On paper, the ornithopter looks much more birdlike (or batlike) than present-day airplanes. Its wings are designed to flap as the pilot turns a crank. This invention demonstrates da Vinci's strong grasp of aerodynamics and modern attempts to reproduce the ornithopter show that it could indeed have flown -- that is, if it were already in the air. Taking off under the weak propulsion supplied by human muscles would have been much trickier.
The parachute and ornithopter were only two of the flying machines concocted by da Vinci in his notebooks. Others include a glider and his helicopter-like aerial screw, which we'll talk about in a few pages. parachute-The speed at which a body falls depends on two factors: the force of the gravity pulling it downward and the resistance of the atmosphere through which it is falling. If there were no atmosphere, a falling body would simply accelerate to higher and higher speeds until it hit a surface, but air tends to slow it down until it reaches its so-called terminal velocity. Different objects have different terminal velocities. The terminal velocity of a human being falling through the earth's atmosphere -- a skydiver with an unopened chute, for instance -- is about 120 mph (193.1 kilometers per hour). That's surprisingly slow, but still fast enough that a person falling from an airplane would make a pretty big splat upon hitting the ground. The idea of a parachute is to reduce a person's terminal velocity and make a long