评论
打印
In our universe, when you change from a non-moving perspective to a moving one or vice versa,
在我们宇宙中，当你从一个静止的视角转换到一个运动的视角，或者反过来，
that change of perspective is represented by what's called a Lorentz transformation,
视角的变化由所谓的“洛伦兹变换”表示，
which is a kind of squeezed stretched rotation of space-time
这是一种压缩的时空旋转，
that I've mechanically implemented with this space-time globe,
我用这个时空球体机械地实现了这种旋转，
a quick reminder, space-time diagrams plot position on the horizontal axis and time on the vertical axis,
作为一种快速提示，时空图在横轴上描绘位置，在纵轴上描绘时间，
so something that moves as time passes traces out a path through space-time called a world line.
因此随着时间流逝而移动的物体描绘出一条穿越时空的路径，称为世界线。
one of the first things you might notice about Lorentz transformations
关于洛伦兹变换，你可能注意到的第一件事是，
is that events that were at different places at the same time before the transformation
在变换之前同时处于不同位置的事件
aren't at the same time after the transformation.
在变换之后不在同一时间。
This means that from the perspectives of people going different speeds,
这意味着从人的不同速度的角度来看，
simultaneous events for one person won't be simultaneous for the other and vice versa.
对某个人来说是同时发生的事，对其他人来说却不同，反之亦然。
For example, if from my perspective these two boxes spontaneously combust at the same time
例如，如果从我的角度看，这两个盒子同时自燃，
and you're moving at 1/3 the speed of light to my right. Then, from your perspective,
而你以1/3光速向我的右边移动。
that is from the perspective in which you're not moving, so your world line is purely vertical.
然后，从你的角度看，也是从你静止的角度看，所以你的世界线是完全垂直的。
From your perspective, the box on the right will combust first, and the box on the left will combust second.
从你的角度看，右边的盒子首先燃烧，然后左边的盒子开始燃烧。
The takeaway here is that our universe has neither an absolute notion of time
这里的结论是，我们的宇宙既没有绝对的时间概念，
nor an absolute sense of simultaneous events,
也没有绝对同时发生的事件，
and that simultaneity breaks down more the farther away from each other two things are.
而且两个事物之间的距离越远，同时性就越糟糕。
A box even farther to the left that from my perspective simultaneously spontaneously combusts with the others,
从我的角度看，更靠左边的盒子同时和其他盒子自燃，
will, from your moving perspective, be even farther out of sync with the box on the right.
从你移动的角度来看，相比于右边的盒子，发生自燃的情况更加不同步。
This is described by the time part of the Lorentz Transformation equations,
这通过洛伦兹变换方程关于对时间的描述，
The part that says: tnew equals gamma times t minus v over c squared times x.
这个方程是：tnew=γ(t-v*x/c²)。
Because of the x in there, the farther away an event is from you,
因为当x事件离你越远，
the more its time from the new perspective will be out of sync with events closer to you.
从新的角度来看，它的时间就越会与离你更近的事件不同步。
Though, because of the factor of c squared in the denominator which is huge.
然而，由于c因子的平方在分母中数值非常大。
It's hard to notice anything being out of sync until
很难注意到任何不同步的东西，
either your speed or diatance to the object in question are really really big.
除非你的速度或者跟物体的距离真的很大。
Like, you'd have to be going half the speed of light
比如，相对于地球和月球之间的距离，
and be comparing things farther apart than the earth and moon
你必须以一半的光速来比较比这距离还要更远的物体，
before things would become more than one second out of sync.
不同步持续的时间差才会超过1秒。
But in that case, events that were simultaneous from my perspective really would be out of sync for you.
但在这种情况下，从我的角度来看，同时发生的事件对你来说确实是不同步的。
As surprising as this may seem, it might feel more familiar and comfortable
就像这看起来一样令人惊讶，
when you remember that this "getting out of alignment" phenomenon
当你记得这个“不同时”现象发生在空间的同一点上时，
happens to points that are at the same point in space too.
你会感觉更加熟悉，容易理解。
from my perspective, this box is at the same position at different times that is it's not moving.
从我的角度来看，这个盒子在不同的时间处于相同的位置，那就是它没有移动过。
But from your moving perspectives, it's at different positions at different times.
但从你移动的角度来看，它在不同的时间处于不同的位置。
It is moving and it's no longer in alignment.
它在移动，但不再与x坐标对齐了。
Relativity of simultaneity is just the other side of the coin,
同时性的相对性只是事物的两面性，
the fact that events that happen at the same time, at different spatial positions
事实是当从移动视角观察时，
happen at different times when viewed from a moving perspective.
在不同空间位置同时发生的事件发生在不同时间。
All together, in our universe, the takeaway is this:
总之，在我们的宇宙中，我们可以得出这样的结论：
events that were previously either all at the same place or all at the same time,
所有发生在同一个地方或在同一时间发生的事件，
get out of alignment with each other when you change to a moving perspective.
当你换到一个移动的视角时，它们之间发生的同步性就会受到影响。
A big thanks again to Mark Rober for making the spacetime globe a reality,
再次感谢Mark Rober使时空球体成为现实，
and to dive more into the details of relativity of simultaneity,
并更深入地研究同时性的相对论。
I highly recommend heading over to Brilliant.org's course on special relativity
我强烈推荐Billiant.org关于狭义相对论的课程，
that they've been developing simultaneously with this vedio series.
这些课程一直与这个系列视频同步
(well, at least, simultaneous from my perspective).
（至少，从我的观点来看是同步的）。
There, you can explore custom scenarios and do actual puzzles and problems
在那里，你可以探索定制的场景，解决实际的难题和问题，
that help you build on what you learned in this video,
帮助你巩固在本视频中所学到的知识，
like figuring out how laser tag would work at relativistic speeds!
比如理解激光射击游戏在相对论速度下是如何工作的！
The special relativity questions on Brilliant.org are specifically
在Brilliant.org上有专门设计的狭义相对论问题，
designed to help you go deeper on the topics I'm including in this series,
是为了帮助你更深入地讨论我在本系列中涉及到的话题，
and you can get 20% off of a Brilliant subscription by going to Brilliant.org/minutephysics.
你可以通过访问Brilliant.org/minutephysics来获得Brilliant订阅的20%的折扣。
Again, that's Brilliant.org/minutephysics
再次说明是这些网站，Brilliant.org/minutephysics，
which gets you 20% off premium access to all of Brilliant's courses and puzzles,
能让你享受所有Brilliant课程和问题的高级访问权限，
and lets Brilliant know you came from here.
让Brilliant网站知道你来自本视频。
