Karen Bakker writes:

More than 400 years ago in the small Dutch town of Middelburg, a father-and-son team stumbled on an invention that would one day change history, but which they dismissed as a dud. By tinkering with glass lenses, Hans and Zacharias Janssen invented the microscope. Yet this was not by design.

The Janssens were leaders in a new and highly lucrative industry: making reading glasses. In their quest for the perfect pair of spectacles, a highly sought-after luxury item, the Janssens discovered that they could magnify objects by aligning two lenses in a cylindrical tube. They were astounded to find that combining two lenses magnifies much more than any one lens does on its own. But the view was blurry and the device too clunky for their clients, so they put their quirky discovery aside.

The Janssens’ magnifying machine lay mostly unnoticed for nearly a hundred years before someone put it to use. Antonie van Leeuwenhoek, a Dutch fabric merchant with a grade school education, first built a few homemade microscopes with a mundane goal: checking the quality of the expensive fabrics he had purchased from overseas. But Van Leeuwenhoek soon turned his attention to the world around him, pointing his microscope at well water, mold, bees, lice, yeast, blood cells, human breast milk (his wife’s) and sperm (his own). Everywhere he looked, his microscopes revealed a strange new world of beings living in every nook and cranny of our world, but unseen by the unaided eye.

Van Leeuwenhoek initially (and wisely) kept his discoveries secret for fear of ridicule. When he eventually revealed what he had seen, polite Dutch society disdained his strange proclivity for magnifying bodily substances; many simply refused to believe in the existence of “animalcules” altogether. Nevertheless, Van Leeuwenhoek penned hundreds of letters to the Royal Society in London, which — after initial suspicion and a visit from a skeptical scientific delegation — eventually accepted his findings. The humble merchant’s research papers were published alongside those of Sir Isaac Newton in the Royal Society’s learned journal.

The new world of microscopic observation soon fascinated scientists and philosophers alike. Microscopes proliferated as a form of visual prosthetics — artificial eyes that helped humanity see new things in new ways, laying the foundation for startling discoveries. The study of the microscopic world renewed interest in atomism — an early theory that the world was composed of fundamental, tiny particles — and would also eventually provide new methods for understanding contagion and disease.

As the historian of science Catherine Wilson argued in “The Invisible World,” the microscope catalyzed the Scientific Revolution. The simple device captured a complex idea: Science could reveal aspects of the natural world that were invisible to naked human perception. Spectacles merely helped us focus on the written word; the microscope enabled humans to perceive entirely new realms, extending the power of both sight and imagination. [Continue reading…]