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Physics

104 lessons across 10 eras, from 600 BC to today. Tap any question to read its lesson.

  1. 600 BC – AD 1350

    Era 1: Sky and Earth

    1. Amber and the featherWhy does a rubbed stone pull a feather?Completed
    2. The ratios of a stringWhy does music follow simple number ratios?Completed
    3. Archimedes and the leverCould a long enough arm lift the Earth?Completed
    4. Archimedes and buoyancyIs the crown pure gold?Completed
    5. Aristotle's theory of motionDoes a heavier body fall faster?Completed
    6. Heron's steam ballCan steam do work?Completed
    7. Ptolemy and looping orbitsWhy do the planets go backwards?Completed
    8. Ibn al-Haytham and the camera obscuraDoes light leave the eye, or enter it?Completed
    9. Kamal al-Din al-Farisi and the rainbowHow does a rainbow form?Completed
    10. Al-Biruni and specific gravityCan a substance be identified without cutting it?Completed
  2. 1543 – 1700

    Era 2: Revolution

    1. Copernicus moves the centreWhat changes if the Sun is at the centre?Completed
    2. Tycho Brahe's naked-eye measurementsHow precisely can you measure without a telescope?Completed
    3. Kepler and the elliptical orbitWhy aren't orbits perfect circles?Completed
    4. Galileo and the inclined planeDo heavy and light things fall at the same time?Completed
    5. Galileo's telescope and the moons of JupiterDoesn't everything go around the Earth?Completed
    6. Galileo's ship and the principle of relativityCan steady motion be felt?Completed
    7. The pendulum and measuring timeHow is time divided into equal parts?Completed
    8. Torricelli and the vacuumDoes air have weight?Completed
    9. Snell and the law of refractionWhy does light bend as it enters water?Completed
    10. Mersenne and the speed of soundHow fast does sound travel?Completed
    11. Guericke and the Magdeburg hemispheresHow strong is a vacuum?Completed
    12. Hooke's law and the springIs there a rule linking force and stretch?Completed
    13. Rømer, Io and the speed of lightDoes light arrive instantly?Completed
    14. Newton and universal gravitationDoes the force that drops the apple also hold the Moon?Completed
    15. Newton's prismIs white light pure?Completed
    16. Huygens and the wave theory of lightCould light be a wave?Completed
  3. 1700 – 1900

    Era 3: After Newton — classical mechanics

    1. Bernoulli's principleWhy does an aircraft wing lift?Completed
    2. Lagrange, Hamilton and least actionWhy does nature choose the laziest path?Completed
    3. Cavendish weighs the EarthHow do you weigh a planet?Completed
    4. Foucault's pendulumCan the Earth's rotation be proved inside a room?Completed
    5. Chladni figures and resonanceCan sound draw shapes on a plate?Completed
    6. Defining the metre and SI unitsWhat makes a metre a metre?Completed
  4. 1700 – 1910

    Era 4: Heat and energy

    1. The birth of the thermometerHow is temperature turned into a number?Completed
    2. Black and latent heatWhy doesn't melting ice get warmer?Completed
    3. Rumford and the cannon barrelIs heat a fluid?Completed
    4. Carnot and the ideal engineHow efficient can an engine possibly be?Completed
    5. Joule churns waterDoes stirred water get warmer?Completed
    6. Conservation of energyCan energy disappear?Completed
    7. Clausius and the arrow of timeWhy doesn't a broken glass put itself back together?Completed
    8. Boltzmann and the statistics of atomsWhat is temperature, really?Completed
    9. Maxwell's demonCan entropy be cheated?Completed
    10. Brownian motionWhy do specks of dust jiggle?Completed
  5. 1750 – 1910

    Era 5: Electricity and magnetism

    1. Franklin and lightningIs lightning electricity?Completed
    2. Coulomb and the torsion balanceCan electric force be measured?Completed
    3. Galvani and the frog's legIs there electricity in living things?Completed
    4. Volta's pileHow do you produce a steady current?Completed
    5. Ørsted's compass needleIs electricity a magnet?Completed
    6. Ampère and currents that attract each otherWhy do two wires push each other away?Completed
    7. Ohm's lawWhat is the current resisting?Completed
    8. Faraday and inductionDoes moving a magnet produce a current?Completed
    9. Faraday's idea of the fieldHow is a force carried across empty space?Completed
    10. Maxwell uncovers the identity of lightIs light an electromagnetic wave?Completed
    11. Hertz catches the waveDoes Maxwell's wave really exist?Completed
    12. Tesla, Edison and the war of the currentsHow did electricity come into the home?Completed
  6. 1800 – 1925

