Famous Scientists

  • Home
  • Top 100 Scientists
  • List of Scientists
  • Blog

Leon Foucault

Lived 1819 – 1868.

Lèon Foucault was a physicist from France who was most famous for his Foucault pendulum device-a delightful instrument that demonstrated the outcome of the rotation made by the Earth.

He was one of the earliest scientists to attempt to measure the speed of light and he was the first to discover eddy currents. He is also credited for naming the gyroscope.

Advertisements

His early years

Jean Bernard Lèon Foucault was born in Paris on 18, September 1819; his father was a publisher and bookseller. During the first years of his life, Lèon was a frail child. He attended the Collège Stanislas where he became friends with fellow student Hippolyte Fizeau. Lèon did not apply himself at college but loved to construct toys and machines. His family thought he would make a good surgeon and Jean went on to study medicine in 1839. However, he developed a blood phobia and dropped medicine in favor of studying physics.

Lèon Foucault became the experimental assistant of bacteriologist Alfred Donne for three years, working with him during the course of his lectures of microscopic anatomy. During this time, Louis Daguerre, also a Frenchman, had devised a photographic process called the “daguerreotype” and this photographic process interested Foucault. He improved on this photography method and developed a process for taking photographs through the lens of a microscope. These photographs were published in “A course of microscopy” in 1845.

Foucault also teamed up with his old school friend Hippolyte Fizeau and together, they took images of the sun, their photographs clearly showing sunspots. They also carried out several studies on the intensity of the sun’s light compared to other types of light. They investigated the light from carbon in an arc lamp and the light of the lime coming from the flame produced by an oxyhydrogen blow pipe. They also undertook research on the interference of infrared radiation.

His middle years

In 1850, Foucault conducted an experiment with the use of “Fizeau-Foucault” optics apparatus so he could measure the speed of light. He calculated a value that was within 1 percent of the correct figure. Foucault’s also demonstrated that light does indeed travel more slowly in water compared to when it travels through air. His light studies put a convincing end to Newton’s corpuscular theory of light (that light was made of particles).

A year later, in Paris, Foucault provided an experiment on diurnal motion (how the earth moved on its axis). He used a heavy, long and freely moving pendulum attached to the Paris Observatory’s roof and he demonstrated, to many invited scientists, the rotation of the plane of oscillation and proof of the earth’s rotation.

The experiment was a huge success and amazed both the masses and the academic crowd. It wasn’t too long before “Foucault pendulums” were seen hanging in the biggest cities in Europe and also in America where they attracted huge crowds. In 1852 Foucault made use of (and named) gyroscopes in experiments.

In 1855 he was awarded the prestigious Copley Medal by the Royal Society in recognition of his remarkable experiments and researches. That same year, he was also given the role of physicist in the Imperial Observatory, Paris.

In September of that same year, He made another remarkable discovery; that the force needed for the rotation of copper discs increases if they are made to turn with their rims placed inside a strong magnetic field. He also found that the discs started heating up, due to eddy current (Foucault currents) acting on the copper.

In 1857, Foucault devised a polarizer calcite prism and in 1858, he invented a test for mirrors used in telescopes. This “Foucault knife-edge” test determined if a mirror was absolutely spherical or if it had defects. Before he discovered this process, testing mirrors for imperfections involved much guesswork.

Foucault travelled to Spain to observe and photograph a solar eclipse in 1860.

His later years

Foucault received many honors in later years. In 1862 he became a member of the Bureau des Longitudes and an Officer of the Legion of Honor. Two years later in 1864, he became a member of the Royal Society of London, becoming a member of the mechanical section of the Royal Society of London the following year.

He also published papers on his findings and modifications of James Watt’s centrifugal speed governor.

Foucault showed people a way to view the sun without injuring the eye by placing a transparent silver film on the outer corner on the object glass of a telescope.

His Death

Foucault fell ill in 1867 and his symptom quickly worsened. He died on 11 February 1868, aged 48 and was buried inside the Montmartre cemetery in Paris. It was said that the cause of his death was probably due to severe multiple sclerosis.

He was such a great man though that his name is one of 72 that are inscribed on the beams that make up the Eiffel tower and he also has an asteroid named after him, 5668 Foucault.

