About 14 minutes with practice. You only need something to take notes with. No real wallet details or payments are part of this lesson.
Course contents · Lesson 7 of 21
- Read the whitepaper as an argument · Marked complete
- Hashes and Merkle commitments · Marked complete
- UTXOs, change and accounting · Marked complete
- Scripts describe spending conditions · Marked complete
- Signatures and what they authorize · Marked complete
- Block headers and the chain of work · Marked complete
- Difficulty, hashrate and noisy observations · Marked complete
- Issuance, fees and incentives · Marked complete
- Mempools and policy are not consensus · Marked complete
- Fee changes: RBF and CPFP · Marked complete
- SegWit and transaction weight · Marked complete
- Taproot and Schnorr: useful, not magical · Marked complete
- HD wallets and derivation paths · Marked complete
- PSBT: separate construction from signing · Marked complete
- Descriptors make a wallet policy portable · Marked complete
- Full nodes, pruning and verification · Marked complete
- Reorganizations and lightweight evidence · Marked complete
- Lightning channels and HTLCs · Marked complete
- Lightning liquidity has direction · Marked complete
- Soft forks, proposals and human coordination · Marked complete
- Capstone: trace a payment end to end · Marked complete
What you will learn
- Explain the purpose of difficulty adjustment.
- Recognize uncertainty in short-term hashrate estimates.
A target controls the search
Proof of work compares a header hash against a target. A more demanding target makes success less likely per attempt. Bitcoin adjusts difficulty at defined intervals based on observed timing under its rules. This mechanism aims to regulate average block production; it does not schedule individual blocks or guarantee that mining revenue remains constant.
Hashrate is not printed in each block
A block proves that a successful candidate was found, not how many unsuccessful attempts preceded it. Network hashrate charts therefore estimate activity from difficulty and observed blocks over a window. Short windows are noisy. A sudden estimated jump does not automatically establish that a particular new mining facility came online.
Match the claim to the measurement
Suppose a newsroom sees several quick blocks and wants a headline declaring a permanent hashrate increase. Ask about the window, estimator, uncertainty and comparison period. Distinguish protocol data from interpretation. A serious technical conversation can support proof of work while acknowledging statistical noise and changing economics. Do not present a point estimate as an exact count of machines or a forecast of future security.
Practice on paper
Two charts use the same chain data but one averages a day and the other a month. Why might their current hashrate estimates differ?
Reveal the worked answer
They use different observation windows. Random block timing affects short windows more strongly, while a longer window smooths recent changes. Neither chart directly counts every unsuccessful hash attempt.
Check your understanding
Choose an answer in your head or on paper, then reveal the explanation. Retry whenever you like. Answers are not submitted or scored; completion marks are your own learning notes.
1. Does difficulty adjustment promise a block at an exact time?
- Yes
- No
Reveal answer 1
No. It concerns expected production over time.
2. Does a block reveal the total number of failed attempts?
- Yes
- No
Reveal answer 2
No. Hashrate is inferred from observations and assumptions.
Take this with you
Treat estimated hashrate as an estimate with a window.
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