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  • I'd like you all to close your eyes, please ...

    翻訳: Mai Endo 校正: Midori T

  • and imagine yourself sitting in the middle of a large, open field

    皆さん 目を閉じて下さい

  • with the sun setting on your right.

    そして 広く 開放的な野原に 座っているところを想像してみて下さい

  • And as the sun sets,


  • imagine that tonight you don't just see the stars appear,


  • but you're able to hear the stars appear

    今宵は 夜空の星が見えるだけでなく

  • with the brightest stars being the loudest notes


  • and the hotter, bluer stars producing the higher-pitched notes.

    一番明るい星々は ひと際 大きな音を立てていて

  • (Music)

    高温の青い星々は 高い音を出しています

  • And since each constellation is made up of different types of stars,


  • they'll each produce their own unique melody,


  • such as Aries, the ram.


  • (Music)

    例えば ヒツジの牡羊座

  • Or Orion, the hunter.


  • (Music)

    そして 狩人のオリオン座

  • Or even Taurus, the bull.


  • (Music)

    さらに ウシの牡牛座も

  • We live in a musical universe,


  • and we can use that to experience it from a new perspective,


  • and to share that perspective with a wider range of people.

    このことを活かして 新しい視点からその宇宙を体験したり

  • Let me show you what I mean.

    その視点を幅広い人々と 共有することもできるのです

  • (Music ends)


  • Now, when I tell people I'm an astrophysicist,


  • they're usually pretty impressed.

    大抵の人は 私が天体物理学者と聞くと

  • And then I say I'm also a musician -- they're like, "Yeah, we know."


  • (Laughter)

    そして 音楽家でもあると伝えると 「ええ 知ってますよ」ってね

  • So everyone seems to know


  • that there's this deep connection between music and astronomy.

    どうも 誰もが

  • And it's actually a very old idea;

    音楽と天文学には深い繋がりがあると 知っているようなのです

  • it goes back over 2,000 years to Pythagoras.

    これは 実は大昔からある概念で

  • You might remember Pythagoras from such theorems


  • as the Pythagorean theorem --


  • (Laughter)


  • And he said:


  • "There is geometry in the humming of the strings,


  • there is music in the spacing of the spheres."


  • And so he literally thought


  • that the motions of the planets along the celestial sphere


  • created harmonious music.

    惑星たちの天球に沿った動きが 協和音を創り出していると

  • And if you asked him, "Why don't we hear anything?"


  • he'd say you can't hear it

    じゃあなぜ何も聞こえないのかと 訊かれたら

  • because you don't know what it's like to not hear it;

    「それは当然だ なぜなら

  • you don't know what true silence is.

    何も聞こえないこと つまり 本当の意味での沈黙を

  • It's like how you have to wait for your power to go out


  • to hear how annoying your refrigerator was.

    停電してはじめて 普段 冷蔵庫がうるさかったことに

  • Maybe you buy that,


  • but not everybody else was buying it, including such names as Aristotle.


  • (Laughter)

    アリストテレスのような人には 理解できなかったみたいですが

  • Exact words.


  • (Laughter)


  • So I'll paraphrase his exact words.


  • He said it's a nice idea,

    アリストテレスの言葉を 噛み砕くと

  • but if something as large and vast as the heavens themselves


  • were moving and making sounds,

    もし天空ほどの莫大な何かが 独りでに動いて

  • it wouldn't just be audible,


  • it would be earth-shatteringly loud.


  • We exist, therefore there is no music of the spheres.

    地球など破壊してしまうほどの 音を出すはずだ

  • He also thought that the brain's only purpose was to cool down the blood,

    我々はここに存在するのだから 天球の音楽などないのだ」

  • so there's that ...

    脳が血液を冷ますためだけのものだ とも説いているような人なので

  • (Laughter)


  • But I'd like to show you that in some way they were actually both right.


  • And we're going to start by understanding what makes music musical.

