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时间膨胀是什么? – 译学馆
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时间膨胀是什么?

Time Dilation - Einstein's Theory Of Relativity Explained!

One evening in the spring of 1905,
1905年春天的一个夜晚
Albert Einstein, then a mere patent clerk in Bern,
爱因斯坦 那时还只是伯尔尼一个专利事务员
after trudging through the day’s work,
辛苦做了一天工作后
decided to board a tram car on his way home.
他决定搭电车回家
[slam]

Einstein would often wrap up his work as soon as possible
爱因斯坦经常会尽快完成他的工作
to contemplate the truths of the universe in his free time.
以便在闲暇时间思考宇宙的真相
It was one of these thought experiments he devised on that tram car
正是他在电车上构思的一个思维实验
that revolutionized modern physics forever.
永久地革新了现代物理学
While receding away from the Zytglogge clock tower,
当电车驶离钟楼时
Einstein imagined what would happen
爱因斯坦在想 如果电车以光速驶离
if the tram car were receding at the speed of light.
会发生什么呢
He realized that if he were to travel at 186,000 miles per second,
他意识到如果他以每秒18600英里的速度移动
the clock’s hands would appear to completely freeze.
那么时钟指针将完全静止
At the same time Einstein knew that
同时爱因斯坦知道
back at the clock tower the hands would tick along at their normal pace.
身后钟塔上的指针会以正常的速度滴答着
For Einstein, time had slowed down.
对于他而言 时间变慢了
This thought blew his mind.
这个想法使他大吃一惊
Einstein concluded that the faster you move through space,
爱因斯坦总结出 在空间上移动越快
the slower you move through time.
在时间上就移动的就越慢
How is this possible?
这怎么可能呢?
Einstein’s work was heavily influenced by two of the most iconic physicists of all time.
爱因斯坦的工作深受两位最具代表性的物理学家的影响
First there were the laws of motion discovered by his idol Isaac Newton,
第一个是运动定律的发现者 他的偶像艾萨克•牛顿
and second were the laws of electromagnetism laid down by James Clerk Maxwell.
第二个是奠定了电磁学的詹姆斯·克莱克·麦克斯韦
Newton’s laws insisted that velocities are never absolute
牛顿的理论坚持速度永远不是绝对的
But always relative, so that their magnitudes must be appended by the phrase”with respect to”
而是相对的 所以它们的大小必须加上”相对于”
For instance,
举个例子
a train travels at 40 km/h with respect to someone at rest;
相对于静止物体 一列火车以40km/h的速度行驶
However, it only travels 20 km/h
但是相对于同向行驶的速度为20km/h的列车
with respect to a train traveling 20 km/h in the same direction;
它的行驶速度只有20km/h
Or it travels 60 km/h
或 相对于以20km/h速度反向行驶的列车
with respect to another train traveling in the opposite direction at 20 km/h.
它的行驶速度则是60km/h
This is also true for the velocities of Earth,
这个理论同样适用于地球
the Sun and the entire Milky Way galaxy.
太阳以及整个银河系的运转速度
On the other hand,
另一方面
Maxwell found that the speed of an electromagnetic wave,
麦克斯韦发现 电磁波的速度是固定的
such as light,is fixed at an exorbitant 299,792,458 m/s
正如光 速度为固定的299792458米/秒
regardless of who observes it.
无论谁来观测(都是这样)
however Maxwell’s notion seems incompatible with Newton’s notion of relative velocities
但是麦克斯韦的理论似乎和牛顿的相对速度理论不相容
If Newton’s laws are truly universal.
如果牛顿的理论是真正的普适理论的话
Why should the speed of life be an exception?
为什么生命的速度就该是个例外?
This presented Einstein with a daunting dilemma
这使得爱因斯坦处于望而却步的两难境地
This conflict between the ideas of Newton and Maxwell
牛顿和麦克斯韦理论间的冲突
can be demonstrated with another of Einstein’s brilliant thought experiments.
