13:22 22 September 2008
NewScientist.com news service
Rachel Courtland 
 

We already know that living in space is no picnic: astronauts frequently suffer sickness and disorientation. Now it seems that zero-gravity can also adversely affect their ability to judge size and distance. The new finding, from a study by French and US researchers, may have implications for the way astronauts pilot spacecraft and perform tasks while on spacewalks.

NASA has long suspected something goes wrong with our visual perception when in space. Some of the Apollo astronauts reported difficulties judging distance while on the moon, for example: far-off rocks and features seemed closer than they really were. It is also well-known that space-shuttle pilots perform better with flight simulators and training aircraft than they do landing the shuttle after real missions.

Confused senses

Some researchers have suggested that these effects could be the result of confinement or the absence of easy landmarks, such as trees or buildings, but the new study pins the blame on the lack of gravity.

Humans orientate in 3D by using otoliths, small crystals of calcium carbonate and protein that shift on hairs in the inner ear. Forces acting on these grains as a person moves mean they can sense acceleration and gravitational pull. The researchers suggested that living in zero gravity would interfere with this process. "When you arrive in microgravity, you don't have this system any more telling you whether you're tilted," Gilles Clément of France's National Centre for Scientific Research in Toulouse, the lead author on the paper, told New Scientist. This, he suggests, impacts an astronaut's sense of perspective, causing them to misjudge common markers that are used to perceive size and distance, like an object's vanishing point. This would render them unable to accurately assess an object's dimensions.

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