People who changed physics
These people came from all over the world. Many were told no. They kept asking questions anyway, and you can too.
Archimedes
Archimedes worked out why things float.
Archimedes studied how things float and how levers work, more than 2,000 years ago in Sicily.
Archimedes' principle says that the upthrust on an object equals the weight of the fluid it pushes aside.
Try this lesson: Floating and sinking: buoyancy and Archimedes, Levers
Zhang Heng
Zhang Heng built a machine that noticed earthquakes.
Zhang Heng presented a seismoscope to the Han court in the year 132. Not all of the scholar's ideas were welcomed, and one proposal to the court was rejected.
A seismoscope responds to the ground shaking. Earthquakes send waves through the ground, which scientists still use today.
Try this lesson: What is a wave?
Ibn al-Haytham
Ibn al-Haytham studied light and how we see.
Ibn al-Haytham wrote the great Book of Optics. The story goes that, after angering a ruler, the author had to hide until that ruler died in 1021.
The Book of Optics, written between 1011 and 1021, is a landmark in the study of light and vision.
Try this lesson: How your eyes see, Light travels in straight lines: shadows
Galileo Galilei
Galileo saw moons going around Jupiter.
Galileo found the four largest moons of Jupiter in 1610. Later, Galileo was put on trial for these ideas about the heavens, and spent years under house arrest.
Jupiter's moons showed that not everything circles the Earth. Galileo's tests of falling objects also changed how we study motion.
Try this lesson: Galileo's falling objects, Orbits: why the Moon doesn't fall down
Johannes Kepler
Kepler worked out how planets move.
Johannes Kepler kept working on the planets even after being forced to leave Graz in 1600 because of religion.
Kepler's laws of planetary motion appeared in 1609 and 1618. The third links a planet's orbit time to its distance from the Sun.
Try this lesson: Planets, the Sun and tides
Isaac Newton
Newton found the rules of how things move.
Isaac Newton explained motion and gravity in one book, the Principia, in 1687. A bitter argument with Leibniz over who invented calculus lasted for years.
The Principia set out the three laws of motion and universal gravitation, showing that one law covers apples and planets.
Try this lesson: Newton's First Law: things keep doing what they're doing, Newton's Second Law: F = m × a, Newton's Third Law: every push pushes back, Newton's law of universal gravitation
Émilie du Châtelet
Émilie du Châtelet wrote great books about physics.
Émilie du Châtelet was once thrown out of a Paris café where scholars met, and came back in men's clothes to be let in. Du Châtelet went on to write a major physics book.
Du Châtelet published Institutions de Physique in 1740, and a French translation of Newton's Principia came out in 1756.
Try this lesson: Movement energy: kinetic energy
Alessandro Volta
Volta made the first battery.
Alessandro Volta built the voltaic pile in 1799. It was not perfect, and it lost power as it ran, but it was the first electric battery.
The voltaic pile gave a steady electric current for the first time. The volt is named after Volta.
Try this lesson: Circuits: current, voltage, resistance
Georg Ohm
Ohm found out how electricity flows in wires.
Georg Ohm published the rule now called Ohm's law in 1827. It was coldly received, and Ohm resigned from a college that did not value the work.
Ohm's law links voltage, current and resistance: V = I × R. The ohm is the unit of resistance.
Try this lesson: Ohm's law
Michael Faraday
Faraday showed that magnets can make electricity.
Michael Faraday found in 1831 how a changing magnetic field can make electricity. After a breakdown in 1839, Faraday later came back to research.
Electromagnetic induction is the idea behind generators, which make most of our electricity.
Try this lesson: Electromagnets and motors, Magnets and magnetic fields
James Joule
Joule showed that movement can make heat.
James Joule reported results to a big science meeting in 1843 and was met with silence. Joule kept testing, and a famous paddle-wheel experiment followed in 1845.
Joule showed that work and heat are both energy. The joule, the unit of energy, is named after this work.
Try this lesson: Energy is never lost: conservation, Work and power
James Clerk Maxwell
Maxwell showed that light is a kind of wave.
James Clerk Maxwell lost a university job in 1860 when two colleges merged. In 1865, Maxwell published a theory that changed physics.
Maxwell's 1865 theory unites electricity, magnetism and light as one electromagnetic field.
Try this lesson: The electromagnetic spectrum
Nikola Tesla
Tesla built motors that run on electricity.
Nikola Tesla patented a new kind of electric motor, licensed in 1888. A later project at Wardenclyffe ran out of money before it could be finished.
The AC induction motor uses alternating current to make a turning magnetic field.
Try this lesson: Electromagnets and motors
Max Planck
Planck found that energy comes in tiny packets.
Max Planck's first law for the light from hot objects did not match experiments, which was frustrating. In 1900, Planck tried a bold new idea.
Planck proposed that energy comes in quanta, with E = h × f. This began quantum physics.
Try this lesson: The tiny world: quantum physics
Marie Curie
Marie Curie found new kinds of atoms.
Marie Curie was refused a place at Kraków University because of sexism. Curie moved on, and found polonium and radium, working with Pierre Curie.
The discovery of polonium and radium showed that atoms can give out energy by themselves, which is called radioactivity.
Try this lesson: Inside the atom
Ernest Rutherford
Rutherford found the tiny middle of the atom.
Ernest Rutherford came from a small place in New Zealand. In 1911, Rutherford worked out that an atom has a tiny nucleus at its centre.
The nuclear model shows that almost all of an atom's mass is in a tiny nucleus.
