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太阳系是以什么样的形式存在的? – 译学馆
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太阳系是以什么样的形式存在的?

Why is the Solar System Flat?

太阳 地球 及所有行星 还有月亮 矮行星
Our sun and the earth, and all the planets and moons and dwarf planets
自己小行星和彗星…简而言之在46亿年前
and asteroids and comets… The Solar System in short
一团由气体和尘埃所组成的星云
formed about 4.6 billion years ago from a nebulous cloud
在引力的作用下聚集在了一起
of swirling gas and dust which coalesced thanks to the irresistibly
形成了太阳系
attractive force of gravity.
然而这个星云或多或少都是形成于一个巨大的不成形的星团
However, this nebula started off more or less as a big shapeless blob.
那么我们的太阳系最终又是怎么让所有的行星
So how did our solar system end up with all the planets
还有月亮以固定的轨迹运行的呢
and their moons orbiting in a flat disk?
我是说 我们都看到过行星的原子模型
I mean, we’ve all seen the planetary model of the atom,
但是从原子角度上来看 这是完全错误的
which is definitely wrong when applied to atoms.
不过也有意见称行星们可能
But it also kind of suggests that planets might revolve
无规律的围着太阳转
around the sun every which way.
那么我们的太阳系存在于平面上某种意义来说是否很特别呢
So is our solar system somehow special in its flatness?
又或者是行星原子模型其实错上加错呢
Or is the planetary model of the atom doubly wrong?
其实宇宙中有很多”太阳系”
Well, our solar system definitely isn’t alone.
许多太阳系外的其他行星系以及
Many exoplanets’ star systems are flat,
许多银河都处在一个平面上
a lot of galaxies are flat,
还有黑洞吸积盘
black hole accretion disks are flat,
土星光环等等
Saturn’s rings are flat,
都处在平面上
etc.
那为什么 什么时候充满了三维宇宙的看法
So why, when there’s all of 3D space to fill,
难道宇宙对平面偏爱有加?
does the universe have this preference for flatness?
答案要从两个角度来看
The answer has to do with two things:
行星碰撞和我们生活在三维世界的事实
collisions and the fact that we live in three dimensions.
原谅我
Bear with me.
宇宙中大量物体被引力吸在一起动能猛增并进行环绕运动
Anytime a bunch of objects held together by gravity are zooming and circling around,
我们无法预测它们中任何一个的运动路线
their individual paths are nearly impossible to predict.
可是 如果把它们合并成一个的时候
And yet, collected together, they have a single total amount
它们就会围着它们共同的中心旋转
that they spin about their center of mass.
可能弄清它们旋转的趋向是件很困难的事
It may be hard to figure out exactly what direction that rotation is in,
不过数学运算表明在星云里一定有一些平面
but the mathematics implies there must be some plane
作为整体在旋转
in which the cloud, taken as a whole, spins.
目前 在二维世界里 于平面中旋转的粒子云
Now, in two dimensions, a cloud of particles rotating in a plane
也是个平面 当然这是在二维世界里
is flat by definition, it’s in two dimensions.
但是在三维世界里 即便星云的旋转是在一个平面内发生的
But in three dimensions, even though the rotation of the cloud is given
粒子依旧可以在那个平面里上窜下跳
by one plane, particles can whiz around far up and down from that plane.
随着粒子相互碰撞 它们所有的运动行为
As the particles bump into each other, all the up and down motion
都会相互抵消 这便是在相互碰撞及凝结中形成的能量流失
tends to cancel out. It’s energy lost in crashing and clumping.
然而整个星团仍然要不停的进行旋转
Yet, the whole mass must continue spinning inexorably,
因为在我们的宇宙 每一个独立星系旋转的总量
because in our universe, the total amount of spinning in any isolated system
是相同的
always stays the same.
所以随着时间推移 通过碰撞运动 星云会失去它的能量
So over time, through collisions and crashes, the cloud loses its loft
并变成一个旋转的粗糙的像太阳系或银河漩涡一样的二维的盘状物
and flattens into a spinning, roughly 2 dimensional disk shape, like a solar system or a spiral galaxy.
然而用数学计算出在四维空间中
However, in 4 spacial dimensions, the math works out such that
可以同时存在两个独立但互补的旋转的平面
there can be two separate and complementary planes of rotation,
但以我们三维思考的大脑要想象出这样的画面非常非常困难
which is both really really hard for our 3D-thinking brains to picture
同样也意味着粒子互相碰撞流失能量的时候不会有上窜下跳的活动
and also means there’s no up and down direction in which particles lose energy by collisions.
所以粒子云可以继续以…云团的形式存在
So a cloud of particles can continue being just that… a cloud.
因此星云和婴儿期银河只有在三维世界里
And thus, only in three dimensions can a nebula or infant galaxy
才能以非平面的形式诞生再转变成平面的形式
start out not flat and end up flat
这显然是个好消息 因为我们需要那些物质以块状形式存在
which is definitely a good thing, because we need all that matter to clump together
以此来形成恒星与行星 以此来形成我们
in order for stars and planets to form, and for us,
即便这些人认为原子就是这样
even those of us who think atoms look like this,
存在的
to exist.
这段minute physics的小视频由我们的赞助者之一
This episode of minute physics is supported in part by
安柏瑞德航空大学部分支持
Embry-Riddle Aeronautical University, one of our subscribers

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视频概述

太阳系是以二维形式存在的还是三维?甚至是…四维?

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https://www.youtube.com/watch?v=tmNXKqeUtJM

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