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发表于 2005-11-13 18:40:15
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Einstein's Special Theory of Relativity
爱因斯坦的狭义相对论
In the late 1800’s, many scientists were comfortable with the existing description of the universe. In fact, many of them thought physics research was winding down and that all they had left to do was work out the details. The problem was that many of the “details” were observations or experimental results that couldn’t be explained by current theories. One such “detail” was that experiments always measured the speed of light as 3x10 8 m/s (186,000 mph).
19世纪末期,大多数科学家都认同于当时对于宇宙的描述。实际上,他们中大部分认为物理学的研究已经相当完善,所剩下的也只是将一些细枝末节了解清楚即可。但问题是许多所谓的细枝末节都是些不能用当时的理论给予解释的观测或实验结果。其中之一就是实验中对光速的测量结果总是在每秒30万公里(也就是时速18.6万英里)。
According to everyday experience, it seems that the speed of light should change depending on how fast you are moving. Imagine a car with a “For Sale” sign in the window going 55 mph.
按照我们的日常经验,光的速度应该是随观测者的移动速度而改变的。想像一辆在车窗上贴着“待售”标牌并以55英里的时速行驶的汽车。
A person standing still on the side of the road would see a car flying by and the sign would be a blur.
一个站在路边的人将看到一辆车飞驰而过,车窗上的标记模糊成一片。
A person driving next to the car at 55 mph could look out the window and copy down the phone number from the sign.
而一个在旁边同样以55英里时速行驶的车上的人就可以将头探出车窗并将标牌上的电话号码抄下来。
A person going down the road in the opposite direction at 55 mph would zoom by the car and probably not even know the sign was there.
但另一个以同样时速却往反方向行驶的人甚至连标牌都看不到。
The speed we see things moving at depends on the difference between how fast the other person is going and how fast we are going.
我们对于物体移动速度的观测结果是依赖于物体与我们自身移动速度的差值的。
The person standing still sees the car going at 55 mph.
静止站立的人看到的车速是每小时55英里。
55 mph (sign) – 0 mph (person) = 55 mph.
每小时55英里(标牌) - 每小时零英里(人) = 每小时55英里。
The person in the car next to the sign sees the car going at 0 mph.
在同样速度的车上的人看到的车速是零。
55 mph (sign) – 55 mph (car) = 0 mph.
每小时55英里(标牌) - 每小时55英里(汽车) = 每小时零英里
The person going the opposite way sees the car going at 110 mph.
往反方向行驶的车上的人看到的车速是每小时110英里
55 mph (sign) - -55 (car) = 110 mph.
每小时55英里(标牌) - (反方向)每小时55英里(车) = 每小时110英里.
Because of this, scientists assumed that if you measure the speed of light in different directions, you should get different speeds since the earth is in orbit around the sun. In 1895 Albert Michelson and Edward Morley performed this experiment and surprisingly, saw no difference in the speed of light for different directions.
因此,科学家们认为,因为地球是在围绕太阳运行,如果我们沿不同方向测量光的速度,将得到不同的结果。1895年,阿尔伯特·迈克尔逊和爱德华·莫雷进行了这个实验,并且出乎意料地末能发现光在不同方向的传播速度有任何的差异。
Albert Einstein resolved this puzzle in 1905 by suggesting that unlike the speed of a car, the speed of light is the same no matter how fast the observer is moving. In other words, even if you ran very fast you would not be any closer to catching up with a light wave than someone standing still. The first principle of Einstein’s Special Theory of Relativity is that the speed of light is always the same regardless of the motion of the observer or the light source.
阿尔伯特·爱因斯坦在1905年解释了这个现象,他认为不同于车的速度,光的速度是恒定的,不会随观察者的移动而变化。换句话说,即使你跑得非常快,你也无法追上光。爱因斯坦的狭义相对论中第一条定律就是光速是恒定的,完全不依赖于观测者及光源的速度。
Einstein also realized that although people see things differently (for example the speed of the “For Sale” sign), the laws of physics have to be the same for all observers. Someone riding on a train should be able to do the same experiments and get the same results as someone sitting in a classroom. If this were not true, people would get conflicting answers about how nature behaves depending on their motion – but nature does what nature does, it can’t follow different predictions depending on who is observing it. Therefore, the second principle of Einstein’s Special Theory of Relativity is that the laws of physics do not depend on the motion of the observer as long as the observer is not speeding up or slowing down.
爱因斯坦也认识到虽然对于同一件事物,不同的人会有不同的看法(比如上面待售车速度的例子),但物理学的法则一定对于所有观测者都是相同的。做同样的实验,火车上的人和教室里的人一定会得到同样的结果。如果不一样,那人们对于自然界的解释将依赖于他们自己的行为,但自然界就是自然界,它不会因为有谁在观察它而表现出什么不同的行为。因此,爱因斯坦的狭义相对论中第二条定律就是物理学的法则并不依赖于观测者的运动,除非观测者的速度有变化。
Principles of the Special Theory of Relativity
狭义相对论的原理
The speed of light is always the same regardless of the motion of the observer or the light source.
光速是恒定的,完全不依赖于观测者及光源的速度。
The laws of physics do not depend on the motion of the observer as long as the observer is not speeding up or slowing down.
物理学的法则并不依赖于观测者的运动,除非观测者的速度有变化。
If these two principles are true, Einstein showed that motion must affect distance and time. Imagine two people watching a beam of light. If one person is standing still, the light will look to her like it is moving at a speed of 186,000 mph. If the other person is in a spaceship traveling 100,000 mph, he still sees the light moving at 186,000 mph. How can this be true? Only if space and time are not absolute.
如果这两条定律都是正确的,爱因斯坦认为运动将会对距离和时间产生影响。设想有两个人在观察一束光。对于静止站立的人,光速是每小时18.6万公里;对于在以10万英里时速飞行的太空船中的人来说,光速仍将是每小时18.6万英里。但是这又怎么可能呢?除非空间和时间都不是绝对的!
According to Einstein’s theory, an object in motion is shorter than when it is at rest. Similarly, a clock in motion ticks more slowly than a clock at rest. In fact, Einstein concluded that distance and time are more accurately described as one thing – spacetime.
按照爱因斯坦的理论,运动中的物体在比它静止时来得短。类似地,运动中的时钟跳得比静止的时钟更慢。实际上,爱因斯坦推断空间和时间可以精确得描述为一个整体 - 时空。
We don’t notice these strange effects on a day-to-day basis because things on earth move significantly slower than the speed of light, so the effects are tiny. As strange as these ideas sound, scientific evidence has continually supported Einstein’s theory.
之所以在日常生活中我们没有注意到这些奇怪的变化是因为地球上物体的移动速度都远远小于光速,因此这些效应显得非常的微弱。虽然这些想法听上去相当奇怪,但不断有新的科学证据被发现可以验证爱因斯坦的理论。 |
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