时间有方向，这是理所当然的。 It's perfectly obvious the time has a direction
我们说这的意思是：过去与未来很不同。 All we mean by that is that the past is different from the future in lots of different ways
以前我们比较年轻，未来的我们也相应地会比现在老。 We were younger in the past, we will be older in the future
我们能记得的是往事，记不了未来的事情。 We remember the past, we don't remember the future
未感到惊讶的是，过去和未来的区别 The surprise is that that difference between past and future
并不能在物理的定律找到. is nowhere to be found in the deep down laws of physics
其实时间和空间很相似，如果你穿着太空服在外空中漂浮， Time is actually a lot like space if you're out in a space suit flying around
上、下、左、右， 不会有任何差别。 there will be no difference between up, down, left, right
相应的，过去与未来在物理定律 likewise, there is no intrinsic difference between the past and the future
没有定制的分别。这并非是一件不可思议的事。 in the laws of physics. Now that's not completely a mystery to us
我们知道在现实世界里，真正的是 we know that what actually happens in the real world
你不但只是从一个、两个微粒碰撞 is that you're not just made of one or two particles
而组成的，你实际上非常复杂， bumping into each other, you're a very very complicated collection
是从很多很多的微粒组成的。而且这些微粒随时间变得更混乱。 of many many particles and they're becoming more disorderly with time.
这等于说熵在增加。 this is just saying that entropy increases.
有趣的是，过去和未来的每一个差别， The interesting thing is that every difference between the past and the future
都是因为过去的熵会比较未来低， will utimately be traced to the fact that the entropy was lower
而且在持续地增加。那就是热力学的第二定律。 in the past and is growing. That's the Second Law of Thermodynamics
世界本来是有秩序的，它变得越来越不条理。 The universe was orderly, it's becoming more disorderly
但这并不奇怪，不条理的形态比条理的多。 That's not a surprise. There is more ways to be disorderly than to be orderly.
奇怪的是世界里的熵一开始已经不低。 The suprise is that the universe was ever low entropy to begin with.
到137亿年从一个很条理的前，大爆炸放生时，世界是 If we go all the way back to the Big Bang, 13.7 billion years ago, the universe began
状态开始。所以宇宙学家正在试以解释 in a highly ordered state. So, modern cosmologists are trying to understand
早期宇宙为何那么精准。 right now why the early universe was in a such precise state.
为什么宇宙的熵那么的低。了解这件事后， why it was so low entropy. Once we understand that,
就能够轻易知道时间的箭头 it will make perfect sense to us why the arrow of time stretches
从过去往未来指的原因。 as it does from the past to today all the way toward the future.
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