How Does a Blockchain Reach Consensus?

A blockchain has a surprisingly difficult job: hundreds or thousands of independent computers need to maintain the same record without a bank, company or administrator deciding which version is correct.It is easy to think of this as a matter of checking whether transactions are valid. But that is only part of the problem. A network also needs a way to decide which transactions belong in the chain, which block comes next and what should happen when different participants temporarily see different