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I have heard people argue that we are in fact in a kind of binary planetary system. No other planet has such a large satellite relative to its size, until you g
by nephihaha 2mo ago
I have heard people argue that we are in fact in a kind of binary planetary system. No other planet has such a large satellite relative to its size, until you get to the likes of Pluto etc.
- Dylan16807 2mo agoThe Earth is closer but I don't think there's any good argument to say it's actually a binary system. Notably the Earth-Moon barycenter stays inside the Earth, and the Sun-Jupiter barycenter doesn't stay inside the Sun. But barycenters are too easy to get outside of objects anyway.
- pdonis 2mo agoAs I understand it, one suggested "double planet" definition was that the barycenter would have to be outside both objects. Earth-Moon doesn't (quite) satisfy that condition, but for example, Pluto-Charon does.
- nephihaha 2mo agoThe Earth-Moon system is certainly anomalous within our Solar System. There is no such equivalent among the three other rocky planets, and while there are large moons around the other planets, the planets themselves are far larger.
- pdonis 1mo agoI assume you're not including Pluto-Charon here (presumably since Pluto is now demoted to "dwarf planet")? Their mass ratio is only about 8:1, which is far smaller than Earth-Moon, 81:1.