History of Relativity Timeline

In his paper 'On the Electrodynamics of Moving Bodies', Albert Einstein postulated that the laws of physics and the speed of light are the same in all inertial frames. This eliminated the need for the aether and led to radical consequences: time dilation, length contraction, and the relativity of simultaneity.

Image source: Special relativity

In a short follow-up paper, 'Does the Inertia of a Body Depend Upon Its Energy Content?', Einstein showed that mass and energy are equivalent through E=mc². This relationship became fundamental to nuclear physics and explained the enormous energy released in nuclear reactions.

Image source: Mass–energy equivalence

Hermann Minkowski reformulated special relativity geometrically, treating space and time as a single four-dimensional continuum called spacetime. His famous declaration that 'space by itself and time by itself are doomed to fade away' gave relativity a powerful mathematical framework.

Image source: Minkowski spacetime

While working at the patent office in Bern, Einstein realized that a person in free fall does not feel their own weight, leading him to the equivalence principle: gravity and acceleration are locally indistinguishable. This insight became the cornerstone of general relativity.

Image source: Equivalence principle

Einstein returned to Zurich and, with help from mathematician Marcel Grossmann, learned Riemannian geometry and tensor calculus. Together they explored how curved spacetime could describe gravitation, producing the influential 'Entwurf' paper of 1913.

Image source: Marcel Grossmann

After years of struggle and a race with David Hilbert, Einstein presented the final form of the general relativistic field equations to the Prussian Academy of Sciences. The equations relate spacetime curvature to matter and energy, replacing Newton's force-based theory of gravity.

Image source: Einstein field equations

Karl Schwarzschild solved Einstein's equations exactly for the spacetime around a spherical mass while serving in World War I. His solution described the gravitational field outside stars and contained what is now recognized as the event horizon of a black hole.

Alexander Friedmann derived dynamic solutions to Einstein's equations describing expanding or contracting universes. Initially dismissed by Einstein, these solutions became the mathematical basis of modern cosmology and the Big Bang theory.

Image source: Alexander Friedmann

Georges Lemaître independently derived expanding-universe solutions and connected them to Edwin Hubble's observations of galactic redshifts. He later proposed the 'primeval atom', an early version of Big Bang cosmology grounded in general relativity.

Image source: Georges Lemaître

Robert Oppenheimer and Hartland Snyder calculated that a sufficiently massive star would undergo continued gravitational collapse, forming what we now call a black hole. Their work was largely ignored until a renaissance of black hole research in the 1960s.

Image source: Oppenheimer–Snyder model

Roger Penrose used global techniques to prove that singularities inevitably form under gravitational collapse, without assuming symmetry. Stephen Hawking extended these theorems to cosmology, showing the Big Bang itself begins in a singularity within classical relativity.

Maarten Schmidt identified quasar 3C 273 as an extraordinarily distant and luminous object. Quasars demanded extreme gravitational physics, energizing research into black holes and strong-field general relativity throughout the 1960s.

Image source: Quasar

Arno Penzias and Robert Wilson accidentally detected the cosmic microwave background, the relic radiation of the hot early universe predicted by relativistic Big Bang models. The discovery firmly established general-relativistic cosmology as standard science.

Image source: Discovery of cosmic microwave background radiation

Jocelyn Bell Burnell and Antony Hewish discovered pulsars—rapidly rotating neutron stars. These ultra-dense objects, whose existence follows from relativistic stellar evolution, became precision tools for testing general relativity.

Image source: Pulsar

Stephen Hawking applied quantum field theory to curved spacetime and found that black holes emit thermal radiation. Hawking radiation linked quantum mechanics, thermodynamics, and general relativity, launching the modern study of quantum gravity.

The Event Horizon Telescope collaboration unveiled the first direct image of a black hole's shadow, in the galaxy M87. The ring-shaped image matched general relativity's predictions with remarkable accuracy, confirming the theory in the strongest gravitational regime yet tested.

Image source: Event Horizon Telescope

Roger Penrose received half of the Nobel Prize in Physics for proving black hole formation is a robust prediction of general relativity, while Reinhard Genzel and Andrea Ghez shared the other half for discovering the supermassive compact object at the center of our Milky Way.

Image source: Nobel Prize in Physics

The NANOGrav collaboration reported evidence for a stochastic background of low-frequency gravitational waves, likely from merging supermassive black hole pairs, using decades of pulsar timing data—opening a new window onto relativistic gravity across the cosmos.

Image source: North American Nanohertz Observatory for Gravitational Waves