History of Energy in Timeline

By Popular Timelines Editorial Team · Updated: February 25, 2026

Energy is a fundamental quantitative property transferred to a body or system, manifesting as the capacity to perform work, heat, or emit light. It adheres to the law of conservation, meaning energy can change forms but cannot be created or destroyed. The standard unit for measuring energy in the International System of Units (SI) is the joule (J).

1900: Henri Poincaré's Contribution to Mass-Energy Equivalence

In 1900, Henri Poincaré derived similar formulas to Einstein's E=mc^2, contributing to the understanding of mass-energy equivalence.

1904: Friedrich Hasenöhrl's Contribution to Mass-Energy Equivalence

In 1904, Friedrich Hasenöhrl derived similar formulas to Einstein's E=mc^2, contributing to the understanding of mass-energy equivalence.

1905: Einstein's Mass-Energy Equivalence

In 1905, Albert Einstein derived the formula E = mc², quantifying the mass-energy equivalence between relativistic mass and energy within the concept of special relativity.

1905: Einstein's theory of special relativity

In 1905, Albert Einstein's theory of special relativity showed that rest mass corresponds to an equivalent amount of rest energy, meaning rest mass can be converted to or from equivalent amounts of non-material forms of energy.

1913: Bohr Theory of the Atom Proposed

In 1913, the notion of quantized energy levels was proposed by Danish physicist Niels Bohr in the Bohr theory of the atom, marking a significant step in understanding atomic structure.

1918: Noether's Theorem Established

In 1918, Noether's theorem was established, stating that any differentiable symmetry of the action of a physical system has a corresponding conservation law. This theorem has become a fundamental tool of modern theoretical physics.

1918: Conservation of energy as consequence of symmetry

In 1918, theorists understood, according to Noether's theorem, that the law of conservation of energy is a direct mathematical consequence of the translational symmetry of the quantity conjugate to energy, namely time.

1926: Development of Quantum Mechanical Theory

In 1926, Erwin Schrödinger and Werner Heisenberg advanced the modern quantum mechanical theory, providing an explanation of energy levels in terms of the Schrödinger equation.