The world's unsolved problems
993 open questions across 14 fields, gathered from Wikipedia. Pick one and start thinking.
110 results in Physics · clear · surprise me
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Neutron lifetime puzzle
While the neutron lifetime has been studied for decades, there currently exists a lack of consilience on its exact value, due to different results from two experimental methods ("bottle" versus "beam").
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Proton decay and spin crisis
Is the proton fundamentally stable? Or does it decay with a finite lifetime as predicted by some extensions to the standard model? How do the quarks and gluons carry the spin of protons?
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Grand Unification
Are the electromagnetic and nuclear forces different aspects of a Grand Unified Theory? If so, what symmetry governs this force and its behaviours?
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Supersymmetry
Is spacetime supersymmetry realized at TeV scale? If so, what is the mechanism of supersymmetry breaking? Does supersymmetry stabilize the electroweak scale, preventing high quantum corrections? Does the lightest supersymmetric particle (LSP) comprise dark matter?
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Color confinement
The quantum chromodynamics (QCD) color confinement conjecture is that color-charged particles (such as quarks and gluons) cannot be separated from their parent hadron without producing new hadrons.
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The QCD vacuum
Many of the equations in non-perturbative QCD are currently unsolved. These energies are the energies sufficient for the formation and description of atomic nuclei. How thus does low energy /non-pertubative QCD give rise to the formation of complex nuclei...
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Generations of matter
Why are there three generations of quarks and leptons? Is there a theory that can explain the masses of particular quarks and leptons in particular generations from first principles (a theory of Yukawa couplings)?
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Neutrino mass
What is the absolute mass of neutrinos? Are they Dirac or Majorana fermions? Is the mass hierarchy normal or inverted? Is the CP violating phase equal to 0?
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Reactor antineutrino anomaly
There is an anomaly in the existing body of data regarding the antineutrino flux from nuclear reactors around the world. Measured values of this flux appears to be only 94% of the value expected from theory. It is unknown whether this is due to unknown...
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Strong CP problem and axions
Why is the strong nuclear interaction invariant to parity and charge conjugation? Is Peccei–Quinn theory the solution to this problem? Could axions be the main component of dark matter?
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Anomalous magnetic dipole moment
Why is the experimentally measured value of the muon's anomalous magnetic dipole moment ("muon ") significantly different from the theoretically predicted value of that physical constant?
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Pentaquarks and other exotic hadrons
What combinations of quarks are possible? Are they a tightly bound system of five elementary particles, or a more weakly-bound pairing of a baryon and a meson?
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Mu problem
A problem in supersymmetric theories, concerned with understanding the reasons for parameter values of the theory.
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Koide formula
An aspect of the problem of particle generations. The sum of the masses of the three charged leptons, divided by the square of the sum of the roots of these masses, to within one standard deviation of observations, is . It is unknown how such a simple...
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Strange matter
Does strange matter exist? Is it stable? Can they form Strange stars? Is strange matter stable at 0 pressure (i.e. in the vacuum)?
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Glueballs
Do they exist in nature?
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Gallium anomaly
The measurements of the charged-current capture rate of neutrinos on Ga from strong radioactive sources have yielded results below those expected, based on the known strength of the principal transition supplemented by theory.
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Solar cycle
How does the Sun generate its periodically reversing large-scale magnetic field? How do other solar-like stars generate their magnetic fields, and what are the similarities and differences between stellar activity cycles and that of the Sun? What caused...
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Coronal heating problem
Why is the Sun's corona (atmosphere layer) so much hotter than the Sun's surface? Why is the magnetic reconnection effect many orders of magnitude faster than predicted by standard models?
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Astrophysical jet
Why do only certain accretion discs surrounding certain astronomical objects emit relativistic jets along their polar axes? Why are there quasi-periodic oscillations in many accretion discs? Why does the period of these oscillations scale as the inverse of...
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Diffuse interstellar bands
What is responsible for the numerous interstellar absorption lines detected in astronomical spectra? Are they molecular in origin, and if so which molecules are responsible for them? How do they form?
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Supermassive black holes
What is the origin of the M–sigma relation between supermassive black hole mass and galaxy velocity dispersion? How did the most distant quasars grow their supermassive black holes up to 10 solar masses so early in the history of the universe?
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Kuiper cliff
Why does the number of objects in the Solar System's Kuiper belt fall off rapidly and unexpectedly beyond a radius of 50 astronomical units?
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Flyby anomaly
Why is the observed energy of satellites flying by planetary bodies sometimes different by a minute amount from the value predicted by theory?
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Galaxy rotation problem
Is dark matter responsible for differences in observed and theoretical speed of stars revolving around the centre of galaxies, or is it something else?
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Supernovae
What is the exact mechanism by which an implosion of a dying star becomes an explosion?
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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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Data last refreshed 2026-10-20 03:01 UTC.