    でも 本当はどちらの言うことも 正しかったということをお見せします

  • It may sound like a silly question,

    まずは 何が音楽を音楽たらしめるのか について理解しましょう

  • but have you ever wondered why it is


  • that certain notes, when played together, sound relatively pleasing or consonant,

    なぜ 同時に奏でた音と音は

  • such as these two --

    こんなにも相対的に心地よく共鳴するのか と思ったことはありませんか

  • (Music)

    例えば この2つの音

  • while others are a lot more tense or dissonant,


  • such as these two.

    あるいは もっと緊迫した 不協和な音もあります

  • (Music)


  • Right?


  • Why is that? Why are there notes at all?

    ほらね なぜでしょう?

  • Why can you be in or out of tune?


  • Well, the answer to that question

    なぜ音程が合ったり 外れたりするのか?

  • was actually solved by Pythagoras himself.


  • Take a look at the string on the far left.


  • If you bow that string,


  • it will produce a note as it oscillates very fast back and forth.


  • (Musical note)

    高速で前後に振動して 1つの音を出します

  • But now if you cut the string in half, you'll get two strings,


  • each oscillating twice as fast.

    この弦を半分に切って 2本の弦にすると

  • And that will produce a related note.


  • Or three times as fast,


  • or four times --


  • (Musical notes)


  • And so the secret to musical harmony really is simple ratios:


  • the simpler the ratio,

    音の協和の秘密は 簡単な比率にあったんですね

  • the more pleasing or consonant those two notes will sound together.


  • And the more complex the ratio, the more dissonant they will sound.

    その2音は心地よく響き合い 協和音になり

  • And it's this interplay between tension and release,

    比率が複雑であるほど 不協和音になってしまうわけです

  • or consonance and dissonance,

    このような 音が持つ 緊張と解放―

  • that makes what we call music.

    あるいは 協和と不協和の 相互作用が

  • (Music)


  • (Music ends)


  • (Applause)


  • Thank you.


  • (Applause)


  • But there's more.


  • (Laughter)


  • So the two features of music we like to think of as pitch and rhythms,


  • they're actually two versions of the same thing,

    次は音楽の特徴である 音の高さとリズムについてです

  • and I can show you.

    実はこの2つも 先ほどの例と同様です

  • (Slow rhythm)


  • That's a rhythm right?


  • Watch what happens when we speed it up.


  • (Rhythm gets gradually faster)


  • (High pitch)


  • (Lowering pitch)


  • (Slow Rhythm)


  • So once a rhythm starts happening more than about 20 times per second,


  • your brain flips.


  • It stops hearing it as a rhythm and starts hearing it as a pitch.


  • So what does this have to do with astronomy?

    その音をリズムとしてではなく 音の高さとして捉えます

  • Well, that's when we get to the TRAPPIST-1 system.


  • This is an exoplanetary system discovered last February of 2017,

    ここでトラピスト1惑星系について お話ししましょう

  • and it got everyone excited

    これは太陽系外惑星系で 昨年2017年2月に発見され

  • because it is seven Earth-sized planets all orbiting a very near red dwarf star.


  • And we think that three of the planets

    近くの赤色矮星を 地球サイズの惑星が 7つも周回していると判明したのです

  • have the right temperature for liquid water.

    そして そのうち3つは

  • It's also so close that in the next few years,

    水が液体でいるのに 適した温度になっています

  • we should be able to detect elements in their atmospheres

    また 地球から近いので 今後数年のうちに

  • such as oxygen and methane -- potential signs of life.

    それらの惑星の大気中に 酸素やメタンのような

  • But one thing about the TRAPPIST system is that it is tiny.

    生命の兆候にあたるかもしれない物質を 検出できるでしょう

  • So here we have the orbits of the inner rocky planets

    しかし このトラピスト惑星系は 非常に小さいのです

  • in our solar system:

    これは 私たちのいる太陽系内にある—

  • Mercury, Venus, Earth and Mars,


  • and all seven Earth-sized planets of TRAPPIST-1

    水星 金星 地球 火星です

  • are tucked well inside the orbit of Mercury.

