In most blockchain systems, including Bitcoin, the difficulty adjustment algorithm takes into account the average time it took to mine a certain number of blocks in the past.
Bitcoin difficulty adjustment does not take a random period of time in the past, it only accounts for the last 2,016 of confirmed blocks and uses the time taken to mine a block averagely to adjust the difficulty.
Considering that both chains are supposed to exist at the same time, and having forked apart from a common block, how would the longer chain have a lower difficulty level if both chains adhered the difficulty retargeting protocol?
As mentioned it depends on if the chains last into the next retargetting, which will result in different amounts of work in the different chains.
- Jay -