I was thinking about one of the many resolutions of the so-called 'twin paradox' within SR framework. I realize many methods of resolving this have been proposed, but I am curious about the particular solution that uses 'acceleration' of the traveling twin, to create the required asymmetry for differential clock rates (time dilation) between the twins. As I understand it, the traveling twin's clock is slowed because (s)he is in a non-inertial frame at some point(s) during the trip because of the acceleration experienced, while the stay-at-home twin always remains in an inertial frame. However, given momentum conservation, even the Earth along with the stay-at-home twin would have to have an acceleration in the opposite direction of the traveling twin, even if by an insignificant amount. This would put the Earth and stay-at-home twin also in a non-inertial frame, however briefly. So, what is the logic behind this particular resolution of the twin paradox that produces the asymmetry between the twins?