If superpowers were real: Flight - Joy Lin

翻译人员: Binglei Shea 校对人员: Catherine Gu

If humans could fly,

如果人类可以飞翔

without tools and machines,

而不是利用工具或者机器，

how fast do you think we would go?

你觉得我们能飞多快？

As of 2012, the world record

截止到2012年，世界

for fastest short-distance sprint speed

短跑最快纪录

is roughly 27 miles per hour.

是大约每小时27英里（约43km/h）。

Running speed depends on how much force

跑步的速度取决于

is exerted by the runner's legs,

跑步者的腿部力量。

and according to Newton's Second Law of Motion,

根据牛顿第二运动定律，

force is the product of mass times acceleration.

力的大小等于质量乘以加速度。

And Newton's Third Law states

牛顿第三定律又说

that for every action,

每一个作用力

there is an equal and opposite reaction.

都有一个大小相等、方向相反的反作用力。

So, that means running requires

所以，这就意味着，跑步需要

having a ground to push off from,

有一个地面来作支撑，

and the ground pushes back against the runner's foot.

地面通过反作用力把跑步者的脚推出去。

So, flying would actually be

所以，飞行事实上

more similar to swimming.

更类似于游泳。

Michael Phelps is currently the fastest human in water

迈克尔·菲尔普斯是目前水里游得最快的人，

and the most decorated Olympian of all time.

也是有史以来最杰出的的奥林匹克运动员。

Guess how fast he swims?

猜猜看，他能游多快？

The answer may surprise you.

答案可能让你不敢相信。

His fastest recorded speed is

他最快的速度记录是

less than 5 miles per hour.

小于每小时5英里（8km/h）。

A child on the ground can easily outrun

一个在地上奔跑的小孩能够很容易超过

Michael Phelps in water,

在水里游泳的菲尔普斯。

but why is that?

但是，这是为什么呢？

Well, let's go back to Newton's Third Law of Motion.

好吧，让我们回到牛顿第三运动定律。

When we run, we move forward

当我们跑步时，我们向前移动，

by pushing against the ground with our feet

利用我们的脚去推地面

and the ground pushes back,

同时，地面反过来

propelling us forward.

推动我们向前。

The ground is solid.

地面是固体。

By definition, it means the particles

根据定义，物质颗粒

are essentially locked into place

基本上被固定在原来的地方，

and must push back instead of getting out of the way,

所以只能推回去，而不是被推走。

but water is liquid and flows easily.

但是水是液体，易流动。

When we move our limbs

当我们移动肢体

to push back against the water,

来排开水的时候，

a part of the water molecules

每一个水分子

can just slide past one another

只会彼此滑过

instead of pushing back.

而不是推回来。

Now, let's think about flying.

现在，让我们来想一想飞行。

Air has a lot more free space

空气种有更多的空间

for particles to move past one another,

让粒子进行自由移动，

so even more of our energy would be wasted.

所以会浪费我们更多的能量。

We would need to push a lot of air backwards

我们需要向后推大量的空气

in order to move forward.

才能向前移动。

Astronauts move around in shuttles

宇航员在航天飞机中，

in zero gravity when they're in outer space

在外层空间的零重力情况下，

by pulling on handles installed on the ceiling walls

能通过拉动安装在航天飞机

and floors of the shuttle.

天花板和地板上的手柄移动。

Now, imagine you were given the ability to float.

现在，想象你有浮动的能力。

How would you move around in the middle of the street?

你会如何在街上移动？

Well, you wouldn't get very far

好吧，在空气中游泳你不会走很远

by swimming in air, would you?

你不会走很远，是吧?

Nah, I don't think so!

不，我不这么认为!

Now, assuming you were granted the ability to float

现在，假设你有漂浮的能力

and the speed to move around efficiently,

和高效的移动速度，

let's discuss the height of your flight.

