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Around nineteen-hundred, all of physics, and particularly Einstein, was in trouble:
大约在1900年前，所有物理学家，尤其是爱因斯坦遇到了麻烦：
they couldn't figure out how anything could move… Now before you complain that I'm exaggerating, check out this cat!
他们没办法理解物体是怎样运动的......在大家抱怨我在夸大事实之前，看看这只猫！
You can clearly see that the cat is moving away from Einstein at a constant velocity…
你可以清楚的看到这只猫正在匀速远离爱因斯坦......
but do a little sliding switcheroo, and suddenly it looks like Einstein's the one moving.
但是做一个小的切换，突然它看起来像爱因斯坦在移动。
This is the old-fashioned principle of relativity
这就是早期的相对论
but the point is that the switcheroo changes relative things, like position and velocity,
但问题是这种平移变换只改变了相对的事物，如位置和速度，
and not absolute ones, like the separation of Einstein from his cat.
而不是绝对的事物，如爱因斯坦和猫之间的距离。
Now for the problem: before Einstein was even born, physicists showed that the speed of light was one of those absolute things
问题是，在爱因斯坦出生前，物理学家就指出光速是绝对的东西
which can't be changed by a switcheroo, so any switcheroo we do has to keep light moving at the same speed.
不受平移变换的影响，所以任何平移变换都不能改变光速。
But then it's obvious that we can't do our sliding switcheroo at all, which means we can't explain how anything other than light can move!
但很明显我们不能做任何平移变换，这意味着我们不能解释除了光以外的物体是怎么运动的！
Ok, I spoke too soon… there is one solution – do you see it?
好吧，我说的太绝对了......还有一种解决方法，大家看到了吗？
We were assuming that our switcheroo had to keep every slice of time at the same, well, time.
我们之前是假设，我们的变换都是基于时间均匀流动的基础上的。
But there's no law of physics that says time is an absolute thing that can't be changed by switcheroos…
但没有哪一条物理定律规定时间是绝对的，不能变化的影响......
so if we just rotate the slices of time while sliding them, then we can keep the speed of light the same, and explain how things can move, too.
所以如果我们平移的时候把时间也旋转一下，我们就可以保证光速不变并解释物体运动。
Of course, Einstein didn't figure out this special principle of relativity in 1905
当然，在1905年，爱因斯坦并没有想出这种特殊的相对性原则
- it was already done by a guy named Lorentz ten years earlier.
洛伦兹早在10年前就发现了它。
But Lorentz just thought this time-rotation was a mathematical trick…
但洛伦兹只是认为这种时间旋转是一种数学把戏，
and it took Einstein to step in, and, you guessed it, propose that 'time-rotation' is real,
后来爱因斯坦更进一步，没错，他提出‘时间旋转’确有其事，
that time really is relative, and that consequently, simultaneous events relative to one observer aren't simultaneous relative to another.
时间是相对的，因此，相对于一个观察者同时发生的事件相对于另一个观察者并不是同时发生的。
Now that's a real switcheroo of perspective.
这才是真正的视角变换。