Advertisements

More from FamousScientists.org:
  • andre marie ampere
    André Marie Ampère
  • louis pasteur
    Louis Pasteur
  • joseph-louis lagrange
    Joseph-Louis Lagrange
  • alfred nobel
    Alfred Nobel
Advertisements

Search Famous Scientists

Scientist of the Week

  • Linda Buck: Discovered how we smell things

Recent Scientists of the Week

  • Jan Ingenhousz: Discovered photosynthesis
  • Barry Marshall: Overturned the Medical Establishment
  • Linus Pauling: Maverick Giant of Chemistry
  • William Röntgen: The Discovery of X-rays
  • Howard Florey: Brought penicillin to the world
  • Henrietta Leavitt: The key to the size of the universe
  • Archimedes: A mind beyond his time
  • Stanley Milgram: The infamous Obedience Experiments
  • C. V. Raman: Color change allows harm-free health check of living cells
  • Rosalind Franklin: Shape-shifting DNA
  • Robert Boyle: A new science is born: chemistry
  • Carl Woese: Rewrote Earth’s history of life
  • Alfred Wegener: Shunned after he discovered that continents move
  • Henri Poincaré: Is the solar system stable?
  • Polly Matzinger: The dog whisperer who rewrote our immune system’s rules
  • Otto Guericke: In the 1600s found that space is a vacuum
  • Alister Hardy: Aquatic ape theory: our species evolved in water
  • Elizebeth Friedman: Became the world’s most famous codebreaker
  • Evangelista Torricelli: We live at the bottom of a tremendously heavy sea of air
  • Eudoxus: The first mathematical model of the universe
  • James Black: Revolutionized drug design with the Beta-blocker
  • Inge Lehmann: Discovered our planet’s solid inner core
  • Chen-Ning Yang: Shattered a fundamental belief of physicists
  • Robert Hooke: Unveiled the spectacular microscopic world
  • Barbara McClintock: A Nobel Prize after years of rejection
  • Pythagoras: The cult of numbers and the need for proof
  • J. J. Thomson: Discovered the electron
  • Johannes Kepler: Solved the mystery of the planets
  • Dmitri Mendeleev: Discovered 8 new chemical elements by thinking
  • Maurice Hilleman: Record breaking inventor of over 40 vaccines
  • Marie Curie: Won – uniquely – both the chemistry & physics Nobel Prizes
  • Jacques Cousteau: Marine pioneer, inventor, Oscar winner
  • Niels Bohr: Founded the bizarre science of quantum mechanics
  • Srinivasa Ramanujan: Untrained genius of mathematics
  • Milutin Milankovic: Proved Earth’s climate is regulated by its orbit
  • Antoine Lavoisier: The giant of chemistry who was executed
  • Emmy Noether: The greatest of female mathematicians, she unlocked a secret of the universe
  • Wilder Penfield: Pioneer of brain surgery; mapped the brain’s functions
  • Charles Nicolle: Eradicated typhus epidemics
  • Samuel Morse: The telegraph and Morse code
  • Jane Goodall: Major discoveries in chimpanzee behavior
  • John Philoponus: 6th century anticipation of Galileo and Newton
  • William Perkin: Youthful curiosity brought the color purple to all
  • Democritus: Atomic theory BC and a universe of diverse inhabited worlds
  • Susumu Tonegawa: Discovered how our bodies make millions of different antibodies
  • Cecilia Payne: Discovered that stars are almost entirely hydrogen and helium

Top 100 Scientists

  • Our Top 100 Scientists

Our Most Popular Scientists

  • Astronomers
  • Biologists & Health Scientists
  • Chemists
  • Geologists and Paleontologists
  • Mathematicians
  • Physicists
  • Scientists in Ancient Times

List of Scientists

  • Alphabetical List

Recent Posts

  • Perfect Numbers and our Tiny Universe
  • What Happens when the Universe chooses its own Units?
  • Hipparchus and the 2000 Year-Old Clue
  • Darwin Pleaded for Cheaper Origin of Species
  • You Will Die For Showing I’m Wrong!
  • Getting Through Hard Times – The Triumph of Stoic Philosophy
  • Johannes Kepler, God, and the Solar System
  • Charles Babbage and the Vengeance of Organ-Grinders
  • Howard Robertson – the Man who Proved Einstein Wrong
  • Susskind, Alice, and Wave-Particle Gullibility




Alphabetical List of Scientists

Louis Agassiz | Maria Gaetana Agnesi | Al-BattaniAbu Nasr Al-Farabi | Alhazen | Jim Al-Khalili | Muhammad ibn Musa al-Khwarizmi | Mihailo Petrovic Alas | Angel Alcala | Salim Ali | Luis Alvarez | Andre Marie Ampère | Anaximander | Carl Anderson | Mary Anning | Virginia Apgar | Archimedes | Agnes Arber | Aristarchus | Aristotle | Svante Arrhenius | Oswald Avery | Amedeo Avogadro | Avicenna

