A gentleman of independent means

Christiaan spent the next several years for the most part in The Hague, but he kept in contact with the learned world across Europe. In 1660-61 and 1663-64, he again went on journeys and spent several months in Paris and London. In The Hague, he lived in the family home. He never married — a condition not unusual for scholars in the seventeenth century.

These years after his university studies, years without a position, were the most productive of his career. His studies produced spectacular discoveries in several areas, some of which he published during this period, and some of which saw the light of day much later.

In the first instance, Huygens made a name especially as a mathematician, an area in which he continued to work for the rest of his life and in which he reached great heights. Most of this work is esoteric and difficult for non-specialists. But one part of it is more accessible: his calculations of the likelihood of winning or losing in games of chance. Huygens was one of the founders of the study of probability.

Besides mathematics, throughout his life Huygens had a love of making devices and instruments. In some cases these were toys, such as the magic lantern invented by him; in other cases they were serious scientific instruments. Together with his brother, he ground and polished lenses and made telescopes and microscopes. His mathematical studies of lenses produced important results, which remained unpublished for the time being. He did, however, publish the discoveries he made with his telescopes. In 1656 he announced that he had found a moon of Saturn, and in his Systema Saturnium (1659) he published the solution to the puzzle of Saturn’s remarkable and always changing appearance: the planet is surrounded by a ring. With these discoveries about Saturn, Huygens achieved international recognition as a scientist.

Huygens also devoted attention to mechanics — here again in connection with his tinkering with instruments. In 1656-57, he invented the pendulum clock. At the time, he published only a brief description; a more exhaustive treatment came much later. His thoughts on more fundamental mechanical problems — collision, centrifugal force — remained for the most part unpublished.