German scientist Alfred Wegener argued that the world's continents had once been joined in a supercontinent he called Pangaea before drifting apart over millions of years. Ridiculed by many geologists at the time for lacking a mechanism to explain the movement, his idea would not gain full acceptance until plate tectonics theory emerged decades later.
Wegener, trained as a meteorologist rather than a geologist, was struck by how neatly the coastlines of South America and Africa seemed to fit together like puzzle pieces, and by matching fossil and rock formations found on opposite sides of the Atlantic. When he presented his continental drift hypothesis, he faced fierce skepticism from established geologists who dismissed the idea because he couldn't explain what force could possibly move entire continents.
Wegener spent the rest of his career defending and refining the theory, publishing 'The Origin of Continents and Oceans' in 1915, but died in 1930 during an expedition to Greenland without seeing it vindicated. It wasn't until the 1960s, when scientists discovered seafloor spreading and developed the theory of plate tectonics, that Wegener's outsider insight was finally recognized as one of the most important breakthroughs in the history of earth science.
Key people: Alfred Wegener