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It's hard to get to space
宇宙への旅
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As much as we all wish there were an easy,
それが簡単になれば
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and affordable way to see our planet floating in the dark
どれほど楽しいだろう
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Right now, the only way is to become an astronaut or a billionaire
今行けるのは宇宙飛行士か 金持ちだ
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But there is a concept that might make it possible
でも宇宙旅行の夢を叶える
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-while serving as the starting point for the exploration of the universe-
ある概念が考案されている
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The space elevator
宇宙エレベーターだ
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How exactly does it work?
どんなものだろう?
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To understand how a space elevator will get us into space
宇宙エレベーターとは何か
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We must first understand what an orbit is
まずは軌道から説明しよう
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Being in orbit basically means falling towards something,
軌道に入るとは つまり
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but moving fast enough to miss
落ち続けるということだ
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If you throw a ball on earth it makes an arch through the air,
物を投げると 弧を描いて地面に付く
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and then hits the ground
宇宙でも同じことが起きるが
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In space, gravity makes you move much the same way,
横に速く進むことで 地面に付かず
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but if you move sideways fast enough
地球を回り続けることができる
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the curvature of the earth makes the ground fall away beneath you
軌道に入るには
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as fast as gravity pulls you towards it
ロケットは速く飛ぶ必要がある
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So, to enter Earth's orbit rockets have to go up
一方 高い位置から飛べば
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and sideways fast
速度を稼ぐことができる
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By contrast, a space elevator taps into energy from Earth's rotation
おもちゃを回す子どもと
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to get the cargo going fast
アリを考えてほしい
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Imagine a child spinning a toy on a rope with an ant on the child's hand
先の方にいるアリは
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As the ant climbs out along the rope
それだけ速く飛べる
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it starts to move faster and faster as it ascends
高い所からロケットを飛ばせば
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Compared to rockets, with cargo launched on an elevator
燃料が少なくて済む
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you only need to provide the energy to go up
地球の遠心力を利用できるのだ
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Fast sideways movement comes free with the Earth's rotation
だが宇宙エレベーターは
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But the space elevator would without a doubt
史上最も高価な建築物になりそうだ
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be the single largest and most expensive structure ever built by humans
作る価値はあるのか?
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So, is it worth it?
計算してみよう
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It all comes down to costs
ロケットは少しの輸送でも
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Rockets burn a huge amount of rocket fuel
大量の燃料を使う
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just to get a small amount of cargo into space
今は1kg送るのに
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At current prices, it costs about $20,000 to put one kilogram of payload into space
2万ドルの費用がかかる
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that's $1.3 million dollars for the average human
人を送れば130万ドル
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$40 million dollars for your car
車なら4000万ドル
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billions for an international space station
宇宙ステーションは億単位だ
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This immense cost is one of the major limitations of human spaceflight
これが宇宙進出の障壁になっている
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Even with advancing technology,
技術が進んでも
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this cost isn't likely to be comparable with the price of an airline ticket anytime soon
まだ飛行機程度にはなりそうにない
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A space elevator would solve this problem
宇宙エレベーターなら大丈夫
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After construction,
一度作れば 費用は大幅に減って
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a space elevator is projected to reduce the cost one hundredfold to $200 per kilogram
1kg200ドルになる
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If an inexpensive space elevator costs 20 billion dollars,
エレベーターが200億ドルなら
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then we'll recoup our losses after launching only one million tons
100万トン分運ぶことで元が取れる
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Close to the weight of two international space stations
宇宙ステーション2機分だ
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So what would a space elevator look like in real life?
どうやって作るのだろうか
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A space elevator has four major components:
主な構成要素が4つある
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the tether, anchor, counterweight and climber
テザー 錨 おもり 上昇機だ
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The elevator part of the space elevator is the tether and the climber
紐状のテザーが地球と終点を繋ぎ
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It extends from the surface of the Earth to space
上昇機がそれを昇る
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The climber is like a conventional elevator carriage
普通のエレベーターのように
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A chamber that works its way up and down the tether
これで昇り降りをする
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At the base would be an anchor
地下には錨を置き
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pinning the tether to the Earth along with a port for climbers
これでテザーを地球に固定して
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At the top is the counterweight which holds up the tether
上からはおもりが引っ張る
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The tether is held tight like a rope
これによりテザーは
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and supported from above by the tension from the counterweight
伸びた状態で安定する
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Located higher than 36,000 kilometers above the Earth's surface
その長さは3万6000キロ以上になる
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At the counterweight could be a space station,
おもりとして使えるなら
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a launching point for all missions from the spaceport elevator
発射台などを置くことも可能だ
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But can we actually build one?
しかし実際 作るのは難しい
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It's hard to say
特にテザーは
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The biggest challenge is the tether
軽くて 安くて
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It needs to be light, affordable
今ある物質より強いものが必要だ
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and more stable than any material we can produce right now
グラフェンやダイアモンドナノ糸は
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There are promising materials like graphene and diamond nanothreads,
強さが不十分だ
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but even they may not be strong enough
強さ以外にも
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And aside from being incredibly strong,
雨による腐食や宇宙の放射線
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the tether would also have to withstand atmospheric corrosion, radiation
デブリに耐える必要がある
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and micrometeorite and debris impacts
さらに 上昇には数日かかるが
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Additionally, it takes several days to climb the elevator
その動力は何なのか
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How do we power the climber?
莫大なエネルギーだ
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It requires a lot of energy to go up
原子炉でも乗せるのだろうか
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Do we need a nuclear reactor on our elevator carriage?
レーザーで何とかできるのか
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Or do we beam it power from the ground with a super powered laser?
テザー3万6000キロ分の材料は?
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And where do we get the raw materials for a 36,000-kilometer-long tether?
地球から伸ばすのか
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Do we make it on Earth and launch it into space?
宇宙から地球に伸ばすのか
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Or do we make it in space and lower it down to the Earth?
小惑星から調達できるか
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Could asteroid mining be the answer?
技術的障壁はまだ山のようにある
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Put simply, there are still some major technological hurdles to overcome
事故の危険性もある
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And a space elevator is not without risk
テザーが切れたら大惨事だ
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Should the tether break, it would collapse in spectacular style
もし地表近くで切れたら
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If it breaks near the anchor
上昇機が落ち テザーは宇宙に逃げる
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the force exerted by the counterweight will cause the entire elevator to rise up
宇宙で切れたら
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ascending into space
テザーが地球に落ちてくる
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Should it break near the counterweight
デブリは将来 大問題になるだろう
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the tether will fall,
もし作るのなら 失敗は許されない
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wrapping around the world and whipping the end off
だからまずは月に作る
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The resulting debris in orbit could pose serious problems to future spaceflight
という案もある
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If we build a space elevator on Earth, we have to do it right the first time
重力が地球より弱いので
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For these reasons some experts have proposed first building
ケブラー等の物質がテザーに使える
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a space elevator on the Moon
困難な挑戦でも
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The Moon's gravity is much weaker than the Earth's
宇宙エレベーターの価値は大きい
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so a flimsier but existing material like kevlar
宇宙進出の真の一歩となるだろう
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could serve as a tether
実現できなくても
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Even with all these challenges,
その過程で多くを学べるはずだ
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the payoff of having a working space elevator would be immense
宇宙の時代が来れば
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It might be the first step to truly becoming a space-faring civilization
輝く未来は夢ではなくなる
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Maybe we will never build a space elevator,
Subtitles by the Amara.org community
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but in trying to do so we might learn an awful lot
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And when it comes to the exploration of the universe,
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there can't be too many dreams of a glorious future
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Subtitles by the Amara.org community