History of physics to simplify their production. In heliocentric models of the Solar system, the Earth orbits the Sun along with other bodies in Earth's galaxy, a contradiction according to the Greek-Egyptian astronomer Ptolemy (2nd century CE; see above), whose system placed the Earth at the center of the Universe and had been accepted for over 1,400 years. The Greek astronomer Aristarchus of Samos (c.310 – c.230 BCE) had suggested that the Earth revolves around the Sun, but Copernicus' reasoning led to lasting general acceptance of this "revolutionary" idea. Copernicus' book presenting the theory ("De revolutionibus orbium coelestium", "On the Revolutions of the
Planets of the Hainish Cycle current estimate. On the other hand, giant stars last 100 million years or so, which is much less time than Earth needed to evolve complex life. It is probable that the native humanoids are of Hainish origin, as are many other indigenous populations in the Hainish Cycle, descendents of genetically modified Hanish colonists from the ancient Hanish colonial epoch, similar to other planets in the cycle. This would account for the successful imbreeding, which should not be possible if they had evolved from completely different biospheres. In 1.5 million years, Eltanin will pass within 28 light years of Earth. At