    Era 6: Light and the spectrum

    1. Young's double slitIs light a wave or a particle?Completed
    2. Fraunhofer linesWhat are the dark lines in sunlight?Completed
    3. Kirchhoff, Bunsen and spectral analysisCan we know what a star is made of?Completed
    4. The Doppler effectDoes motion change sound and light?Completed
    5. Michelson–Morley and the missing aetherWhat does light travel through?Completed
    6. Röntgen and X-raysCan there be an invisible ray?Completed
    7. Cecilia Payne and the composition of the starsWhat are the stars made of?Completed
  7. 1905 – 1930

    Era 7: Relativity

    1. Special relativityWhat happens if the speed of light looks the same to everyone?Completed
    2. Time dilation and the twin paradoxDoes someone moving fast age less?Completed
    3. E=mc²Can mass be turned into energy?Completed
    4. The equivalence principleIs there weight in a falling lift?Completed
    5. General relativity and curved spacetimeIs gravity a force, or geometry?Completed
    6. The 1919 solar eclipseDoes light bend as it passes a mass?Completed
    7. Schwarzschild and black holesCould there be a place not even light can escape?Completed
    8. Relativity and GPSWhy do satellites correct their clocks?Completed
  8. 1900 – 1935

    Era 8: Quantum

    1. Planck and the black bodyWhy does energy come in pieces?Completed
    2. Einstein and the photoelectric effectDoes light also behave like a particle?Completed
    3. Rutherford's gold foilIs the atom empty inside?Completed
    4. Bohr's model of the atomWhy doesn't the electron fall into the nucleus?Completed
    5. De Broglie and matter wavesCan an electron be a wave too?Completed
    6. Compton scatteringDoes light hit the way a ball does?Completed
    7. Stern–Gerlach and spinCan a property take only two values?Completed
    8. Heisenberg's uncertainty principleCan both position and speed be known?Completed
    9. The Schrödinger equation and the catCan something be in two states at once?Completed
    10. The Pauli exclusion principleWhy can't we pass through each other?Completed
    11. Dirac and antimatterCan an equation predict a particle that doesn't exist?Completed
    12. The double slit in quantum physicsWhy does it change when you look?Completed
    13. Quantum tunnellingCan a particle pass through a wall it cannot get over?Completed
  9. 1930 – present

    Era 9: Particles and the cosmos

    1. Chadwick and the neutronWhat else is in the nucleus?Completed
    2. Fission and the chain reactionWhat happens if a nucleus splits?Completed
    3. Bethe and fusion in the starsWhat does the Sun burn?Completed
    4. The Chandrasekhar limitHow does a star die?Completed
    5. Hubble and the expanding universeWhy are the galaxies moving away from us?Completed
    6. The cosmic microwave backgroundCan a trace of the Big Bang be found?Completed
    7. Feynman diagramsWhat happens when particles collide?Completed
    8. The Standard Model and quarksWhat is matter made of at the very smallest?Completed
    9. The hunt for the neutrinoCan a particle that hits nothing be caught?Completed
    10. The Higgs bosonWhere does mass come from?Completed
    11. Dark matter and dark energyWhere is 95% of the universe?Completed
    12. Mayor, Queloz and the first exoplanetDo other stars have planets too?Completed
    13. Bell's inequality and entanglementCan two particles be linked at a distance?CompletedHands-on version →
    14. LIGO and gravitational wavesDoes spacetime itself tremble?Completed
  10. 1900 – present

    Era 10: From physics to technology

    1. Kamerlingh Onnes and superconductivityCan resistance be zero?Completed
    2. Tsiolkovsky and the rocket equationHow does something escape the Earth's gravity?Completed
    3. The transistorHow small can a switch get?Completed
    4. The laserHow is light brought into line?Completed
    5. Magnetic resonance and MRICan we see inside without cutting?Completed
    6. The solar cell and the semiconductorCan light be turned straight into electricity?Completed
    7. The atomic clockHow is time measured most precisely?Completed
    8. The quantum computerWhat is gained if computing goes quantum?Completed