  It was not recognized at first that the General Theory of Relativity could be applied to the Universe as a single, whole, individual object, thereby producing a new cosmological theory, one completely different from its predecessors. Although the mathematics involved are extremely difficult, two solutions, one by Einstein himself, the other by the Dutch astronomer Willem de Sitter, were produced in just a short time in 1917. Unfortunately, the universes predicted by the two solutions were extreme: Einstein’s universe would be densely packed with matter, whereas de Sitter’s would be essentially empty.