Unsolved problems in physics

thumb|A high-temperature superconductor levitating above a magnet. A persistent electric current flows on the surface of the superconductor, acting to exclude the magnetic field of the magnet (Meissner effect). This current effectively forms an electromagnet that repels the magnet.

powerful explosion that occurred near the Podkamennaya Tunguska River

repulsive property with constant energy density theorized to make up most of the universe’s energy content to account for its observed expansion

propagating spacetime ripple

solid, in which atoms and/or molecules are disordered like in a liquid

extremely rare unexplained atmospheric electrical phenomenon

structure formed by diffuse material in orbital motion around a massive central body

hypothetical particle with one magnetic pole

hypothetical type of exotic star

the observation that, in some circumstances, warmer water can freeze faster than colder water

right|thumb|Single-bubble sonoluminescence – a single, cavitating bubble Sonoluminescence is luminescence induced by sound waves, such as in the emission of light from imploding bubbles in a liquid when excited by sound. Sonoluminescence is sometimes considered a kind of mechanoluminescence. However, mechanoluminescence is typically defined as pertaining to solids, while sonoluminescence usually pertains to liquids. The related terms acoustoluminescence and sonotriboluminescence have been used to describe sound-induced luminescence in solids (e.g., crystals suspended in slurries).

type of physical field theory unifying fundamental forces

materials that behave as superconductors at unusually high temperatures

Wikimedia list article

Wikimedia list article

In physical cosmology, baryogenesis (also known as baryosynthesis) is the physical process that is hypothesized to have taken place during the early universe to produce baryonic asymmetry, the observation that only matter (baryons) and not antimatter (antibaryons) is detected in the universe (other than in cosmic ray collisions). Since it is assumed in cosmology that the particles we see were created using the same physics we measure today, and in particle physics experiments today matter and antimatter are always symmetric, the dominance of matter over antimatter is unexplained.

alternative explanation of the non-Newtonian rotation of galaxies

phenomenon preventing hadrons (quarks bound by the strong force using gluons) from being separated into free individual quarks

mechanism by which a celestial body generates a magnetic field

In particle physics, a glueball (also gluonium, gluon-ball) is a hypothetical composite particle. It consists solely of gluons, without valence quarks. Such a state is possible because gluons carry color charge and experience the strong interaction between themselves. Glueballs are extremely difficult to identify in particle accelerators, because they mix with ordinary meson states. In pure gauge theory, glueballs are the only states of the spectrum and some of them are stable.

perception of the passing of time

abundance of matter (baryons) and lack of antimatter (antibaryons) in our Observable Universe

Degenerate matter made from strange quarks

unexplained light usually seen in the Hessdalen valley in Norway

why is gravity weaker, compared to other fundamental forces

theories attempting to explain the deficiencies of the Standard Model, Quantum field theory and general relativity

A strangelet (pronounced ) is a hypothetical particle consisting of a bound state of roughly equal numbers of up, down, and strange quarks. An equivalent description is that a strangelet is a small fragment of strange matter, small enough to be considered a particle. The size of an object composed of strange matter could, theoretically, range from a few femtometers across (with the mass of a light nucleus) to arbitrarily large. Once the size becomes macroscopic (on the order of meters across), such an object is usually called a strange star. The term "strangelet" originates with Edward Farhi a

atmospheric phenomenon

physical phenomenon in which the Hall conductance of 2D electrons shows precisely quantized plateaus at fractional values of e²/h

problem in cosmology, solved by cosmic inflation

Millennium Prize Problem

number of theorized phases of matter whose degrees of freedom include quarks and gluons

theoretical upper limit on the energy of cosmic ray protons

unexplained empirical equation in particle physics

unexplained observed excessive energy during Earth flybys of spacecraft

the fact that the number of observed dwarf galaxies is orders of magnitude lower than expected from numerical cosmological simulations

Millennium Prize Problem

conceptual conflict between general relativity and quantum mechanics

discrepancy between flat central dark matter density profiles inferred by observation and density profiles predicted by cosmological simulations with density increasing steeply at small radii

instrument for conducting a spectrographic survey of distant galaxies

whether the mathematical axiomatic method may be extended to physics

star

the observation that the θ angle in quantum chromodynamics that would violate CP symmetry seems fine-tuned to 0

anomalous radio echo

a set of orthonormal bases, where each vector of a given basis has the same overlap with all the vectors of other bases

facet of general relativity