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A force is an influence that can cause an object to change its velocity unless counterbalanced by other forces. The concept of force makes the everyday...

The expansion of the universe is the increase in distance between gravitationally unbound parts of the observable universe with time. It is an intrinsic...

The joule (pronounced /ˈdʒuːl/, JOOL or /ˈdʒaʊl/ JOWL; symbol: J) is the unit of energy in the International System of Units (SI). It is equal to the amount...

In electromagnetism, the magnetic moment or magnetic dipole moment is the combination of strength and orientation of a magnet or other object or system...

The term "thermal energy" is used loosely in various contexts in physics and engineering, generally related to the kinetic energy of vibrating and colliding...

In quantum physics, a quantum fluctuation (also known as a vacuum state fluctuation or vacuum fluctuation) is the temporary random change in the amount...

James Prescott Joule FRS FRSE (/dʒuːl/; 24 December 1818 – 11 October 1889) was an English physicist, mathematician and brewer, born in Salford, Lancashire...

In theoretical physics and mathematical physics, analytical mechanics, or theoretical mechanics is a collection of closely related formulations of classical...

In materials that exhibit antiferromagnetism, the magnetic moments of atoms or molecules, usually related to the spins of electrons, align in a regular...

In audio signal processing and acoustics, an echo is a reflection of sound that arrives at the listener with a delay after the direct sound. The delay...

The Ka band (pronounced as either "kay-ay band" or "ka band") is a portion of the microwave part of the electromagnetic spectrum defined as frequencies...

Extremely low frequency (ELF) is the ITU designation for electromagnetic radiation (radio waves) with frequencies from 3 to 30 Hz, and corresponding wavelengths...

An inductively coupled plasma (ICP) or transformer coupled plasma (TCP) is a type of plasma source in which the energy is supplied by electric currents...

In thermodynamics and solid-state physics, the Debye model is a method developed by Peter Debye in 1912 to estimate phonon contribution to the specific...

The green flash and green ray are meteorological optical phenomena that sometimes occur transiently around the moment of sunset or sunrise. When the conditions...

A Lichtenberg figure (German Lichtenberg-Figur), or Lichtenberg dust figure, is a branching electric discharge that sometimes appears on the surface or...

Curved space often refers to a spatial geometry which is not "flat", where a flat space has zero curvature, as described by Euclidean geometry. Curved...

The High Altitude Water Cherenkov Experiment or High Altitude Water Cherenkov Observatory (also known as HAWC) is a gamma-ray and cosmic ray observatory...

Alan Paige Lightman (born November 28, 1948) is an American physicist, writer, and social entrepreneur. He has served on the faculties of Harvard University...

Since its introduction in 1960, the base units for the International system of units, known as SI, have changed several times. Tables in this article summarize...