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Albert Einstein
1905· Person
ProvenTested many times; part of working physics.
German-born physicist (1879-1955), later Swiss and American, who rebuilt our ideas of space, time, gravity and energy.
See it on the Science map →How it works
In 1905, while working as a patent clerk in Bern, he published four landmark papers: light comes in packets, atoms are real, special relativity, and E = mc². He then spent eight more years turning gravity into the curvature of spacetime, finished in November 1915. His method was the thought experiment: picture riding a light beam, or falling off a roof, and ask what must be true. He trusted simple principles over complicated fixes.
Why it matters
He showed that space, time, mass and energy are linked and flexible. GPS, nuclear power, black-hole science and modern cosmology all build on his work.
How the work held up
Mercury's orbit (1915), the 1919 eclipse, atomic clocks, particle accelerators and LIGO's 2015 gravitational waves all matched his predictions. He won the 1921 Nobel Prize for explaining the photoelectric effect.
Still a mystery
He never accepted that quantum physics is truly random, and spent his last 30 years failing to unify gravity with electromagnetism. Joining gravity and quantum theory is still unsolved.
Connections (11)
▸Albert Einstein created Special relativityProven
The relationship
Einstein started from two principles, the sameness of physical laws and the constancy of light speed, and deduced the consequences without the ether or hidden mechanisms. Lorentz and Poincaré had much of the math, but Einstein reinterpreted it as a change in the nature of space and time themselves.
How the link was found
Submitted to Annalen der Physik in June 1905 (published that September) while Einstein was a 26-year-old patent clerk in Bern.
Why it's proven
Every prediction, from slowed muon decay to particle-collider energies, has been confirmed for over a century.
Open questions and mysteries
Historians still discuss how much credit belongs to Lorentz and Poincaré.
▸Albert Einstein created General relativity: gravity is curved spacetimeProven
The relationship
Einstein spent eight years extending relativity to gravity. Starting from the equivalence principle, he learned new geometry from his friend Marcel Grossmann and made several false starts. In November 1915 he presented the final field equations, describing how mass and energy curve spacetime and how that curvature guides motion.
How the link was found
Einstein, 1907-1915, finishing in Berlin; presented the field equations to the Prussian Academy on 25 November 1915.
Why it's proven
It explained Mercury's orbit at once, and has passed every test since, from eclipses to black-hole images.
Open questions and mysteries
Hilbert derived the same equations almost simultaneously; priority was debated but historians generally credit Einstein with the theory.
▸Albert Einstein made a founding rule of The speed of light is constantProven
The relationship
Others saw the constant speed of light as a puzzle needing explanation by ether effects. Einstein simply declared it a law of nature: every observer measures the same speed. Making it a starting rule, rather than something to explain away, forced space and time to adjust instead.
How the link was found
Einstein's second postulate, stated in his June 1905 paper. He said he had puzzled over riding a light beam since age 16.
Why it's proven
The constancy has been tested to extreme precision, and everything Einstein deduced from it has been confirmed.
Open questions and mysteries
Some theories of quantum gravity suggest tiny variations at extreme energies; none have been observed.
▸Albert Einstein explained (his Nobel Prize) Photoelectric effect: light comes in particlesProven
The relationship
Einstein took Planck's packets seriously as physical things, proposing that light itself travels as quanta, each with energy set by its frequency. One quantum frees one electron, so color, not brightness, decides whether electrons escape and how fast. This explained 1902 measurements by Philipp Lenard that wave theory could not.
How the link was found
Einstein, in a March 1905 paper, part of his 'miracle year' that also produced special relativity. He was a 26-year-old patent clerk in Bern.
Why it's proven
Millikan's careful 1914–1916 experiments confirmed Einstein's prediction exactly. Compton scattering (1923) showed photons carry momentum. Einstein's 1921 Nobel Prize cites this work, not relativity.
Open questions and mysteries
Einstein himself described the light-quantum idea as very revolutionary, yet later stayed uneasy with the quantum theory it helped create.
▸Albert Einstein challenged quantum theory with The EPR paradox: "spooky action at a distance"Proven
The relationship
Einstein accepted that quantum mechanics predicted correctly but believed it was incomplete. With Podolsky and Rosen he designed a thought experiment: two linked particles fly apart, and measuring one seems to fix the other's properties instantly. Either reality holds hidden extra details, or there is instant influence at a distance. He judged the second absurd.
How the link was found
Einstein, Boris Podolsky and Nathan Rosen at Princeton, in a May 1935 Physical Review paper. Podolsky wrote the text; Einstein felt it buried his main point.
Why it's proven
The historical link is fully documented, and Bohr replied within months. Later Bell tests confirmed the correlations EPR described are real, but showed Einstein's preferred local hidden-detail explanation cannot work.
