@gavinisdie the challenge I'm talking about is basically "try to find a number that turns this other number into a specific format".
Computers try millions of hashes per second to find this special number by brute force. That number is not special though. We just say "these are the rules that must be met" - we could also instead do different rules and most of that energycost would just vanish.
I can't overstate how arbitrary and insane this is.
claudius