Einstein’s workshop in the mind

Thought Lab

Einstein did not find his physics in a laboratory but in his head – in thought experiments. Here you play them through yourself: place your bet, try it out, then see what he concluded. Every experiment you try lights up a star on your map.

Missions

The 26 experiments on this site, sorted by four big questions. Each card takes you straight to the experiment in its chapter.

Mission 1

Light & relativity

0 of 9 tried
Chasing a beam of light Chase a beam of light at 90 % of the speed of light – how fast does it fly past you? On the page: Special Relativity tried Train and lightning Two lightning strikes, simultaneous – or not? Find out why “now” depends on where you stand. On the page: Special Relativity tried Synchronising the Bern clocks Set three station clocks by signal – and see why a moving train has a different “now”. On the page: The Bern patent office tried Six patent files Made-up inventions on Einstein’s desk: find the impossible part and stamp “Patent rejected”. On the page: The Bern patent office tried The light-clock Send a clock made of light on a journey and watch it tick more slowly. On the page: Special Relativity tried Your own twin journey Fly to a star at your real age – and work out how old you are when you come back. On the page: Special Relativity tried Cycling through slow light Ride through a town where light travels at 30 km/h – and watch houses shrink and clocks drift apart. On the page: A world with slow light tried Energy calculator How much energy is locked in a paperclip? E = mc² to work out yourself. On the page: E = mc² — Mass & Energy tried The nuclear scale Build a helium nucleus from two protons and two neutrons and weigh it: the finished nucleus is lighter than its parts. On the page: E = mc² — Mass & Energy tried

Mission 2

Gravity & cosmos

0 of 7 tried
Two cabins, one result Gravity or acceleration? From the inside you cannot tell – try it. On the page: General Relativity tried The dent in the sheet Set the mass, give a ball a push and watch it circle the dent. On the page: General Relativity tried The ellipse that turns The puzzle Newton’s theory could not solve: Mercury’s orbit creeps round. On the page: General Relativity tried Stars at the edge of the Sun In 1919 stars shifted in the sky – by about as much as Einstein had predicted, and not by half as much as Newton’s theory implied. On the page: General Relativity tried Eddington’s light table Lay the 1919 eclipse plate over the night plate and measure for yourself how far the stars near the Sun have moved. On the page: General Relativity tried The gravitational lens Move your mouse or finger across the starry sky on the home page: your mass bends the light of the stars behind it. On the home page tried GPS without the relativity correction What happens if you leave Einstein out of navigation? Worked out day by day. On the page: Death, Brain & Legacy tried

Mission 3

Quanta & energy

0 of 2 tried
Light vs. electrons Turn the colour of the light and find out when electrons jump out of the metal – and why brightness does not count. On the page: Quanta & the Great Debate tried Einstein and Bohr: three rounds Follow Einstein's objections, predict Bohr's reply – and see what experiments decided. On the page: The great debate tried

Mission 4

History & responsibility

0 of 8 tried
The year 1905, day by day Four papers that changed physics – when he wrote, submitted and published them. On the page: 1905 — The Miracle Year tried Einstein's path through life From Ulm to Princeton: the places of his life on a map, step by step. On the page: Timeline tried Spring 1933: a journey with no return From Pasadena via Antwerp and De Haan to Princeton – eight stops with a map, documents and sources. On the page: Exile & Princeton tried Network of companions Besso, Mileva Marić, Elsa, Planck, Curie, Bohr and others: who came into Einstein’s life when – with an age slider. On the page: Family & Personal Life tried How he thought when he was stuck The violin “Lina”, the sailing boat “Tümmler” and the tongue photo of 1951 – and how much of it is documented. On the page: Later Years & the Final Quest tried When Einstein was your age … Enter your age and see what Einstein was going through at that age. On the page: Timeline tried The letter in full The letter to Roosevelt in the original – with a transcript and notes on every delicate passage. On the page: The Letter & the Bomb tried Cuckoo-egg detector Genuine Einstein or planted sentence? Look at the clues, throw the lever and see the stamp with the evidence. On the page: Quotes tried

Learning journey

Three stages with predictions: at every station you commit to an answer first, then check your guess yourself in the experiment.

Stage 1 · 3 stations

What does “at the same time” really mean?

The train and lightning, the twin journey and GPS: predict first, then check.

Start the stage

Stage 2 · 3 stations

Why does everything fall alike?

The windowless lift, the rubber sheet and Mercury, the eclipse of 1919: predict first, then check.

Start the stage

Stage 3 · 3 stations

What is light made of?

The photoelectric effect, E = mc² and the miracle year 1905: predict first, then check.

Start the stage

Question of the day

A new question every day – the same for everyone. Answer on several days in a row and your streak grows.

Question of the day

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Your knowledge map

The 20 key terms around Einstein – and how they connect. A term lights up as soon as you have tried a matching experiment or answered a matching quiz question correctly. Choose a dark term to see how to light it up.

