シャドーイング練習: Where Did Earth's Water Come From? - 動画で英語スピーキングを学ぶ
レッスンを作成中...
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Unlike every other planet in our solar system, Earth's surface is 70 % liquid water, which while useful for life, is also kind of weird,
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because everything we know about how and when our planet formed says Earth's surface should be bone dry.
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The story goes like this.
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Our solar system formed from the collapse of a large cloud of dust and gas.
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The dense blob of gas at the center ignited to form the sun, which as a young unstable star unleashed a fierce solar wind.
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And over time, this stream of charged particles pushed the remaining gas cloud farther and farther out, leaving only solid particles behind to clump together into rocks,
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planetesimals, and finally, the rocky planets of the inner solar system that we know today.
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And here's the problem.
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Water, in the form of ice, couldn't have been one of the solid particles that stuck around to form our planet, because the early inner solar system was far too hot for frozen water,
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and any water vapor would have been blasted away by the solar wind.
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So if Earth didn't start off with water, how did we end up with such splendid oceans?
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We know H2O wasn't manufactured here over the eons, because natural processes like combustion,
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breathing and photosynthesis create and destroy roughly equal amounts of water, and either way, the amounts in question are so minuscule that they can't account for the abundance of water on the planet.
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Since Earth's water was neither part of the original package nor manufactured here, it must have flown in from far away, on meteoroids or comets or other bodies originating in the outer solar system,
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where they were far enough from the sun for frozen water to survive.
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The dirty ice balls we call comets are a logical candidate for the source of our water, but were ruled out when we discovered that they were far richer in heavy hydrogen than earth water.
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Heavy hydrogen has a neutron as well as a proton in its nucleus, and for every million hydrogen atoms in earth water, about 150 are heavy ones,
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while typical comet water has twice that many.
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These mismatched chemical signatures suggest that Earth's water couldn't have arrived on comets.
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It turns out that the most likely source for Earth's water is a type of meteorite called a carbonaceous chondrite.
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Chondrite is just the name given to the class of stony meteoroids that most commonly strike the Earth.
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But only the carbonaceous chondrites contain water, as well as lots of carbon if you couldn't tell from their name.
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They have water in them because they formed out beyond the sun's frost line, and what's more, their water has levels of heavy hydrogen similar to that of earth water,
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strongly suggesting that these earth crashers are the source of our ice caps, clouds, rivers, and oceans.
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And thus the water that turned our planet into a blue marble came, quite literally, out of the blue.
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このレッスンの語彙とスピーキングのポイント
このB2レベルのスピーキングレッスンは、動画「Where Did Earth's Water Come From?」を教材にしています。 繰り返し出てくる語は次のとおりです：solar, planet, earth, comet, hydrogen。 この動画には、シャドーイング用の文が25文、単語が496語あります。 音声の長さは2:24です。 話す速さは速く、1分あたり約206語です。音のつながりや弱く発音される音が多くなります。 英語の頻出3,000語に含まれる単語は80%だけなので、語彙は難しめです。
この動画の重要語彙
動画の中で特に難しい単語15語を、発音と意味つきで紹介します。
| 単語 | 発音 | 意味 |
|---|---|---|
| comet 名詞 | /ˈkɒmɪt/ | 彗星, 箒星 |
| hydrogen 名詞 | /ˈhaɪdɹəd͡ʒ(ə)n/ | 水素 |
| particle 名詞 | /ˈpɑɹtək(ə)l/ | 粒子 |
| freeze 動詞 | /ˈfɹiːz/ | 凍る |
| ignite 動詞 | /ɪɡˈnaɪt/ | 火を点ける |
| meteorite 名詞 | /ˈmi.ti.əˌɹaɪt/ | 隕石 |
| minuscule 名詞 | /ˈmɪnəˌskjul/ | 小文字 |
| neutron 名詞 | /ˈnu.tɹɑn/ | 中性子 |
| photosynthesis 名詞 | /ˌfoʊ.toʊˈsɪn.θə.sɪs/ | 光合成 |
| proton 名詞 | /ˈpɹoʊ.tɑn/ | 陽子 |
| unleash 動詞 | /ʌnˈliʃ/ | 束縛を解く |
| vapor 名詞 | /ˈveɪpɚ/ | 気体, 蒸気 |
| combustion 名詞 | /kəmˈbʌs.t͡ʃən/ | 燃焼 |
| nucleus 名詞 | /ˈnuː.kli.əs/ | 核, 核心 |
| atom 名詞 | /ˈætəm/ | 原子, アトム |
動画に出てくる句動詞
| 単語 | 意味 |
|---|---|
| rule out 動詞 | 除外する, 排除する |
注意したい発音
話し手はcouldn't, can't, didn'tなど、短縮形や弱形を6回使っています。聞こえたとおりの短い形で発音しましょう。
- 「sh」と「zh」の音: carbonaceous /kɑːbəˈneɪʃəs/, unleash /ʌnˈliʃ/
- 長い単語（アクセントの位置に注意）: carbonaceous /kɑːbəˈneɪʃəs/, meteorite /ˈmi.ti.əˌɹaɪt/, originate /əˈɹɪd͡ʒɪneɪt/, photosynthesis /ˌfoʊ.toʊˈsɪn.θə.sɪs/
日本語話者が苦手な音：
- /r/ と /l/ の区別 — /l/ は舌先を歯茎につけ、/r/ はどこにもつけない: particle /ˈpɑɹtək(ə)l/, marble /ˈmɑɹ.bəl/
- /f/ — 「フ」ではなく、上の歯と下唇で出す: freeze /ˈfɹiːz/, photosynthesis /ˌfoʊ.toʊˈsɪn.θə.sɪs/, fierce /fɪɹs/, frost /fɹɔst/
- 子音の連続 — 間に母音を入れない: chondrite /ˈkɒndɹaɪt/, freeze /ˈfɹiːz/, minuscule /ˈmɪnəˌskjul/, proton /ˈpɹoʊ.tɑn/, splendid /ˈsplɛndɪd/
この動画での練習方法
- まず声を出さずに動画を最後まで聞き、知らない単語をメモします。
- まず0.75倍速で一文ずつシャドーイングし、慣れてきたら通常の速度に戻します。
- 自分の声を録音して元の音声と比べます。comet, hydrogen, particleなどの単語に特に注意しましょう。
シャドーイングとは？英語上達に効果的な理由
シャドーイング（Shadowing）は、もともとプロの通訳者養成プログラムで開発された言語学習法で、多言語習得者として知られるDr. Alexander Arguelles によって広く普及されました。方法はシンプルですが非常に効果的：ネイティブスピーカーの英語を聞きながら、1〜2秒の遅延で声に出してすぐに繰り返す——まるで「影（shadow）」のように話者を追いかけます。文法ドリルや受動的なリスニングと異なり、シャドーイングは脳と口の筋肉が同時にリアルタイムで英語を処理・再現することを強制します。研究により、発音精度、抑揚、リズム、連音、リスニング力、そして会話の流暢さが大幅に向上することが確認されています。IELTSスピーキング対策や自然な英語コミュニケーションを目指す方に特におすすめです。