I know that the transactions stay in the block and hashed alongside few other things and that hash is stored in the next block. And I understand that if you try to tamper with one of the transactions, the hash will change and it will affect all the blocks that come after it.
However, how does a block know that its transactions have tampered with in the first place?
Assume that block #1000 has 10 transactions. Now, the hash has been calculated and stored in block #1001
so, if I go back to block #1000 and add one more transaction, this will change the hash and it wont be the same one stored in #1001. However, how the hash of block #1000 changes in the first place if it was already calculated? does this mean that the hash of each block is recalculated regularly?