  • Relativity
  • Gravity & cosmos
  • Quanta & atoms
  • Life & work
Special relativityGeneral relativitySpacetimeTime dilationLength contractionSpeed of lightMass–energy equivalencePhotoelectric effectPhotonQuantum mechanicsBrownian motionGravitational wavesGravitational lensingBlack holeEquivalence principleCosmological constantQuantum entanglementNobel Prize in PhysicsUnified field theoryAnnus mirabilis (1905) SpecialrelativityGeneralrelativitySpacetimeTimedilationLengthcontractionSpeed oflightMass–energyequivalencePhotoelectriceffectPhotonQuantummechanicsBrownianmotionGravitationalwavesGravitationallensingBlack holeEquivalenceprincipleCosmologicalconstantQuantumentanglementNobel Prizein PhysicsUnifiedfield theoryAnnus mirabilis(1905)
All connections as a list

20 terms · 29 connections

Einstein or not Einstein?

Few names are signed under so many lines their owner never said. Each round draws ten out of 24 quotes: half of the pool is documented as genuine – with date and source – and the other half was demonstrably pinned on him. Every answer reveals the true origin.

This quiz needs JavaScript. All questions and answers can also be checked in the linked sources.

Keyboard: 1 / 2 to choose, Enter or → for next, ← to go back.

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Sources of the quotes:
  1. Wikiquote: Albert Einstein – sourced quotes plus “Disputed” and “Misattributed”
  2. Wikiquote (German): Albert Einstein – sourced quotes and “falsely attributed or doubtful”
  3. Quote Investigator – research on Einstein quotations
  4. Falschzitate – quotation research by Gerald Krieghofer (German)

Knowledge quiz: life & physics

Ten questions from a pool of 27, spanning all thirteen chapters of this site – from the child’s compass to gravitational waves. Every answer has been checked against Wikipedia and the sources listed below.

This quiz needs JavaScript. All questions and answers can also be checked in the linked sources.

Keyboard: 1–4 to choose, Enter or → for next, ← to go back.

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Sources of the questions:
  1. Wikipedia: Albert Einstein; einstein-website.de: What happened to the Nobel Prize money
  2. Annus mirabilis papers; Tests of general relativity; Eddington experiment; First observation of gravitational waves
  3. Error analysis for the Global Positioning System; Bose–Einstein condensate; Mileva Marić; Einstein–Szilárd letter; Einsteinium; Cosmological constant; Schwarzschild metric; Unified field theory

Crossword puzzles

Two puzzles built from terms in the glossary and the knowledge quiz of this site: one to get started, one for the practised. Pick a square or a clue and solve word by word – every word you solve without revealing it counts toward your learning progress.

Easy

Einstein: the basics

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1234567891011121314

Across

  1. 1Astronomer whose 1929 observations showed the universe is expanding , 6 letters
  2. 4Brownian motion is key evidence that they are real , 5 letters
  3. 6A single particle of light, with energy proportional to its frequency , 6 letters
  4. 7What his father showed him as a child, filling him with wonder , 7 letters
  5. 9His theories of 1905 (special) and 1915 (general) , 10 letters
  6. 12Small packet in which energy comes, in the physics of the very small , 7 letters
  7. 13Charged particles that light knocks out of a metal, as Einstein explained , 9 letters
  8. 14E = mc²: mass is a form of it , 6 letters

Down

  1. 2Its speed is the same for every observer , 5 letters
  2. 3Swiss city of the patent office where Einstein worked in 1905 , 4 letters
  3. 5Four-dimensional fabric that mass and energy curve , 9 letters
  4. 8Town of the Institute for Advanced Study, his workplace until death , 9 letters
  5. 10Physicist who won the 1921 Nobel Prize for the photoelectric effect , 8 letters
  6. 11City of the Polytechnic where Einstein studied , 6 letters

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Hard

Einstein: physics and people

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123456789101112

Across

  1. 1Bose-Einstein …: new state of matter, first made in a lab in 1995 , 10 letters
  2. 4British astronomer who confirmed the bending of starlight in 1919 , 9 letters
  3. 5Wrote the 1939 letter to Roosevelt that Einstein signed , 7 letters
  4. 6In general relativity, gravity is the … of spacetime , 9 letters
  5. 8First name of his first wife, who received the Nobel prize money , 6 letters
  6. 10Journal “… der Physik” that carried the four papers of 1905 , 7 letters
  7. 11A photon's energy is proportional to it , 9 letters
  8. 12Massive objects bend passing light like a cosmic … , 4 letters

Down

  1. 1Cosmological …: Einstein added it in 1917 to hold the universe static , 8 letters
  2. 2Element 99, found in the debris of the first hydrogen bomb , 11 letters
  3. 3The P in the 1935 EPR thought experiment , 8 letters
  4. 6Before marrying her in 1919, Elsa Löwenthal was his … , 6 letters
  5. 7The R in the 1935 EPR thought experiment , 5 letters
  6. 9Planet whose orbit puzzle general relativity solved in 1915 , 7 letters
  7. 11His unfinished final quest was a unified … theory , 5 letters

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Proving GroundDoes the idea hold?On the Proving Ground you test whether an idea really holds: patent files full of reasoning errors, genuine and fake quotes.To the Proving Ground

Read on

More sourced sayings – and the most famous fakes in detail – are on the Quotes page. To follow the stations of his life in order, see the Timeline.