Since the launch of the first artificial satellite in 1957, governments, companies, and research institutions have been planting flags among the stars. 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. 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.
自 1957 年第一颗 人造卫星发射以来, 政府、公司和研究机构 一直在给行星们添上旗帜。 虽然宇宙空间不可估量, 有些天文位置比其他更有价值。 这其中每一个点都是拉格朗日点 (Lagrange point), 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, Lagrange points are rare places of equilibrium in our constantly shifting universe. All celestial bodies exert a gravitational force on nearby objects, pulling them in and out of orbits. And gravity acts alongside several apparent forces to determine what those orbits look like. However, Lagrange points are places where all these forces balance out. So if we place a relatively low mass object here, it will maintain a constant distance from the massive bodies pulling on it. Essentially, Lagrange points are celestial parking spaces— once an object is there, it requires little to no energy to stay put. 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.
拉格朗日点为推导出其位置的 18 世纪数学家而命名, 它在我们不断运动的宇宙中, 是罕见的平衡点。 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。 重力与几种表观力一起作用, 确定了这些轨道形状。 但是,拉格朗日点是所有 这些力平衡的地方。 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。 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。 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. Pairs of massive bodies in our solar system generate sets of five Lagrange points. This means our Sun has five points with every planet, and our planets have five points with each of their moons. Adding these up, there are over 1,000 Lagrange points in our solar system— but only a few are useful for human purposes. Many are in locations that are too difficult to reach or simply not very useful. And for reasons we'll explain in a bit, many others are unstable. Currently, only two of these points are heavily used by humans. But we’ll likely use many more in the future— making these limited points exclusive real estate. Which begs the question: what exactly should we park in them?
但是,停车位只有那么多。 太阳系中每对大型天体 会产生五个拉格朗日点。 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。 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。 许多点的位置难以到达, 或是用处不大。 许多点也不稳定, 这我们会稍后解释。 目前,其中只有两个点 被人类广泛使用。 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。 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. Consider the five Lagrange points generated by the Sun and the Earth. L1 is located inside Earth's orbit, about 1.5 million kilometers away from the planet. With this panoramic view of the Sun, unobstructed by Earth’s shadow, L1 is the perfect place for solar-observing satellites. 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. 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. L3 is in a particularly mysterious location that can never be directly observed from Earth’s surface. This has made L3 a frequent locale in science fiction, though it hasn’t offered much use to scientists yet.
这个答案 取决于每个点在哪里。 以太阳和地球产生的 五个拉格朗日点为例。 L1 位于地球轨道内, 距离地球约 150 万公里。 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 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。 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 位于一个特别神秘的地方, 永远无法从地球表面观察到。 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. In every set of five, the first three Lagrange points are slightly unstable. This means objects will slowly drift away from them, though keeping what we’ve parked there in place is still energetically cheap. The stability of L4 and L5, however, varies from set to set. If the heavier of the two bodies generating the points has less than 25 times the mass of the lighter body, these points are too unstable to park things in. 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, making them our most stable parking spots. 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.
而 L4 和 L5 和其余的略有不同。 在每五个点中, 前三个拉格朗日点略微不稳定。 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。 而 L4 与 L5 的稳定性 取决于天体对。 如果两个天体中较重的天体 质量不足较轻天体的 25 倍, 这些点就会不稳定, 物体无法在其中停靠。 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, 使它们成为最稳定的停车点。 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. Some might be perfect for scavenging construction materials from drifting asteroids. Others might make ideal gas stations for ships headed to deep space, or even host entire human colonies. These points are already home to advanced technological achievements, but soon, they could become our stepping stones to the stars.
太阳系中的每个 拉格朗日点都有其特点。 有些可能非常适合 从漂移的小行星中开采建筑材料。 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。 这些地点已经存在着先进技术设备, 但不久,它们也许成为 我们通往星空的基地。