It's a combination of physics and psychology. The dancer moveshis legs into a split as he approaches the highest point in thejete and sometimes raises his arms as well. Now, his center ofgravity still follows the parabolic path it must. But moving hisarms and legs that way shifts the center of gravity in his bodyupward (that's the physics part). So his torso and head *don't*follow that parabolic path; the path is flattened. But after alifetime of seeing flying objects--balls, darts, crockery--andhaving internalized that parabolic path (that's the psychologypart), we see this flattened trajectory and it makes us think thedancer is just floating in midair.
This is a condensed explanation; I hope it's clear for all that.You can get the whole story in Kenneth Laws's book, Physics,Dance, and the Pas de Deux (Schirmer Books, 1994).
Tom Parsons