[Jedi Master Pikachu]

Isn't this idea old, and a theory for why Uranus (the planet) is 'sideways?'

Or did that end with the discovery of Neptune?

[SunkenCiv]

“Isn’t this idea old, and a theory for why Uranus (the planet) is ‘sideways?’ Or did that end with the discovery of Neptune?”

[two months later]

Somehow missed that one. Harrington and Van Flandern theorized the existence of a planetary interloper which tore loose at least one satellite of Neptune — a satellite now known as Pluto — and tipped Uranus (heh heh heh heh), perhaps by terminal impact. Uranus’ moons orbit in the ecliptic, while Uranus axis is nearly 90 degrees out of perpendicular. TVF now attributes the tipping to an exploding planet, I believe (too lazy to check).