History of Solar System formation and evolution hypotheses with Uranus having a 98° tilt. The Moon being relatively large with respect to the Earth and other moons which are in irregular orbits with respect to their planet is yet another issue. It is now believed these observations are explained by events which happened after the initial formation of the Solar System. Attempts to isolate the physical source of the Sun's energy, and thus determine when and how it might ultimately run out, began in the 19th century. At that time, the prevailing scientific view on the source of the Sun's heat was that it was generated by gravitational
Orbit of the Moon rearward loops in the Moon's solar orbit. Considering the Earth–Moon system as a binary planet, its centre of gravity is within Earth, about or 72.6% of the Earth's radius from the centre of the Earth. This centre of gravity remains on the line between the centres of the Earth and Moon as the Earth completes its diurnal rotation. The path of the Earth–Moon system in its solar orbit is defined as the movement of this mutual centre of gravity around the sun. Consequently, Earth's centre veers inside and outside the solar orbital path during each synodic month as the Moon