Mass-Energy Equivalence
The fundamental relativistic principle stating that mass and energy are directly proportional and interchangeable physical quantities.
Governing formula
E = m c² = γ m₀ c²
SI unit
Joules or MeV / GeV
In depth
Proved by Einstein in 1905. Demonstrates that mass possesses rest energy E₀ = m₀ c². A tiny amount of mass defect Δm converts into immense energy E = Δm c² because c² ≈ 9 × 10¹⁶ m²/s².
Examples in the real world
Nuclear fission and fusion converting ~0.1% to 0.7% of nuclear rest mass directly into explosive thermal and radiative energy.