Seems like, after changing places with Jupiter, Neptune became smarter, and not alone. (SolarBalls Neptune) Sol Arranged all the planets by size. Now The norm is: 1. Mercury 2. Mars 3. Venus 4. Earth 5. Neptune 6. Uranus 7. Saturn 8. Jupiter All the cause, is because planets keep going away from their orbits. (Also Neptune knows one: the orbits sorted by size will result an end of Solar System.)