National Geographic : 2011 Sep
on the control bar was painfully tight as I ran down the lip of the dune. Suddenly I was run- ning in thin air. Flying! A er a few seconds the instructor shouted "Flare!" I pushed the control bar over my head and landed, unsteady but on my feet---then headed back uphill. I wanted to feel again that strange, lovely moment alo . A glider wing is an e cient way to generate li , but my seconds-long ight proved that run- ning o a dune doesn't generate much speed. Glider ight is a controlled descent; pilots gain altitude only if they catch rising air and ride it alo . Birds don't have that problem; they y with great e ciency and more precision than any aircra . Sooty shearwaters log almost 40,000 miles migrating from New Zealand to Alaska and back, while ruby-throated hummingbirds can y 20 hours without stop migrating across the Gulf of Mexico. Scientists still struggle to understand the physiology of avian ight, but light bones and an intricate collaboration among chest and wing muscles appear essen- tial. A hummingbird's chest muscles account for 20 percent of its mass, according to Bret Tobal- ske, a University of Montana physiologist. "If a human had that mass of muscles, it would stick out like a 55-gallon drum," he says. "It would be freakin' enormous." Legend has it Icarus fell from the sky because hubris led him too close to the sun, melting the wax that held the feathers on his wings. More likely, his arms just gave out. Uncounted num- bers of "birdmen" have died over the centuries a er leaping from tower or cli , not realizing 1935 Spreading homemade canvas wings at 10,000 feet, "Bird-man" Clem Sohn rides the wind for 75 seconds. Two years later, a horrified crowd sees the stunt artist's parachute fail. 1948 Aerospace engineer Francis Rogallo and his wife invent the flexible "paraglider" wing as a sort of parachute for space capsules. Human fliers latch on to it. 1955 On the Hiller Flying Platform, a pilot stands atop twin fans and steers by leaning. It proves too unwieldy for military use. "If a human had [a hummingbird's] mass of muscles, it would stick out like a 55-gallon drum. It would be freakin' enormous."