The main purpose of mining is to set the history of transactions in a way that it is computationally impossible to modify by any one entity. By downloading and checking the blockchain, bitcoin nodes come to a consensus on the classification of events in bitcoin. Mining is also the mechanism used to introduce Bitcoins into the system: miners receive all transaction costs, as well as a “grant” of newly created coins. This makes it possible both to distribute new coins in a decentralized way and to motivate people to ensure the security of the system. Bitcoin mining is so called because it resembles the mining of other commodities: it requires a physical effort and gradually puts new units at the disposal of all those who wish to take part. An important difference is that the supply does not depend on the amount of extraction. In general changing total miner hashpower does not change how many bitcoins are created long term. Mining is intentionally designed to use a lot of resources and be difficult, so that the number of blocks found every day by the miners remains stable. Individual blocks must contain proof of work to be considered valid. This proof of work is verified by other Bitcoin nodes each time they receive a block.