还表现在爱因斯坦另一个绝妙思维实验上
Einstein imagined himself on a train platform,
爱因斯坦想象自己在火车站月台上
witnessing two lightning bolts strike on either side of him.
目击两道闪电从他两边擦过
Now because Einstein stands precisely in the middle of the two strikes,
此刻 因为他恰巧站在两道闪电正中间
he receives the resulting beams of light from both sides at the same time.
他同时感觉到两边闪电产生的光束
However, things get more complicated
然而 在一辆以光速运行的火车上
when someone on a passing train views this event,
某人经过爱因斯坦身边 目睹这一幕时
while whizzing past Einstein at the speed of light.
事情就变得更复杂了
If the speed of light conforms to the rules of relativity,
如果光速也遵循相对论定律
then the person on the train wouldn’t witness the lightning strike simultaneously.
那么 火车上的这个人将不会同时目睹两次闪电袭击
Logically, the light closer to the man on the train would reach him first.
逻辑上讲 离火车上的这个人更近的闪电 会先到达此人处
A measurement of the speed of light made by both men would differ in magnitude,
两个人所测量的光速会大小不同
this would contradict an apparently fundamental truth of the universe.
这将与一个显而易见的宇宙基本原理相矛盾
Einstein had to make a difficult choice.
爱因斯坦必须做一个艰难的选择
Either Newton’s laws were incomplete,
要么牛顿的理论是不完全的
or the speed of light was not a universal constant.
要么光速不是一个普适常数
Einstein realized that the two notions could coexist
爱因斯坦意识到 牛顿的理论稍作调整
with a small tweak in Newton’s laws
这两个理论就可以共存
To get rid of the discrepancy in the measurements,
为了消除测量上的偏差
Einstein suggested the time itself for the man on the train must slow down
爱因斯坦提出火车上人的时间必须调慢
to compensate for the decrease in speed,
来弥补速度的下降
such that the magnitude remains a constant.
这样光速大小仍然是常数
Einstein called this absurdity”Time Dilation” and his newfound theory”Special Relativity”
爱因斯坦称此谬误为“时间膨胀”和他新发现的学说“狭义相对论”
Newton believed the time moved unflinchingly in a single direction forward
牛顿认为时间单向不可逆地向前移动
Einstein, however, had just realized the time stretches and contracts varying with velocity.
然而 爱因斯坦意识到时间随着速度变化而延展和收缩
Due to its malleability,
由于时间具有可塑性
time, like space, deserved its own dimension.
时间应该像空间一样拥有自己的维度
In fact, Einstein claimed that the two were one and the same.
事实上 爱因斯坦断言二者为同一个维度
Together, they formed a four-dimensional fabric or continuum called space-time,
它们形成一个四维结构或者叫时间空间闭联集
upon which the mundane events of the universe would unfold
宇宙间的事件将在此之上展开
Einstein Suggested that massive objects like the Sun
爱因斯坦认为如太阳般巨大的物体
didn’t pull bodies, like earth, with a mysterious inexplicable tug,
并没有以一个神秘的无法解释的拉力拉动地球
but rather curved the fabric of space-time around them,
而是弯曲了它们周围时间空间构造
forcing earth to fall down into this steep valley.
迫使地球掉落入这陡峭的“谷底”
A highly simplified analogy
打个极简单的比方
is the dip in a trampoline made by a falling bowling ball.
就像一个下降的保龄球落入弹簧垫形成的凹陷
If a marble were placed on that trampoline,
如果这时在弹簧垫上放一个弹珠
the marble would immediately roll towards the bowling ball in the center.
弹珠将立刻滚向中心的保龄球
This is also true for Earth’s gravity.
这也同样适用于地心引力
We are pinned to the ground,
我们被限制在地面上
because space so distorted by the Earth’s mass pushes us down from above.
是因为被地球质量如此扭曲的空间 从上向下压住我们
However, the slump in the fabric around Earth is not uniform.
然而 地球周围构造的塌陷并不均匀一致
And Earth’s gravity grows more intense as we move towards its center,
越靠近地心 地心引力变化越剧烈
where the curvature is at a maximum.
