A fair approach. Incidentally, I just drew some diagrams and with the assumptions that the Earth is not at the centre of expansion, Earth orbit has extremes (f

A fair approach. Incidentally, I just drew some diagrams and with the assumptions that the Earth is not at the centre of expansion, Earth orbit has extremes (for parallax), and all light only takes straight routes, my second question has a negative answer. But if one puts a gravitational lens on the view of one of the two stars then (based on a fast doodle though) it looks like maybe expansion could be detected.