The following is a list of notable unsolved problems grouped into broad areas of physics. Some of the major unsolved problems in physics are theoretical, meaning that existing theories seem incapable of explaining a certain observed phenomenon or experimental result. The others are experimental, meaning that there is a difficulty in creating an experiment to test a proposed theory or investigate a phenomenon in greater detail. There are still some questions beyond the Standard Model of physics, such as the strong CP problem, neutrino mass, matter–antimatter asymmetry, and the nature of dark matter and dark energy. Another problem lies within the mathematical framework of the Standard Model itself—the Standard Model is inconsistent with that of general relativity, to the point that one or both theories break down under certain conditions (for example, within known spacetime singularities like the Big Bang and the centres of black holes beyond the event horizon).

General physics

Quantum gravity

Quantum physics

Cosmology and general relativity

High-energy/particle physics

Astronomy and astrophysics

Nuclear physics

Fluid dynamics

Condensed matter physics

α .

Quantum computing and quantum information

Plasma physics

Biophysics

Foundations of physics

Problems solved since the 1990s

General physics/quantum physics

Cosmology and general relativity

High-energy physics/particle physics

Astronomy and astrophysics

Nuclear physics

Rapidly solved problems

Footnotes