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Q&A How technological advanced a civilization would need to be to prove the existance of the shadow Earth?

In a short sci-fi story i am writing, Earth has a shadow twin. A planet with the same chemical/geological characteristics as Earth and wildlife very similar (but different species because evolution...

2 answers  ·  posted 8y ago by Mindwin‭  ·  last activity 6y ago by Mindwin‭

Question reality-check planets orbital-mechanics earth counter-earth