Category:Open problems

Unsolved problems: category for problems of a theoretical nature. See list of unsolved problems.
 * Not for factual questions (e.g. Mary Celeste, etc.): these belong in Category:Mysteries, or another of its subcategories, like Category:Unsolved crimes.
 * Not for practical disputes (e.g. pollution, Middle East conflict). Perhaps try Category:Controversies or Category:Conflict.