Sometimes when we search for an expert in a particular field, not just a general programmer, we ask increasingly deep questions, to estimate how deep is the kno

Sometimes when we search for an expert in a particular field, not just a general programmer, we ask increasingly deep questions, to estimate how deep is the knowledge. It's expected that at some point candidate would not know the answer. The goal is to hire a person that is more experienced than we are. It doesn't mean we knew it ourselves.