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SciShow Space is supported by Brilliant.org.
《太空科学秀》由Brilliant.org赞助播出。
No matter what your mission is, one of the biggest obstacles to getting to space is fuel.
无论要执行什么任务，去往太空最大的难关之一就是燃料。
Obviously, you need some to get off the ground.
这是显而易见的问题，离开地面总要需要点推力的。
But fuel is also heavy, so if you want to lift a full rocket, you're going to need more of it.
但燃料质量也很大，所以如果想让满载燃料的火箭发射升空的话，就需要更多的推力才行。
But that just makes everything heavier, so then you need even more fuel. And on and on.
但这样的话，火箭整体就更沉了，需要更多的燃料，如此反复。
This is a part of what keeps us from sending probes to lots of different places in one trip:
这也是我们想要将多个探测器一次性送往不同地方的问题上所遇到的一个阻碍。
Moving around just takes so much heavy fuel.
发射升空需要太多的燃料了。
But back in the 1980s, scientists found a loophole, a way of touring the solar system on almost no fuel at all.
上世纪80年代的时候，科学家发现了一个漏洞，即在太阳系中飞行，却不需要任何燃料。
It's called the Interplanetary Superhighway.
这就是著名的星际高速公路。
These days, moving between objects in the solar system, like going from Earth-orbit to Mars, generally requires what's called a Hohmann transfer.
现在，在太阳系中的不同物体间穿梭，比如从地球轨道去往火星，基本上都需要霍曼转移。
You fire your rocket and speed up until your orbit around Earth gets so big that it crosses Mars's orbit around the Sun.
火箭加速升空后，其绕地球的轨道会变得越来越大，然后会穿过太阳附近的火星轨道。
Then, once you pass near Mars, you use your rocket to slow down and officially begin to orbit the Red Planet.
然后，经过火星的时候，会通过火箭来减速，并开始正式环绕火星飞行。
All that speeding up and slowing down burns a lot of fuel, but Hohmann transfers are one of the most efficient ways of getting between any two bodies in space.
这个过程中，无论是加速还是减速，都会消耗大量燃料。但霍曼转移是进入太空中两个物体之间最有效的方法之一。
Then, there are also gravity assists, which can be even more efficient.
此外，还有引力助推。引力助推也会加快效率。
In them, a craft speeds up by using a different planet's gravity to slingshot past it without burning much fuel.
所谓引力助推就是借助另一颗行星的引力来减少燃料的使用。
They're used all the time to get probes far from Earth.
我们一直通过这种方式来将探测器送到地球之外。
But if a spacecraft needs to orbit somewhere after a gravity assist, it still has to slow down when it gets there.
但如果有了引力助推后航天器要环绕什么物体飞行的话，那么航天器依然会减速。
And, again, that takes a lot of fuel. So in the 1980s, a few scientists tried approaching things a little differently.
而这样的减速依然会消耗大量燃料。上世纪80年代，一些科学家尝试过用稍微不同的方式来接近一些物体。
By thinking of gravity more like a landscape than a slingshot, they stumbled upon the Interplanetary Superhighway.
他们将引力作用想成了一种地形，而非弹弓一样的存在。它们会在星际高速公路上受到牵绊。
Its entrance and exit ramps are Lagrange Points: Five regions where gravity and rotational forces balance.
其入口坡道和出口坡道都是拉格朗日点，即5个引力和旋转力作用相平衡的地方。
They exist whenever one body orbits another, and they're creatively named L1 through L5.
一旦某个物体环绕另一个物体飞行的时候就会有拉格朗日点，我们创造性地将它们命名为L1和L5。
If you stick a spaceship at a Lagrange point, it will stay there, because gravity doesn't pull it more in one direction than another.
如果将某个宇宙飞船放在拉格朗日点上，那么宇宙飞船会保持不动，因为各个方向上的引力作用相互抵消了。
But not all Lagrange points are made equal. Some points are stable: In other words, if you're there and you move away a bit, gravity tends to pull you back, kind of like a ball at the bottom of a valley.
但不是所有拉格朗日点上的作用力都是平衡的。一些点很稳定：换言之，如果某个物体在拉格朗日点上，然后挪动了一点，那么引力的作用会将这个物体往回拉，就像谷底的一颗皮球一样。
Other points are unstable: If you move away a little, gravity keeps pulling you farther out.
其他的拉格朗日点都是不稳定的：稍微挪动一点，引力就会将物体拽的更远。
Spacecraft at these points are like balls on a hilltop:
处于这些拉格朗日点上的宇宙飞船就很像山顶上的皮球了。
They'll stay if they're delicately balanced or if you hold them, but the slightest breeze will send them speeding downhill.
如果各方向的力能达到平衡或者说如果能通过外力作用使之平衡的话，宇宙飞船就可以实现静止不动。但即便些许作用力也能让它们从“山顶”上滚落下去。
Normally, getting around the solar system requires accounting for and navigating all these hills and valleys, burning a bunch of fuel along the way.
正常情况下，在太阳系里移动需要考虑到山体和山谷的地形以及导航问题，所以沿途会消耗很多燃料。
But instead of just dealing with all these Lagrange points, the Interplanetary Superhighway puts them to work.
但星际高速公路却没有纠结于拉格朗日点的问题，而是将它们的作用也考虑在内。
See, there are five Lagrange points for every stable orbit, the Moon around the Earth, the Earth around the Sun, each of Saturn's moons around Saturn, you name it.
每个稳定的轨道都有5个拉格朗日点，比如月球环绕地球的轨道、地球环绕太阳的轨道以及环绕土星的卫星的轨道，都是如此。此外还有很多。
So they're everywhere, although they aren't always in the same place.
