Technically, there is not one ledger. This post is being pedantic, but the parent is wrong, technically, on the central point of its post. Every node keeps a c

Technically, there is not one ledger. This post is being pedantic, but the parent is wrong, technically, on the central point of its post. Every node keeps a copy of the blockchain and occasionally one node adds a block to the blockchain (upon successful mining), then notifies other networked nodes of the new block. As soon as a block is mined, the lucky miner has a different ledger than the rest of the network. It's not until that new block propagates across the entire Bitcoin network that the ledger is updated. Because of differences in protocol implementations, not all nodes accept the new block (this happened at least once). With the new BTC fork, it will be obvious that any stragglers on the old fork (or the new fork, if the protocol change brings insufficient consensus) will have their own fork of the blockchain, which will mean the ledger is forked.