what does it really mean to "orbit the sun?" We follow an elliptical path around the sun from the perspective of the reference frame of the sun. From the perspe

what does it really mean to "orbit the sun?" We follow an elliptical path around the sun from the perspective of the reference frame of the sun. From the perspective of the reference frame of the earth the sun and planets move around us in complicated epicycles. From the perspective of an external reference frame, outside the solar system, the earth moves in a sinusoidal manner as the sun orbits the galaxy. At the largest scale space is expanding and no orbits are cyclical. We never return to the same space twice. Rotation is said to be absolute while linear motion is relative but since space is expanding at the largest space and time scales are not orbits illusory? Due to gravity objects follow curved paths through space and time as the fabric of the Universe expands but if you think about it you never really return to the same place twice so might also at large scales apparent angular motion also be relative or convergent on linear motion, e.g. through fourier decomposition?