Everyone loves the story of penicillin: One day, pharmacologist Alexander Fleming returned from a two-week vacation to Scotland, only to peer into a moldy Petri dish and find the world’s first antibiotic. We love this story because it’s such a neat discovery, and also because it’s so rare. Typically the process of science is molasses-slow, far more tedious than transcendent. Breakthroughs take years, even lifetimes, of work, and are usually less about individual genius than about building upon a collective foundation of knowledge.
Sometimes, however, a commonly held understanding really is overturned in one fell swoop. As science fiction writer Issac Asimov is said to have quipped, the exclamation that heralds such discoveries isn't really “Eureka!” but “That's funny.”
There's no doubt that the history of science is filled with fortuitous finds and moments of unanticipated connection. Chinese alchemists are said to have invented gunpowder while testing a prescription for eternal life; Archimedes discovered principles of volume while sloshing about in his bath. Hard evidence for these ancient tales is lacking, but a host of more recent scientific breakthroughs were definitely the result of happy chance—coupled with the fact that they occurred before watchful eyes and scientific minds trained to observe them.
Research engineer Richard Gaughan has studied centuries’ worth of just such discoveries for his book Accidental Genius: The World's Greatest By-Chance Discoveries. As he tells Smithsonian.com, calling these discoveries “accidental” can be a bit misleading. “When preparation, opportunity, and desire come together,” Gaughan says, “the result can be an accidental discovery that changes our understanding of the world.” Here are seven scientific moments that changed the world.
Newton's Law of Universal Gravitation (1666)
The story of Issac Newton's apple-driven “Eureka!” moment is such an old chestnut that it's often dismissed as folklore. But Newton himself always insisted this version of events was true (well, except the part about the apple hitting him on the head). Newton spoke of the incident to many people, including his pen pal Voltaire. In 1726 gave a description to his friend John Conduitt that remains the earliest written record of the event.
“He first thought of his system of gravitation which he hit upon by observing an apple fall from a tree,” Conduitt recounts in the letter, documented by researchers at the University of York. Newton wondered why the apple, or anything else, always fell in the same direction: down.
In fact, what's believed to be the legendary tree still stands at Woolsthorpe Manor, where it had already become famous as early as the 18th century. Over 350 years old, the tree has been re-rooted twice but still stands in the garden of Newton's old home, dropping apples that fall straight to the ground every single time.