Adherents of the modern flat-Earth model propose that a dome-shaped firmament encloses a disk-shaped Earth. They may also claim, after Samuel Rowbotham, that the Sun is only 3,000 miles above the Earth and that the Moon and the Sun orbit above the Earth rather than around it. Modern flat-Earthers believe that Antarctica is not a continent but a massive ice flow, with a wall 150 feet or higher, which circles the perimeter of the Earth and keeps everything (including all the oceans' water) from falling off the edge.