How to motivate miners to switch from POW to POS?

When the Ethereum network switches from the POW mechanism to the POS mechanism, the mining equipment and mining pools that miners have spent a lot of money and energy to buy will become worthless; at that time, perhaps many miners will prefer to stay on the old chain and continue mining, which will lead to another split of Ethereum. In order to avoid this situation, the development team introduced the "difficulty bomb" mechanism.

The "difficulty bomb" was proposed on September 7, 2015. Its working principle is to modify Ethereum's mining difficulty adjustment algorithm to increase its mining difficulty coefficient exponentially, thereby extending the block time until miners can hardly mine any blocks on the old chain. This process is also called Ethereum's "Ice Age". By then, miners will have no choice but to move to the new POS chain for mining.

The difficulty bomb mechanism can be implemented mainly because cryptocurrencies based on the POW algorithm generally have a difficulty adjustment mechanism in order to maintain the stability of the block speed. Taking Bitcoin as an example, its mining difficulty is adjusted every 2016 blocks, and the difficulty coefficient is proportional to the block speed. Bitcoin stipulates that a new block is generated every 10 minutes; if the block time is less than 10 minutes, the difficulty coefficient increases, otherwise the difficulty coefficient decreases, and Ethereum also uses a similar protocol.

It is understood that the "difficulty bomb" that was originally planned to be detonated during the Byzantium hard fork phase at the end of 2017 has now been postponed to the "Constantinople" phase to be carried out this year.