De revolutionibus orbium coelestium Earth's axis rigidly to a Sun-centered sphere. The unfortunate consequence was that the terrestrial rotation axis then maintained the same inclination with respect to the Sun as the sphere turned, eliminating the seasons." To explain the seasons, he had to propose a third motion, "an annual contrary conical sweep of the terrestrial axis". It was not until the Great Comet of 1577, which moved as if there were no spheres to crash through, that the idea was challenged. In 1609, Kepler fixed Copernicus' theory by stating that the planets orbit the sun not in circles, but ellipses. Only after Kepler's
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