Does a boomerang thrown in space return to its pitcher? It does if it was thrown inside an airy environment like the International Space Station, a Japanese astronaut proved last week. But scientists say he would have had different results if he had tossed the boomerang outside the orbiting outpost.

Takao Doi, an astronaut with the Japan Aerospace Exploration Agency, did the experiment while visiting the space station as part of NASA's latest space shuttle mission, which is scheduled to land on Wednesday.

The boomerang behaved no differently than on Earth, flying back to Doi after he threw it. "It flew just like on Earth, and I was really surprised and impressed," Doi told his wife in a chat from space, according to Japan's Mainichi Daily News.

World boomerang champion Yasuhiro Togai gave the paper boomerang to Doi and asked him to try throwing it in space. "It was a gift," JAXA spokesperson Kumiko Tanabe told New Scientist. Togai also gave Doi pointers on how to throw it.

The result is exactly what the science behind boomerangs predicts, says David Caughey an aerodynamics expert at Cornell University in Ithaca, New York, US. "I'm not terribly surprised by the fact that it came back in the absence of gravity," Caughey told New Scientist. "Gravity pretty much is irrelevant."

The looping paths that boomerangs are famous for are the result of uneven forces on the curved devices exerted by the air they travel through - not the influence of gravity, Caughey says.

The effect is similar to tilting a bicycle while it is moving - an act that makes the bicycle turn, he says. Uneven forces on a boomerang as it moves through the air cause it to turn in a similar way.

The forces from the air are uneven because of the boomerang's spin. The section of the boomerang moving in the same direction as its forward motion moves faster through the air than the part moving in the opposite direction.

The unevenness of the force causes the boomerang to turn and follow a circular path, eventually bringing it right back to the thrower. As long as there is air to provide the necessary forces, then, a boomerang will return to its thrower, even in the weightlessness of Earth orbit.

If, however, the boomerang had been thrown outside the space station in the vacuum of space, there would be no aerodynamic forces to make it return to its thrower, Caughy says. In that case it would behave like a rock or any other object thrown from the space station, moving along a 'straight' path that would only be bent by Earth's gravity or a collision with another object.

Doi did the experiment in his spare time on Tuesday, inside the space station's Harmony node. The school bus-sized node connects the US Destiny laboratory, the Japanese Kibo laboratory, and the European Columbus laboratory.

In 2006, a cosmonaut hit a golf ball from the space station as a publicity stunt for a golf company. The ball sailed away from the space station and was expected to burn up in the atmosphere within a few days.