Someone please correct me, but here's my best explanation.
When you first connect to the Bitcoin network, how do you find out what the true blockchain is? You connect to other nodes and ask them. They may tell you anything. However, it's easy to verify whether a blockchain given in a response is valid. That is, it's easy to tell if a given blockchain is following all of the rules.
But what if you receive a few valid blockchains that are different from one another? Which one is the true blockchain for the world?
You simply choose the longest blockchain that you hear about.
Why the longest? It's the one that has had the most computing power focused on it. Anyone can compute a very small, self-serving, malicious blockchain of a few blocks. But to compute the longest blockchain in the world requires vast computing resources. The longest blockchain is supposed to be uncontrollable by any single party or network of colluders because it is supposed to be too hard to acquire the majority of the computing resources in the world.
Unfortunately, it looks like someone did just this and controlled >51% of all computing resources in the world dedicated to Bitcoin Gold. If you have enough resources, you can generate the longest blockchain in the world, add a self-serving transaction, get some goods or service in return, then recompute a new longest chain in the world where that transaction is no longer there. Everyone by default accepts the longest blockchain because it's supposed to be the most safe, but they are wrong.
I'm not well versed in the block chain tech but it is surprising that there is an inherent big ass monopoly type manipulation you can run ... inherent to the system.
That seems very much not what Bitcoin would "intend" and yet there it is, very available.
When you first connect to the Bitcoin network, how do you find out what the true blockchain is? You connect to other nodes and ask them. They may tell you anything. However, it's easy to verify whether a blockchain given in a response is valid. That is, it's easy to tell if a given blockchain is following all of the rules.
But what if you receive a few valid blockchains that are different from one another? Which one is the true blockchain for the world?
You simply choose the longest blockchain that you hear about.
Why the longest? It's the one that has had the most computing power focused on it. Anyone can compute a very small, self-serving, malicious blockchain of a few blocks. But to compute the longest blockchain in the world requires vast computing resources. The longest blockchain is supposed to be uncontrollable by any single party or network of colluders because it is supposed to be too hard to acquire the majority of the computing resources in the world.
Unfortunately, it looks like someone did just this and controlled >51% of all computing resources in the world dedicated to Bitcoin Gold. If you have enough resources, you can generate the longest blockchain in the world, add a self-serving transaction, get some goods or service in return, then recompute a new longest chain in the world where that transaction is no longer there. Everyone by default accepts the longest blockchain because it's supposed to be the most safe, but they are wrong.