Real-life sci-fi worlds #3: the oscillating Earth

Welcome to Real-life Sci-fi worlds.  We are using science to explore life-bearing worlds that are the settings for science fiction stories.  Up today: the oscillating Earth. Setting Earth’s orbit is not fixed.  Gravitational kicks from the other planets change the shape of Earth’s orbit.  Earth’s orbit oscillates between being perfectly circular (having an “eccentricity” of…