You are a detective today. Remember Ben's big idea? "Only 21 million bitcoin will ever exist. So the price can never fall!"
Is Ben right?
Bitcoin's price has crashed more than once. Each time, it lost more than half of its worth. In 2018 it lost over 8 in every 10.
The 2018 fall came after a huge rise in 2017. A China trading ban and hacks of trading sites played a part. The 2022 fall came after two big crypto projects failed. Another fall began in late 2025. Nobody can promise it won't fall again.
Source: Bitcoin (Wikipedia) · Bitcoin: you need to know (bitcoin.org) · Blockchain.com: daily bitcoin price data
A fixed amount is not a fixed price.
Rare things can still lose their fans. Bitcoin's price goes up and down.
The special computers that add new pages use lots of electricity. Some say that is a waste. Others say it helps keep Bitcoin safe. Chapter 11 shows how.
Keep your own coins, and secret recovery words open them. Lose the words, and the coins are gone. In 2013, someone threw away a hard drive with the key to 7,500 bitcoin.
Nobody can reset the words. Without the key, nothing else proves the coins are yours. One careful guess says about one in five bitcoins is lost.
Source: Bitcoin (Wikipedia) · Bitcoin: you need to know (bitcoin.org)
Ali lets a big kid mind her marbles. If he loses the box, or locks it, she is stuck. A company holding your bitcoin can fail or freeze your money too.
Both ways have risks.
Keep your own coins, and no company can freeze them, but you must guard the words. Let a company keep them, and you must trust it.
Ben taps send, but he picked the wrong person by mistake.
Can Ben press undo?
Now imagine sweets got cheaper every single week.
When would you buy yours?
In the UK, the Bank of England aims for prices to rise 2% a year. It warns that falling prices can make people wait. Then jobs could be lost.
Some experts think a fixed amount of money could make prices fall. Others say prices can also fall when things get cheaper to make. It is an argument, not a fact.
Time to decide. Tap a card, then its bucket: real worry, myth, or still argued.
Check both sides. Then decide.
You have seen the doubts and the answers. A good detective weighs both, then makes up their own mind.
One big question is left. Who guards the shared notebook from cheats?
How does Bitcoin stay safe? Find out in chapter 11.
🧠 What you learned
- Rare is not safe: the price has crashed more than once
- Real worries: lost words, failing companies, no undo
- Check both sides, then decide
🎯 Question 1 of 12 · Easy
Only 21 million bitcoin will ever exist. What does that tell you about its price?
Cara keeps her own coins, then loses her phone and the paper with her recovery words. What happens?
Ben sends coins to the wrong person. Can he press undo?
Bitcoin's price has crashed more than once. About how much did it lose each time?
Some say Bitcoin's electricity use is a waste. What do others say?
Ali lets a company hold her bitcoin. What is the risk?
What is true if you keep your own coins?
Why do some experts worry about prices that keep falling?
A shop will only ever have 21 rare stickers. Can the price of one still fall?
Which of these is still argued about, not settled?
A friend says: "Bitcoin is perfect and has no risks." What is the best answer?
Which pair are both real worries from this chapter?
Well done!
You earned a badge: Honest doubts
Education, not financial advice. Never put in money you can't afford to lose.
👩🏫 Grown-up corner · 1 of 10
Who is telling you this?
This site leans on Michael Saylor for the case for Bitcoin, so weigh that. He is a Bitcoin supporter and executive chairman of Strategy Inc., a company that holds bitcoin, so a higher price helps it. Critics are easy to find. Wikipedia lists economists, including Nobel winners Joseph Stiglitz, James Heckman and Paul Krugman, who have called bitcoin a bubble. In 2018 The Economist ran a leading article headlined "Bitcoin and other cryptocurrencies are useless". As of 2025, Harvard's Kenneth Rogoff says it is rarely used in shop payments. Read both sides and check the sources.
