&gt; On either side of the fork is bitcoin, not the &quot;original&quot; bitcoin and an &quot;altcoin&quot;.<p>The point is that on one side you have the original protocol in use, and on the other side you have a different protocol in use. Both of them are <i>called</i> Bitcoin and use the same database up to the point of the fork, but they&#x27;re not the same protocol in much the same way that Dogecoin is not the same protocol as Bitcoin - someone who attempts to use the pre-fork protocol will not be able to achieve consensus with someone attempting to use the post-fork protocol.<p>&gt; In the case of most forks, you fork via voting by &quot;x% of the last 1000 blocks were mined by this implementation&quot;.<p>That is not the only way to implement a fork. As I say, you can fork the chain simply by convincing enough users to use your fork - there&#x27;s no hard requirement for any miner-level voting to be done at all.