tömegenergia

Tömegenergia refers to the mass–energy equivalence in special relativity, the idea that mass and energy are interchangeable aspects of the same physical quantity. In modern physics, the invariant mass m0 (rest mass) is related to total energy E and momentum p by E^2 = (m0 c^2)^2 + (pc)^2. For a particle at rest, E0 = m0 c^2, which is the rest energy. The more energy a system has (through motion or other forms), the more massive it effectively becomes from the viewpoint of a given frame. In general, scientists prefer to speak of energy and momentum rather than "relativistic mass".

The key equation E = m c^2; where c is the speed of light in vacuum. For a particle at rest, its energy equals its rest mass times c^2. When moving, total energy increases with momentum according to the relation above. The equation implies that small amounts of mass can release large amounts of energy in nuclear reactions or particle processes.

History and significance. Proposed by Albert Einstein in 1905 as part of special relativity, the mass–energy equivalence has been confirmed experimentally in many contexts, such as nuclear reactions, particle decays, and annihilation events. In contemporary physics, the invariant (rest) mass is a fundamental property; energy-momentum describes dynamics across reference frames.

Applications and examples. In nuclear binding energy, the mass of a nucleus is less than the sum of its constituents, with the differences released as energy. In particle physics, pair production and annihilation convert between mass and energy. In astrophysics, mass-energy considerations apply to stellar processes and compact objects.