Why Earth Is Our Cosmic Prison, And How to Escape It[1]
為什麼說地球是「宇宙監獄」?又該如何才能「逃獄」成功呢?
Sitting on our pale blue dot and staring out at the Universe, it's easy to get excited about all the places we could go.
坐在地球這個「暗淡藍點」上注視著宇宙，自然而然地會對我們能夠到達的各個地方感到欣喜若狂。
But despite advances in rocket science, the reality is that our species remains trapped on Earth. Our technology has reached the edge of the Solar System, but no human has yet set foot on another planet. And there's a good reason for that - we each owe the Universe a debt that's around 4.5 billion years old.
雖然我們在火箭科學上所取得的進展已經相當高，但實際上，人類卻還是被困在地球上。我們的技術已經能夠讓我們到達太陽系的邊緣，卻還是沒有一個人能夠踏上另一個星球。而能夠解釋這個局面的理由就是，所有的人類都欠了宇宙一筆大約長達45億年的債。
As the episode of Kurzgesagt - In a Nutshell explains below, when our planet was formed, it cost the Universe a great deal of energy. And we have to pay that energy back if we want to escape Earth and the Moon, and spread ourselves to the distant regions of space.
正如以下Kurzgesagt-In a Nutshell的影片中所解釋的那樣，由於地球形成的時候耗費了宇宙相當龐大的能量，所以若是想要逃離地球和月球的話，得先償還這些能量才能離開這裡，到達遙遠的太空之中。
But how can we possibly owe the Universe an energy debt when we've only been around for a tiny portion of the Universe's existence?
可是，宇宙存在了這麼久，而人類才只占了宇宙生命中的一小部分而已，又怎麼可能會欠宇宙這麼一筆能量債務呢？
As the video above poetically explains, it's "because your atoms were once part of the dust the Universe expended energy on to get to this place".
就像上面的影片饒富詩意的解釋一樣，這是「因為我們身體中的原子曾是宇宙塵埃中的一部分，是宇宙消耗了能量在這些塵埃上，我們才能到達地球。」
In other words, it took energy to make our planet, and so we need energy to escape it.
換句話說，因為需要消耗能量才能製造出地球，所以若要離開它，也得用足夠的能量來換。
That sounds weird, but it actually makes sense when you break it down. It's all due to the fact that, in our Universe, things don't want to change speed or direction. To do so, you need to spend some energy.
這聽起來有點怪，不過若去仔細解讀它的話，就會發現這確實很有道理。這全是因為在宇宙之中，物體並不會想去改變自身的速度或方向。若想改變的話，就得花一些能量。
It's also a fact that everything with mass in the Universe attracts every other thing with mass - a phenomenon we call gravity.
除此之外也是因為宇宙中任何具有質量的物體都會吸引其他具有質量的物體，這個現象就是我們所稱的引力。
Around 4.5 billion years ago, gravity convinced trillions and trillions of particles of dust to come together and form our planet - something that cost a significant amount of energy.
大約45億年前，引力聚集了無數的塵埃粒子形成地球，而這可得花上相當龐大的能量。
The effort of this planetary formation created a gravity prison, trapping us in the process. You can think of it like the gravity well in the image below, the further down the well you fall, the more energy you need to get out.
這種行星形成的作用就建造出一座「引力監獄」，將我們困在這個過程之中。可以把這種作用想像成下圖的「引力井」，在井中跌得越深，想出去，所需的能量就越多。
Kurzgesagt - In a Nutshell/YouTube
To escape from Earth, which is right at the bottom of that well, we need to spend as much energy as it took for the planet to be formed.
想要脫逃深陷井底的地球，需要花費的能量就得和形成這顆星球所需要花費的能量一樣多才行。
How do we do that? It's something scientists are working on right now, with the creation of complex, energy-exchanging machines - better known as rockets.
怎樣才能做得到呢？這是目前科學家們正在研究的問題，而他們的辦法就是創造出複雜的能量交換器，也就是眾所皆知的火箭。
Rockets use some of the most energetic chemical reactions we know about to explode fuel in a controlled way. This converts chemical energy into kinetic energy, and directs exhaust outwards to push a rocket away from Earth.
火箭的原理是利用目前所知的一些最強勁的化學反應，在能夠控制的情形下引爆燃料，將化學能轉化為動能，並藉由向外排出廢氣，將火箭推離地球。
By expending these crazy amounts of energy, we're increasing our gravitational potential energy, which, as the video explains, is just a complicated way of saying we're paying back our energy debt to gravity.
藉由消耗這些浩瀚的能量，我們就能增加我們的引力勢能。根據影片所解釋的，這個其實就是「我們就能償還欠引力的那些能量」的複雜說法而已。
But it's not as simple as just pumping enough energy out of your rocket and heading into space - unfortunately, the process of burning fuel causes rockets to lose a lot of energy as heat.
不過這可不是從火箭中打出足夠的能量然後就可以進入外太空這麼簡單，遺憾地是，燃燒燃料的過程會使火箭產生熱能而損失大量的能量。
Then there's also atmospheric drag to take into account, not to mention the weight of all this fuel and the people and equipment you're trying to get into space in the first place.
然後還得考慮大氣的阻力，更不用說首先還得考慮所有燃料的重量以及想帶入太空中的人和裝備的重量。
The more fuel you add, the more rocket you need to carry that fuel, and engineers generally end up needing to build a rocket 100 times the weight of whatever they want to launch into space.
加的燃料越多，需要用來攜帶這些燃料的火箭就越多。所以工程師通常最後需要製造出一個比他們想要發射到太空中的東西還要重100倍的火箭。
And it doesn't end there. It turns out there's a limit to how heavy something can be before it simply won't launch anymore.
而且事情並未就此結束。原來，能夠承載多重是有上限的，超過了就會無法發射出去。
Kurzgesagt calls this the "tyranny of the rocket equation" and it's one of the main reasons that humans remain trapped in our cosmic prison here on Earth.
Kurzgesagt稱之為「火箭方程的暴政」，而這也是人類被困在地球這個宇宙監獄中的主要原因之一。
But if we want to survive as a species, one day we're going to have to make it off Earth for good. And it's not as impossible as it sounds.
但是，若想要成為一個能夠一直續存下去的物種的話，總有一天人類將不得不永遠地離開地球。不過這也不是完全做不到。
Check out the video above to find out what it's going to take. And if it's a little bit too much for your brain to handle, don't worry - it is rocket science, after all.
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