Meanings of open problem in English

The localization of persons in indoor environments is nowadays an open problem.

However, the mechanistic origin of resting state is obscured by large-scale models' complexity, and a close structure-function relation is still an open problem.

This question was one of the outstanding open problems of his day.

He seems more concerned with precise measurements than with questionings as to the open problems of his science.

Yet he had always thought that he possessed a strong paternal instinct, an interest in young life, in opening problems.

But a breakthrough from scientists at Berkeley Lab could be the solution the planet needs for this eye- opening problem -recyclable plastics.