As much as we all wish there were an easy, and affordable way to see our planet floating in the dark.

儘管我們都希望能有一個更簡單、更負擔得起的方法從深邃的太空中看看我們的星球。

Right now, the only way is to become an astronaut or a billionaire.

目前為止，能做到這件事的就只有成為太空人，或億萬富翁才行。

But there is a concept that might make it possible, while serving as the starting point for the exploration of the universe.

但有個概念或許能夠成為探索宇宙的起點。

The space elevator.

那就是太空電梯。

How exactly does it work?

究竟這是如何辦到的呢?

To understand how a space elevator will get us into space, we must first understand what an orbit is.

要了解太空電梯如何帶我們進入太空，我們必須先了解何謂運行軌道。

Being in orbit basically means falling towards something but moving fast enough to miss.

運行在軌道上，代表物體正在朝向某樣東西墜落，但是墜落速度又快得足夠避開那樣東西。

If you throw a ball on earth, it makes an arch through the air, and then hits the ground.

如果你在地球上朝空中丟一顆球，那顆球將會在空中劃出一道弧線，然後墜落到地上。

In space, gravity makes you move much the same way, but if you move sideways fast enough, the curvature of the earth makes the ground fall away beneath you as fast as gravity pulls you towards it.

在太空中，重力以相同的方式運作，但如果你的橫向速度夠快的話，地球軌道的曲率會使你遠離地面，速度與被重力拉向地球相等。

So to enter Earth's orbit, rockets have to go up and sideways fast.

所以，如果想要進入地球軌道，火箭得要向上，並同時快速橫向飛行。

By contrast, a space elevator taps into energy from Earth's rotation to get the cargo going fast.

相對地，太空電梯則利用地球自轉的能量使得送上太空的貨物達到能運行於軌道的速度。

Imagine a child spinning a toy on a rope with an ant on the child's hand.

試著想像一個孩子用一條繩子甩動玩具，而手握住繩子那端上有一隻螞蟻。

As the ant climbs out along the rope, it starts to move faster and faster as it ascends.

當螞蟻沿著繩子向上爬時，它的速度將會隨著越往上爬越快。

Compared to rockets, with cargo launched on an elevator, you only need to provide the energy to go up.

相較於發射火箭，藉由太空電梯將貨物運送至外太空時，僅需要提供向上的能量即可。

Fast sideways movement comes free with the Earth's rotation.

運行於軌道的橫向速度則由地球自轉本身產生的能量提供。

But the space elevator would, without a doubt, be the single largest and most expensive structure ever built by humans.

但是建造一個太空電梯毫無疑問會是人類有史以來所造出的最大且最貴的一個建築。

So is it worth it?

所以這一切真的值得嗎?

It all comes down to costs.

一切都跟價格有關。

Rockets burn a huge amount of rocket fuel just to get a small amount of cargo into space.

光將少量的貨物運送上太空，就需消耗巨大的火箭燃料。

At current prices, it costs about 20,000 dollars to put one kilogram of payload into space.

就目前的價格來說，將一公克的貨物送上太空將要花上大約兩萬美元。

That's 1.3 million dollars for the average human, 40 million dollars for your car, billions for an international space station.

也就是平均送一個人上太空需要花一百三十萬美元，一台車是四千萬美元，以及數十億美元讓國際太空站得以到達外太空。

This immense cost is one of the major limitations of human spaceflight.

這樣巨大的花費是目前限制人類進入太空的一個重大瓶頸。

Even with advancing technology, this cost isn't likely to be comparable with the price of an airline ticket anytime soon.

就算科技不斷進步，短期內上太空的花費內還是比不了現在的機票價格。

A space elevator would solve this problem.

然而太空電梯可以解決這個問題。

After construction, a space elevator is projected to reduce the cost one hundredfold to 200 dollars per kilogram.

經過建造之後，太空電梯將使運送成本降低至原本的百分之一，使每公克運送成本只有兩百美金。

If an inexpensive space elevator costs 20 billion dollars, then we'll recoup our losses after launching only one thousand tons.

假設一個低成本的太空電梯造價為200億美金，這樣只需運送一百萬噸就可以回本。

Close to the weight to two international space stations.

接近兩個國際太空站的重量。

So what would a space elevator look like in real life?

那太空電梯在現實世界中會是什麼樣子？

A space elevator has four major components: the tether, anchor, counterweight and climber.

太空電梯將有四個主要構造：纜線、基座、平衡物，與升降艙。

The elevator part of the space elevator is the tether and the climber.

而太空電梯中的「電梯」部分則主要是由纜線與升降艙組成。

It extends from the surface of the Earth to space.

