Q:Why does it always seem brighter and quieter outside right after it snows?
—Eileen Graumlich, Santa Fe, New Mexico
A:Freshly fallen snow is second only to quartz in its reflective properties. Each individual snowflake is a six-sided crystal that acts like a microscopic discoball, reflecting 90 percent of the incoming solar radiation, 70 percent more than the same patch of bare ground (which is why it's wise to lather up with sunscreen on a sunny powder day). Fluffy new snow is also filled with billions of air pockets. While a hard, flat surface like a frozen lake reflects and amplifies sound waves, a fresh, porous snowfield absorbs sound waves like a sponge absorbs water, causing the wave to lose amplitude. But a snowfall's silent glow doesn't last long. As more flakes fall, the crystals underneath are compressed, broken, and melted into grains that pack closely together. The rounded flakes, with less surface area to reflect light, lose brilliance, and since the snowpack is much denser, sound waves skim past it unhampered.
Q:Why can't a life-raft castaway drink seawater to survive? My friend insists you can train yourself to tolerate it.
—Katherine Pass, Culver City, California
A: Salt, which facilitates virtually every bodily function, is essential—in moderation. The World Health Federation defines potable drinking water as containing no more than 500 parts per million dissolved salt. However, downing several glasses of seawater (35,000 parts per million) will kick off a nasty chain reaction powered by osmosis, an inexorablephenomenon in which a semipermeable membrane (such as the stomach lining, cell walls, or blood vessels) separates two different solutions—in this case, one that is very salty water and the other that is only slightly salty—but the water travels across the membrane until the two concentrations equalize. A stomach full of Pacific Ocean pulls water away from the blood to dilute its salt concentration, causing the salt concentration in the blood to increase, which in turn pulls water from the body's cells to dilute the blood. The kidneys work overtime filtering salt out of the blood, but ultimately, after about three days, they fail. The body overdoses on sodium and becomes extremely dehydrated, which leads to seizures, irregular heart rhythms, brain shrinkage, and eventually coma. You can train your body to avoid this dire scenario about as well as you can train oil and water to mix.
Q:Does any other species spend 18 years raising its offspring?
—Rex Linville, Wye Mills, Maryland
A:Humans get the parental-endurance award for feeding and sheltering their young into their mid- to late teens, but there are two notable contenders in the wild world of kid-rearing: The South American discus fish secretes protein-rich mucus over its body to ensure that its babies, who nibble on the stuff, stay close for several months, roughly one-tenth of its three-year existence. And African elephants, with a life span of up to 70 years, the largest and longest-living (apart from humans) land mammal, deserve honorable mention. When the 200-pound Loxodonta africana newborn finally arrives after a 22 to 24 month gestation, the mother gives it milk and teaches it how to pull grass with its trunk and eat it. Even when the young are weaned from their mothers at age five or six years, they aren't yet full-fledged adults. Adolescent males join a roaming bachelor herd and don't mate until they're anywhere from 15 to 20 years old. Females remain with the female-only herd, helping other mothers care for their newborns, and usually don't begin procreating until around 17—the same age their human counterparts are choosing gowns for their senior proms.
Q:I've come across an assertion that the weight of water backed up behind dams and stored in reservoirs has changed the degree of the tilt of the Earth's axis. Can this be true?
—Rick Sylvester, Squaw Valley, California
A:Yes and no. The world's dams and reservoirs hold a total of ten trillion tons of water, the largest percentage of it in Canada and Russia. This has shifted the collective mass of the world's water closer to the North Pole than it would be if it were flowing freely. This redistribution of mass, explains Benjamin Fong Chao, a geophysicist at NASA's Goddard Space Flight Center, has increased the speed of the earth's rotation enough to shorten the length of a day by .02 millionths of a second over the past 40 years. "It's the same as an ice-skater putting her arms up over her head to spin faster," says Chao. Because Russia has built even more dams than Canada over the past 50 years, Earth's center of mass has shifted ever so slightly toward Russia. This has caused the axis to tilt a fraction of a degree away from the weight and the North Pole to move 27.3 inches in the general direction of Hawaii. (Imagine Chao's ice-skater with a one-pound weight in her left hand—the extra mass makes her imaginary axis tilt an inch or two to the right to keep equilibrium.) The scale of those changes is pretty small, partly thanks to other forces that happen to be canceling out the dam effect, in particular "postglacial rebound," the gradual rise of landmasses after the glaciers weighing them down have melted. All told, in the last 100 years the North Pole has tilted 32.8 feet toward the eastern United States.
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