Q) How much does Mount Everest weigh?
J. Joshua Placa, Sedona, Arizona
A) YOU POSE AN interesting question, grasshopper, but one fraught with many dangerous curves. For starters: What is Mount Everest? "Does it start at Base Camp, at 17,500 feet?" asks Roger Bilham, a geophysics professor at the University of Colorado, "or 25 miles lower, in the earth's crust? Or somewhere in between?" For the sake of this exercise, let's go with Base Camp. Our next challenge is determining the density of the rock. While the 29,035-foot-high summit is mostly limestoneand clays and silts make up the section at about 26,000 feet that climbers call the Yellow Bandthe rest of the mountain is basically a big hunk of granite and gneiss, rocks with densities of about 170 pounds per cubic foot. Calculating the mountain's volume in cubic feet is trickier: Since Everest is more or less a cone, and a cone's volume is one-third of the base area times the height, we need to find the base area. To do so, square the radiuswhich averages out to 2.5 milesand multiply that by ¹ to get an answer of 547 million square feet. Going with our height of 11,500 feet from Base Camp to summit, we can peg the volume at 2.1 trillion cubic feet. Multiply that by the density and eureka! Everest tips the scale at a honking 357 trillion pounds. And then there's the snow and ice.
Q) Is a $50 shirt with a 50+ SPF rating more protective than my old Iron Maiden T-shirt?
Jim Cox, Birmingham, Alabama
A) ALL THE CLOTHING in your wardrobe (save for the mesh muscle shirt) provides some protection from the sun's ultraviolet rays. Its effectiveness is indicated by its UPF, or ultraviolet protection factor. Similar to a sunscreen's SPF, UPF gauges how much UV radiation can pass through a garment. Created in 1996 by the Australian Radiation Protection and Nuclear Safety Agency (Australia being the skin-cancer capital of the world), the UPF standard is used by apparel makers everywhere. Seattle-based Ex Officio's Sunblock shirts are UPF 30, meaning they let through one-thirtieth of all UV raysconsidered adequately protective. (A new white T-shirt has a UPF of only 5.) Royal Robbins makes 40+ shirts, and the GoSo polo shirt, made Down Under by the Sun Protection Shop, scores the highest rating, 50+. Some clothes are sewn with airier weaves, so you won't sweat to death, and treated with UV-absorbing chemicals like Tinofast. Meanwhile, Rit Sun Guard, which you can throw in the wash cycle, renders your clothes more UV-absorbingit's like lathering them up with SPF 30 lotion, without the greasy feeling. If you're loyal to the basic cotton tee, stick with black: Dark colors feel hotter, but they absorb more of those killer UV rays.
Q) If I'm riding my bike during a lightning storm, will the tires keep me grounded?
Chuck Pengilly, Fairbanks, Alaska
A) THAT'S A NEGATIVE. While it's true that rubber is a good insulator, a half-inch or so of tread is simply not enough to keep a bolt of lightning carrying tens of millions of volts from obliterating you in its effort to reach the ground. "Think of it like this," says Paul Krehbiel, a physics professor at the New Mexico Institute of Mining and Technology, who has had many close calls studying electrical storms. "Air is a superb insulator, too, so if a lightning bolt traveling at 75 miles per second makes it through two or three miles of atmosphere, a measly old tire is unlikely to offer much help." That also goes for your car, which protects you only because its steel cage diverts any electrical charge into the ground. So what's a poor biker who gets caught in a storm to do? The National Lightning Safety Institute advises that you ditch your bike, stay away from trees, water, and metal objects, adopt a low crouching position, and cover your ears.