Some superheros can move faster than the wind.
有些超级英雄能移动得比风速还快。
The men in Apollo 10 reached a record-breaking speed of around 25,000 miles per hour
在阿波罗10号载人航天器里的人们达到了这个打破了纪录的速度，大约每小时25000英里，
when the shuttle re-entered the Earth's atmosphere in 1969.
那是在1969年阿波罗十号重返地球表面时。
Wouldn't we save a lot of time to be able to move that fast? But what's the catch?
假如我们能移动得这么快，不是省下了很多时间吗？但这有何内幕呢？
Air is not empty. Elements like oxygen and nitrogen, even countless dust particles, make up the air around us.
空气并非无杂质。像是氧及氮元素，甚至数不尽的尘埃微粒，组成了环绕四周的空气。
When we move past these things in the air, we're rubbing against them and creating a lot of friction, which results in heat.
当我们移动时，会和空气中这三样物质擦身而过，进而制造许多摩擦力来产生热能。
Just like rubbing your hands together warms them up or rubbing two sticks together makes fire,
就像是摩擦双手取暖或者摩擦两根棍子取火，
the faster objects rub together, the more heat is generated.
其摩擦的速度越快，就能产生越多热能。
So, if we're running at 25,000 miles per hour, the heat from friction would burn our faces off.
所以如果我们每小时跑到两万五千英里，因摩擦力而产生的热能会把我们的脸烧掉。
Even if we somehow withstood the heat,
即使人体能够承受这一热度，
the sand and dirt in the air would still scrape us up with millions of tiny cuts all happening at the same time.
空气中的沙粒及尘土仍会同时以数百万的微小切割来刮伤我们的肌肤。
Ever seen the front bumper or grill of a truck?
有观察过一辆卡车的前保险杠吗？
What do you think all the birds and bugs would do to your open eyes or exposed skin?
你认为那些飞着的鸟和虫子会对你睁着的眼或者暴露在外的皮肤产生什么样的伤害？
Okay, so you'll wear a mask to avoid destroying your face.
好吧！你会因此戴上防护面具来避免脸部遭受损害。
But what about people in buildings between you and your destination?
但在你和目的地间的大楼里的人们又会如何呢？
It takes us approximately one-fifth of a second to react to what we see.
我们大约要花五分之一秒的时间来对自己看到的事物做出反应。
By the time we see what is ahead of us and react to it
在我们看见眼前事物的当下就得做出反应，
time times velocity equals distance equals one-fifth of a second times 25,000 miles per hour equals 1.4 miles
时间×速度=距离，也就是1/5秒×每小时25000英里=1.4英里，
we would have gone past it or through it by over a mile.
我们可能已经穿过建筑物超过一英里了。
We're either going to kill ourselves by crashing into the nearest wall at super speed or, worse, if we're indestructible,
我们要么是以超高速度撞到距离最近的墙而自杀，要么，更糟的是，如果我们没死，
we've essentially turned our bodies into missiles that destroy everything in our path.
我们会把自己的身体变成导弹，摧毁行经道路的一切事物。

So, long distance travel at 25,000 miles per hour would leave us burning up, covered in bugs, and leaves no time to react.
因此，以时速两万五千英里长途旅行，会把自己烧成灰烬，会被各种虫子冲撞，而且还没时间反应。
What about short bursts to a location we can see with no obstacles in between?
那么短距离冲刺到一个放眼所及没有障碍物的地方又如何呢？
Okay, let's say a bullet is about to hit a beautiful damsel in distress.
这么说好了！一颗子弹快要打到一位漂亮、需要帮助的女子。
So, our hero swoops in at super speed, grabs her, and carries her to safety.
而我们的英雄以超高速俯冲去抓住她，把她带到安全的地方。
That sounds very romantic, but, in reality, that girl will probably suffer more damage from the hero than the bullet if he moved her at super speed.
听起来很浪漫，但事实上，这女孩可能会因英雄的快速移动而遭受比起子弹更大的损伤。
Newton's First Law of Motion deals with inertia, which is the resistance to a change in its state of motion.
牛顿第一运动定律，即惯性定律，它是关于物体应对改变其原有的运动状态的抵抗性的阐述。
So, an object will continue moving or staying at the same place unless something changes it.
除非被外力改变，否则物体会持续移动或待在相同地方。
Acceleration is the rate the velocity changes over time.
加速度是指速率随着时间的改变。
When the girl at rest, velocity equals zero miles per hour,
当那位少女静止的时候，也就是说她的速度是零，
begins accelerating to reach the speed within seconds, velocity increases rapidly to 25,000 miles per hour,
然后，她开始加速，在几秒内速度就达到了每小时25000英里，
her brain would crash into the side of her skull.
她的大脑会被挤压到头骨边缘。
And, when she stops suddenly, velocity decreases rapidly back to zero miles per hour,
而当她突然停下来，速率快速回归于零，
her brain would crash into the other side of her skull, turning her brain into mush.
她的大脑会被挤压到另一边头骨边缘，把大脑变成糊状。
The brain is too fragile to handle the sudden movement. So is every part of her body, for that matter.
大脑太脆弱，以致无法承受快速运动。身体的任何部位也同样如此。
Remember, it's not the speed that causes the damage because the astronauts survived Apollo 10,
记住，那并不是速度所造成的损害，因为阿波罗十号里的航天员是活着的，
it's the acceleration or sudden stop that causes our internal organs to crash into the front of our bodies
是加速或突然静止造成我们内部器官挤压到身体前端，
the way we move forward in a bus when the driver slams on the brakes.
就像公交车司机猛踩刹车时我们的身体会往前移动。
What the hero did to the girl is mathematically the same as running her over with a space shuttle at maximum speed.
英雄带着女孩的快速移动，在数学上相当于搭乘航天飞机到达极大速度。
She probably died instantly at the point of impact.
她很可能会在碰撞时当场死亡。
He's going to owe this poor girl's family an apology and a big fat compensation check. Oh, and possibly face jail time.
英雄将欠下这可怜女孩的家人一个道歉以及庞大的赔偿费用。哦，可能还得面对牢狱之灾。
Doctors have to carry liability insurance just in case they make a mistake and hurt their patients.
医生们必须肩负起责任保险，以防万一误诊而伤了病患。
I wonder how much superhero insurance policy would cost.
我想知道超级英雄的保单费用会有多高。
Now, which superpower physics lesson will you explore next?
那么，你下一个想要探索的超能力物理课是什么呢？
Shifting body size and content, super speed, flight, super strength, immortality, and invisibility.
改变身体的大小和构成身体的物质，超快的速度，飞行，力大无比，长生不老还是隐身。