How does Bitcoin keep the average block time close to 10 minutes?
Correct answer
Answer C: The mining difficulty is adjusted every 2,016 blocks.
Quick explanation
If blocks are found too quickly on average, mining becomes harder. If they are found too slowly, it becomes easier. This keeps the average block time close to ten minutes over the long term.
Detailed explanation
Bitcoin's computing power is not constant. New mining equipment can join, while uneconomic equipment can be switched off. Without adjustment, rising hashrate would permanently make blocks faster and falling hashrate permanently make them slower.
Bitcoin therefore checks roughly how long each 2,016-block period took. If it was much shorter than the targeted two weeks, the target becomes harder. If longer, it becomes easier. Technically, the permitted block-header hash target changes; difficulty is a representation derived from it.
The adjustment does not enforce an exact ten-minute rhythm. Individual blocks may appear within seconds or after a longer wait because hash searching is random. The mechanism only stabilizes the long-term average. It sets no transaction fees and is separate from halving: difficulty adjustment affects work required, while halving affects the subsidy amount.
Example or everyday application
If total hashrate doubles, blocks are initially found faster. At the next adjustment, the target becomes harder, bringing the average back toward its intended level.
Common misconception
Beginners confuse difficulty with halving or expect a block exactly every ten minutes. The explanation distinguishes averages from individual events.
Sources used
Bitcoin Developer Guide - Block Chain
This source is mainly intended for developers. The relevant information may therefore be harder to find.
Check original sourceBitcoin Developer Guide - Mining
This source is mainly intended for developers. The relevant information may therefore be harder to find.
Check original source