Principles of Flight	(3/7)
Objects fly because of pressure differences and fluid wind dynamics.

Notice just how the malachite sunbird is hovering. Sort of like a humming bird does, but with not quite the same buzz. She furiously builds spinning waves of air. Using the opposing vortexes to stay in the same spot. Have you ever noticed seagulls hover without even flapping? As long as they have a good headwind they can even soar upwards without a single flap. Fixed wing gliding is quite different to both the flapping flight and buzzing flight. But they all require a pressure difference to give them buoyancy in the air.

To simply say that pressure differences cause flight is not enough. If the gliding wild goose above had no horizontal movement it would not fly. The pressure is built up by the force of the air against the wing, causing lift. We already knew this last century. But not quite. The spinning of the air is too subtle for smoke and wind tests. However, with logic we can see that the golf ball and the cogs exhibit the same mathematical relationships. It seems obvious that the gliding wing must also kick up low pressure vortexes which form distinct systems via their spinning motion. They are separated from the air around them by the movement, making the combined system of goose and air pocket, lighter than the surrounding air. Or at least equally as dense on average to achieve a perfect horizontal glide.

Now try this cool experiment. Throw an ordinary ruler so that it spins backwards, like the golf ball. See how it flies !!! You can even throw it downwards and it arcs up ! It has more lift than the golf ball, because it has a bigger ratio of aspect volume to mass. By Aspect volume, I mean the volume of air that is effected by the area of moving wing. The horizontal spin is just so much more effective at building a low pressure cavity, than any other form of mechanized flight. Welcome to the 21st century!