By Elizabeth Royte
How exactly does poison ivy wreak its havoc?
Poison ivy wouldn't be poisonous without a certain oily sap known as urushiol, which lurks in almost every part of the plant. Contact with as little as one millionth of a gram can trigger the chain of dermatological reactions that leads to the usual blistery, suppurating mess. Urushiol is an evil, evil thing. An extremely stable compound, it's been
found, in an active state, in desiccated plants more than 100 years old. It sticks around in dead vines, it clings to dogs that you pet and shoelaces that you tie, it lingers on gardening tools that you neglect to rinse with isopropyl alcohol. Burn poison ivy and the oil will go airborne, where it can torture you with unspeakable, unreachable itchiness in
your lungs and trachea. Of all animals, only we humans seem to suffer poison ivy's epidermal ravages: Some birds eat its berries, rodents nest among its leaves, bears sleep on it. Urushiol appears to have been created merely to make humans miserable — while giving calamine merchants a purpose in life.
— Isabel Holmes, Seattle, Washington
Why is Bangladesh continually clobbered by natural calamities?
— Kelly Higgason, Houston, Texas
Low-lying Bangladesh is situated at the head of the Bay of Bengal, a spawning ground for typhoons and tornadoes, not to mention the occasional roving tsunami, and the country lies in the floodplain of the Ganges, Brahmaputra, and Meghna Rivers, which swell every spring with Himalayan snowmelt. Add to this mix an intense monsoon season and a population
density of more than 2,100 people per square mile, and you have an ongoing formula for natural disasters — like 1991's Typhoon Walt, which lashed Bangladesh with 143-mile-per-hour winds and 20-foot waves, killing 138,000 people. Year after year, it's a grim illustration of the adage, "geography is destiny."
Can a sailboat go faster than the wind?
— Andrew Newcomb, Andover, Massachusetts
Yes, but you probably can't afford it. Under ideal conditions, certain superlight, multihull sailboats benefit from a phenomenon called apparent wind — the true wind combined with the wind that comes over the bow as you move forward.
All sailboats experience apparent wind, but any gain on wind speed is usually checked by the drag of the hull. Boats that routinely outsail the wind are rare because they're extremely expensive and uncomfortable, the esoteric trimaran designs of speed-obsessed engineers. The world speed record — 46.52 knots — was set by one of these
vessels sailing off the coast of France in 1993. By comparison, the most impressive speed ever clocked by an America's Cup yacht was a relatively languorous 22 knots.
Why is Europe considered a continent?
— Max Jenkins, Madison, Tennessee
A continent is defined as "a large, continuous mass of land," though how large and how continuous are open to interpretation. The line of size demarcation falls somewhere between Australia (the world's smallest continent) and Greenland (the largest island). Europe meets the size definition; it's the continuity criterion that creates problems, for a
casual glance at a map tells you that Europe is really only a western addendum to Asia. While some experts use the term "Eurasia," most consider the Ural Mountains, which extend from the Arctic Ocean to the Caspian Sea, a boundary of continental proportions. Perhaps, but Europe's lofty landmass status still seems specious somehow (as does the term
"continental breakfast"). When we asked a spokesman at atlas-publisher Rand McNally about this, he began to free-associate: "It's a gestalt, if you will. The cartographers looked at huge chunks of land and said, 'That's the way it is.' Some things we can't explain, despite all our education."
|On Independence Day, Earth will be at aphelion, its farthest distance from the Sun, 94.5 million miles. Two days later, celebrate the 310th anniversary of the publication of Newton's Principia Mathematica, which laid out the laws of gravity. The full Moon falls on the 19th.
On the morning of the 25th, the Moon will be near Saturn, whose rings will be tipped about 12 degrees. This will be the most pronounced tipping of Saturn's rings in 1997 and will be an ideal time to study the planet if you happen to have a small telescope. On the mornings of the 28th, the 29th, and the 30th, look for the Delta Aquarid meteor shower,
which will have a peak rate of approximately 20 meteors per hour. — David N. Schramm
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