L04: Consensus Mechanisms

Watch proof-of-work mining in real-time, explore distributed consensus, and compare block production across networks.

Distributed Consensus Demo

Distributed Blockchain Demo — see how multiple peers maintain consensus across a network

Link mempool.space

Go to mempool.space (opens in new tab)
Look at the block visualization at the top of the page. The rightmost block is currently being mined.
Watch it fill with transactions as miners compete to find the next valid block.
When a new block is found, note how long it took since the previous block.
Check 5 consecutive blocks — are they all approximately 10 minutes apart?

Discussion: Why does Bitcoin target exactly 10-minute block times? What mechanism adjusts the mining difficulty?

Embed Anders Brownworth

In the embedded demo above, you can see 3 peers (Peer A, Peer B, Peer C), each with their own copy of the blockchain.
Mine a block on Peer A by entering data and clicking "Mine."
Observe: Peer B and Peer C do NOT automatically get the new block — they have different chains now.
Try mining different data on Peer B. Now the peers have conflicting chains (a "fork").
In real Bitcoin, the network resolves forks by following the "longest chain rule."

Discussion: What happens when two miners find a valid block at almost the same time? How does the network eventually agree on one chain?

Link Etherscan

Go to etherscan.io/stat/staking (opens in new tab)
Note: total ETH staked, total number of active validators, and the current staking APR.
Go to etherscan.io/nodetracker to see the geographic distribution of Ethereum nodes.
Compare: the number of validators to the number of Bitcoin miners (hint: there are far fewer major mining pools).

Discussion: How does the number of validators affect network decentralization? Is more validators always better?

Link Blockchair

Go to blockchair.com/bitcoin/blocks — note the average block time (~10 minutes).
Go to blockchair.com/ethereum/blocks — note the average block time (~12 seconds).
Go to blockchair.com/litecoin/blocks — note the average block time (~2.5 minutes).
Calculate: How many blocks does Bitcoin produce in 1 hour? Ethereum? Litecoin?
Think about: more blocks per hour means faster confirmations, but also more chain reorganization risk.

Discussion: What are the tradeoffs of faster block times? Why didn't Bitcoin simply use 1-second blocks?