Have you ever seen a lizard hurtling over your head? How about a frog sailing down from the tree tops? I’m not making these animals up. They belong to one of earth’s most astonishing groups of animals.
Gliders travel through the air, but they don’t fly. Instead, they glide. What’s the difference? Well, to get itself off the ground, a bird, bat, or insect has to generate a force called lift. A flying animal generates lift using its wings, which are attached to powerful flight muscles. These wings move and bend in complicated motions to counteract the force of gravity.
Gliding animals do not have muscle-powered wings. Instead, most gliding animals have special flaps or folds of skin called patagia. Like wings, the patagia generate lift—but only after the animal is already moving through the air.
When chased by a snake, a Draco lizard leaps from its tree. Instead of plunging to its death, it spreads out its rib cage into two elegant airfoils covered with skin. As air rushes over them, these airfoils—the patagia—generate lift to keep the lizard from falling straight down. The lizard does steadily descend toward earth, but it is also riding the air. It can change directions, pull a U-turn, and control where it wants to go. In the process it can travel hundreds of feet before landing on another tree or on the ground.
The patagia of Wallace’s frogs lie between their toes. These frogs usually live up in the trees, but when it is time to mate or lay eggs, they leap, spread out their toes, and glide to earth.
Earth’s most astonishing gliders may be five species of gliding snakes. These snakes don’t have patagia. Instead, they flatten out their bodies and “crawl” through the air. Scientists aren’t sure if the crawling motion helps generate lift, or if lift comes mainly from a snake’s flattened shape, but the animals can glide more than 100 feet before landing.
Most of earth’s gliding animals live in Southeast Asian rainforests, which are home to more than eighty species of gliding lizards, frogs, snakes, and mammals. In North America, we have only two gliding animals: Northern and Southern flying squirrels. Despite their name, flying squirrels don’t fly. They glide—and are adorably cute! Want to see one? Try shining a flashlight on a bird feeder at night!
A male Draco lizard extending his gular flag (throat flap) and patagi (wings). While not capable of powered flight Dracos often obtain lift in the course of their gliding flights. Glides as long as 200 feet have been recorded, Wikimedia
Wallace's frogs live almost exclusively in the trees, and leap and "fly" from tree to tree or to bushes. The membranes between their toes and loose skin flaps on their sides catch the air as they fall, helping them to glide, sometimes 50 feet or more, to a neighboring tree branch or even all the way to the ground. They also have oversized toe pads to help them land softly and stick to tree trunks. Wikimedia
Flying squirrels are able to glide from one tree to another with the aid of a patagium, a furry, parachute-like membrane that stretches from wrist to ankle. Their long tail provides stability in flight. Wikimedia
There are five recognized species of flying snake, found from western India to the Indonesian archipelago. They flatten out their bodies and parachute or glide using their ribs to become flat, and then they whip their bodies in a fast, rhythmic S-shape to stay airborne. Wikimedia
Illustrated with arresting photographs, Sneed B. Collard's Catching Air: Taking the Leap with Gliding Animals takes us around the world to learn why so many gliders live in Southeast Asia, and to find out why this gravity-defying ability has evolved in Draco lizards, snakes, and frogs as well as mammals. Why do gliders stop short of flying, how did bats make that final leap, and how did Homo sapiens bypass evolution to glide via wingsuits and hang gliders―or is that evolution in another guise?
MLA 8 Citation
Collard, Sneed B., III. "Meet Earth's Incredible Gliders." Nonfiction Minute,
iNK Think Tank, 11 Apr. 2018, www.nonfictionminute.org/
The Explainer General
Since he was a boy, John Collins has been fascinated by paper airplanes. Who isn’t? Most of us have folded the familiar dart-shaped classroom airplane. Good fun. And it’s science.
Big and small aircraft depend on the same four principles: weight (of the craft), drag (wind resistance over the craft), lift (upward force from air passing over the craft’s flight surfaces), and thrust (what pushes the craft). A 747 Jumbo Jet and a paper airplane depend on the same forces.
Collins wanted to fold this aeroscience into paper. But how to build (fold) complex principles into something so small?
He found the ancient Japanese art of origami and used its sculptural tricks. He created paper aircraft that do astonishing things. One comes back in a horizontal circle, like a boomerang. Another flies up, turns over and comes back vertically. One actually flaps its wings as it glides slowly. To John, they’re all working science experiments: every flight leads to some knowledge and to new ideas for tweaking the aircraft so it flies better.
John Collins became “The Paper Airplane Guy.” He believes that scientific research happens everywhere, every day. He says, “It doesn’t take computers, lab coats, microscopes and the like. It takes a hunger to know. Science is just the structured way we find stuff out. The science you can do with a simple sheet of paper is no less important than what can be done with an electron microscope.”
