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• mass–energy equivalence
  mass–energy equivalence

  noun

  the principle that energy and mass, even though existing as different forms, are interchangeable forms of the same physical quantity, as represented by Einstein's signature equation, E = mc², in which E is energy, m is mass, and c is the speed of light.
• mass-energy equivalence
  mass-energy equivalence

  An equation derived from Einstein's theory of Special Relativity expressing the relationship between the mass and energy of objects with mass. The equation is E = mc ², where E is the energy of the object in joules, m is its relativistic mass in kilograms, and c is the speed of light (approximately 3 × 10 ⁸ meters per second). Mass-energy equivalence entails that the total mass of a system may change, although the total energy and momentum remain constant; for example, the collision of an electron and a proton annihilates the mass of both particles, but creates energy in the form of photons. The discovery of mass-energy equivalence was essential to the development of theories of atomic fission and fusion reactions.

mass–energy equivalence

American  

noun

Physics.

1. the principle that energy and mass, even though existing as different forms, are interchangeable forms of the same physical quantity, as represented by Einstein's signature equation, E = mc², in which E is energy, m is mass, and c is the speed of light.

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mass-energy equivalence Scientific  

1. An equation derived from Einstein's theory of Special Relativity expressing the relationship between the mass and energy of objects with mass. The equation is E = mc ², where E is the energy of the object in joules, m is its relativistic mass in kilograms, and c is the speed of light (approximately 3 × 10 ⁸ meters per second). Mass-energy equivalence entails that the total mass of a system may change, although the total energy and momentum remain constant; for example, the collision of an electron and a proton annihilates the mass of both particles, but creates energy in the form of photons. The discovery of mass-energy equivalence was essential to the development of theories of atomic fission and fusion reactions.

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Example Sentences

In a book on special relativity, you might expect to meet Einstein's mass–energy equivalence, E = mc2, close to the beginning.

From Nature • Sep. 19, 2017