To play Angry Birds, you must use a catapult to lob little birds at structures in the hope of knocking them down on pigs. It's the verb "lob" that intrigues me. There is something much more satisfactory about an object tracing a parabolic ballistic trajectory through space towards its target than either following a straight line or propelling itself.Predicting parabolas is something humans just seem to find intriguing. How else do you explain golf? Or the awe in which we hold good quarterbacks in football and good spin bowlers in cricket? Our bodies are uniquely good at throwing things at targets. The trajectory must be prefigured in the brain before the projectile leaves the fingers. Our shoulders rotate, our scapulas slide, our pelvises pivot, our arms flex and our fingers extend.