国家地理:Surviving the Tornado 龙卷风来袭大难不死

A tornado rips across the Missouri Plains. Winds over 150 miles per hour shred everything in the twister's path. When it smashes a trailer home, one man is sucked into the heart of the storm, spun and shaken horrifically. His limp body drops out of the sky a quarter of a mile away.
"It was crazy. I knew that I wasn't where I supposed to be, and it took me a minute to realize, you know, what was happening."
Matt hasn't broken a single bone. How could that be? Scientists estimate Matt hit the ground traveling at least 30 miles an hour. Yet his bones protected his internal organs from being smashed.
"Lock the door."
"Got it."
Our skeleton is made up of 206 bones, from the largest in our legs and arms to the tiny bones in our toes and fingers. They give us the tough flexible frame that lets us push and pull on our will.
Bone is incredibly strong.
Pound for pound, bone is stronger than concrete. It has a strength-to-weight ratio found in no other natural material on earth.
The secret of bone's strength and lightness lies inside. It is a matrix of hollow cells; its walls are as thin as paper.
Bone gets its rigidity from calcium and phosphorus, materials found in seashells and teeth. But astonishingly, almost half of our bone mass is soft and alive, allowing our bones to bend.
Every seven years, a healthy human body completely replaces every single bone cell. This renewal keeps our bones incredibly strong and uniquely adaptable.
Notes:
strength/weight ratio: The relationship between the structural strength of a material and its weight.
bone mass: The amount of mineral in a bone. Although this is different from bone density, the terms are often used interchangeably.
参考中文翻译：
龙卷风在密苏里平原肆虐横行。风速高达每小时150英里，撕碎了前进路上的一切障碍。当它打道回府的时候，一名男子被吸进风眼，恐怖地旋转摇摆。他软弱的身体最终从1.25英里的高空落下。
“简直太疯狂了。我知道我应该在哪里。你知道，我用了一分钟的时间才明白发生了什么事。”
Matt毫发未损。为什么会这样呢?科学家估计Matt落到地面时的速度至少每小时30英里。但是他的骨头保护他的内脏器官免收损害。
“锁门。”
“收到。”
我们的骨架由206块骨骼组成，从四肢的最大的骨骼到手指脚趾的细小的骨头，组成了我们坚硬有弹性的框架，使我们可以伸缩自如。
骨骼坚硬的不可思议。
均等重量下，骨头比水泥还坚硬。它有这很高的力量重量比率，地球上的其他物质都没有发现。
骨头的力量大，重量却很轻，秘密在于骨头里面。它是由一系列空细胞组成的，细胞壁像纸一样薄。
骨骼坚硬是由于钙和磷，这些物质同样存在于贝壳和牙齿中。但是令人惊讶的是，我们骨骼中几乎一半的物质是柔软的，活动，可以使我们的骨骼弯曲。
每七年，健康的人体的骨骼细胞会更新一遍。这种更新使我们的骨骼异常坚硬，适应性奇强。