I did not know that yesterday!

I visited the Yahoo! Directory and browsed through recreational boomerang sites and assorted commercial boomerang sites from manufacturers and vendors on several continents. I read about the origins and operating principles of this ancient throwing stick, used by Australian Aborigines and also found in ancient Egypt, Stone Age Europe, the southwestern United States, and the Indian subcontinent.

My search for a comprehensive answer to how boomerangs work led to the always dependable HowStuffWorks. Tom Harris' article covers returning boomerangs -- lightweight devices that fly through the air in a circular path (when crafted and thrown correctly) -- and their predecessors, non-returning boomerangs. These throwing sticks travel far and fast and are well-suited as tools for hunters.

Made of wood, metal, or plastic, a boomerang consists of two component parts (wings) joined together so that they spin around a central point. The wings are set at a slight tilt, and have an airfoil design. This means they are rounded on one side and flat on the other, like an airplane or propeller wing. Because air moves more rapidly over the rounded top of the wing, a difference in air pressure is created, and the greater pressure below causes lift. Think of the boomerang as an unattached propeller, spinning on its axis as it is thrown forward through the air.

Five forces affect the flight of a boomerang and must be balanced correctly for a boomerang to fly and return to the thrower successfully:

gravity
the force caused by propeller motion
the force of the throw
the force caused by the uneven speed of the wings (Bernoulli effect) wind
An aeronautics site for kids explains and illustrates the flight of a boomerang in terms of this list of aerodynamic principles:
"Bernoulli's relation, gyroscopic stability, gyroscopic precession,
and Newton's laws of motion."

Australian Aborigines use a non-returning boomerang, called a kylie or killer stick, as a hunting tool, and are frequently credited with inventing the boomerang. The U.S. Boomerang Association suggests that aerodynamic throwsticks have been around since the Stone Age, some 15,000 years ago.