Famous Things That Were Invented by Accident

In August 1928, Alexander Fleming went on vacation from his London lab, leaving a stack of Petri dishes cultured with staphylococcus on his desk. When he returned in early September, he saw mold on one of them, with a clear ring around it: bacteria hadn't grown there. That observation later led to penicillin.

Several accidents came together here. A mold spore most likely drifted in from the lab downstairs, where they worked with fungi. The dish wasn't put in an incubator but left at room temperature. And London weather turned cool for a while, then warmed up again.

This exact sequence was crucial. In the 1960s, bacteriologist Ronald Hare tried to recreate the finding and discovered that it wouldn't repeat in warmth: staphylococcus takes over the whole dish before the mold can begin to interfere. The cool days gave the mold a head start, and the warming came later.

Fleming described the observation in 1929, and then almost nothing happened for 10 years. A different team in Oxford made the medicine: they learned to isolate and purify the substance around the start of the 1940s, and mass production was underway by the end of the war. Between the spoiled dish and the vial lay about 15 years of other people's work.

The accident takes the same form in all 3 stories: the result wasn't what was planned. The difference is what the person did next. Mold on Petri dishes is ordinary and gets thrown out every day; glue that's too weak is made regularly. The details of these stories are known mostly from company retellings. This is what Pasteur meant back in 1854: chance favors the prepared mind - someone who already has a question in mind that the oddity answers.