Charles Babbage | Francis Bacon | Alexander Bain | John Logie Baird | Joseph Banks | Ramon Barba | John Bardeen | Charles Barkla | Ibn Battuta | William Bayliss | George Beadle | Arnold Orville Beckman | Henri Becquerel | Emil Adolf Behring | Alexander Graham Bell | Emile Berliner | Claude Bernard | Timothy John Berners-Lee | Daniel Bernoulli | Jacob Berzelius | Henry Bessemer | Hans Bethe | Homi Jehangir Bhabha | Alfred Binet | Clarence Birdseye | Kristian Birkeland | James Black | Elizabeth Blackwell | Alfred Blalock | Katharine Burr Blodgett | Franz Boas | David Bohm | Aage Bohr | Niels Bohr | Ludwig Boltzmann | Max Born | Carl Bosch | Robert Bosch | Jagadish Chandra Bose | Satyendra Nath Bose | Walther Wilhelm Georg Bothe | Robert Boyle | Lawrence Bragg | Tycho Brahe | Brahmagupta | Hennig Brand | Georg Brandt | Wernher Von Braun | J Harlen Bretz | Louis de Broglie | Alexander Brongniart | Robert Brown | Michael E. Brown | Lester R. Brown | Eduard Buchner | Linda Buck | William Buckland | Georges-Louis Leclerc, Comte de Buffon | Robert Bunsen | Luther Burbank | Jocelyn Bell Burnell | Macfarlane Burnet | Thomas Burnet

Benjamin Cabrera | Santiago Ramon y Cajal | Rachel Carson | George Washington Carver | Henry Cavendish | Anders Celsius | James Chadwick | Subrahmanyan Chandrasekhar | Erwin Chargaff | Noam Chomsky | Steven Chu | Leland Clark | John Cockcroft | Arthur Compton | Nicolaus Copernicus | Gerty Theresa Cori | Charles-Augustin de Coulomb | Jacques Cousteau | Brian Cox | Francis Crick | James Croll | Nicholas Culpeper | Marie Curie | Pierre Curie | Georges Cuvier | Adalbert Czerny

Gottlieb Daimler | John Dalton | James Dwight Dana | Charles Darwin | Humphry Davy | Peter Debye | Max Delbruck | Jean Andre Deluc | Democritus | René Descartes | Rudolf Christian Karl Diesel | Diophantus | Paul Dirac | Prokop Divis | Theodosius Dobzhansky | Frank Drake | K. Eric Drexler

John Eccles | Arthur Eddington | Thomas Edison | Paul Ehrlich | Albert Einstein | Gertrude Elion | Empedocles | Eratosthenes | Euclid | Eudoxus | Leonhard Euler

Michael Faraday | Pierre de Fermat | Enrico Fermi | Richard Feynman | Fibonacci – Leonardo of Pisa | Emil Fischer | Ronald Fisher | Alexander Fleming | John Ambrose Fleming | Howard Florey | Henry Ford | Lee De Forest | Dian Fossey | Leon Foucault | Benjamin Franklin | Rosalind Franklin | Sigmund Freud | Elizebeth Smith Friedman

Galen | Galileo Galilei | Francis Galton | Luigi Galvani | George Gamow | Martin Gardner | Carl Friedrich Gauss | Murray Gell-Mann | Sophie Germain | Willard Gibbs | William Gilbert | Sheldon Lee Glashow | Robert Goddard | Maria Goeppert-Mayer | Thomas Gold | Jane Goodall | Stephen Jay Gould | Otto von Guericke

Fritz Haber | Ernst Haeckel | Otto Hahn | Albrecht von Haller | Edmund Halley | Alister Hardy | Thomas Harriot | William Harvey | Stephen Hawking | Otto Haxel | Werner Heisenberg | Hermann von Helmholtz | Jan Baptist von Helmont | Joseph Henry | Caroline Herschel | John Herschel | William Herschel | Gustav Ludwig Hertz | Heinrich Hertz | Karl F. Herzfeld | George de Hevesy | Antony Hewish | David Hilbert | Maurice Hilleman | Hipparchus | Hippocrates | Shintaro Hirase | Dorothy Hodgkin | Robert Hooke | Frederick Gowland Hopkins | William Hopkins | Grace Murray Hopper | Frank Hornby | Jack Horner | Bernardo Houssay | Fred Hoyle | Edwin Hubble | Alexander von Humboldt | Zora Neale Hurston | James Hutton | Christiaan Huygens | Hypatia

Ernesto Illy | Jan Ingenhousz | Ernst Ising | Keisuke Ito

Mae Carol Jemison | Edward Jenner | J. Hans D. Jensen | Irene Joliot-Curie | James Prescott Joule | Percy Lavon Julian

