Mining: what is the lowest possible target? Could it be a block hash of all zeros? I had a basic question about Bitcoin mining. I understand that as the bitcoin difficulty adjustment becomes harder the hash output will require more 0s in the beginning of the hash. Is it theoretically possible that the Bitcoin difficulty adjustment would be so large that the hash output would just be all 0s? I know this is theoretical bit I'm just curious.
The retargeting every 2016 blocks is computed as follows:


previous_target * (T2-T1) / (20160 minutes)


Where:


T2: timestamp of previous block
T1: timestamp of block at current height - 2016
Target adjustment bounded to factor 4


Ignoring the target adjustment limit: For the resulting target to be zero, T2-T1 would need to equal zero. That would require an infinite amount of hash-rate. Therefore we can approach your scenario, but never reach it.