not added to the box until it's half-filled with cereal. The cereal creates a barrier, preventing the raisins from falling to the bottom. As the cereal is shipped and consumed, the raisins distribute themselves throughout the box.
Why do doughnuts have holes?
The hot oil used to cook doughnuts couldn't easily reach the center of a solid doughnut. Without the hole, the middle of the doughnut might be ... doughy. "The hole helps even out the process," Feldman says.
He may have been answering life's riddles for nearly 20 years, but David Feldman has a few imponderables he's never been able to solve.
For example, Mr. Feldman says he has been trying to find out why snooze alarms on clock radios are set for nine minutes ever since his second book was published in 1988.
"It's just ridiculous," Feldman says. "It's not like I devote an hour a day to it, but every time I start a new book, I say, 'Let's try this one again,' and nothing ever happens."
Other imponderables that are still imponderable to Feldman:
• Why don't we sneeze when we're asleep?
• Why are salad forks shorter than dinner forks?
• Why does a nod of the head mean "yes" and a shake mean "no"?
Feldman's advice to anyone trying to answer them: Don't believe the first answer you are given - especially if it's the conventional wisdom.
"When I get three people who make sense [and] agree on something, that's a good sign," Feldman says. He also recommends calling experts rather than searching online or in books.
If you think you've solved an imponderable - or have one you'd like Feldman to try to answer - you're invited to e-mail Feldman at: firstname.lastname@example.org