I read this article blockchaing stored and now I am bit confused. In this article it is described, that the transaction needs 15 seconds to propagate to the whole blockchain network. I know that the new transaction block contains the hash of the previous block. So my question is, if anyone in this 15 seconds create another transaction, how the systems doesn't crash?
To make my question a little bit more clear, I make one example. Let's say the hash of the previous block was "11b83f1dbb421b7539f755". If I make a transaction (Transaction A) for about 1 BTC and 1 second after me someone other makes new a transaction (Transaction B), which transaction becomes the previous hash "11b83f1dbb421b7539f755", because it needs 15 seconds till every node knows the new chain? So after one second not every node, knows about the Transaction A.
Thank you very much in advance!
PS: English is not my mother language :)