World Solve — A living repository of problems worth solving.

Repository of problems worth solving

World Solve is a public institutional repository for identifying real unresolved problems across science, society, health, governance, economics, and local systems. Each entry is intended to be citable, inspectable, and actionable.

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4194Total

4194Open

0Solved

9Humans

We do not fully understand the cosmic reionization history.

open Global / Unspecified, Global

Timing and sources of reionization remain uncertain. 21cm experiments and high-z galaxy observations can map it.

science-space global-unspecified reionization not fully understand cosmic history timing sources remain uncertain know matter actually dark what

WS01843

By Ian Patel · 2026-07-22T15:14:00Z

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WS01843 | World Solve | https://www.worldsolve.org/index.php?view=problem&id=1843