What Causes A Boomerang to return?

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There's an old joke: "What do you call a boomerang that does not return?" A stick!
This object is one of the oldest heavier-than-air flying inventions. Aboriginal Australians used boomerangs to hunt and to use in warfare, as far back as 10,000 years.
The original boomerangs were heavy objects, launched by hunters to knock down the target with accuracy and speed. Boomerangs were not supposed to return, until someone unknowingly carved the weapon in the precise shape needed for it to spin!