This is a quote from the book "On Zero Confirmation Transactions" by Chris Pacia
...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
versed (or ‘double spent’) by the sender, assuming he has some technical ability. This means someone could pay you for some merchandise, then steal back the coins afterwards. The more time t...