How Come?

Why does metal feel colder than clothing if they are both at room temperature? asks a reader.

Have you ever climbed into a cast-iron tub before it’s filled, and touched your bare back to the metal? Even in a warm room, the tub will make you flinch. Or stepped barefoot on marble tiles after walking across a carpet? Common sense tells you that the carpet and the marble are probably at the same temperature. But your bare feet, acting as a handy thermometer, tell a different story: The marble feels much cooler.

While your skin may not be the most accurate thermometer, it is sensing a real difference between materials. It all comes down to the movement of heat between one object and another.

(more…)

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.

(more…)

How come your hands get all wrinkled after they’ve been in water? asks Kelsey Steck, a student in Holtsville, NY.

While nearly everyone gets pruny fingers after a long bath, their exact cause is still a mini scientific controversy.

Part of the explanation involves how skin responds to water. While skin is a good protective covering for our bones and organs, it isn’t waterproof. In fact, skin is nourished and plumped up by water, even absorbing it from the air around us.

The skin’s outer layer, the epidermis, is attached to the thicker layer underneath, called the dermis, but there is some “give” between the two. Hair follicles in the dermis pump out sebum, an oil that protects and lubricates the skin. But the undersides of fingers and toes (as well as palms and soles) don’t have hair, and don’t have as much protective oil.

(more…)

Why do songs get stuck in your head? asks a reader.

It could be the pop song they played on the radio from morning until evening (”I’m gonna soak up the sun…”). It could be the jingle from a commercial you saw last night (”Break me off a piece of that Kit-Kat bar…”). Or it could be the boat ride you went on at Disney World (”It’s a small world after all….”). Whatever the trigger, you’ve got a snippet of music playing over and over in your mind. And it’s driving you a little crazy.

Like yawning, catchy tunes– especially those with words– seem to be contagious. Just mention a song like “Dancing Queen” (or nearly any Abba tune, for that matter), and someone within hearing distance will get it stuck in their head. Others can’t hear the words “My Sharona” without enduring hours of relentless repetition, thanks to The Knack.

(more…)

How does ice cream give you brain freeze? asks Anthony Pena, a student in Woodside, NY.Ice cream, milkshakes, snow cones, frozen Cokes—if icy concoctions cause a stabbing or searing pain across your forehead, you’re not alone: Some 40 to 80 percent of people occasionally get “brain freeze” after eating or drinking something frigid. While your brain doesn’t really freeze, studies show that the temperature in your head does drop when you eat something very cold over a few minutes.

Up to 93 percent of migraine sufferers say they also get ice cream headaches. But even the normally headache-free often suffer a brain freeze attack at the local Baskin-Robbins. The pain usually peaks in a minute, and then quickly fades. Theories abound about what, exactly, causes the stabbing pain. Some say the headache is a referred pain from iced nerves in the palate and throat. Others say that blood vessels in the mouth and throat, constricted by the cold, cause blood vessels in the rest of the head to expand, triggering a headache.

However, many have noted that they don’t have to be eating anything to get brain freeze. A faceful of snow during a winter snowball fight, a blast of icy wind on an exposed forehead, or a slap in the face by a cold ocean wave can produce the same brief, excruciating pain as chugging a milkshake.

(more…)

How come some cereals make a popping sound when you pour on milk? And why do we get white spots on our fingernails? asks Karen Perez, via email.

While Rice Krispies may be the noisiest cereal, other puffed cereals may also snap, crackle and pop when doused with ice-cold milk. Just as corn is popped into popcorn, rice, wheat, and other grains can be puffed up into fluffier versions of themselves. In the case of puffed rice, cereal makers oven-toast the rice, which has been conditioned with water. As the water turns to steam, rice kernels puff out like microwaved popcorn.

Unlike the compact, hard walls of an uncooked rice kernel, the walls of puffed rice are stretched very thin, making each kernel quite fragile. When cold milk is poured on, the shock causes the walls to crack like a thin glass crystal. As the milk is (unevenly) absorbed by the puffed rice grains, the snapping, crackling and popping sounds come from the fracturing of the walls and the escape of air bubbles trapped inside the kernels.

(more…)