In the good old days of moonwalks, NASA astronauts fell over quite a lot. But they weren't being clumsy or struggling with their suits: despite what you might think, low gravity actually makes it harder for astronauts to say upright.

New research from York University in Toronto, Canada, reveals that the low gravity on the moon actually makes it hard to distinguish up from down. To figure that out, the researchers span volunteers on giant rotating arms—just like in the movies—to simulate different gravitational fields. Then, they had them look at pictures of landscapes or the letter "p"—which can be read as a "d" if your perception of up and down is screwed.


Turns out that we need to experience 15 percent of the Earth's gravitational force to have any hope of knowing which way is up; less than that, and the subjects regularly couldn't tell which was was up. Given the moon has a field of just 17 percent of our planet and provided a new landscape to cope with, it's no surprise that astronauts took a tumble or three. Worth knowing before we go colonize Mars, eh? [PLoS One via New Scientist]

Image by NASA

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