Physics

Thermal conductivity is the material property that relates conductive heat flux to a temperature gradient.

A state in which a system has no spontaneous macroscopic changes or net dissipative flows under its imposed constraints.

The thermodynamic limit takes particle number and volume to infinity at fixed density, providing a mathematical foundation for bulk thermodynamics and sharp phase transitions.

A thermodynamic system is a selected quantity of matter or region of space studied through its properties and exchanges with its surroundings.

Thermodynamics studies energy transfers, macroscopic properties of matter, and the constraints governing equilibrium and physical change.

Time is the dimension in which events are ordered and durations measured; it is central to physics, philosophy, and measurement.

Time dilation is the relativistic difference in elapsed time associated with relative motion or differences in gravitational potential.

Torque measures the turning effect of a force about a point or axis and governs changes in angular momentum.

Total internal reflection is the complete reflection of light at a boundary with a lower-index medium when the incidence angle exceeds a critical value.

Chinese-born American theoretical physicist who shared the 1957 Nobel Prize in Physics for investigating parity violation in weak interactions.

A quantum principle placing limits on the simultaneous sharpness of certain physical quantities and on the precision of their joint measurement.

A universality class groups systems with different microscopic structures that share the same large-scale scaling behavior, especially near continuous phase transitions.

Vacuum polarization is the quantum modification of electromagnetic propagation and interactions by fluctuations of charged fields, producing charge screening and measurable radiative corrections.

A virtual particle is an internal contribution to a quantum-field-theory calculation, generally off shell, rather than an independently detectable particle.

Viscosity measures a fluid’s resistance to deformation during flow, relating viscous stress to the rate at which the fluid deforms.

W and Z bosons are massive elementary particles that mediate the weak interaction and form a central part of electroweak theory.

A wave function is a complex-valued representation of a quantum state from which probabilities of measurement outcomes can be calculated.

The weak interaction is a fundamental interaction responsible for beta decay, neutrino scattering, and transformations between types of elementary particles.

Weight is the force associated with gravity acting on a body, distinct from mass and from the support force measured as apparent weight.

German theoretical physicist who developed matrix mechanics and the uncertainty principle and helped shape twentieth-century physics.

Work is energy transferred by a force acting through a displacement or by related macroscopic processes.

The work–energy theorem states that the net work done on a particle equals the change in its kinetic energy.

X-rays are high-energy electromagnetic radiation used to image internal structures, investigate matter, and observe energetic cosmic phenomena.

A Yukawa interaction couples a scalar or pseudoscalar field to fermions, underpinning meson-exchange models of nuclear forces and Higgs-generated fermion masses.

Zero-point energy is the residual ground-state energy of a quantum system, underlying molecular vibrations, vacuum fluctuations, and questions about gravity.