Open questions and mysteries
Einstein's real concern, that physics should describe a reality independent of observation, is still debated among interpretations of quantum theory.
▸Albert Einstein debated quantum reality with Niels BohrProven
The relationship
From 1927 until Einstein's death in 1955, the two argued over whether quantum mechanics is complete. Einstein devised thought experiments to beat the uncertainty principle; Bohr found the flaw in each, once using Einstein's own general relativity. The debate sharpened both sides and clarified what quantum theory does and does not claim.
How the link was found
Face to face at the Solvay Conferences in Brussels in 1927 and 1930, then in print, notably Bohr's 1935 reply to EPR.
Why it's proven
Well documented in letters, papers and memoirs, including Bohr's 1949 essay recounting the discussions.
Open questions and mysteries
Who 'won' is still argued. Experiments favored the quantum predictions, but Einstein's core question about what is real remains open.
▸Albert Einstein called his "happiest thought" the Equivalence principle: gravity = accelerationProven
The relationship
Sitting at his desk in the Bern patent office, Einstein realized that a person falling freely would not feel their own weight. From that, he reasoned that gravity and acceleration are locally indistinguishable, so gravity could be treated as a property of motion and space rather than a force. He later called this the happiest thought of his life.
How the link was found
Einstein, 1907, while writing a review article on relativity. He described the "happiest thought" in a 1920 manuscript.
Why it's proven
Free-fall experiments, from Eötvös to the MICROSCOPE satellite, confirm all materials fall alike to about one part in a thousand trillion.
Open questions and mysteries
Whether the principle holds exactly for quantum objects, such as atoms in superposition, is still being tested.
▸Albert Einstein derived E = mc²Proven
The relationship
Einstein imagined a body giving off two bursts of light in opposite directions and compared how it looked to a moving observer. Energy bookkeeping only worked if the body lost mass equal to the light's energy divided by light speed squared. He concluded that mass is a measure of a body's energy content.
How the link was found
Einstein, in a three-page paper submitted in September 1905 and published that November, "Does the Inertia of a Body Depend Upon Its Energy Content?"
Why it's proven
Nuclear reactions release exactly the energy matching their lost mass. A 2005 test by teams at MIT and NIST confirmed the equation to better than one part in a million.
Open questions and mysteries
Historians and physicists have debated whether his first 1905 derivation was fully general; later derivations settled the physics.
▸Albert Einstein with Rosen, first found WormholesSpeculative
The relationship
Einstein and Rosen were trying to describe particles as smooth features of spacetime rather than points. They found a solution where two sheets of spacetime join through a narrow throat, a bridge. They did not intend it as a travel route, and the bridge collapses too fast for anything to cross.
How the link was found
Albert Einstein and Nathan Rosen, in a 1935 paper in Physical Review; John Wheeler coined "wormhole" in 1957.
Is it proven?
The bridge is a valid mathematical solution of general relativity. Nothing like it has ever been observed.
Open questions and mysteries
In 2013 Maldacena and Susskind speculated that such bridges are linked to quantum entanglement, an untested idea called ER=EPR.
▸1919 eclipse: gravity bends light made world-famous Albert EinsteinProven
The relationship
When the eclipse results were announced in London in November 1919, newspapers presented them as a revolution overthrowing Newton. Coming just after World War I, a British team confirming a German-born scientist's theory caught the public imagination. Einstein, known mainly to physicists until then, became a worldwide celebrity almost overnight.
How the link was found
Results announced at a joint meeting of the Royal Society and Royal Astronomical Society on 6 November 1919; The Times and New York Times ran headlines within days.
Why it's proven
The press coverage and Einstein's sudden fame are thoroughly documented in newspapers, letters and his lecture tours of the early 1920s.
Open questions and mysteries
Historians debate how much the fame came from the science versus postwar politics and the press's appetite for a story.
▸Albert Einstein introduced, then regretted, The cosmological constant (Λ)Proven
The relationship
Applying his new theory to the whole universe in 1917, Einstein assumed, as nearly everyone then did, that it was static. But matter's gravity would make a static universe collapse. He added Λ, a gentle cosmic repulsion, to balance it. In 1930 Arthur Eddington showed the balance was unstable, like a pencil on its tip. After Hubble's data, Einstein dropped the term in 1931.
How the link was found
Einstein's paper 'Cosmological considerations in the general theory of relativity', February 1917. Willem de Sitter found that same year a universe with Λ and no matter, later understood to be expanding.
Why it's proven
Hubble's 1929 data ended the static universe. The 1998 supernovae revived Λ itself: the term was legitimate, but its original purpose was wrong.
Open questions and mysteries
Did Einstein call it his 'biggest blunder'? The phrase comes only from George Gamow's later recollections, and historians still debate it. A 1931 manuscript, identified in 2014, shows Einstein briefly tried using Λ in a steady-state universe.