让我们来讨论一下你飞行的高度。

According to the Ideal Gas Law,

根据理想气体定律，

P-V N-R-T,

PV=NRT （P理想气体压强，V理想气体体积，N气体物质的量，R理想气体常数，T理想气体的热力学温度）

pressure and temperature has a positive correlation,

压强和温度呈正相关，

meaning they increase and decrease together.

这意味着它们同时增加或减少。

This is because the air expands in volume

这是因为减小压强，可以使

with less pressure,

空气体积膨胀，

so the molecules have more room to wander around

因此，空气分子有更多的空间来四处游荡

without colliding into each other and creating heat.

不会互相碰撞产生热量。

Since the atmospheric pressure is a lot lower

在高海拔地区，

in high altitudes,

由于大气压力很小，

it would be freezing cold

气温会降低。

if you were flying above the clouds.

如果你在云层上面飞行，

You'd need to wrap yourself up

你需要把自己包得严严实实

to keep your core body temperature

来保持你的正常体温

above 95 degrees Fahrenheit,

华氏 95 度以上（35摄氏度）

otherwise you'd start shivering violently,

否则你就会开始猛烈地颤抖，

gradually becoming mentally confused

逐渐变得神智恍惚，

and eventually drop out of the sky

并最终从天空坠落，

due to loss of muscle control

无法控制肌肉因为低温

from hypothermia!

无法控制肌肉 ！

Now, the Ideal Gas Law implies

现在，理想气体定律暗示

that as the pressure decreases,

随着压力减小，

gas volume increases.

气体体积增大。

So, if you were to fly straight up too quickly,

所以，如果你垂直向上飞得太快了，

在你的身体中的惰性气体将迅速膨胀，

the inert gas in your body would rapidly expand

the way soda fizzes up when shaken.

就像苏打水被摇了一摇。

The phenomenon is called "the bends,"

这种现象被称为"the bens"

decompression sickness,

减压病，

or "divers disease"

或"潜水员病"，

since deep sea scuba divers experience this

因为深海潜水员浮出水面的速度过快时，

when they come up too quickly.

也会出现这种情况。

This results in pain,

这会导致疼痛、

paralysis,

麻痹、

or death,

甚至死亡，

depending on how foamy your blood becomes.

这取决于你血液的泡沫化程度。

Okay, well, let's say you want to fly

好吧，让我们说说你想要在飞行

just a few meters above the ground

仅高于地面数米飞行，

你还可以看到道路标志，

where you can still see the road signs

and breath oxygen with ease.

并轻松地呼吸氧气。

You'll still need goggles and a helmet

你仍然需要护目镜和头盔

to protect you from birds,

保护你免受鸟、

insects,

street signs,

昆虫、

路牌、

electrical wires,

电线、

and other flying humans,

和其他飞行的人的撞击，

including flying cops

包括飞行的警察

ready to hand you a ticket

准备递给你一张罚单，

if you don't follow the flying rules, buddy.

理由是你不遵守飞行规则，伙计。

Now remember, if you have a collision mid-air

现在，记住，如果你在半空中发生碰撞，

that knocks you unconscious,

足以把你撞昏，

you would experience free fall

你会体验自由落体

until you hit the ground.

直到你落到地面。

Without society or the laws of physics,

没有社会或物理定律，

flying would be a totally awesome ability to have.

飞行会成为一种完全令人敬畏的能力。

But, even if we could all just float around

但是，即使我们可能都只是四处飘浮

a few feet above the ground

离地面几英尺高，

and only moving at a snail's pace,

仅以蜗牛的速度移动

I'm telling you, it's still a cool ability that I'd want,

我告诉你，它仍然是一种我想要的很酷的能力，

wouldn't you?

不是吗？

Yeah, I thought so.

我就是这样认为的。

Now, which superpower physics lesson

现在，超能力物理课

will you explore next?

下一个你想探索的是？

Shifting body size and content,

改变身才大小和内容、

super speed,

超高速、

flight,

飞行、

super strength,

超强力量、

immortality,

长生不老

and

和

invisibility.

隐形。