Once a miner successfully creates a new block, it is communicated to all other miners who restart the process. But what happens if two miners submit a valid block simultaneously?
In the case of an accidental fork, two competing chains exist briefly. Very quickly, one chain attracts greater mining hash power and becomes dominant. The other becomes orphaned — no more work is done on it.
A deliberate fork — a hard fork — creates a permanent split. During 2017 there were many deliberate hard forks creating new forms of BTC. Most failed quickly, though a few survive today, notably Bitcoin Cash (BCH) and Bitcoin Satoshi Vision (BSV). Both pale into insignificance next to BTC's $2 trillion market cap.
Anyone can create a new hard fork, but if it attracts no users or miners, it remains merely a technical curiosity.
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