On February 26, 2012, John and Joe Ayoob stood in a big, windless aircraft hangar with John’s best-so-far flyer, Suzanne. (He named it after his wife.) Joe was a professional football quarterback who learned to throw Suzanne hard but steady, not like a football but like a delicate piece of origami. Joe threw Suzanne up, up, and it dived down to fly – really fly – 226 feet and 10 inches, the Guinness World Record for distance thrown.
John wanted paper airplanes to welcome young people into science. He started a National Paper Airplane Contest called the Kickstarter Project with a big prize for anyone who throws Suzanne farther than Joe. Or you could throw your own better, more aeronautically elegant paper airplane. It was a simple, scientific task. Every paper airplane and every flight would be a new experiment, just as important as the Wright Brothers’ Kittyhawk flight. Science isn’t just geeks and labs; we’re all part of it. The project didn’t get support and ended. John would like to direct people to www.TheNationalPaperAirplaneContest.com. Air and Science museums across the country will be hosting events. The museums get three Fly for Fun Days; STEM education days that teach basic flight concepts and skills for the national contest.
Jan Adkins is a member of iNK's Authors on Call and is available for classroom programs through Field Trip Zoom, a terrific technology that requires only a computer, WiFi, and a webcam. Click here to find out more.
MLA 8 Citation
Adkins, Jan. "Flat Paper Flight." Nonfiction Minute, iNK Think Tank, 9 Apr.
As any paper airplane pilot knows, getting into the air and staying up in the air are two different things. An out-of-control, unstable paper airplane quickly ends up on the floor—no matter how powerfully you threw it. Controlling an airplane was the problem yet to be solved in the late 1890s. Many of the inventors racing to be the first to build a powered flying machine didn’t understand that controlling an airplane is different from controlling other vehicles of the time. But the Wright Brothers did.
Unlike a car or boat, an airplane moves in three directions: pitch, yaw, and roll. Stable flight takes correctly controlling all three.
When you steer a boat, you move a rudder to go left or right. This is yaw. Turn a rudder on its side and you get an elevator, which controls a submarine as it dives and surfaces. This is pitch. Airplanes also have elevators and rudders. But flying takes more than up-down and right-left control. An airplane also tilts side to side, in a motion called roll. Think of a jet tilting its wings as it changes direction. Or a little kid zooming around with tilted arms spread wide.
Controlling the roll of an airplane was the secret to stable, sustained flight. And this is where the Wright Brothers had an edge. They built bicycles. A bicycle is an unstable vehicle when it isn’t moving. In fact, it falls over. A moving bicycle is much easier to balance than a stopped one. And steering a moving bicycle is more than just turning the handlebars right or left. The rider must lean into turns, tilting his body to keep balanced. Sound familiar? It’s the same kind of motion as roll.
Orville and Wilbur Wright knew about roll and worked on a way to control it even while experimenting with gliders. They controlled roll through wing-warping, a system of cables attached to the wings that twisted their shape, like twisting an empty aluminum foil box. The pilot controlled which way the wings warped by moving his hips as he lay on the airplane in a kind of cradle. Soon ailerons, those flaps on the backside of airplane wings, became the controller of roll. But the brothers of the Wright Cycle Company figured it out—and flew—first.
If you look at pitch, roll and yaw together you can see that each type of motion helps control the direction and level of the plane when it is flying. The ailerons raise and lower the wings. The pilot controls the roll of the plane by raising one aileron or the other with a control wheel. The rudder works to control the yaw of the plane. Pressing the right rudder pedal moves the rudder to the right. This yaws the aircraft to the right. Used together, the rudder and the ailerons are used to turn the plane. The elevators which are on the tail section are used to control the pitch of the plane. Lowering the elevators makes the plane nose go down and allows the plane to go down. By raising the elevators the pilot can make the plane go up.
First successful flight of the Wright Flyer, by the Wright brothers. The machine traveled 120 ft (36.6 m) in 12 seconds. Orville Wright was at the controls of the machine, lying prone on the lower wing with his hips in the cradle which operated the wing-warping mechanism. Wilbur Wright ran alongside to balance the machine. Library of Congress
Mary Kay Carson's The Wright Brothers for Kids: How They Invented the Airplane, 21 Activities Exploring the Science and History of Flight tells the amazing true story of how two bicycle-making brothers from Ohio, with no more than high-school educations, accomplished a feat on the beaches of Kitty Hawk, North Carolina, that forever changed the world.
MLA 8 Citation
Carson, Mary Kay. "How Did Building Bikes Help the Wright Brothers Invent the
Airplane?" Nonfiction Minute, iNK Think Tank, 28 Mar. 2018,