    そしてトラピスト1に属する 地球サイズの7惑星は

  • I have to expand this by 25 times


  • for you to see the orbits of the TRAPPIST-1 planets.

    この写真を25倍に拡大して やっと

  • It's actually much more similar in size to our planet Jupiter and its moons,


  • even though it's seven Earth-size planets orbiting a star.

    地球サイズの7惑星が 恒星を周回していると言いましたが

  • Another reason this got everyone excited was artist renderings like this.

    大きさでいえば 実は 木星と その衛星系にずっと近いのです

  • You got some liquid water, some ice, maybe some land,

    皆を興奮させた もう1つの理由は アーティストが描いた惑星の予想図です

  • maybe you can go for a dive in this amazing orange sunset.

    水もあれば 氷も存在する  もしかしたら陸地もある

  • It got everyone excited,

    このような綺麗な夕日を前に 泳げるかもしれません

  • and then a few months later, some other papers came out


  • that said, actually, it probably looks more like this.

    すると数ヶ月後 違う論文が発表され

  • (Laughter)

    実はこんな場所かもしれないと 言うのです

  • So there were signs


  • that some of the surfaces might actually be molten lava


  • and that there were very damaging X-rays coming from the central star --


  • X-rays that will sterilize the surface of life and even strip off atmospheres.

    中心の星からは非常に有害なX線が 出ていると言う兆候があったそうです

  • Luckily, just a few months ago in 2018,

    地上を不毛にすると共に 大気をも消し去ってしまうようなX線です

  • some new papers came out with more refined measurements,

    幸いにも 数ヶ月前 2018年に入って

  • and they found actually it does look something like that.

    より精巧な測定結果を記した 新たな論文がいくつか出てきて

  • (Laughter)

    先ほどの美しい予想図に近いものに 落ち着きました

  • So we now know that several of them have huge supplies of water --


  • global oceans --

    トラピスト1の惑星のいくつかには 豊富な水があると分かっています

  • and several of them have thick atmospheres,


  • so it's the right place to look for potential life.

    また いくつかは 厚い大気で覆われているので

  • But there's something even more exciting about this system,

    生命の可能性を探るには うってつけの場所です

  • especially for me.

    しかし もっと興味深いことが この惑星系にはあるのです

  • And that's that TRAPPIST-1 is a resonant chain.


  • And so that means for every two orbits of the outer planet,

    それは トラピスト1が 鎖状の共鳴関係だということ

  • the next one in orbits three times,


  • and the next one in four,


  • and then six, nine, 15 and 24.


  • So you see a lot of very simple ratios among the orbits of these planets.

    続いて6周 9周 15周 24周と 軌道を重ねています

  • Clearly, if you speed up their motion, you can get rhythms, right?

    これらの惑星の軌道周期が とても簡単な比率であると分かりますね

  • One beat, say, for every time a planet goes around.

    1周毎に1ビート鳴らすとして 周回速度を上げると

  • But now we know if you speed that motion up even more,


  • you'll actually produce musical pitches,

    ですが 周回速度をもっと上げてみると

  • and in this case alone,


  • those pitches will work together,


  • making harmonious, even human-like harmony.


  • So let's hear TRAPPIST-1.

    人間の音楽のようなハーモニーさえ 生み出します

  • The first thing you'll hear will be a note for every orbit of each planet,


  • and just keep in mind,

    最初に聞いてもらうのは それぞれの惑星の軌道の音です

  • this music is coming from the system itself.


  • I'm not creating the pitches or rhythms,

    この音楽は惑星系自身が 奏でているということ

  • I'm just bringing them into the human hearing range.

    私は音程やリズムを いじっていません

  • And after all seven planets have entered,

    ただ人間が聞き取れる 周波数帯域にしただけです

  • you're going to see --


  • well, you're going to hear a drum for every time two planets align.


