60秒科学:大象能负重的原因

大多数四条腿动物用后腿前进，前腿停步，而研究表明，大象用四条腿来加速和“刹车”。

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 [John R. Hutchinson et al] 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 infrared⁶ video cameras to monitor their gait. And they found that elephant legs actually do bend enough to provide significant leverage⁷ when on the move. More surprising is that pachyderms’ front and rear legs are on equal footing when it comes to acceleration⁸ 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 acting⁹ 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.

—Karen Hopkin
 

1 rugged   

adj.高低不平的，粗糙的，粗壮的，强健的

参考例句：

• Football players must be rugged.足球运动员必须健壮。
• The Rocky Mountains have rugged mountains and roads.落基山脉有崇山峻岭和崎岖不平的道路。

2 cargo   

n.(一只船或一架飞机运载的)货物

参考例句：

• The ship has a cargo of about 200 ton.这条船大约有200吨的货物。
• A lot of people discharged the cargo from a ship.许多人从船上卸下货物。

3 proceedings   

n.进程，过程，议程；诉讼(程序)；公报

参考例句：

• He was released on bail pending committal proceedings. 他交保获释正在候审。
• to initiate legal proceedings against sb 对某人提起诉讼

4 locomotion   

n.运动，移动

参考例句：

• By land,air or sea,birds are masters of locomotion.无论是通过陆地，飞越空中还是穿过海洋，鸟应算是运动能手了。
• Food sources also elicit oriented locomotion and recognition behavior patterns in most insects.食物源也引诱大多数昆虫定向迁移和识别行为。

5 sensors   

n.传感器，灵敏元件( sensor的名词复数 )

参考例句：

• There were more than 2000 sensors here. 这里装有两千多个灵敏元件。 来自《简明英汉词典》
• Significant changes have been noted where sensors were exposed to trichloride. 当传感器暴露在三氯化物中时，有很大变化。 来自辞典例句

6 infrared   

adj./n.红外线(的)

参考例句：

• Infrared is widely used in industry and medical science.红外线广泛应用于工业和医学科学。
• Infrared radiation has wavelengths longer than those of visible light.红外辐射的波长比可见光的波长长。

7 leverage   

n.力量，影响；杠杆作用，杠杆的力量

参考例句：

• We'll have to use leverage to move this huge rock.我们不得不借助杠杆之力来移动这块巨石。
• He failed in the project because he could gain no leverage. 因为他没有影响力，他的计划失败了。

8 acceleration   

n.加速，加速度

参考例句：

• All spacemen must be able to bear acceleration.所有太空人都应能承受加速度。
• He has also called for an acceleration of political reforms.他同时呼吁加快政治改革的步伐。

9 acting   

n.演戏，行为，假装；adj.代理的，临时的，演出用的

参考例句：

• Ignore her,she's just acting.别理她，她只是假装的。
• During the seventies,her acting career was in eclipse.在七十年代，她的表演生涯黯然失色。