升降艙一路從地表延伸到太空。

The climber is like a conventional elevator carriage, a chamber that works its way up and down the tether.

它的運作方式就跟傳統的電梯一樣，是一個可以上升與下降的載體。

At the base would be an anchor pinning the tether to the Earth along with a port for climbers.

在地表的部分則是由基座將纜線固定在地上，並提供進出電梯艙的出入口。

At the top is the counterweight which holds up the tether.

在最上方的平衡物將纜線固定住。

The tether is held tight like a rope and supported from above by the tension from the counterweight.

纜線就像一條繩索一樣連結在平衡物上，由平衡物所產生得張力來支撐。

Located higher than 36,000 kilometers above the Earth's surface.

平衡物位於距離海平面三萬六千公里的高度。

At the counterweight could be a space station, a launching point for all missions from the spaceport elevator.

這個平衡物可以是一個太空站，並作為與這座太空電梯相關太空任務的發射基地。

But can we actually build one?

但我們真的造得出太空電梯嗎？

It's hard to say.

現在還不好說。

The biggest challenge is the tether.

目前最大的挑戰是建造纜線。

It needs to be light, affordable and more stable than any material we can produce right now.

纜線的材質必須要輕巧、造價合理，並比我們目前所有能製造得出來的材質還要堅韌。

There are promising materials like graphene and diamond nanothreads, but even they may not be strong enough.

目前有可能的材質包括石墨烯與奈米鑽石線，但這兩者也可能不夠堅固。

And aside from being incredibly strong, the tether would also have to withstand atmospheric corrosion, radiation and micrometeorite and debris impacts.

纜線的材質不但要強韌，還必須要可以承受大氣腐蝕、輻射線，與微小隕石和殘骸的撞擊。

Additionally, it takes several days to climb the elevator.

除此之外，升降艙要到達頂端需要數天。

How do we power the climber?

我們要如何提供升降艙所需的能量？

It requires a lot of energy to go up.

要到達頂端需要很多能量。

Do we need a nuclear reactor on our elevator carriage?

我們需要一個核反應爐在升降艙上嗎？

Or do we beam it power from the ground with a super powered laser?

還是我們使用強大的雷射將能量從地表輸送上去？

And where do we get the raw materials for a 36,000-kilometer-long tether?

而且我們要從哪裡取得建造一條三萬六千公里纜繩的原物料？

Do we make it on Earth and launch it into space?

我們要從地表建造再延伸到太空嗎？

Or do we make it in space and lower it down to the Earth?

還是我們在太空建造再把纜線垂吊下來？

Could asteroid mining be the answer?

從小行星採礦會是解決方案嗎？

Put simply, there are still some major technological hurdles to overcome, and a space elevator is not without risk.

總而言之，我們還有很多主要的技術瓶頸需要突破，並且一座太空電梯並不是沒有風險。

Should the tether break, it would collapse in spectacular style.

如果纜線斷裂，整座太空電梯將會大規模坍塌。

If it breaks near the anchor, the force exerted by the counterweight will cause the entire elevator to rise up, ascending into space.

假設纜線在接近地表處斷裂，由上方平衡物所造成的張力將會把整座太空電梯向上拉到太空。

Should it break near the counterweight, the tether will fall, wrapping around the world and whipping the end off.

假設在接近平衡物的地方斷裂，整條纜線將會坍塌，並甩向地表。

The resulting debris in orbit could pose serious problems to future spaceflight.

所產生的軌道碎片將會影響到未來太空飛行的安全。

If we build a space elevator on Earth, we have to do it right the first time.

如果我們要建造一個太空電梯，我們必須從一開始就正確地建造。

For these reasons, some experts have proposed first building a space elevator on the Moon.

基於這些安全原因，有些專家建議先在月球上建造太空電梯。

The Moon's gravity is much weaker than the Earth's, so a flimsier but existing material like kevlar could serve as a tether.

月球的重力遠低於地球，所以一些比較脆弱但已存在的材質，例如像克維拉（防彈纖維） 可以被用來建造纜線。

Even with all these challenges, the payoff of having a working space elevator would be immense.

即使有這些困難的挑戰，一座可運作的太空電梯將會帶來可觀的報酬。

It might be the first step to truly becoming a space-faring civilization.

這也許是我們要成為一個真正星際文明所要邁出的第一步。

Maybe we will never build a space elevator, but in trying to do so, we might learn an awful lot.

也許我們永遠建造不出太空電梯，但在試圖建造的過程中會讓我們學到許多新的知識。

And when it comes to the exploration of the universe, there can't be too many dreams of a glorious future.

並且在太空探索方向上，邁向宏偉未來的夢想永遠不嫌多。