Physicists used to think that the universe had existed forever, unchangingly,
because that’s what their observations of the night sky suggested. Needless to say,
this view clashed with the origin or creation stories of most major religions
which hold that the universe had a beginning.
So it’s not surprising that it was a Catholic priest, Georges Lemaître, who was one of
the first major proponents of a new scientific viewpoint – that the universe did have a beginning.
Lemaître, of course, was also an excellent mathematician and scientist and based this
conviction not (just) on his religious beliefs but upon new experimental evidence from Edwin
Hubble that showed the universe was expanding. This evidence, combined with the mathematics
这一结论 结合广义相对论的数学模型 使勒梅特得以追溯宇宙过往
of general relativity allowed Lemaître to “rewind” cosmic history and calculate that
并计算得出 时间越久远 宇宙就越小
the farther back in time you go, the smaller the universe had to be. The natural conclusion
自然而然 我们得出结论 当前可见宇宙的一切
is that everything we can currently see in the universe was at one point in time more
or less at one point in space. Lemaître called this idea the “primeval atom”, but of course
today we know it as “the big bang theory”.
Except “big bang” is a horrible name – it would be much more accurate to call it “the
everywhere stretch”. Because one of the most common misconceptions about the big bang is
that it implies that the entire universe was compressed into a single point from which
it then somehow expanded into the surrounding… nothingness? It is true that the observable
universe, that is, the part of the whole universe we can see from earth, was indeed shrunk down
to a very very small bit of space, but that bit of space was not a single point, nor was
the rest of the Universe also in that same bit of space.
The explanation for this is the magical power of infinity. The whole universe is really big
current data show it’s at least 20 times bigger than the observable universe,
but that’s just a lower bound – it might be infinite. And if you have an infinite amount of space,
你可以将其缩小 一切都缩到微观尺寸 而空间仍是无限的
you can scale space down, shrink everything to minuscule proportions, and still have an
infinite amount of space. Kind of like how you can zoom out as much as you want from
a number line, but it’ll still be an infinite number line.
本质上 空间不需要伸展至“何处” 它可以在自身内膨胀
Essentially, space doesn’t need anywhere to expand “into” because it can expand into itself
并且不消耗空间 事实上 即使空间并非无穷大
and still have plenty of room. In fact, this is possible even if space turns out not to
be infinite in size, though the reasons are complicated and have to do with the infinite
differentiability of the metric of spacetime…
总之 被不幸命名为“大爆炸”的事件 指的是很久前的一个时间点
But anyway, the event unfortunately known as the big bang was basically a time, long ago，
when space was much more squeezed together, and the observable universe, that is,
everything that we see from earth, was crammed into a very very small piece of space.Because the
entire early universe was dense and hot everywhere, spacetime was curved everywhere and this curvature
manifested itself as a rapid expansion of space throughout the universe. And although
虽然人们称之为“大爆炸” 但它不止是“大” 而且无处不在
people call this “the big bang”, it wasn’t just big, it was everywhere. And it wasn’t
really an explosion – it was space stretching out. It’s really quite unfortunate that “the
Everywhere Stretch” isn’t nearly as catchy as “the Big Bang”.
Which brings us to the “big bang singularity”, which is an even horribler name because every
它的每一个字都是误导 我是说 “奇点”似乎暗示是在某一点发生的事情
single word is misleading. I mean, “singularity” seems to imply something that happened at
a single point. Which isn’t at all what it’s referring to – it SHOULD be called “the part
of the Everywhere Stretch where we don’t know what we’re talking about.” Basically, our
current physical models for the universe are unable to properly explain and predict what
was happening at the very very beginning when the universe was super super scaled down.
But rather than call it the “time when we don’t have a clue what was happening, anywhere”,
for some reason we call it a “singularity”.
This ignorance, however, does conveniently answer the question What happened before the
big bang? Because it tells us the question isn’t well defined – back when space was so
incredibly compressed and everything was ridiculously hot and dense, our mathematical models of
the universe break down so much that “time” doesn’t even make sense. It’s kind of like
这就类似 在北极点时 “北”的概念失去了意义
how at the north pole, the concept of “north” breaks down – I mean, what’s north of the
north pole? The only thing you can say is that everywhere on earth is south of the north
同样 宇宙中任意时刻 也是在“开端”之后
pole, or similarly everywhen in the universe is after… the beginning.
但无论时间是什么 一旦它开始后 宇宙中的空间就以难以想象的速度膨胀一段时间
But once time began, whenever that was, space expanded incredibly quickly all throughout
接着膨胀速度放缓 宇宙冷却 物质形成
the universe – for a little while. Then expansion slowed, the universe cooled, stuff happened,
and after a few billion years, here we are.
One thing we still don’t know is why this Everywhere Stretching happened – that is,
why did the universe start off in such a funny, compressed state, and why did it follow the
seemingly arbitrary laws of physics that have
governed its expansion and development ever since?
对乔治•勒梅特来说 这就是上帝介入 来解释科学力所不能及的事的时候了
For Georges Lemaître, this might be where God finally comes into the picture to explain
the things science can’t. Except that experimental evidence doesn’t actually rule out the possibility
that there may indeed be a time “before” the beginning, a previous age of the universe
这段时间里 宇宙的前身自我坍缩 变得相当炙热稠密
that ended when space collapsed in on itself, getting quite compressed and dense and hot,
but not enough to mangle up our ideas of what time is. It would have then bounced back out,
stretching in a fashion similar to what we call the big bang, but without the “we don’t
know what we’re talking about” singularity part. So, physics may actually be nudging
所以 物理学可能又将我们推回了“宇宙亘古不变 开端并不存在”的观点
us back to the view that the Universe is eternal and didn’t begin after all. In which case
Professor Lemaître might have to rethink his interpretation of the words “in the beginning.”
宇宙解密 S1 • E3 科学，宗教与大爆炸