國家地理:Surviving the Tornado 龍卷風來襲大難不死

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.
參考中文翻譯：
龍卷風在密蘇里平原肆虐橫行。風速高達每小時150英里，撕碎了前進路上的一切障礙。當它打道回府的時候，一名男子被吸進風眼，恐怖地旋轉(zhuǎn)搖擺。他軟弱的身體最終從1.25英里的高空落下。
“簡直太瘋狂了。我知道我應(yīng)該在哪里。你知道，我用了一分鐘的時間才明白發(fā)生了什么事。”
Matt毫發(fā)未損。為什么會這樣呢?科學家估計Matt落到地面時的速度至少每小時30英里。但是他的骨頭保護他的內(nèi)臟器官免收損害。
“鎖門。”
“收到。”
我們的骨架由206塊骨骼組成，從四肢的最大的骨骼到手指腳趾的細小的骨頭，組成了我們堅硬有彈性的框架，使我們可以伸縮自如。
骨骼堅硬的不可思議。
均等重量下，骨頭比水泥還堅硬。它有這很高的力量重量比率，地球上的其他物質(zhì)都沒有發(fā)現(xiàn)。
骨頭的力量大，重量卻很輕，秘密在于骨頭里面。它是由一系列空細胞組成的，細胞壁像紙一樣薄。
骨骼堅硬是由于鈣和磷，這些物質(zhì)同樣存在于貝殼和牙齒中。但是令人驚訝的是，我們骨骼中幾乎一半的物質(zhì)是柔軟的，活動，可以使我們的骨骼彎曲。
每七年，健康的人體的骨骼細胞會更新一遍。這種更新使我們的骨骼異常堅硬，適應(yīng)性奇強。