Open problems.
Clear explanations.
A place to explore what we don’t yet understand in science, mathematics, and society.
Find your way into a subject
NotSolved is a free collection of open problems across fields. Each entry has one primary category for browsing; topics and connected problems let you follow links across fields. Read what’s known, what remains unresolved, and why an answer could matter.
Research directions offer ways to go deeper where they’re useful. These are selected starting points for further reading. Connected topics link to other entries in the collection.
Follow the evidence
We write original summaries and link to supporting sources. Partial results stay attributed and scoped; a useful result can clarify part of a subject while leaving other aspects unresolved.
The evidence-check date is separate from a source’s publication date and from ordinary page edits. Claims and proposed solutions need review before they change an entry’s description.
A collection that can grow
The collection grows as entries and their sources are reviewed. It offers a sample across fields, with room for more. You can browse without an account. Suggestions and corrections are reviewed privately before publication.
Rights in linked work belong to their respective authors.