Gravity and the human body - Jay Buckey

地心引力與人體 － Jay Buckey

譯者: wai ki ng 審譯者: Jessie Lee

Some of the issues that are important

如果你想長時間住在太空

if you want to have people in space

有幾件事

for long periods of time.

是非常重要的

One is that people will tend to lose

其中一樣就是人類會慢慢失去

bone and muscle mass.

骨骼及肌肉

We know this.

這點我們是知道的

If you have to put a cast on your leg,

如你在一條腿上打石膏

and you take the cast off after a few weeks,

幾星期後把石膏拆掉

you'll see that your muscles have shrunk in size.

你會發現你的肌肉縮小了

And if you measured the bone strength,

如果你測量骨骼強度

you'd also see that might have gone down a little bit, too.

你也會發現骨骼強度可能降低了些

And so, it's very interesting that our body has that ability

所以，可見我們的身體有能力

to adapt to the loads that are put on it,

去適應加諸於身體的重量

so that bones and muscles aren't static,

骨骼和肌肉並不是固定不變的

they're always changing.

而是經常改變的

While we think of bone as being a solid thing

當我們想骨骼是一樣

that doesn't change very much,

不怎麼變的東西

it changes too.

其實它也會改變的

And it turns out that in weightlessness,

在無重力狀態下

you lose bone.

你失去骨骼

And then you also cause the muscles

然後使那些

that work against gravity,

對抗地心引力的肌肉

what are called the postural muscles,

我們稱為姿勢性肌肉

they'll start to shrink and lose strength.

開始萎縮且失去力量

There are other things in the cardiovascular system,

還有在心血管系統中

the heart and blood vessels.

的心臟及血管

And if you think about it,

你若想想

standing up in gravity

要在有地心引力的環境中站立

means you have to work against gravity

表示你要與地心引力對抗

in order to keep blood pumping to your head.

才能將血液輸送到頭部

So, if you couldn't keep blood pumping in the head,

如果你不能持續將血液輸送到頭部

you'd pass out every time you stood up

每次站立時你就會暈倒

because when you're lying down,

因為在躺下時

you don't have to push against gravity.

你不用與地心引力抗衡

But when you stand up,

但當你起身時

you got to work against gravity

你就要與地心引力對抗

to keep blood flowing to your head.

讓血液流到頭部

And your heart and blood vessels

而你的心臟及血管

have a really nicely worked-out system

有一個很完善的系統

to make that happen every time.

來達成這項任務

But that system can also change in weightlessness.

但在無重力狀態下，這系統也會受到影響

And then the other area that changes

另一個受影響的部份

is the system that has to do with balance.

是保持平衡的系統

Again, maintaining your balance

同樣地，保持平衡

is something that you're doing against gravity, right?

也是你與地心引力對抗， 不是嗎？

If you didn't have gravity present,

如果沒有地心引力的存在 你不須擔心跌倒

you wouldn't have to worry about falling.

如果沒有地心引力的存在 你不須擔心跌倒

But you obviously do have to worry about falling,

但明顯地你的確是要擔心跌倒的

and we have a very highly developed sense of balance

我們有非常發達的平衡感

to keep us upright

保持我們直立

and to prevent us from falling.

及防止我們跌倒

And when you see what skaters do,

當你見到滑冰者的動作

you realize just how exquisite a system it is.

你就會明白這系統的極致

But when you go into weightlessness,

但當你走入無重力狀態中

your balance system changes.

你的平衡系統要作出改變

You don't really notice it

當你身處無重力狀態時

while you are in weightlessness,

你未必真正察覺到

but when you come back,

但當你回來後

you do notice it,

你發現到你的平衡感改變了

that your balance has changed

and you have a little bit of trouble

你發現到你的平衡感改變了

而你會有一點

maintaining your balance.

保持平衡的困難

And what it shows is that while you're in space,

由此可見當你在太空中

your brain is trying to allow you

你的大腦嘗試讓你

to function in weightlessness.

能夠在無重力下運作

And so, it re-adapts you to be weightless,

讓你重新適應無重力狀態

which you don't notice until you come back

在你回去之前不會察覺

and find out that you're now back on Earth

但當你返回地球時就會發現

with a balance system that's been adapted to space.

你的平衡系統已適應了太空的環境

You know, all life developed here on Earth

你知道，所有地球上的生物

with gravity being present,

都在有地心引力的環境成長

so life evolved under the influence of gravity,

都在地心引力的影響下進化

and then we grow up with gravity being present,

而我們在地心引力的存在下成長

so we learn how to walk

學習走路

and catch a ball

接球

and ice skate

溜冰

or whatever,

或做其他事情

all with gravity being present.

全都在有地心引力的環境之下

And what if you were to grow up without gravity?

而如果在無重力狀態下成長又會如何？

What about the systems that depend on gravity,

那些依賴地心引力的系統又會如何？

like your muscles

像是你的肌肉

or your balance system

或平衡系統

or the heart and blood vessels?

或心臟及血管？

Would they develop normally,

它們會正常發展？

or would they be different in some way?

或會有所不同？

One reason why you might think

一個原因令你相信

that it would go down a different pathway

它們會有所不同

is from an experiment

就是在以前

that was done some time ago

由兩位名為 Hubel 和 Wiesel 的神經學家

by two neuroscientists

由兩位名為 Hubel 和 Wiesel 的神經學家

called Hubel and Wiesel.

所做的一個實驗

And what they did is they had a kitten,

實驗中有一隻小猫

and they put a patch over the eye of the kitten.

他們在小猫一隻眼上戴了眼罩

And then the kitten grew up to be a cat,

小猫長大後

and they removed the patch.

他們把眼罩拿掉

And so, the question is,

問題就是

can the cat see out of that eye?

戴眼罩的那隻眼睛看得見嗎？

Now, there's nothing wrong with the eye, right?

現在那隻眼睛並沒有問題，對吧？

But it just hasn't seen anything,

但它就是看不到任何東西

there hasn't been any light coming in.

沒有光進去

And the answer is that the cat can't see out of that eye

那隻猫也不能用這隻眼睛看東西

because what happens is that the brain

因為大腦

goes down a different pathway when it develops

在成長時走了一條不同的路

and the connections that would ordinarily develop

正常情況下會與那隻眼形成的連結

to that eye don't develop.

並無法得到發展

And that can't be undone,

而這是不可逆轉的

that's a permanent change.

永久性的改變

So, the brain of that cat

所以那隻猫的大腦

is fundamentally different from the brain of a cat

跟雙眼可以看得見的猫的腦

that grew up seeing out of that eye.

是根本不同的

That cat grew up with a different brain, in essence.

本質上，那隻猫是用不同的腦袋成長的

So, then you wonder,

所以你會想

well, what about gravity?

那地心引力呢？

What if you don't have the forces

如果沒有地心引力的力呢？

that gravity produces?

如果沒有地心引力的力呢？

Is your balance organ going to develop

你的平衡器官還是會一樣的發展？

in the same way,

你的平衡器官還是會一樣的發展？

or will it be different?

抑或會有所不同？

If somebody grew up in space,

如果有人在太空成長

could they come back to Earth and function,

他們可以回到地球正常地生活？

or would they really be a different person?

或者他們真的會是個跟我們不一樣的人？