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Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measured with a thermometer. It reflects...

Physics is the natural science of matter, involving the study of matter, its fundamental constituents, its motion and behavior through space and time,...

The Big Bang is a physical theory that describes how the universe expanded from an initial state of high density and temperature. It was first proposed...

The Higgs boson, sometimes called the Higgs particle, is an elementary particle in the Standard Model of particle physics produced by the quantum excitation...

The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness":...

Entropy is a scientific concept that is most commonly associated with a state of disorder, randomness, or uncertainty. The term and the concept are used...

Plasma (from Ancient Greek πλάσμα (plásma) 'moldable substance') is one of four fundamental states of matter (the other three being solid, liquid, and...

Light, visible light, or visible radiation is electromagnetic radiation that can be perceived by the human eye. Visible light spans the visible spectrum...

Unsolved problem in physics: What is dark matter? How was it generated? (more unsolved problems in physics) In astronomy, dark matter is a hypothetical...

Frequency (symbol f), most often measured in hertz (symbol: Hz), is the number of occurrences of a repeating event per unit of time. It is also occasionally...

In physics, string theory is a theoretical framework in which the point-like particles of particle physics are replaced by one-dimensional objects called...

In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic...

In quantum mechanics, Schrödinger's cat is a thought experiment, sometimes described as a paradox, of quantum superposition. In the thought experiment...

A proton is a stable subatomic particle, symbol p , H+, or 1H+ with a positive electric charge of +1 e (elementary charge). Its mass is slightly less than...

General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by...

An electric current is a flow of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is defined as the net...

The Planck constant, or Planck's constant, denoted by h {\textstyle h} , is a fundamental physical constant of foundational importance in quantum mechanics:...

Nuclear fusion is a reaction in which two or more atomic nuclei, usually deuterium and tritium (hydrogen isotopes), combine to form one or more different...

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word...

The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. At 20 °C (68 °F), the speed of...