  • That's when they kind of get close to each other

    2つの惑星が隣り合うたびに ドラムの音を鳴らします

  • and give each other a gravitational tug.

    この時 2惑星は互いに近づき

  • (Tone)


  • (Two tones)


  • (Three tones)


  • (Four tones)


  • (Five tones)


  • (Six tones)


  • (Seven tones)


  • (Drum beats)


  • (Music ends)


  • And that's the sound of the star itself -- its light converted into sound.


  • So you may wonder how this is even possible.

    これは この星自身の音であり その輝きを音へと変換したものです

  • And it's good to think of the analogy of an orchestra.

    こんなことがあり得るのかと 思いますよね

  • When everyone gets together to start playing in an orchestra,

    オーケストラに似ていると 考えれば良いと思います

  • they can't just dive into it, right?


  • They have to all get in tune;


  • they have to make sure


  • their instruments resonate with their neighbors' instruments,


  • and something very similar happened to TRAPPIST-1 early in its existence.

    ちゃんと周りの楽器と 共鳴させなければなりません

  • When the planets were first forming,

    トラピスト1の発生初期に これとよく似たことが起こっていました

  • they were orbiting within a disc of gas,


  • and while inside that disc,

    惑星たちが 円盤状のガスの中に 軌道を描いていて

  • they can actually slide around


  • and adjust their orbits to their neighbors


  • until they're perfectly in tune.

    避けて通り 軌道修正をくり返すことで

  • And it's a good thing they did because this system is so compact --


  • a lot of mass in a tight space --


  • if every aspect of their orbits wasn't very finely tuned,

    この小さな惑星系は 狭い空間に大きい質量が詰まっているので

  • they would very quickly disrupt each other's orbits,

    もし この協和状態に 少しでも狂いがあったなら

  • destroying the whole system.

    あっという間に 互いの軌道を邪魔し合い

  • So it's really music that is keeping this system alive --


  • and any of its potential inhabitants.

    なので まさに音楽が この惑星系と そこに存在しうる生命を

  • But what does our solar system sound like?


  • I hate to be the one to show you this, but it's not pretty.

    では 私たちの太陽系の音はというと

  • (Laughter)

    あまり言いたくはないですが 心地良い音ではありません

  • So for one thing,


  • our solar system is on a much, much larger scale,


  • and so to hear all eight planets,

    私たちの太陽系はトラピスト1より はるかに大規模なので

  • we have to start with Neptune near the bottom of our hearing range,


  • and then Mercury's going to be all the way up

    まず人間の可聴域の下限付近の 海王星から始まり

  • near the very top of our hearing range.


  • But also, since our planets are not very compact --

    音域を目一杯 使わなければなりません

  • they're very spread out --

    それに 太陽系の惑星は密集しておらず

  • they didn't have to adjust their orbits to each other,


  • so they're kind of just all playing their own random note at random times.


  • So, I'm sorry, but here it is.

    惑星たちは それぞれの音を 思い思いに鳴らしてるだけなのです

  • (Tone)

    では 心苦しいですが その音色をお聴きください

  • That's Neptune.


  • (Two tones)


  • Uranus.


  • (Three tones)


  • Saturn.


  • (Four tones)


  • Jupiter.


  • And then tucked in, that's Mars.


  • (Five tones)

    そして更に 火星が合わさります

  • (Six tones)


  • Earth.


  • (Seven tones)


  • Venus.


  • (Eight tones)


  • And that's Mercury --


  • OK, OK, I'll stop.

    そして 最後に水星

  • (Laughter)

    うーん 止めましょう

  • So this was actually Kepler's dream.


  • Johannes Kepler is the person

    実はこれは ケプラーにとって夢でした

  • that figured out the laws of planetary motion.


  • He was completely fascinated by this idea


  • that there's a connection between music, astronomy and geometry.


  • And so he actually spent an entire book

    何か関係性があると 強く信じてやみませんでした