The Known Universe is a constantly expanding region of space-time bounded by mankind’s ability for exploration. Until the beginning of the first millennium CE (Common Era), the Known Universe for Europeans was the continental masses of Africa and Eurasia. By the twentieth century the Known Universe was entire Earth. In 1969 CE the United States Space Program added the Moon to the Known Universe. By the end of the twenty-first century, Mars, Jupiter’s moons and the larger asteroids had been added. It was not until the early twenty-third century that the new age of exploration gained enough momentum to expand the Known Universe beyond the Home System of Sol.