Updated theory.

notebooks/II. Building a General Purpose Cryptocurrency.ipynb

@@ -120,7 +120,9 @@
    "source": [
     "### 1.4 Mempools\n",
     "\n",
-    "Mempools form the transaction pools for the distributed peer-to-peer (P2P) networks. There exists a mempool for each node in the network. Essentially a mempool is a staging area for the transactions where performed transactions go to wait for inclusion in a mined block. When a transaction is added to a node's mempool, it is then relayed to the whole network. A single block can contain about 2000 transactions and mempools hold an average of 9000 pending transactions. Whenever a block is mined, the transactions selected for the mined block are then removed initially from the mining node and then from the whole network through relaying the information about the changed mempool."
+    "Mempools form the transaction pools for the distributed peer-to-peer (P2P) networks. There exists a mempool for each node in the network. Essentially a mempool is a staging area for the transactions where performed transactions go to wait for inclusion in a mined block. When a transaction is added to a node's mempool, it is then relayed to the whole network. A single block can contain about 2000 transactions and mempools hold an average of 9000 pending transactions. Whenever a block is mined, the transactions selected for the mined block are then removed initially from the mining node and then from the whole network through relaying the information about the changed mempool.\n",
+    "\n",
+    "Whenever there are competing claims for the next block added to the chain, the one mined later usually gets orphaned. Or to be more precise, the block resulting in longer chains wins and the smaller chain gets orphaned. The transactions in the oprhaned block are not however lost, but returned the mempool. A rule of thumb is to wait for six confirmed blocks to be sure that the transaction within a mined block has been accepted and solidified into the chain."
    ]
   },
   {