Physics

Magnetization is magnetic dipole moment per unit volume, describing the magnitude and direction of a material’s magnetic state.

Marie Curie was a Polish-born French physicist and chemist who discovered polonium and radium and received Nobel Prizes in two sciences.

Mass is a physical quantity that measures inertia, participates in gravitation, and corresponds to a system’s rest energy.

Mass number is the total number of protons and neutrons in an atomic nucleus, distinguishing isotopes without measuring their actual mass.

Mass–energy equivalence relates a system’s invariant mass to its rest energy through Einstein’s equation E₀ = mc².

Max Planck was a German theoretical physicist whose work on thermal radiation introduced energy quanta and helped establish quantum theory.

Maxwell’s equations describe how electric and magnetic fields arise, interact, and propagate, providing the foundation of classical electromagnetism.

The measurement problem concerns how quantum theory’s continuous evolution and superpositions relate to definite measurement outcomes and their probabilities.

Measurement uncertainty quantifies the dispersion of values reasonably attributed to a measured quantity, using the information available about the measurement.

The Meissner effect is the expulsion of magnetic fields from a superconductor’s bulk in its equilibrium low-field state, distinguishing superconductivity from perfect conductivity.

A meson is an integer-spin hadron, conventionally described as a bound state of a quark and an antiquark.

The metre is the SI base unit of length, defined through the exact speed of light in vacuum and the duration of the second.

The Metre Convention is the 1875 treaty establishing permanent international cooperation on measurement standards and the institutions that oversee the International System of Units.

Metrological traceability links a measurement result to a specified reference through a documented, unbroken calibration chain with evaluated uncertainties.

Metrology is the science of measurement, encompassing units, standards, calibration, uncertainty, and the comparability of measurement results.

Michael Faraday was an English experimental scientist whose discoveries established fundamental principles of electromagnetism and electrochemistry.

An instrument that reveals structures too small for unaided vision by forming images with light, electron beams, or scanning probes.

Miller indices are integer labels that describe crystal-plane orientations and identify diffraction reflections relative to a chosen crystallographic basis.

Moment of inertia measures how mass is distributed about an axis and determines a body's response to rotational acceleration.

Momentum is a vector quantity describing motion, conserved in isolated systems and fundamental to classical, relativistic, and quantum physics.

A muon is an unstable elementary particle similar to the electron but about 207 times heavier, important in cosmic radiation, precision physics, and materials research.

An electrically neutral elementary particle that interacts weakly with matter, occurs in three known flavors, and exhibits oscillations demonstrating nonzero neutrino masses.

Neutrino oscillation is the quantum-mechanical change of neutrino flavor during propagation, revealing that neutrinos mix and have nonzero mass differences.

An electrically neutral subatomic particle that forms atomic nuclei with protons and plays essential roles in nuclear reactions and materials research.

The newton (N) is the SI unit of force, equal to one kilogram metre per second squared.

Three foundational laws of classical mechanics describing inertia, the relationship between force and acceleration, and reciprocal forces between interacting bodies.

Niels Bohr was a Danish physicist whose work on atomic structure, quantum theory, and nuclear physics helped establish modern physics.

An international award established by Alfred Nobel’s will, recognizing important discoveries and inventions in physics since 1901.

Noether’s theorem connects continuous symmetries of an action with conserved quantities, explaining the mathematical origin of many conservation laws in physics.

Nuclear binding energy is the energy required to separate an atomic nucleus completely into its constituent protons and neutrons.

A proposed timekeeping device that would use a nuclear transition, most prominently in thorium-229, as its frequency reference instead of an electronic transition.

Nuclear fission is the splitting of a heavy atomic nucleus into smaller nuclei, releasing energy and usually neutrons that can sustain a chain reaction.

Nuclear fusion combines light atomic nuclei into heavier nuclei, powering stars and providing the physical basis for experimental fusion energy systems.

Nuclear magnetic resonance is the resonant response of magnetic atomic nuclei to radiofrequency fields, enabling molecular analysis and magnetic resonance imaging.

Nuclear physics studies atomic nuclei, their constituents and interactions, and the transformations and forms of matter arising from nuclear processes.

A nucleon is a proton or neutron, the two closely related composite particles that constitute ordinary atomic nuclei.

Nucleosynthesis is the formation of atomic nuclei through nuclear reactions, explaining the cosmic origins and abundances of chemical elements and their isotopes.

Ohm’s law describes the proportional relationship between voltage and electric current in a conductor whose resistance remains constant under specified conditions.

Optical coherence describes correlations in a light field across space and time, governing interference visibility and the statistical properties of photodetection.

Optics is the branch of physics concerned with light, its propagation and interaction with matter, and the formation and manipulation of images.

An order parameter is a quantity that distinguishes phases of a physical system and characterizes the type and degree of ordering.

Pair production is the creation of a particle and its antiparticle from energy supplied by radiation, collisions, or an external field.

Paramagnetism is a magnetic response in which an applied field induces magnetization in the same direction, without spontaneous magnetic ordering.

Parity describes how physical quantities and quantum states transform under spatial inversion, a symmetry conserved by electromagnetic and strong interactions but violated by weak interactions.

A particle accelerator uses electromagnetic fields to increase the energy of charged particles, producing beams for fundamental research, medicine, and industry.

A particle jet is a collimated spray of particles produced in high-energy interactions, usually associated with an energetic quark or gluon.

Particle physics investigates the fundamental constituents of matter and the interactions governing their behavior.

A partition function normalizes statistical weights and connects microscopic states to thermodynamic properties and probabilistic models.

The path-integral formulation expresses quantum evolution as a sum of amplitudes over possible histories, weighted by their action.

A quantum principle forbidding identical fermions from occupying the same single-particle state, underlying atomic structure, the stability of matter, and degeneracy pressure.

Permittivity describes the relationship between electric displacement and electric field, governing a medium’s polarization response, capacitance, and electromagnetic-wave behavior.

Perturbation theory approximates a difficult mathematical or physical problem through systematic corrections to a simpler, understood problem.

The phase problem is the loss of wave-phase information in intensity measurements, which complicates reconstructing structures from diffraction data.

Phase space represents all possible states of a dynamical system, allowing its evolution to be studied through trajectories, geometry, and statistical distributions.

A phase transition is a change between distinct states of matter or collective organization as physical conditions vary.

A phonon is a quantum of collective vibration in matter, central to the microscopic description of sound, heat capacity, and thermal transport.

The photoelectric effect is the emission of electrons from matter after absorbing electromagnetic radiation, providing foundational evidence for the quantum nature of light.

A photon is a quantum of the electromagnetic field, carrying energy and momentum and mediating electromagnetic interactions.

Physics is the natural science that studies matter, energy, motion and force, and the basic interactions that govern the universe from subatomic particles to the cosmos.

Pierre Curie was a French physicist whose research established key findings in piezoelectricity, magnetism, and radioactivity.