所以拉格朗日点到处都是，也不只是某个地方才存在。
The points always follow the less massive object around its orbit, and that creates a constantly changing landscape of gravitational hills and valleys throughout the solar system.
拉格朗日点总是跟着轨道附近质量稍小的物体，这就使得太阳系里引力的形势总是在发生变化。
In other words, the distribution of gravitational forces in the solar system changes over time:
换言之，太阳系里引力的分布会随着时间的变化而变化：
Sometimes, a spot might be mostly pulled to the Sun, sometimes mostly to a planet, and sometimes neither or both, when a Lagrange point passes by.
有时候，一个点可能被拉得离太阳更近，有时候离某颗行星更近，有时候可能离两者都很近或者都很远，这些都有可能在拉格朗日点经过的时候发生。
The metaphor of hills and valleys just helps all of us, professional and non-professional scientists, get a better grip on that abstract idea.
将这个问题用山体和山谷来做比喻，我们这些天文爱好者、专业人士以及非专业科学家也都更容易理解这个抽象的概念了。
Occasionally, in space, some hills pass near each other or even overlap.
有时候，在太空里，一些山体会经过彼此甚至相互重叠。
And when they do, space travel can get really efficient.
当发生这种情况的时候，太空旅行的效率就会更高。
For example, if you're on a gravitational hill that overlaps a valley, you can just roll right down into it.
比如，当置身于引力山体上而且该山体恰好与某个山谷相互重叠时，太空飞船就可以直接滑到里面去。
Or if you're on one hilltop that overlaps another, you can just move from summit to summit.
而当太空飞船处于某个山顶，而该山顶恰好与另一个山顶相重叠的时候，就可以从一个山顶去往另一个山顶了。
When Lagrange points from different orbits get near each other, it takes almost no effort to get from one to the next.
当不同轨道的拉格朗日点彼此相近的时候，从一个进入另一个完全不费事儿。
That means, if you're willing to wait for the right overlaps, you can hop from orbit to orbit, say, from Earth to Mars to Jupiter and beyond, with almost no fuel.
也就是说，如果愿意等待重叠期的话，就能从一个轨道进入另一个轨道，比如从地球进入火星再进入木星甚至其他恒星，却不消耗任何燃料。
That's the idea behind the Superhighway: It uses this ever-evolving network of Lagrange points to let you to travel between orbits practically for free, no fuel required.
这就是星际高速公路的理念。星际高速公路。通过不断变化的拉格朗日点组成的网络，让太空飞船可以不消耗一点燃料就在不同的轨道间穿梭。
Officially, all these moves between points are known as low-energy transfers, and they have been used in a couple of missions.
这种在不同点之间移动的方式，其官方说法是低能量转移。这种做法在多次任务中都有用到过。
One of the better known ones was a successful last-ditch effort to save a Japanese lunar probe in 1991, where there wasn't enough fuel to salvage the mission the conventional way.
其中一个著名的案例是：最后走投无路时用了这个方法，成功地解救了日本的月球探测器，那是1991年的事情。那时候，用传统的方法已经无法挽救探测器了，因为燃料不够了。
Unfortunately, though, we can't use these transfers for every mission, because it can sometimes take years or even millennia for Lagrange points to favorably overlap.
不过，不幸的是，这种转移方式无法应用到每个太空任务中，因为有时候需要数年甚至一千年的时间才能等到拉格朗日点重合。
But if we were willing to wait, we could send a probe out somewhere in space, where it could collect data for a while and wait for a good overlap.
但如果我们愿意等的话，我们可以将探测器发送到太空中，让他收集一段时间的数据，然后等待重叠。
Then, when one popped up, it could glide over and collect data somewhere else until another alignment appeared.
这样的话，当出现一个拉格朗日点的时候，就可以滑动过去，然后收集数据，并等待下一个拉格朗日点出现。
The craft could wander through the solar system almost indefinitely, inspecting whatever happened to get close enough and teaching us a lot along the way.
而探测器可以在太阳系里四处转悠，近距离观测一些情况，沿途还能带给我们很多有用的信息。
Admittedly, it would be a pretty different type of space exploration than what we're doing now, but it could be a promising option for a future long-term mission.
无可否认的是，这种太空探测方式跟我们现在的方式很不一样，但这是未来长期太空任务很有希望的一种选择。
And it would all be thanks to the Interplanetary Superhighway.
这一切都要归功于星际高速公路。
But what if I want to explore the universe now?!
但如果现在就想探索宇宙的话，要怎么办呢？
Luckily I can always pretend to be an astronaut from the future with this Brilliant.org quiz on interstellar travel.
好在Brilliant.org上关于星际旅行的测试让我可以体验一把未来宇航员的感觉。
If you liked this episode, I think you'll really enjoy the whole Astronomy course on Brilliant, and this quiz addresses a lot of the challenges of space travel we've been talking about.
如果您喜欢本集的话，我觉得您也会喜欢Brilliant上有关天文学的所有内容，而这个测试就可以解答我们讨论过的太空旅行的很多挑战。
Right now, our friends at Brilliant are offering the first 200 SciShow Space viewers that go to brilliant.org/SciShowSpace a 20% discount on an annual premium subscription.
现在，我们的合作伙伴Brilliant给前200名登录brilliant.org/SciShowSpace的《太空科学秀》粉丝一个订阅费打8折的机会。
You'll sharpen your math and science skills, and maybe help humanity get one step closer to traveling the interplanetary superhighway.
通过学习，既能磨砺数学和科学知识，也许也能帮助人类离实现星际高速公路更近一步。
So, get going! Time's a-wastin'!
心动不如行动，莫要浪费时间啦！