👩🏫 Grown-up corner · 2 of 10
Rare is not safe
Bitcoin's rules cap the total at 21 million coins, and the last one is expected around the year 2140. That is a fixed amount, not a fixed price. Daily average prices (Blockchain.com, rounded, checked 23 October 2026) show falls of about 83% from December 2017 to December 2018, 77% from November 2021 to November 2022, and 53% from October 2025 to July 2026. The same series shows earlier falls of half or more too, in 2011 and from late 2013 to early 2015. Those are peak-to-bottom figures, not what every buyer lost. The network began on 3 January 2009, so its record is short. Nobody can promise the next ten years.
👩🏫 Grown-up corner · 3 of 10
Bitcoin and chapter 2's tests
Chapter 2 gave money five tests. Hard to make more of: yes, by rule, up to 21 million. Lasts: the record stays, but its worth has swung a lot. Light and easy to send: yes, anywhere, though bitcoin.org says a payment usually takes about 10 to 60 minutes to confirm. Splits into small bits: yes, to eight decimal places. Easy to check: yes, every payment is stored publicly. The test it passes least well so far is keeping a steady worth.
👩🏫 Grown-up corner · 4 of 10
Waste or safety?
Critics point to the power bill. Mining consumes large quantities of electricity. As of 2025, a Cambridge study (not peer reviewed) estimated that mining used about 0.5% of the world's electricity, and that natural gas and coal made up about 47% of the power it surveyed, which covered 48% of mining. Supporters say the energy is the point. Michael Saylor argues that miners turn raw energy into a wall attackers must climb, that proof of work is what makes the record hard to change, and that miners can soak up surplus power. Chapter 11 shows the wall.
👩🏫 Grown-up corner · 5 of 10
The 2% view
In the UK, the Government sets the Bank of England an inflation target of 2%. Chapter 5's Grown-up corner explains why central banks aim for 2%. That target is UK policy. The Bank's inflation page is about prices in general. It says nothing about Bitcoin or a fixed amount of money.
👩🏫 Grown-up corner · 6 of 10
Would a fixed amount make prices fall?
Some economists argue that a money with a fixed amount could make prices drift down over time. Wikipedia's article on deflation calls that the natural result when money does not grow with the economy, and says falling prices give people a reason to delay buying. In 2011 Paul Krugman, in a post called "Golden Cyberfetters", said Bitcoin makes its own private gold standard, and that such a standard is open to hoarding, falling prices and depression. In 2014 The Economist suggested that "chronic deflation" may keep Bitcoin from displacing government money.
👩🏫 Grown-up corner · 7 of 10
How supporters answer
Supporters of Bitcoin see it the other way: they argue that printing money mostly moves wealth from savers to whoever gets the new money first. Wikipedia also notes that prices can fall because production gets cheaper, and then buying power rises. Which kind of fall a fixed amount of money would bring is the argument. It is an argument, not a proven fact, so weigh both sides.
👩🏫 Grown-up corner · 8 of 10
Your keys, or a company's?
Bitcoin's own website spells out the trade. Leave your coins with an exchange, and you rely on that company's security and honesty to give them back. Hold your own keys, and that risk goes away, but you must guard the recovery words and backups yourself. No one can recover funds you permanently lose from your own wallet. Wikipedia reports an estimate that about 20% of all bitcoin is lost. Nobody can count exactly, because a coin that has not moved may be lost or just held.
👩🏫 Grown-up corner · 9 of 10
Is it gold all over again?
Gold went one way: people left it with banks and got paper notes (chapter 3). Whether Bitcoin repeats that is an open question. Michael Saylor gives the example of an elderly buyer who could not manage a hardware wallet and would rather buy through an adviser they already trust. That is a choice to trust someone, which brings back the risks of trusting a company. This is learning, not financial advice.
👩🏫 Grown-up corner · 10 of 10
Who holds Bitcoin?
Chapter 6 asked who gets new money first. The same question fits Bitcoin. Wikipedia says blockchain analysts estimate that its creator, Satoshi Nakamoto, mined about one million bitcoins, and that as of 2021 the top 0.01% of owners held 27% of all bitcoin. Treat those figures as rough. Whether early owners earned their gains or simply got a head start is an argument.