英语听力文摘马腿为什么那么瘦？

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Skinny Legs and All

Why do horses have skinny legs? Find out on this Moment of Science.

Why do horses have skinny legs?

Okay, they aren’t entirely skinny — it’s mostly the (1)bottom half, with a big muscle up at the top.That’s odd. Human legs are kind of like that too — bigger on the (2)top half. Come to think of it, dogs’ legs are like that. And cat legs. Wait a minute. Deer legs are really skinny on the bottom and much thicker at the top. Antelopes. Gazelles. Giraffes. Elephants.

No, wait. Elephant legs aren’t really like that. Neither are duck legs, or panda bear legs. So it can’t be a prerequisite for any leg. What’s the use of a skinny leg?

Answer? Running. The skinniest lower legs belong to the fastest runners.Ok,so why is that?

It’s because when you run, or indeed walk, you are constantly swinging the bottom halves of your legs. For humans, one foot is stopped and essentially resting on the ground while the other is moving twice as fast as your overall speed. Then that foot stops and the other one accelerates. And so on.

Thinner, lighter things are easier to accelerate than heavy, massive ones. So if you want speed, put the muscles up high and the skinny down low. If you really want speed, you could even go further and (3)pare down the foot, to decrease lower leg mass even more. A few million years of evolution and you’ll (4)wind up with…you guessed it. A hoof.

Notes:

(1)bottom half 下半区(抽签);下半部分

Then put the hamburger on the bottom half of the hamburger bun.

然后把牛肉饼放在下面半个汉堡面包上面。

(2)top half 上半部;顶部

The lower half apparently does not matter, but the top half is sacrosanct .

下半口显然不要紧，但上半口则是神圣不可侵犯的。

(3)pare down 减少;削减

It will be necessary to pare this budget down considerably.

有必要大大地削减这笔预算。

(4)wind up with 以 ... 结束

I love waking up in the morning and not knowing what's going to happen,or who i'm going to meet,where i am going to wind up.