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I'm new to blockchain field and I read one article. article

In this article of Authorization chapter, it is said that "For a public blockchain, the decision to add a transaction to the chain is made by consensus. This means that the majority of “nodes” (or computers in the network) must agree that the transaction is valid."

But, I can't imagine the agreement situation by nodes.

How do all nodes agree on that new block  should be added to blockchain ? Do nodes have to agree or disagree manually like by clicking a "Agree!!" or "Disagree!!" button?

Also, doesn't it take soooooo long time? I mean that there are tons nodes in the network and to gather all nodes agreement, it'll be sooooo long time I guess.

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  • Read the bitcoin wiki at bitcoin.it instead.
    – Mercedes
    Oct 10, 2021 at 11:20

2 Answers 2

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I'm new to blockchain field and I read one article. article

...

How do all nodes agree on that new block  should be added to blockchain ? Do nodes have to agree or disagree manually like by clicking a "Agree!!" or "Disagree!!" button?

They run the "blockchain" software, and the software automatically accepts or rejects blocks based on what exact software they are running and what exact configuration the software they are running is using. The only manual steps are choosing the version or modification the node operator will choose to run, and configuring it.

Also, doesn't it take soooooo long time? I mean that there are tons nodes in the network and to gather all nodes agreement, it'll be sooooo long time I guess.

Accepted blocks are propagated on the network fast. Generally rejected blocks are propagated fast among the nodes who accept them, but their propagation will be slower because not every node accepts and broadcasts.

Things will be slightly different depending on if the choice creates a soft fork or a hard fork.

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Consensus in Bitcoin is not really a consultative operation.

In the case of Bitcoin, consensus does not mean that all nodes have to communicate with each other to argue back and forth about whether a block should be accepted.

Each full node makes their decision in isolation without consulting other nodes.


Consensus is not absolute, and need not be

In a way, the network never reaches 100% consensus because some nodes may be offline for days or weeks, new nodes are always being added, those new nodes may spend considerable time synchronising.

The important thing is that enough nodes are applying the same set of validation rules. That means at any given instant, the number of nodes that consequently have the same UTXOs set is sufficient to sustain a currency.

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