シャドーイング練習: Will YouTube Ever Run Out Of Video IDs? - 動画で英語スピーキングを学ぶ
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Every YouTube video has a unique ID.
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It's up there in the URL, a string of 11 characters that uniquely identifies which video you want.
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Now, YouTube has millions and millions of videos.
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The last stats that they released said that they have 400 hours of video being uploaded every minute.
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So, are they ever going to run out of those IDs?
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Well, to find out, let's talk about counting systems.
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People count in base ten.
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Zero to nine.
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That'll be, hopefully, familiar to you.
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Computers count in base two, in binary.
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But that's difficult for humans to read.
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It gets too long to write really, really quickly.
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So, often computers will display it in base sixteen.
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Hexadecimal.
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You have zero to nine, and then A to F, and then you start adding to the next column.
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Humans can't understand that easily, but it's efficient if we have to type it in somewhere.
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And sixteen, two to the power of four, is also easy for computers to deal with.
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So how about base 64?
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That'd be a ridiculous counting system, right?
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Except 64 is another one of those easy numbers for computers.
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It is 2 to the power of 6.
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And humans can get to 64 very easily.
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0 to 9, then capital letters A to Z, then small letters A to Z, and two other characters.
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Most Base64 uses slash and plus, but they don't work so well in URLs, so YouTube uses hyphen and underscore.
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That YouTube URL, that unique ID, is really just a random number in Base64.
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They could have picked Base10 or Base16, but they didn't.
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They went with 64, because it will let you cram a huge number into a small space
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and still make it vaguely human-readable.
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Author and programmer Sam Hughes, by the way, pushed this to the limit and invented base 65,536,
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which includes basically every character from every language.
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It is ridiculous and unnecessary, but when has that ever stopped programmers?
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So, why didn't YouTube just start counting at one and work up?
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Well, first, they would have to synchronise their counting between all the servers handling the video uploads.
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Or they'd have to assign each server a block of numbers.
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Either way, there's a lot of tracking to do, a lot of making sure that it's never duplicated.
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Instead, they just generate a random number for each video, see if it's already taken, and if not, use it.
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And secondly, it is a really, really bad idea to just count one, two, three, or so on in URLs.
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Incremental counters, as they're called, can be a big security flaw.
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If you see video 283 up there, then you might wonder, what's video 284?
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Or video 282?
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It's easy to enumerate, as it's called, to run through the entire list.
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YouTube unlisted videos, the ones that don't appear publicly, but that you can send a link to people, those wouldn't work.
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And by the way, lots of badly designed sites do use incremental counters and it is a terrible idea.
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It might tell your competitors exactly how many customers you have, because they can just count them.
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It might let people download all your records easily, because they can just run through them.
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And in one site that someone in Florida emailed me about this week, it lets you look at other people's personal details.
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Don't use incremental counters.
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If you're building a website, use a random number.
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Which brings me to the question, just how big are the numbers that YouTube uses?
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Well, let's work it out.
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One character of base 64 lets you have 64 ID numbers.
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Two characters, that is 64 by 64, or 4096.
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Three characters, 64 times 64 times 64, or 64 to the power of 3, that is already more than a quarter of a million.
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And if we go to four, well, now we're above 16 million.
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If you used base 64, then you can assign an ID number to everyone who lives in London down there twice over,
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and you'll only need four characters.
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This gets big fast.
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We can keep on doing this, and by seven characters, we are already at four quadrillion.
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Now I assume that YouTube checks through a dictionary and doesn't allow any actual words to appear up there,
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particularly anything rude, but that is going to be a tiny minority of their URLs, so for our purposes, we can pretty much just ignore that.
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At YouTube's 11 characters, we are at 73 quintillion 786 quadrillion 976 trillion 294 billion 838 million 206 thousand and 464 videos.
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That is enough for every single human on planet Earth to upload a video every minute for around 18,000 years.
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YouTube planned ahead.
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Can they run out of URLs?
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Technically, yes.
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Practically, no. And if they did, they could just add one more character.
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Oh, one take!
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One take!
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Yes!
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この動画で身につけるスピーキングスキル
「英語シャドーイング」に最適な、論理的な説明のスピードとリズムを学べます。また、技術的な用語（例：base 64、incremental counters）を自然に会話に組み込む方法や、質問を提起して答える流れを練習できます。さらに、「動画で英語学習」を通して、日常的なトピック以外の内容もスムーズに理解し発話する能力が向上します。
聞き取りに注意すべき音のつながり
この動画では、以下のようなリンキングやリダクションが多く見られます。「count in Base 10」では「count in」が「カウントイン」ではなく「カウンティン」とつながり、「it's a really bad idea」では「really」が「リアリー」ではなく「リアリ」と短縮されます。また、「64 to the power of 3」の「to the」が「トゥザ」と弱化して発音されるので、注意が必要です。
ネイティブのように話すコツ
ネイティブスピーカーのリズムとストレスを真似るには、重要な単語を強調しましょう。例えば「Technically, yes. Practically? No.」では「Technically」と「Practically」を強調し、間に短いポーズを入れることで、対比的なニュアンスが伝わります。また、数字の読み方（例：73 quintillion）は速くても明確に発音し、「shadow speech」のように繰り返し練習することで、自然な流れが身につきます。
「英語の発音を良くする」ためには、動画を何度も再生してシャドーイングを行い、自分の発音とネイティブの発音を比較することが効果的です。「shadowing site」を利用して、正確な発音を確認しながら練習するのもおすすめです。
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。