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The renowned Dutch astronomer Christian Huygens was probably short-sighted, a new study found in the telescopes he built more than 300 years ago. The results even suggest what glasses the astronomer could have worn, potentially making this the world’s first posthumous prescription for glasses.
Huygens (1629-1695) was a polymath who made important contributions to the fields of mathematics, physics, engineering and astronomy. He is best known for inventing the pendulum clock, claiming that light is made of waves, unraveling the mysteries of Saturn’s rings, and discovering Titan, Saturn’s largest moon. The European Space Agency Huygens probe (opens in new tab)that landed on Titan on January 14, 2005 was named in his honor.
Huygens built his own telescopes with his brother Constantijn, which he used to make his astronomical discoveries. However, despite Huygens’ success in this field, later analysis of his telescopes has shown that although the lenses he made were of the highest quality, his instruments did not produce images with as clear a resolution as those of his contemporaries.
In a new study published in the journal March 1 Notes and records: the Royal Society Journal of the History of Science (opens in new tab), Alex Pietrow (opens in new tab)a researcher at the Leibniz Institute for Astrophysics in Potsdam in Germany, took a closer look at how the lenses used in Huygens’ telescopes matched the instruments’ eyepieces and found that the astronomer was probably short-sighted.
“Because Huygens didn’t need glasses in everyday life, he probably didn’t think about it when making telescopes,” Pietrow said in one opinion (opens in new tab). “So he subconsciously incorporated that eye defect into his designs.” This may have prevented Huygens from building even more powerful telescopes than those he built, Pietrow added.
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Nearsightedness, also called myopia, is a common vision disorder in which close objects appear clear while distant objects appear blurry. The condition is often caused by an elongation of the eyeball. When light rays bend or refract into the eye in people without eye conditions, the light focuses on the retina at the back of the eyeball, which sends signals to the brain that are interpreted into an image. But in people with myopia, the shape of the eyeballs causes light rays to focus slightly in front of the retina, making the resulting image a little blurry, according to the researchers Mayo Clinic (opens in new tab).
Huygens built his telescopes through trial and error, fitting together different combinations of lenses and eyepieces. After perfecting this process, Huygens created a mathematical table listing the optimal lens-eyepiece pairings that he used to manufacture all of his subsequent telescopes.
Pietrow believes that Huygens inadvertently compensated for his short-sightedness, making the images from his telescopes appear clear to him. Based on the mathematical table written by Huygens, Pietrow believes that Huygens’ vision could have been corrected by glasses of −1.5 diopters, suggesting that the astronomer’s myopia was not as severe. As a result, Huygens would not have needed glasses in his day-to-day life and was probably completely unaware of his condition.
In today’s world, myopia is more commonly diagnosed when people have trouble reading distant road signs while driving, which Huygens says wasn’t a problem when Huygens built his telescopes.
Being able to pinpoint exactly how myopic Huygens was means that “this is probably the first posthumous eyeglass prescription ever,” Pietrow said. The fact that it was made for someone who lived almost 330 years ago is even more special, he added.
