51% is possible, but it only leads to chain reorgs, not the actual consensus rules.
In practice the actual cost and the uncertainty of an attack ensures that it is almost never attempted in practice for secure* blockchains:
1. You would need much greater hash rate share than 50% for good chances(forgoing the block rewards $$ incase of failure!), the social coordination is the bigger challenge, see mining pool distribution[1].
In practice the actual cost and the uncertainty of an attack ensures that it is almost never attempted in practice for secure* blockchains:
1. You would need much greater hash rate share than 50% for good chances(forgoing the block rewards $$ incase of failure!), the social coordination is the bigger challenge, see mining pool distribution[1].
[1] https://btc.com/stats/pool