Flight

Things that fly need air. Even though we walk through it, breathe it, and sneeze it, air seems to be a whole   bunch of nothing. But air is there, and it's powerful. Balloons inflate because air presses on the insides   and outsides of the balloon. Air pressure in tires supports the weight of bikes, buses, trucks, cars, and   planes. But air doesn't need to be inside something to exert pressure. Air that moves around pushes,   too.   What do birds, planes, kites, Frisbees, and helicopters have in common? They fly because moving air   creates lift, or a push up. Airplane wings are shaped to push air down. The momentum of the air going   down pushes wings up. Air above the wing gets going faster than the air underneath. Fast-moving air   zips along, without pushing as hard side to side or up and down. The slow air pushes up from below   harder than the fast air pushes down from above ... and you're airborne!   Every flying thing, from the tiniest flying insect to the biggest airplane, us