Unit 1 · Level 1 · What is a blockchain
Nodes, miners & validators
No company runs Bitcoin or Ethereum. Thousands of volunteers do, by running free software on ordinary computers called nodes. Full nodes check every single transaction against the rules; miners (Proof of Work) and validators (Proof of Stake) propose the new blocks. A modest home PC and a few hundred gigabytes of disk is enough to run a Bitcoin full node yourself.
Free to play. No ads, no token, no account needed to start.
What you get asked
What is the job of a FULL NODE?
Nodes are the referees. A block that breaks the rules, even one from the biggest miner on Earth, simply gets ignored by every honest node.
Match each participant to what they do
Proposers suggest, nodes inspect. The power to CHECK is spread even wider than the power to produce blocks, and that spread is the network's real immune system.
Anyone can run a full ___ at home and verify the blockchain without asking permission.
'Don't trust, verify' is the culture's motto. You never have to take an exchange's or influencer's word for what's on the chain. Your own node can tell you.
Why does decentralization make a blockchain harder to scam?
With thousands of independent checkers, there's no manager to bribe and no headquarters to raid. Careful though: the LEDGER is protected, but you can still be tricked into sending coins to a crook.
A new coin advertises: 'Relax, our team can freeze or reverse any transaction!' What is that really telling you?
If one team can freeze or rewrite the ledger, they can also freeze YOU, and 'decentralized' is just marketing paint. Always ask: who can change the rules here? 🐜
The rest of this unit
Blocks, consensus, and why any of this works without a boss.