Fly

It's because flies are still working out their own theory of Relativity. They fly around the light-bulb when it is off to check their belief that they fly faster with the speed of light. Double blind experiments show that when the light is off they hit many more obstructions - hence their theory of 'Dark Matters' Since they don't yet understand Relativity they still think that a straight line is the fastest flight-path between two points. While the basic four-line circle is used for convenience in poor visibility often more eloborate polygons are skilfully executed in the light. It is rumoured that fly 'Enlightenment' is just around the corner and that once achieved no fly will ever try to fly through window-panes again. Of course since the flies keep going around in cirles it could be a long time before they actually do make this quantum leap in understanding.

They do it for our entertainment... pure and simple... when you aren't looking, they do nothing of the sort... flies are put on this Earth to entertain us... :-) * P * :-) ( Read my blog! - www.oddcourgette.blogspot.com )