Edison thought in terms of reverse salients and critical problems.
“Reverse salients are areas of research and development that are lagging in some obvious way behind the general line of advance. Critical problems are the research questions, cast in terms of the concrete particulars of currently available knowledge and technique and of specific exemplars or models that are solvable and whose solutions would eliminate the reverse salients. ”
What strikes you as as important current example of a reverse salient, and the associated critical problem or problems?