This is a quote from the book "On Zero Confirmation Transactions" by Chris Pacia
...“unconfirmed” or “pending” inclusion in Bitcoin’s ledger ― the blockchain. Approximately once every 10 minutes a mining pool collects these transactions from memory, organizes them i
nto a block, and adds that block of transactions to the blockchain. This process repeats every 10 minutes on average.
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We sometimes hear people say that Bitcoin transactions are irre
versible. That’s not technically true, or at least not true of transactions that have been made recently. In the first number of minutes after a transaction is made, it can theoretically be re...