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Portrait of Christiaan Huygens

Science · Physics

Christiaan Huygens

1629–1695 · Dutch

Physics, astronomy and mathematics; Scientific Revolution

Christiaan Huygens, from The Hague, was the leading Dutch scientist of the 17th century. He discovered Saturn's largest moon Titan, explained that Saturn is surrounded by a thin flat ring, and invented the pendulum clock. His wave theory of light and Huygens' principle remain central to optics.

How to spot them

  • ▸Discovered Titan (1655) and explained the true shape of Saturn's rings
  • ▸Invented the pendulum clock (1656–57); Horologium Oscillatorium
  • ▸Wave theory of light; Huygens' principle of secondary wavelets; Traité de la Lumière
  • ▸ESA's Huygens probe, which landed on Titan in 2005
  • ▸Son of the poet and diplomat Constantijn Huygens

Key discoveries & works

Discovery of Titan, Saturn's largest moon (1655)

The first moon of Saturn to be found, observed with a telescope he built with his brother Constantijn

Systema Saturnium (1659)

Explained Saturn's changing appearance as a thin, flat ring not touching the planet

Invention of the pendulum clock (1656–1657)

Designed in 1656 and patented in 1657, it made timekeeping vastly more accurate

Horologium Oscillatorium (1673)

Mathematical treatise on pendulum clocks, including the cycloidal pendulum and centrifugal force

Traité de la Lumière (Treatise on Light) (1690)

Set out the wave theory of light and explained reflection, refraction and double refraction

De Ratiociniis in Ludo Aleae (1657)

One of the first published books on probability, about reasoning in games of chance

Key ideas

  • Huygens' principle: every point on a wavefront acts as a source of secondary wavelets whose envelope forms the new wavefront
  • Light is a wave travelling through a medium, in contrast to Newton's corpuscular theory
  • The pendulum as a regulator for clocks; a cycloidal path makes the swing truly isochronous
  • Correct formula for centrifugal force in circular motion

Quick-fire facts

  • •Born in The Hague on 14 April 1629 and died there on 8 July 1695
  • •His father, Constantijn Huygens, was a poet, composer and secretary to the Princes of Orange
  • •A founding member of the French Académie des Sciences (1666), he lived in Paris for about 15 years
  • •Tutored the young Gottfried Leibniz in mathematics in Paris
  • •Elected a Fellow of the Royal Society in 1663
  • •Also developed a balance spring for watches (1675), leading to a priority dispute with Robert Hooke
  • •His posthumous Cosmotheoros (1698) speculated about life on other planets

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Sources