A spiral is a curve in which the distance from a point to a center (pole) increases for increasing angles.[br]Experiment:[br][list][*]Wind a rope around a pencil and attach the end of the rope.[/*][*]Now unwind the rope holding the rope thight.[/*][*]Unwinding the rope the pencil will draw a spiral.[/*][/list]You can describe a spiral mathematically. For the relation between the radius (= distance between pole and point) and the angle you can use different equations, each producing a slightly different shape. Here we use so-called parabolis spirals. The equation only matters to draw points on it and to illustrate the math behind sunflowerseeds. [br]

A parabolic spiral is a curve with equation [math]r=\sqrt{\theta}[/math], in which [math]0\le\theta\le n[/math].[br][math]\theta[/math] is an angle (in radials) n defined the number of radaials.[br][list][*]For [math]\theta=0[/math] the spiral starts in the origin.[/*][*]The bigger the angle [math]\theta[/math], the closer the distance between the windings.[/*][/list]Note: While increasing n very much, the windings wil be so close that it becomes diffucult to distinguish them.