Homework on Mining and Proof of Work - Questions
- Why is it important to make sure that miners spend money (on electricity) while mining?
Because it motivates them to make money and the only way to make money it to play by rules.
- Why would it be very difficult for someone to go back change a previously added block?
Because it will collapse the network through changing the hashes of the every block that subsequenting the changed block. To be able to overwrite the network someone will need to have 51% hashrate to change and catch up the original network, in the end overtake it and create longer chain to convience the network about the truth of the change. It would cost a lot of money so probably it would be more porfitable for that person to become miner in the original network and earn money by consensus.
- How does the network regulate mining difficulty?
By adjusting the mining target, the more miners are in the network, the lower this number is, the more difficult it is to guess the nonce.