>In block chain, 51% of the network can decide to modify the ledger to do things that aren't true. 51% is not enough to modify the ledger. A hard fork requires

>In block chain, 51% of the network can decide to modify the ledger to do things that aren't true. 51% is not enough to modify the ledger. A hard fork requires an overwhelming majority to support it. Otherwise, the cost of fragmentation would be immense, and outweigh any benefit those effecting the hard fork could hope to gain from the hard fork.