The Expanse (novel series) a future in which humanity has colonized much of the Solar System, but does not have interstellar travel. In the asteroid belt and beyond, tensions are rising between Earth's United Nations, Mars, and the outer planets. The series initially takes place in the solar system, using many real world locations such as Ceres and Eros in the asteroid belt, several moons of Jupiter, with Ganymede and Europa the most developed, and small science bases as far out as Phoebe around Saturn and Titania around Uranus, as well as well-established domed settlements on Mars and the Moon. As the series progresses,
Moon to the planet's equatorial plane. The Moon's orbit is subtly perturbed by the Sun and Earth in many small, complex and interacting ways. For example, the plane of the Moon's orbit gradually rotates once every 18.61 years, which affects other aspects of lunar motion. These follow-on effects are mathematically described by Cassini's laws. The Moon is exceptionally large relative to Earth: Its diameter is more than a quarter and its mass is 1/81 of Earth's. It is the largest moon in the Solar System relative to the size of its planet, though Charon is larger relative to the dwarf planet