シャドーイング練習: How Bitcoin Works in 5 Minutes (Technical) - 動画で英語スピーキングを学ぶ
練習モードを選ぶ
各モードは全画面の練習ルームで開きます。
29 文
文が短すぎたり長すぎる場合は、Editをタップして調整してください。
1
At a very basic level, Bitcoin is just a digital file or ledger that contains names and balances, and people exchange money by changing this file. When Bob sells Carol a lawn mower for 5.2 Bitcoins, Bob's balance goes up by 5.2, and Carol's down by 5.2. There's no gold or government issued money backing these numbers.
2
Bob is only willing to trade his real-life lawn mower for a higher number in this digital file because he has faith that other people will also trust the system.
3
So who maintains this ledger and makes sure no one cheats? One goal of Bitcoin is to avoid any centralized control, so every participant maintains their own copy of the ledger.
4
One surprising consequence of this is that everyone can see everyone else's balances, although the real system only uses account numbers and not names, so there's some level of anonymity.
5
If everyone maintains their own ledger, how are all the ledgers kept in sync as money is transferred? At a basic level, when you want to send money, you simply tell everyone else by broadcasting a message with your account number, the receiver's, and the amount.
6
Everyone across the entire world then updates their ledger.
7
As a quick aside, I'm describing how Bitcoin works for power users--people who help maintain the system. You can also just use the system to send a receive money, though, without maintaining a ledger.
8
If sending money is as simple as creating a message with some account numbers, what's to stop a thief, Alice, from spending Bob's money by using his account number? Like a pen and paper check, Bitcoin requires a kind of signature to prove that the sender is the real owner of an account, but it's based on math rather than handwriting.
9
When a new account number is created, it comes along with a private key mathematically linked to that account number. If you've heard of a Bitcoin wallet, these keys are what it holds, and are what allow you to create signatures.
10
To create a signature, a private key and the text from a transaction are fed into a special cryptographic function. Another function allows other people to check the signature, making sure it was created by the account owner, and that it applies to that specific transaction.
11
Unlike the handwritten version, these signatures can't be copied and reused in the future, as they're unique to each transaction.
12
While the mathematical signatures prove who sent a transaction, they can't prove when it was sent, and this turns out to be problematic.
13
In our traditional banking system, if Alice wrote two checks, but only had enough money to cover one of them, the bank would pay the first person attempting to cash his check, but refuse the 2nd, because Alice's account would be empty.
14
So the order of these checks is critical, because it determines who should get paid.
15
Unfortunately, order is much harder to determine in Bitcoin, where instead of single bank, there are individuals all over the world. Network delays might cause transactions to arrive in different orders at different places, and fraudsters could lie about timestamps.
16
Two recipients might both think their transaction is first and ship a product, effectively allowing Alice to spend her money twice! Bitcoin prevents this by providing a way for the entire world to decide on transaction order.
17
As new transactions are created, they go into a pool of pending transactions. And from here, they'll be sorted into a giant chain that locks in their order.
18
To select which transaction is next, a kind of mathematical lottery is held. Participants select a pending transaction of their choice, and begin trying to solve a special problem that will link it to the end of the chain. The first person to find a solution wins, and gets to have their transaction selected as the next in the chain.
19
So what's this linking problem? It's based on a special function called a cryptographic hash. As scary as this sounds, it just mixes up its inputs and spits out a number, but it's special because it's irreversible. There's no easy way to start with an output and then find an input that generates it other than making lots of guesses. And this is literally what people are doing in Bitcoin--feeding this function random numbers until the output meets certain criteria.
20
Besides a random guess, you also input a transaction from the pending pool and chain, which is where the linking part comes in.
21
So the lottery provides a way for the entire world to decide which transaction is next, but the math behind it also helps ensure that everyone agrees about past transactions, too.
22
Suppose you're joining the network for the first time, and request a copy of the transaction chain to get caught up, but receive several different versions. Which one should you trust?
23
Ideally, you would trust the one that the majority of people are using, but determining this on the internet is difficult. What would stop a single person from voting millions of times? Bitcoin prevents this by requiring people to solve math problems to vote. This causes each vote to have a cost in computing power, making it unlikely that a single person or group could ever afford to outvote or out-compute the majority of users.
24
The transaction ordering process described before actually provides the voting system.
25
Part of the input to the linking problem is a transaction from the end of a chain, so each guess is effectively a vote for that chain. But how are all the votes tallied?
26
Because the cryptographic hash function has well defined statistical properties, you can look at any given answer and estimate how many guesses it took to find it, just like estimating how many coin flips it would take to get 100 heads in a row. So the links in a chain not only put transactions in order, but also act as an effective vote tally, making it easy to see which chain most people are using.
27
Finally, how does the money get created? Every time someone wins the lottery to pick the next transaction in the chain, new Bitcoins are created out of thin air and awarded to their account.
28
Solving these problem is commonly called "mining," as this is how money enters the system, but the main purpose of the math is to make sure everyone's ledgers agree. The math simply provides a convenient way to randomly distribute money into the world. In fact, sometime around 2140, no more money will be created, and participants will only be paid from fees added on to transactions.
