A boomerang is a simple implement used for various purposes. It is primarily associated with Australian Aborigines, but has been found amongst peoples of North East Africa, Sardinia, Arizona, southern California Native Americans, and in India.

Boomerangs come in many shapes and sizes depending on their geographic/tribal origins and intended function. The most recognizable type is the returning boomerang, a kind of throwing stick that, when thrown correctly, travels in a curved path and returns to its point of origin. Other types of boomerang are of the non-returning sort, and indeed, some are not thrown at all but are used in hand-to-hand combat by Aboriginal people.

Boomerangs can be variously used as hunting weapons, percussive musical instruments, battle clubs, fire-starters, decoys for hunting waterfowl, and as recreational play toys. The smallest boomerang may be less than 10 cm from tip-to-tip, and the largest over 2 meters in length. Tribal boomerangs may be inscribed and/or painted with designs meaningful to its maker. Most boomerangs seen today are of the tourist or competition sort, and are almost invariably of the returning type.

Australian Aboriginal boomerangs

Boomerangs are probably the first heavier-than-air flying machine ever invented by human beings. The oldest Australian Aboriginal boomerangs are ten thousand years old but older hunting sticks have been discovered in Europe, where they seem to have formed part of the stone age arsenal of weapons. One boomerang that was discovered in a cave in the Carpathian Mountains in Poland was made of mammoth's tusk and is believed, based on AMS dating of objects found with it, to be about 30,000 years old. King Tutankhamun, the famous Pharaoh of ancient Egypt, who died 2,000 years ago, owned a collection of boomerangs of both the straight flying (hunting) and returning variety.

No one knows for sure how the returning boomerang was first invented, but some modern boomerang makers speculate that it developed from the flattened throwing stick, still used by the Australian Aborigines and some other tribal people around the world, including the Navajo Indians in America. A hunting boomerang is delicately balanced and much harder to make than a returning one. Probably, the curving flight characteristic of returning boomerangs was first noticed by stone age hunters trying to "tune" their hunting sticks to fly straight.

The name of the boomerang comes from the language of the Indigenous Australian Turuwal tribe of Aborigines who lived south of Sydney, Australia. They were also mistakenly referred to as a woomerang, in confusion with the woomera.

Modern sports boomerangs

 Modern Use

Today, boomerangs are mostly used as sporting items. There are different types of throwing contests: accuracy of return; aussie round; trick catch; maximum time aloft; fast catch; and endurance.  Modern sport boomerang (often referred to as a 'boom' or 'rang'), is made of Finnish birch plywood, hardwood, plastic or composite materials and comes in many different shapes and colors. Most sport boomerangs typically weigh less than 100 grams, with MTA boomerangs (boomerangs used for the maximum time aloft event) often under 25 grams.

In 2008, Japanese astronaut Takao Doi verified that boomerangs also function in zero gravity as they do on Earth. He repeated the same experiment that German Astronaut Ulf Meerbold did aboard Spacelab in 1992 and French Astronaut Jean-François Clervoy aboard MIR in 1997.

Hunting

It is believed that the shape and elliptical flight path of the returning boomerang makes it useful for hunting. Noise generated by the movement of the boomerang through the air, and, by a skilled thrower, lightly clipping leaves of a tree whose branches house birds, would help scare the birds towards the thrower. This was used to frighten flocks or groups of birds into nets that were usually strung up between trees or thrown by hidden hunters.

Boomerangs (termed "throwsticks") for hunting larger prey, such as kangaroo, were used for small prey as well. These throwsticks fly in a nearly straight path when thrown horizontally and are heavy enough to take down a kangaroo on impact to the legs or knees. For hunting emu, the throwstick is thrown toward the neck, breaking it.

Communication

It has been documented that Western Victorian "aboriginals" used the returnable boomerang, in addition to hunting, as a means of communication over long distances. This visual communication is especially useful when winds or distance make impossible other well known methods of communication such as cooee.

Design

Boomerangs for sale at the 2005 Melbourne Show

A boomerang is an airfoil. Though it is not a requirement that the boomerang be in its traditional shape, it is usually flat. A falling boomerang starts spinning and most then fall in a spiral. When the boomerang is thrown with high spin, the wings produce lift. Larger boomerangs are used in hunting, thus they drop on the ground after striking the target. Smaller ones are used in sport, and are the only boomerangs that return to the thrower. Because of its rapid spinning, a boomerang flies in a curve rather than a straight line. When thrown correctly a boomerang returns to its starting point.

Returning boomerangs consist of two or more arms or wings, connected at an angle. Each wing is shaped as an airfoil, so air travels faster over one side of the wing than the other. This difference in air speed creates suction or lift along what is roughly a plane which intersects the airfoil at a near right angle along the long axis of the wing.

These wings are set so that the lift created by each wing opposes the lift of the other, but at an angle such that the flight pattern is constantly shifted as the forces of lift, drag, speed, rotational inertia etc. 'attempt' to reach equilibrium.

Gyroscopic precession is what makes the boomerang return to the thrower when thrown correctly. This is also what makes the boomerang fly straight up into the air when thrown incorrectly. With the exception of long-distance boomerangs, they should not be thrown sidearm or like a Frisbee, but rather thrown with the long axis of the wings rotating in an almost-vertical plane. When throwing a returning boomerang correctly it is important to follow the correct instructions to achieve a successful return.

 Throwing technique

A right-handed boomerang makes a counter-clockwise flight (as seen from above), while a left-handed boomerang is constructed as a mirror image, and circles clockwise. Most sport boomerangs are in the range of about 2.5 to 4 ounces. The range on most of these is between 25 and 40 yards/metres. A right- or left-handed boomerang can be thrown with either hand, but the flight direction will depend upon the boomerang, not the thrower.

Throwing a boomerang with the wrong hand requires a throwing motion that many throwers may find awkward. The wings of the boomerang should be at a 15 degree angle. The other way also works, but many people find it easier to learn this way. The boomerang should be held by the tip using the thumb and one, two or three fingers, and then launched forward quickly while trying more for force than for very much spin.
 
It should flatten out midflight and arc around, sometimes coming to rest a little in front of the thrower or behind the thrower, but ideally it should hover gently and allow the thrower to catch it as a sort of sandwich between the thrower's hands. Returning boomerangs shouldn't be thrown level like a flying disc, as it will turn in the direction of the top of its airfoils, so if that direction happens to be up rather than to the side it may fly high enough that the landing causes damage to the boomerang or whatever it lands on.

Wind speed and direction are very important for a successful throw. A right-handed boomerang is thrown to the right of the wind. Angle to the wind depends on the boomerang, but starting with a 45 degree angle is recommended. Depending on where the boomerang lands, this angle can be modified so that a closer return is achieved. For example, if the boomerang lands too far on the left, throw more to the right of the wind the next time. As for the wind speed, a light wind is ideal. If the wind is strong enough to fly a kite, that's usually too strong for boomerangs.