The world's unsolved problems
993 open questions across 14 fields, gathered from Wikipedia. Pick one and start thinking.
59 results in Astronomy · clear · surprise me
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How do galactic history and dark matter halos impact the observable properties of galaxies?
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How did the intergalactic medium and the first sources of radiation evolve from cosmic dawn through the epoch of reionization?
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Gravitational singularities
Does general relativity break down in the interior of a black hole due to quantum effects, torsion, or other phenomena?
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No-hair theorem
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Supermassive black holes
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The formation of high-redshift quasars
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Black hole information paradox and black hole radiation
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Firewalls
Do firewalls exist around black holes?
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Final parsec problem
Supermassive black holes appear to have merged, and what appears to be a pair in this intermediate range has been observed, in PKS 1302–102. However, theory predicts that when supermassive black holes reach a separation of about one parsec, it may take...
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What are the astrophysical formation channels behind the binary black hole mergers observed through gravitational waves?
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Naked singularity
Is the cosmic censorship hypothesis correct? Can a naked singularity exist?
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What are the mass and spin distributions of stellar mass black holes?
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Cosmological principle
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Dark matter
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Dark energy
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Baryon asymmetry
Why is there far more matter than antimatter in the observable universe?
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Cosmological constant problem
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Size and shape of the universe
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Cosmic inflation
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Horizon problem
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Hubble tension
If ΛCDM is correct, why are measurements of the Hubble constant failing to converge?
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Axis of evil
Some large features of the microwave sky at distances of over 13 billion light-years appear to be aligned with both the motion and orientation of the Solar System. Is this due to systematic errors in processing, contamination of results by local effects,...
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Origin of the Universe
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Fate of the universe
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Multiverse
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Is there other life in the Solar System? Especially
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Is there other life in the Universe? Especially
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Nature of Wow! signal
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How do habitable environments arise and evolve within the context of planetary systems? How can the signs of habitable life be identified…
How do habitable environments arise and evolve within the context of planetary systems? How can the signs of habitable life be identified and interpreted in the context of planetary systems?
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Data last refreshed 2026-10-20 03:01 UTC.