What is an economic node? To understand that, you need to first conceptually understand how a user interacts with the Bitcoin network in the first place. 

Bitcoin is a database, and a network to facilitate the updating and synchronization of updates to that database, used for the primary purpose of people transacting bitcoin (entries in the database). 

The primary concern of a user making use of Bitcoin for this purpose is the validity of the transactions sent to them, i.e. is the money they have received valid in the sense that when they go forward in the future to spend it somewhere else that other people will also widely accept it as valid. If that is not the case, then it…

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