Michio Kaku | Heike Kamerlingh Onnes | Pyotr Kapitsa | Friedrich August Kekulé | Frances Kelsey | Pearl Kendrick | Johannes Kepler | Abdul Qadeer Khan | Omar Khayyam | Alfred Kinsey | Gustav Kirchoff | Martin Klaproth | Robert Koch | Emil Kraepelin | Thomas Kuhn | Stephanie Kwolek

Joseph-Louis Lagrange | Jean-Baptiste Lamarck | Hedy Lamarr | Edwin Herbert Land | Karl Landsteiner | Pierre-Simon Laplace | Max von Laue | Antoine Lavoisier | Ernest Lawrence | Henrietta Leavitt | Antonie van Leeuwenhoek | Inge Lehmann | Gottfried Leibniz | Georges Lemaître | Leonardo da Vinci | Niccolo Leoniceno | Aldo Leopold | Rita Levi-Montalcini | Claude Levi-Strauss | Willard Frank Libby | Justus von Liebig | Carolus Linnaeus | Joseph Lister | John Locke | Hendrik Antoon Lorentz | Konrad Lorenz | Ada Lovelace | Percival Lowell | Lucretius | Charles Lyell | Trofim Lysenko

Ernst Mach | Marcello Malpighi | Jane Marcet | Guglielmo Marconi | Lynn Margulis | Barry Marshall | Polly Matzinger | Matthew Maury | James Clerk Maxwell | Ernst Mayr | Barbara McClintock | Lise Meitner | Gregor Mendel | Dmitri Mendeleev | Franz Mesmer | Antonio Meucci | John Michell | Albert Abraham Michelson | Thomas Midgeley Jr. | Milutin Milankovic | Maria Mitchell | Mario Molina | Thomas Hunt Morgan | Samuel Morse | Henry Moseley

Ukichiro Nakaya | John Napier | Giulio Natta | John Needham | John von Neumann | Thomas Newcomen | Isaac Newton | Charles Nicolle | Florence Nightingale | Tim Noakes | Alfred Nobel | Emmy Noether | Christiane Nusslein-Volhard | Bill Nye

Hans Christian Oersted | Georg Ohm | J. Robert Oppenheimer | Wilhelm Ostwald | William Oughtred

Blaise Pascal | Louis Pasteur | Wolfgang Ernst Pauli | Linus Pauling | Randy Pausch | Ivan Pavlov | Cecilia Payne-Gaposchkin | Wilder Penfield | Marguerite Perey | William Perkin | John Philoponus | Jean Piaget | Philippe Pinel | Max Planck | Pliny the Elder | Henri Poincaré | Karl Popper | Beatrix Potter | Joseph Priestley | Proclus | Claudius Ptolemy | Pythagoras

Adolphe Quetelet | Harriet Quimby | Thabit ibn Qurra

C. V. Raman | Srinivasa Ramanujan | William Ramsay | John Ray | Prafulla Chandra Ray | Francesco Redi | Sally Ride | Bernhard Riemann | Wilhelm Röntgen | Hermann Rorschach | Ronald Ross | Ibn Rushd | Ernest Rutherford

Carl Sagan | Abdus Salam | Jonas Salk | Frederick Sanger | Alberto Santos-Dumont | Walter Schottky | Erwin Schrödinger | Theodor Schwann | Glenn Seaborg | Hans Selye | Charles Sherrington | Gene Shoemaker | Ernst Werner von Siemens | George Gaylord Simpson | B. F. Skinner | William Smith | Frederick Soddy | Mary Somerville | Arnold Sommerfeld | Hermann Staudinger | Nicolas Steno | Nettie Stevens | William John Swainson | Leo Szilard

Niccolo Tartaglia | Edward Teller | Nikola Tesla | Thales of Miletus | Theon of Alexandria | Benjamin Thompson | J. J. Thomson | William Thomson | Henry David Thoreau | Kip S. Thorne | Clyde Tombaugh | Susumu Tonegawa | Evangelista Torricelli | Charles Townes | Youyou Tu | Alan Turing | Neil deGrasse Tyson

Harold Urey

Craig Venter | Vladimir Vernadsky | Andreas Vesalius | Rudolf Virchow | Artturi Virtanen | Alessandro Volta

Selman Waksman | George Wald | Alfred Russel Wallace | John Wallis | Ernest Walton | James Watson | James Watt | Alfred Wegener | John Archibald Wheeler | Maurice Wilkins | Thomas Willis | E. O. Wilson | Sven Wingqvist | Sergei Winogradsky | Carl Woese | Friedrich Wöhler | Wilbur and Orville Wright | Wilhelm Wundt

Chen-Ning Yang

Ahmed Zewail

Return to top of page

Famous Scientists - Privacy - Contact - About - Content & Imagery © 2025