The landing methodology of oracle machines can refer to the solution of P/NP problems. P/NP problem refers to a problem that is difficult to solve but easy to verify. This type of problem is the core idea of oracle machines. Analogous to the Turing machine, 'everything that appears computable can be computed'. The oracle puts the solution into one type of formal system and the verification into another type of formal system, thus linking the two types of formal systems together. The longest chain of Bitcoin ("oracle machine") places the nonce solution of POW into formal systems such as Miner, and the verification into formal systems such as UTXO. Thus, the longest chain is obtained by formal systems such as Miner competing to do work, and the results are sent to formal systems such as UTXO for simple verification, ensuring the security and usability of UTXO and other formal systems.