If I understand correctly, it's highly likely that the planets in a twin-Earth binary planet system would be tidally locked. But is it totally impossible for them to be much farther apart—say, at several times the distance between the Earth and the moon—and rotate independently? (As a cheat, if necessary, could such a system at least be stable for several million years if it were created by an incredibly advanced civilization with god-like technologies and resources?)
A few bonus questions, assuming that their co-orbital period is several months:
- What would this mean for their day/night cycles? Obviously the combination of rotating independently and orbiting each other would cause some eccentricities here, but I'm trying to puzzle it out and it's making my brain hurt.
- Tidal effects would be pretty severe, yes? What's the least severe possible tidal effect each planet could expect to experience?
- Is it possible for both planets to have seasons, e.g. if their axes and/or co-orbital plane was offset to that of their solar orbit?