Alfred Wegener was a German meteorologist who achieved fame for his theory of continental drift. This was a theory he put forth in 1912 that the continents had not always been in their present locations, but instead, drifted across the ocean towards and away from each other. His theory was based upon the general shape and appearance of the continents looking like they were pieces of a huge jigsaw puzzle. He substantiated his theory with evidence such as similar rock and fossil formations on the continents of South America and Africa. His theory was not initially accepted, as he could not explain the mechanism by which this drifting occured. It was not until about 35 years later, during World War II, Harry Hess provided the mechanism of sea floor spreading that the theory of continental drift started gaining acceptance.