Since the launch of the first artificial satellite in 1957, governments, companies,
自 1957 年第一颗 人造卫星发射以来，政府、公司
and research institutions have been planting flags among the stars.
和研究机构一直在给行星们添上旗帜。
But while it might seem like there's plenty of room in this vast expanse, some pieces of celestial real estate are more valuable than others.
虽然宇宙空间不可估量，有些天文位置比其他更有价值。
Each of these dots is a Lagrange point, and as far as human space exploration is concerned, they may be the most important places in our solar system.
这其中每一个点都是拉格朗日点，而对人类太空探索而言，它们可能是我们太阳系中最重要的地点。
Named after the 18th century mathematician who deduced their positions,
拉格朗日点为推导出其位置的 18 世纪数学家而命名，
Lagrange points are rare places of equilibrium in our constantly shifting universe.
它在我们不断运动的宇宙中，是罕见的平衡点。
All celestial bodies exert a gravitational force on nearby objects, pulling them in and out of orbits.
所有天体会对附近的物体施加引力，将它们拉入和拉出轨道。
And gravity acts alongside several apparent forces to determine what those orbits look like.
重力与几种表观力一起作用，确定了这些轨道形状。
However, Lagrange points are places where all these forces balance out.
但是，拉格朗日点是所有这些力平衡的地方。
So if we place a relatively low mass object here, it will maintain a constant distance from the massive bodies pulling on it.
因此，如果我们在这里放置一个质量相对较低的物体，它将与吸引它的巨大天体保持恒定的距离。
Essentially, Lagrange points are celestial parking spaces— once an object is there, it requires little to no energy to stay put.
从本质上讲，拉格朗日点像天体停车位—— 一旦物体在那里，它几乎不需要任何能量便可留在原地。
So whenever humans want to keep an object in one place for a long time without using tons of fuel, it needs to be orbiting a Lagrange point.
因此，当人类希望不消耗大量燃料将物体长时间保留在一个地方时，它得绕着拉格朗日点运行。
However, there are only so many of these parking spots.
但是，停车位只有那么多。
Pairs of massive bodies in our solar system generate sets of five Lagrange points.
太阳系中每对大型天体会产生五个拉格朗日点。
This means our Sun has five points with every planet, and our planets have five points with each of their moons.
这意味着我们的太阳与每个行星都有五个点，而我们的行星与各颗卫星也有五个点。
Adding these up, there are over 1,000 Lagrange points in our solar system— but only a few are useful for human purposes.
加起来我们太阳系中的拉格朗日点超过1,000个，但只有少数对人类有用。
Many are in locations that are too difficult to reach or simply not very useful.
许多点的位置难以到达，或是用处不大。
And for reasons we'll explain in a bit, many others are unstable.
许多点也不稳定， 这我们会稍后解释。
Currently, only two of these points are heavily used by humans.
目前，其中只有两个点被人类广泛使用。
But we'll likely use many more in the future— making these limited points exclusive real estate.
但在未来我们可能会使用更多的点—— 把这些有限的点转成特权地点。
Which begs the question: what exactly should we park in them?
这就引出了一个问题：我们到底应该在里面停什么？
That answer depends on where each point is.
这个答案取决于每个点在哪里。
Consider the five Lagrange points generated by the Sun and the Earth.
以太阳和地球产生的五个拉格朗日点为例。
L1 is located inside Earth's orbit, about 1.5 million kilometers away from the planet.
L1 位于地球轨道内，距离地球约150万公里。
With this panoramic view of the Sun, unobstructed by Earth's shadow, L1 is the perfect place for solar-observing satellites.
L1不被地球遮挡，可见到太阳全景，是太阳观测卫星的理想地点。
L2 is at the same distance from Earth but outside its orbit and shielded from the Sun, making it the perfect spot to observe outer space.
L2 与地球的距离相同，但在轨道之外，在太阳的阴影中，使其成为观测外部太空的理想地点。
In 2022, the James Webb Space Telescope went online here, in a spot where the Sun and Earth only occupy a tiny fraction of the sky.
2022年，詹姆斯·韦伯太空望远镜在这里部署；在这里，太阳和地球只占天空的很小一块。
L3 is in a particularly mysterious location that can never be directly observed from Earth's surface.
L3 位于一个特别神秘的地方，永远无法从地球表面观察到。
This has made L3 a frequent locale in science fiction, though it hasn't offered much use to scientists yet.
这使得 L3 在科幻小说中经常出现，尽管它对科学家们用处不大。
L4 and L5, however, are a bit different from their siblings.
而L4和L5和其余的略有不同。
In every set of five, the first three Lagrange points are slightly unstable.
在每五个点中，前三个拉格朗日点略微不稳定。
This means objects will slowly drift away from them, though keeping what we've parked there in place is still energetically cheap.
这意味着物体会慢慢地远离它们，但使我们停在那里的东西留在原地并非难事。
The stability of L4 and L5, however, varies from set to set.
而L4与L5的稳定性取决于天体对。
If the heavier of the two bodies generating the points has less than 25 times the mass of the lighter body,
如果两个天体中较重的天体质量不到较轻天体的25倍，
these points are too unstable to park things in.
这些点就会不稳定，物体无法在其中停靠。
However, if the heavier body is massive enough— like it is in Sun-Earth set— then the relevant forces will always return objects to these equilibrium points,
但是，如果较重的物体足够大，如太阳、地球这组天体，那么这些力会使物体待在平衡点，
making them our most stable parking spots.
使它们成为最稳定的停车点。
That's why points like these naturally accumulate space objects, such as the Sun-Jupiter set's L4 and L5, which host thousands of asteroids.
这便是为什么类似的点会积聚太空物体的原因，例如太阳、木星的L4和L5，聚集着上千个小行星。
Every Lagrange point in our solar system has its quirks.
太阳系中的每个拉格朗日点都有其特点。
Some might be perfect for scavenging construction materials from drifting asteroids.
有些可能非常适合从漂移的小行星中开采建筑材料。
Others might make ideal gas stations for ships headed to deep space, or even host entire human colonies.
其他可以成为前往深空中飞船的理想加油站，甚至容纳完整的人类殖民地。
These points are already home to advanced technological achievements, but soon, they could become our stepping stones to the stars.
