Double Planets & Rocheworlds
Why Worldbuilding Stack Exchange recommends it
Worldbuilding Stack Exchange answerers point people to it for realistic physics of binary planets and Rocheworlds when asking what such worlds would look like or how they behave.
Recommended by 2 people across 2 different months, 2017 to 2019.
What it is
A 13-minute Isaac Arthur explainer on double planets, covering what conditions would let both worlds be Earth-like, tidal locking, eclipses and reflected light. It ends with Rocheworlds, where two close planets share an atmosphere or begin merging. The description links an orbital period calculator.
What people said
Recommends stux · 2018-10 · Worldbuilding Stack Exchange · on “What geological consequences would result from a binary planet system?”
Everything would more or less be the same as on earth in each planet, even the plateau. Everything you'd want to know is in this video: "Double Planets and Rocheworlds" [this video] by Isaac Arthur. It even links to an orbital period calculator. Per the video, the other planet would simply appear 'stationary' in space, while you still have your normal day/night cycles. I would imagine that you would have frequent eclipses. However, the video mentioned that the other planet would reflect sunlight and would be many times brighter than the moon! The animations in the video also illustrate how all parts of each planet would have regular day/night cycles. Some exceptions: If you bring the two planets
Recommends elemtilas · 2019-01 · Worldbuilding Stack Exchange · on “What would an earth-sized world be like if shaped like Ultima Thule?”
Nice image! That's a Roche world: [LINK] Such a planetary system would be double locked and can share an atmosphere. Eventually they'll end up sharing ocean and land and over the course of geo-theiological time will form a peanut shaped roche world (such as Ultima Thule seems to be) and will eventually collapse into a larger single planet. Nice views while it lasts! Double Planets and Roche Worlds [this video] : cue it up to about 10:01 to get to the roche world description.
Cites Lot-Of-Malarkey · 2017-10 · Worldbuilding Stack Exchange · on “How Would It Feel To Walk On A Rocheworld?”
A while back I saw this video [this video] talking about the habitability of double planets and Rocheworlds. I haven't seen any questions about the latter case here, so I decided to take a swing at it. For some background, a Rocheworld is a double planet system that is so close together that the two planets share an atmosphere and have started to merge together. This would eventually result in the two planets violently becoming one large planet. Hypothetically, it could be possible to travel from one of the planet components to the other over the region they overlap. I think that since these are two planets overlapping, this could lead to some intersting gravitational effects that could impede tr