地心区域的曲度达到最大值
Therefore, like the marble on the trampoline,
因此 像弹簧垫上的弹珠
an object that falls towards the earth accelerates,
一个坠向地球的物体
as it races towards the center of the planet.
在朝地球中心运动时 会加速
It falls faster when just above the surface
它在几乎靠近地球表面时
than it does say when it is slightly above the atmosphere
要比在大气层以外下降得更快
But, hey! according to special relativity,
但是 嘿 根据狭义相对论
the faster you move through space, the slower you move through time.
在空间里运动得越快 在时间里就运动得越慢
This means that time runs slower on Earth’s surface
那就是说 时间在地球表面流逝得
than it does above the atmosphere.
要比大气层外更慢
Now Because different planets have different masses,
因为不同的星球有不同的质量
and thus different gravitational strengths.
因此各自有不同的重力强度
They also accelerate objects at different rates.
它们也以不同的速度使物体加速
As we have learned, this means a variable passage of time.
正如我们所知道的 这意味着时间流逝是可变的
This is what happens in the movie interstellar,
这正是星际电影里发生的
when the protagonists land on a planet in the proximity of a black hole.
当主角着陆在黑洞附近的一个星球上
The gravity on the planet is so severe
这个星球的引力那么强烈
that one hour on the surface is equivalent to seven years on earth.
以致于它表面的一小时相当于地球上七年时间
To understand how motion affects time,
为了理解运动如何影响时间
let’s consider the simplest timekeeping mechanism.
来看下这个最简单的计时装置
A second passes each time the photon is reflected.
每过去一秒光子就反弹一次
Let’s imagine two people-
让我们想象这样两个人
one in a spaceship slightly above Earth’s atmosphere,
一个人在略高于大气层的宇宙飞船上
and the second on top of a small hill just above the Earth’s surface.
第二个人在略高于地表的小山顶上
Both are watching a man fall from space towards the ground.
两人都目睹一个人从空中落下
Let’s say that the falling man is carrying the photon clock explained a moment ago.
假设降落的人携带着刚才解释过的光子时钟
What do each of the two men observe as the man falls past them?
当这个人从他们身边降落时 他们两人各自观察到了什么
What they observe is eerily similar to what a stationary person would observe
他们所观察到的与一个静止的人在移动的火车上
when watching a ball bounce in a moving train.
看一个球弹跳时会观察到的惊人得相似
As the man falls from space,
当这个人从空中降落
the light in his clock would appear to move in triangles to the two observers
在这两个观察者看来 他时钟里的光会以三角形移动
This would mean that the light travels a longer distance,
这意味着光走过的距离更长
consequently stretching the duration of a second.
因此延长了一秒钟的持续时长
It is obvious that the length of triangles the light traces.
光所走过的三角形的长度是很明显的
And therefore the duration of a second is proportional to the velocity of the falling man.
因此一秒钟的持续时长 与降落者的速度成正比
When we recall that objects closer to the center of the planet fall faster,
当我们回想起距离地球中心更近的物体下落得更快
we can determine the time would appear to pass slower to the man on the hill
我们能确定对于山上的那个人来说 时间似乎过得
than it does to the man in the spaceship above.
比上面飞船上人要更慢一点
Of course, the difference is infinitesimal.
当然 这其中的不同是极微小的
The difference between the time measured by clocks
山顶的时钟和地球表面的时钟
at the tops of mountains and at the surface of Earth
所测出的时间差
is a matter of nanoseconds.
就是一纳秒的事
Time dilation affects every clock,
时间膨胀影响着每一个时钟
whether it relies on basic electromagnetism
无论是根据基本的电磁学
or a complex combination of Electromagnetism and Newton’s laws of motion.
或者是电磁学和牛顿运动定律的复杂结合
In fact, even biological processes are slowed down.
事实上 甚至生物过程也会减慢
Yes, that’s right your head is slightly older than your feet.
没错 你的头会比你的脚稍微老一点

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