Try this lesson: Inside the atom
Lise Meitner
Lise Meitner explained how big atoms can split.
Lise Meitner lost a job under anti-Jewish laws, and fled to the Netherlands in 1938. Meitner kept working, and helped to explain nuclear fission.
With Otto Frisch, Meitner explained fission and named it in 1939, showing that a nucleus can split and release energy.
Try this lesson: Energy from the Sun: nuclear fusion, Inside the atom
Albert Einstein
Einstein found new ideas about time and light.
Albert Einstein failed part of a university entrance exam in 1895. Ten years later, Einstein's theory of relativity changed how we think about space and time.
Special relativity (1905) gave us E = mc², and general relativity (1915) explains gravity as the shape of space and time.
Try this lesson: Einstein's big ideas
Emmy Noether
Emmy Noether used maths to show why energy is kept.
Emmy Noether proved a beautiful theorem in 1918. In 1933, the Nazi government dismissed Jewish teachers, and Noether moved to the USA.
Noether's theorem links symmetry to conservation laws, explaining why energy and momentum are conserved.
Try this lesson: Energy is never lost: conservation, Momentum
Niels Bohr
Niels Bohr drew a new picture of the atom.
Niels Bohr's doctoral thesis got little notice outside Scandinavia, because it was written in Danish. In 1913, Bohr's model of the atom made a much bigger splash.
The Bohr model gave electrons fixed energy levels, which explains why atoms give out certain colours.
Try this lesson: The tiny world: quantum physics, Inside the atom
C. V. Raman
Raman found that light can change colour when it scatters.
C. V. Raman was told by a doctor not to travel to England because of illness. Raman went on to make a famous discovery about light in India in 1928.
In the Raman effect, scattered light changes wavelength, which reveals what molecules are present.
Try this lesson: Rainbows and colour
Edwin Hubble
Hubble found that there are many other galaxies.
Edwin Hubble showed in 1924 that some fuzzy patches in the sky are galaxies far beyond our own. Many astronomers opposed the idea at first.
Hubble's law (1929) shows that further galaxies move away faster, which is evidence that the universe is expanding.
Try this lesson: The universe: the Big Bang and star stuff
Satyendra Nath Bose
Bose found a new way to count tiny particles.
Satyendra Nath Bose had a paper rejected by a journal in 1924, and sent it to Albert Einstein instead. That paper led to Bose–Einstein statistics.
Bose–Einstein statistics describe how particles such as photons behave. Those particles are called bosons, after Bose.
Try this lesson: The tiny world: quantum physics
Cecilia Payne-Gaposchkin
Cecilia Payne found what stars are made of.
Cecilia Payne showed in 1925 that stars are mostly hydrogen and helium. A senior reviewer disagreed, and Payne had to write that the results were almost certainly not real. Payne was right.
Payne used the spectra of starlight to work out that hydrogen and helium are by far the most common elements in stars.
Try this lesson: Rainbows and colour, Energy from the Sun: nuclear fusion
Subrahmanyan Chandrasekhar
Chandrasekhar worked out how heavy some dead stars can be.
Subrahmanyan Chandrasekhar first calculated a limit for dying stars in 1930. A famous astronomer, Arthur Eddington, attacked the work in 1935, but the limit was right.
The Chandrasekhar limit, about 1.44 Suns, is the largest possible mass of a white dwarf star.
Try this lesson: The universe: the Big Bang and star stuff
Chien-Shiung Wu
Chien-Shiung Wu did a test that surprised all of physics.
Chien-Shiung Wu faced prejudice against Asian students early on. In 1957, the Wu experiment overturned something that physicists had long assumed.
The Wu experiment showed that parity is not conserved in weak interactions: nature can tell left from right.
Try this lesson: Inside the atom
Katherine Johnson
Katherine Johnson did the maths for space flights.
Katherine Johnson worked in an office labelled "Colored Computers" under segregation. Johnson calculated the path for Alan Shepard's flight into space in 1961.
Calculating a spaceflight path means applying gravity and motion very precisely, from launch to landing.
Try this lesson: Orbits: why the Moon doesn't fall down
Abdus Salam
Abdus Salam showed that two forces are really one.
Abdus Salam was once turned down for a railway job after failing an eyesight test. Salam went on to share the Nobel Prize in Physics in 1979.
Electroweak theory unites the electromagnetic and weak forces into one interaction.
Try this lesson: The electromagnetic spectrum
Vera Rubin
Vera Rubin found hints of hidden stuff in space.
Vera Rubin tried to join the astronomy programme at Princeton, and was barred because of gender. Rubin became an astronomer anyway, and studied how galaxies spin.
Stars at the edges of galaxies orbit too fast for the matter we can see, which is evidence for dark matter.
Try this lesson: The universe: the Big Bang and star stuff
Stephen Hawking
Stephen Hawking studied black holes.
Stephen Hawking was diagnosed with motor neurone disease at 21, and it slowly caused paralysis. Hawking carried on, and changed what we know about black holes.
In 1974, Hawking claimed that black holes emit radiation. This is called Hawking radiation.
Try this lesson: Einstein's big ideas, The universe: the Big Bang and star stuff
Jocelyn Bell Burnell
Jocelyn Bell Burnell found stars that pulse like clocks.
Jocelyn Bell Burnell spotted the first radio pulsar in 1967. When the 1974 Nobel Prize went to work on pulsars, Bell Burnell was controversially left out.
A pulsar sends out regular pulses of radio waves. It is an example of how waves carry information across space.
Try this lesson: The electromagnetic spectrum, The universe: the Big Bang and star stuff