ballet and physics

i was bored and randomly surfing websites when i came across this:
[i didnt know ballet and physics had things in common] (:

"To perform the more demanding routines, a ballet dancer must appear to defy gravity while working within its constraints. Basic physics and the science of human perception provide insight into how this is accomplished.
For example, during the grand jeté, the dancer may appear to hover. Physically, his/her center of mass describes a parabola, as does a ball, when thrown (or, indeed, any object when in flight and acted upon by only the gravitational force alone). However, advantage is taken of the limitation in the human ability to calculate center of mass when a projectile changes its configuration in flight. When leaping, the dancer extends the arms and legs and lowers the head. The manoeuvre camouflages the fall and leads the audience to perceive the dancer is floating.
A Pas de Chat (step of the cat) creates a similar illusion. The dancer starts from a plié, then during the ascending phase of the leap, successively lifts and rotates each shin inward. For a moment, the dancer appears suspended in air.
The fall must be performed carefully. The laws of physics decree that momentum must be dissipated but a crash landing would destroy the impression of airiness and likely injure the dancer. Part of the solution is a floor designed to absorb shock. The dancer also bends at the knees and rolls the foot from toe to heel. For artistic as well as safety reasons this technique must be taught by a qualified instructor.
Depending on where the dancer places his or her arms and legs, the dancer can make them look longer or shorter depending on their preference. By placing them farther behind the body it creates the illusion of shorter arms or legs, and by moving them forward, longer."