A prescription for glasses for Christiaan Huygens after 330 years Story-level

Christiaan Huygens built excellent lenses in the 17th century, but his telescopes lacked sharpness compared to what was possible at the time. In a recent study, Dr. Alex Pietrow, a researcher at the Leibniz Institute for Astrophysics in Potsdam (AIP), investigated Huygens’s calculations and concluded that the Dutch astronomer and mathematician was likely myopic and would have needed glasses to enhance his telescopes.

Christiaan Huygens was a 17th century Dutch scientist who revolutionized the fields of optics, mechanics, timekeeping, and astronomy. For example, he invented the grandfather clock, created a wave theory of light, discovered Saturn’s moon Titan, and described the true nature of Saturn’s rings. His telescopes and lenses are known to be of excellent quality for the time, but nonetheless could not achieve the same sharpness as those built by his rivals.

A new study recently published in the journal Notes and Records: The Royal Society Journal of the History of Science takes an unusual look at Huygens’ work and suggests that the lack of sharpness in his lenses was due to a deficiency in Huygens’s eyesight: the scientist may have had nearsightedness (nearsightedness), a condition that makes distant objects appear blurry .

The study was conducted by Dr. Alex Pietrow, AIP Postdoctoral Researcher in Solar Physics and a history of science enthusiast. She examined the rules and equations established by Huygens for designing telescopes and found that they were poor in performance compared to modern optical principles.

Huygens’ approach to lens making was experimental and based on trial and error, meaning that he would try combinations of various lenses and eyepieces to find the best working telescope. Once he did, he created tables and equations, which he then used to build telescopes with the desired magnification.

However, the telescopes that the Dutch scientist designed using these equations did not reach the theoretical optimum. For example, a former director of the Leiden Observatory in the Netherlands, Frederik Kaiser, claimed in 1846 that Huygens built virgin lenses, but his telescopes had markedly lower resolving power compared to contemporary refracting telescopes.

The new study suggests that Huygens’ eyesight may have been the reason. The difference between his equations and modern optics could be explained by prescribing Huygens glasses with –1.5 diopters. “This is probably the first posthumous prescription for glasses, and it was made for someone who lived 330 years ago,” says Alex Pietrow. Huygens’ myopia was mild enough not to cause any problems in daily life in the 17th century, and therefore went largely unnoticed.

A person with this visual defect can read well at close range, but has trouble deciphering letters that are far away. This is problematic in the modern world when recognizing traffic signs or driving a car, but 300 years ago this would not have been a problem. Even if Huygens had been aware of his vision deficiencies, he would not have needed glasses.

Alex Pietrow elaborates: “My theory is that because Huygens didn’t need glasses in everyday life like his father, he probably didn’t think of it when making telescopes. So he unconsciously included this ocular defect in his designs.” This would also explain why Huygens failed to overcome this arbitrary limitation of his telescopes: he could not discern any further improvements.