29
I hope this gives you a quick sense for how Bitcoin works. If you'd like a more detailed summary, check out my 22 minute video: How Bitcoin Works Under the Hood.
アプリをダウンロード
流暢に話すために必要なすべて
AI発音採点文ごとに採点
IPA練習すべての音をマスター
単語学習自分の単語帳を作る
単語ゲーム遊びながら覚える
✨ おすすめ動画
B22
123 文
What is Bitcoin? Bitcoin Explained Simply
Business EnglishUniversity StudentsWorking Adults
C1480 文
Everything Valuable from an MBA in 25 minutes
Business EnglishUniversity StudentsWorking Adults
C16
277 文
Distributed Transactions Explained: 2 Phase Commit vs Saga Pattern
Business EnglishUniversity StudentsWorking Adults
C12
146 文
How a CPU Works in 100 Seconds // Apple Silicon M1 vs Intel i9
American AccentBusiness EnglishUniversity StudentsWorking Adults
C11
80 文
The Most Confused Concepts in Engineering
Business EnglishUniversity StudentsWorking Adults
C14
413 文
Exposing The Flaw In Our Phone System
Business EnglishUniversity StudentsWorking Adults
C11
267 文
How to Feel Rich When Your Bank Account Doesn't Agree Yet
Business EnglishUniversity StudentsWorking Adults
C18
102 文
World Models explained in 10min..
Business EnglishUniversity StudentsWorking Adults
C12
86 文
System Design: Why is Kafka Popular?
Business EnglishUniversity StudentsWorking Adults
C125
180 文
Podcast Nâng Cao - Cùng Mình Nói Về Tiền | Học 37 Từ Vựng Hàng Ngày | Tập 23
Business EnglishDaily ConversationUniversity Students
C11
124 文
How to Make Anything - Learn to Think Like an Engineer
Business EnglishUniversity StudentsWorking Adults
B23
151 文
How Ad Blockers Work
Business EnglishUniversity StudentsWorking Adults
このレッスンの語彙とスピーキングのポイント
この動画には、シャドーイング用の文が29文、単語が1139語あります。 音声の長さは5:18です。 話す速さは速く、1分あたり約215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
動画に出てくる覚えておきたい単語15語を、発音と意味つきで紹介します。
| 単語 | 発音 | 意味 |
|---|---|---|
| transaction 名詞 | /tɹænˈzækʃən/ | 処理 |
| signature 名詞 | /ˈsɪɡ.nə.t͡ʃə/ | 署名, サイン |
| mathematics 名詞 | /mæθ(.ə)ˈmæt.ɪks/ | 数学 |
| select 動詞 | /sɪˈlɛkt/ | 選ぶ |
| solve 動詞 | /sɒlv/ | 解決する |
| pending 形容詞 | /ˈpɛndɪŋ/ | 差し掛かった |
| lottery 名詞 | /ˈlɑtɚi/ | くじ, 宝くじ |
| participant 名詞 | /pɑːɹˈtɪsəpənt/ | 参加者, 関与者 |
| output 名詞 | /ˈaʊtpʊt/ | 出力 |
| estimate 名詞 | /ˈɛs.tɪ.mət/ | 推定 |
| lawn 名詞 | /lɔːn/ | 芝生 |
| hash 名詞 | /ˈhæʃ/ | ハッシュドビーフ |
| thin 形容詞 | /ˈθɪn/ | 薄い, 細い |
| delay 名詞 | /dɪˈleɪ̯/ | 遅れ, 遅延 |
| broadcast 名詞 | /ˈbɹɔːd(ˌ)kɑːst/ | 放送 |
動画に出てくる句動詞
| 単語 | 意味 |
|---|---|
| check out 動詞 | 試験する, 検査する |
| go up 動詞 | 上がる, 登る |
この動画の文法
話し手がよく使っている文型を、動画の実際の表現とともに紹介します。
| 文型 | 動画での表現 |
|---|---|
| 受動態 be + 過去分詞 — 誰がするかより、何が起きるかに焦点を当てる | is transferred · is created · are fed |
| 関係詞節 who / which + 節 — 人や物について情報を加える | people who help · chain, which is |
注意したい発音
話し手はcan't, I'm, they'llなど、短縮形や弱形を8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。
- 「th」の音: mathematics /mæθ(.ə)ˈmæt.ɪks/, mathematical /ˌmæθ(.ə)ˈmæt.ɪ.kəl/, thin /ˈθɪn/, thief /ˈθiːf/
- 「sh」と「zh」の音: transaction /tɹænˈzækʃən/, hash /ˈhæʃ/
- 長い単語（アクセントの位置に注意）: mathematics /mæθ(.ə)ˈmæt.ɪks/, participant /pɑːɹˈtɪsəpənt/, mathematical /ˌmæθ(.ə)ˈmæt.ɪ.kəl/, statistical /stəˈtɪs.tɪ.kəl/, recipient /ɹəˈsɪp.i.ənt/
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。transaction, signature, mathematics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。