SSS 2010-03-30

（单词翻译）

This is Scientific American's 60-Seconds Science. I'm Karen Hopkin. This will just take a minute.

Elephants. They’re the SUVs of the animal kingdom. They’re big and rugged¹, and can carry lots of cargo². And now a study in the Proceedings³ of the National Academy of Sciences suggests they come equipped with the quadruped version of all-wheel drive.

When it comes to locomotion⁴, elephants are not exactly fleet of foot. And they seem to hold their legs straighter than other animals do, at least when they walk. So scientists set out to examine more closely how elephant limbs mechanically move all that mass around.

Six Asian elephants walked or ran over a sidewalk equipped with pressure sensors⁵, as the scientists used high-speed video cameras to monitor their gait. And they found that elephant legs actually do bend enough to provide significant leverage⁶ when on the move. More surprising is that pachyderms’ front and rear legs are on equal footing when it comes to acceleration⁷ and braking. All other four-legged animals, like dogs or cats or horses, divvy up those duties. With their rear legs powering the push forward, and their front legs acting⁸ as brakes.

That arrangement lets elephants trade speed for stability. Sadly, it does nothing for their fuel economy. Of course, they do have the roomiest trunk.

Thanks for the minute for Scientific American's 60-Seconds Science. I'm Karen Hopkin.