The world's unsolved problems
993 open questions across 14 fields, gathered from Wikipedia. Pick one and start thinking.
Showing all 993 problems · surprise me
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p-nuclei
What astrophysical process is responsible for the nucleogenesis of these rare isotopes?
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Ultra-high-energy cosmic ray
Why is it that some cosmic rays appear to possess energies that are impossibly high, given that there are no sufficiently energetic cosmic ray sources near the Earth? Why is it that (apparently) some cosmic rays emitted by distant sources have energies...
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Rotation rate of Saturn
Why does the magnetosphere of Saturn exhibit a (slowly changing) periodicity close to that at which the planet's clouds rotate? What is the true rotation rate of Saturn's deep interior?
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Origin of magnetar magnetic field
What is the origin of magnetar magnetic fields?
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Large-scale anisotropy
Is the universe at very large scales anisotropic, making the cosmological principle an invalid assumption? The number count and intensity dipole anisotropy in radio, NRAO VLA Sky Survey (NVSS) catalogue is inconsistent with the local motion as derived from...
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Age–metallicity relation in the Galactic disk
Is there a universal age–metallicity relation (AMR) in the Galactic disk (both "thin" and "thick" parts of the disk)? Although in the local (primarily thin) disk of the Milky Way there is no evidence of a strong AMR, a sample of 229 nearby "thick" disk...
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The lithium problem
Why is there a discrepancy between the amount of lithium-7 predicted to be produced in Big Bang nucleosynthesis and the amount observed in very old stars?
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Ultraluminous X-ray sources (ULXs)
What powers X-ray sources that are not associated with active galactic nuclei but exceed the Eddington limit of a neutron star or stellar black hole? Are they due to intermediate-mass black holes? Some ULXs are periodic, suggesting non-isotropic emission...
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Fast radio bursts (FRBs)
What causes these transient radio pulses from distant galaxies, lasting only a few milliseconds each? Why do some FRBs repeat at unpredictable intervals, but most do not? Dozens of models have been proposed, but none have been widely accepted.
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Origin of cosmic magnetic fields
Observations reveal that magnetic fields are present throughout the universe, from galaxies to galaxy clusters. However, the mechanisms that generated these large-scale cosmic magnetic fields remain unclear. Understanding their origin is a significant...
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Quantum chromodynamics
What are the phases of strongly interacting matter, and what roles do they play in the evolution of the cosmos? What is the detailed partonic structure of the nucleons? What does QCD predict for the properties of strongly interacting matter? What...
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Quark–gluon plasma
Where is the onset of deconfinement: 1) as a function of temperature and chemical potentials? 2) as a function of relativistic heavy-ion collision energy and system size? What is the mechanism of energy and baryon-number stopping leading to creation of...
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Specific models of quark–gluon plasma formation
Do gluons saturate when their occupation number is large? Do gluons form a dense system called colour glass condensate? What are the signatures and evidences for the Balitsky–Fadin–Kuraev–Lipatov (BFKL), Balitsky–Kovchegov (BK),...
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Nuclei and nuclear astrophysics
What is the nature of the nuclear force that binds protons and neutrons into stable nuclei and rare isotopes? What is the explanation for the EMC effect? What is the nature of exotic excitations in nuclei at the frontiers of stability and their role in...
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Under what conditions do smooth solutions exist for the Navier–Stokes equations, which are the equations that describe the flow of a…
Under what conditions do smooth solutions exist for the Navier–Stokes equations, which are the equations that describe the flow of a viscous fluid? This problem, for an incompressible fluid in three dimensions, is also one of the Millennium Prize Problems...
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Turbulent flow
Is it possible to make a theoretical model to describe the statistics of a turbulent flow (in particular, its internal structures)?
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Granular convection
why does a granular material subjected to shaking or vibration exhibit circulation patterns similar to types of fluid convection? Why do the largest particles end up on the surface of a granular material containing a mixture of variously sized objects when...
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High-temperature superconductivity
What is the mechanism that causes certain materials to exhibit superconductivity at temperatures much higher than around 25 kelvins? Is it possible to make a material that is a superconductor at room temperature and atmospheric pressure? What is the origin...
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Amorphous solids
What is the nature of the glass transition between a fluid or regular solid and a glassy phase? What are the physical processes giving rise to the general properties of glasses and the glass transition?
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Universality of low-temperature amorphous solids
why is the small dimensionless ratio of the phonon wavelength to its mean free path nearly the same for a very large family of disordered solids? This small ratio is observed for very large range of phonon frequencies.
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Cryogenic electron emission
Why does the electron emission in the absence of light increase as the temperature of a photomultiplier is decreased?
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Sonoluminescence
What causes the emission of short bursts of light from imploding bubbles in a liquid when excited by sound?
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Topological order
Is topological order stable at non-zero temperature? Equivalently, is it possible to have three-dimensional self-correcting quantum memory?
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Gauge block wringing
What mechanism allows gauge blocks to be wrung together?
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Fractional Hall effect
What mechanism explains the existence of the 1=u = 5/2 state in the fractional quantum Hall effect? Does it describe quasiparticles with non-Abelian fractional statistics?
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Liquid crystals
Can the nematic to smectic (A) phase transition in liquid crystal states be characterized as a universal phase transition?
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Semiconductor nanocrystals
What is the cause of the nonparabolicity of the energy-size dependence for the lowest optical absorption transition of quantum dots?
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Metal whiskering
In electrical devices, some metallic surfaces may spontaneously grow fine metallic whiskers, which can lead to equipment failures. While compressive mechanical stress is known to encourage whisker formation, the growth mechanism has yet to be determined.
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Superfluid transition in helium-4
Explain the discrepancy between the experimental and theoretical determinations of the heat capacity critical exponent α.
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Scharnhorst effect
Can light signals travel slightly faster than c between two closely spaced conducting plates, exploiting the Casimir effect?
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Data last refreshed 2026-10-20 03:01 UTC.