Jonah: Your reader is all wet. Relative to distant galaxies — the nearest we have to a true inertial frame of reference, the earth and the sun rotate about their common center of mass — a point that, because the sun is so immensely more massive than the earth, is actually inside the body of the sun. So to a first approximation, the earth goes round the sun. And the moon does too, on a rather interesting path, one that is at no point ever concave towards the sun–counterintuitive, but a standard result in celestial mechanics.