Shared between mathematics, physics and astronomy, both theoretician and experimenter, Christiaan Huygens was one of the precursors of the modern scientific spirit, in the tradition of Copernicus and Galileo. Worthy representative of the intellectual bubbling that made the Netherlands an oasis in the middle of the European obscurantism of the seventeenth century, Huygens designed, among other things, the principle of the clock pendulum, paving the way for the development of precision watchmaking .

So even though he is not only a watchmaker, he is one of the great inventors who revolutionized this field.

Christiaan Huygens and his century

Christiaan Huygens was born on April 14, 1629, in a family of dignitaries of the House of Orange, in The Hague. His father, Constantijn, both poet and diplomat, provides him an exemplary education until the age of 16, and gives him benefit from his circle of friends, including René Descartes. The young Christiaan is therefore at a good school. It is perhaps for this reason that he develops, very early, a special attraction for the functioning of machines and the mysteries of nature. While conducting his first child experiments on mills, he is fascinated by the undulations produced on the surface of the water by a single stone.

After studying law and mathematics in Leiden and Breda, he sets his sights on the physical sciences and astronomy, two disciplines in which he integrates the mathematics he loves so much. Christiaan is fortunate to have grown up in a country that, in the 17th century, embodies an oasis of free thought and scientific foresight, made possible by total freedom of worship, in the heart of a Europe stunned by religious obscurantism. This is called the “golden age,” which saw many European thinkers take refuge in Holland to work in peace, like Descartes.

It is in this context that the young Christiaan conducts his first scientific works: the elucidation of the rules of shock, in 1652; the publication, in 1657, of his first work (and the very first of its kind) on the calculation of probabilities; the calculation of the centrifugal force; as well as his work on oscillating pendulum theory, with the desire to make the measurement of time more precise. Discoveries and publications are linked together in astronomy, physics and mathematics.

In 1666, he moved to Paris, under the protection of Colbert. Thanks to the intervention of the latter, Christiaan receives a large pension paid by King Louis XIV – a financial serenity that allows him to devote himself entirely to its work. During the fourteen years he spent in France, he was elected to the Academy of Sciences (in 1666), after having been admitted to the Royal Society of England, and participated in the construction of the Observatoire de Paris, completed in 1672.

Christiaan Huygens finally found his country in 1680, when he flees the persecutions that are worsening in France against the Protestants. Seriously ill, he died in The Hague, his birthplace, July 8, 1695.

A man of science (s)
In his bestseller Cosmos, astrophysicist Carl Sagan pays tribute to Christiaan Huygens while highlighting the grandeur of the Dutch “golden age” that allowed such men to develop their thinking. He describes in a few lines some of the impressive discoveries of Huygens, who was the first to:

• Calculate the size of a planet other than the Earth;
• Speculate on the presence of a layer of clouds all around Venus;
• Spot dark spots on the surface of Mars and use them to estimate the duration of the Martian day;
• Discover the rings of Saturn and observe that they are made of rocks;
• Discover Saturn’s largest satellite, Titan.
  And all that, says Carl Sagan, before leaving for France, between his 20s and 30s! (See Cosmos, American edition at Ballantine Books, New York, 1958, 118).

And it’s far from everything. In the three disciplines he mastered, Huygens was still the discoverer or the perpetuator of many theories that had an impact well beyond his death: the observation of the Orion nebula (whose brightest part bears the name “Huygens region”), the calculation of centrifugal force, the wave theory of light (explained in its Traité de la lumière in 1690), or the highlighting, in 1673, of the principle of the motor internal combustion (a metal cylinder emptied of its air and filled with gunpowder which, under the effect of the warming, displaces a piston), which will lead to the invention of the automobile … two centuries later!

For Sagan, as for most of the astrophysics community, Huygens is also the man who supported the Copernican hypothesis of a Earth turning around the Sun, which explained the idea that the stars of the celestial vault are as much of suns close to ours, and who decreed that around these suns should turn other planets similar to the Earth, with their inhabitants.

Christiaan Huygens and watchmaking

It is, however, in the discipline of physics that Huygens makes his most remarkable discoveries. These innovations have mainly concerned the field of clocks and watches, and have helped to perfect these devices.

In 1656, Huygens invents the clock pendulum. For this, it is based on the work of Galileo and Bürgi, and entrusted the realization to the Dutch watchmaker Samuel Coster. He takes up Galileo’s formula on the isochronism of the pendulum, which he perfected to adapt it to clocks and make them more precise, by replacing the foliot with a pendulum as a regulator of movement.
In 1659, he further perfected the isochronism of the pendulum, producing the cycloid pendulum. He places, near the point of suspension of the pendulum, two cycloidal cheeks which constrain the semi-rigid stem to describe a cycloid; thus, the period of oscillation is constant, whatever the amplitude (correcting, in passing, the demonstrations of Galileo).
In 1673, he published Horologium Oscillatorum, a volume in which he explains the operation and the assembly of a pendulum clock. This book follows a first opus, Horologium, published in 1658, which described the innovative model of the pendulum and its exhaust system, without venturing into horological applications.
In 1675, he developed the spiral spring, and presented a first model of pendulum-balance watch at the Royal Society the same year, made by the French watchmaker Isaac Thuret. He was the first to apply this invention convincingly, but he failed to compensate for errors due to temperature changes.
The impact of Christiaan Huygens has therefore been major, both on watchmaking and other scientific disciplines. The world of astronomy, in particular, was eager to pay tribute to him by repeatedly naming his name – an asteroid, a part of the Orion nebula, the module taken by the Cassini spacecraft to land on Titan . But without it, clocks and watches would not be what they are today.