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The Universe, informally, means everything there is - mountains and oceans and the moon
宇宙，通俗的解释是所有东西—山、海洋和月亮
and hot nuclear balls of hydrogen and a whole lot more.
以及热核氢和各种东西。
But if the Universe is 'everything', does that mean it includes the things that we don't know that we don't know exist?
但如果宇宙是一切，那么这是否意味着宇宙也包括我们不知道其存在的东西呢？
Or even the things that we believe exist but haven't yet seen or observed? For example, is the future a part of the universe?
甚至是那些我们相信存在但却还没看到或观察到的事物呢？例如，未来是宇宙的一部分吗？
In physics, we usually distinguish between these two notions of universe as
在物理学中，我们通常把宇宙概念区分为：
1) the 'observable universe', which is everything whose existence we've thus far been able to confirm or observe, or could in principle observe if we pointed our telescopes at it
1. 可观测宇宙，也就是我们迄今为止能够确认或观察到的所有事物，或者如果我们把望远镜对准它，原则上能观察到它
and 2) 'The Universe' with a capital U, or, 'The Whole Universe' which is everything that exists, has existed,
以及2. 大写U的宇宙或‘整体宇宙’，指的是所有存在、已经存在
or will exist, any time, anywhere, regardless of whether or not we're aware of it yet (or ever will be).
或将会存在的一切事物，不管我们有没有意识到它们(或将会意识到)。
Of course, the main reason for this distinction is so that we can talk scientifically about parts of the universe we haven't yet been able to observe,
当然，这样区分的主要原因是为了用科学理论来讨论我们尚未观察到的宇宙的某角落，
and the two biggest reasons we might not have been able to observe a piece of the universe yet are
并且我们可能还没观察到宇宙一部分的主要原因有两点
either it's in the future or it's so far away that light from it hasn't had time to reach us - yet.
要么它还在未来，要么它距离我们太远，它发射的光还没有足够的时间达到地球。
To explain: as far as we know, the universe had a beginning and is now around 13.8 billion years old.
解释一下：据我们所知，宇宙有一个开端且现在已有约138亿年的历史。
Light takes time to travel through space, so anywhere too far away from us just isn't visible yet in the same way
光线在太空中穿梭是需要时间的，所以任何离我们太远的地方，我们都是看不到的
that thunder from a distant lightning strike isn't audible - until you wait long enough.
就像是听不到远处的雷声一样—除非等待足够长的时间。
If you were blind, the thunder would be the first sign you have of the storm's existence,
如果你是盲人，那么雷声将是你预知风暴存在的第一迹象，
though once you hear it, you can infer that the storm must have existed all along.
虽然一旦你听到雷声，你可以推断风暴一定存在。
So within the observable universe, what do we know 'exists'?
所以在可观测宇宙中，我们怎么知道‘存在’呢？
Pretty much just three things: spacetime, particles, and the physical laws that describe
三件事：空间、粒子以及描述空间和那些粒子
how spacetime and those particles interact to give rise to gravity and matter and forces and everything else.
如何相互作用，产生重力、物质、力和其他一切的物理定律。
It's open for debate whether or not mathematics is a part of the universe or
数学是否是宇宙的一部分，或者
if it exists 'outside' the universe in some sort of mathematical heavens -
它是否存在于宇宙之外的某个数学天堂之中—这是有争议的
but if you think that mathematics exists and if The Universe is everything that exists, then, well, I'll leave that up to you.
但如果你认为数学存在，并且宇宙是所有存在的东西，那么我把这个问题留给你。
There's one other thing, though - you may have heard of parallel universes, or 'Multiverses'
还有一件事—大家或许听说过平行宇宙或‘多元宇宙’
an idea proposed by researchers or sci-fi fanatics that perhaps what we think of as
这是研究人员或科幻小说爱好者提出的想法，也许我们所认为的宇宙
The Universe is actually just a small piece of a larger thing which is really 'everything there is' but that's anotherverse in the story.
实际上只是一个更大的东西的一小部分，而这个更大的东西实际上是“所有的东西”，但这是另一篇故事了。
