Continental Drift Theory says the Earth's continents drift across the ocean bed relative to each other. It can be proved by geometric fit of the displaced continents and the similarity of rock ages and Paleozoic fossils in corresponding bands or zones in adjacent or corresponding geographic areas. If you want to test it out, get a world map, cut all the continent plates out and try to put them together like putting puzzles together. Around the borders where the continents can "fit" together people can find fossils of organisms which used to live during the same time period. Rock ages around these borders are also the same.