  The motion of astronomical bodies and the centre of mass of the system is not
always well perceived by students. One of the struggles is the conceptual
change of reference frame, which is the same that held back the acceptance of
the Heliocentric model over the Geocentric one. To address the question, the
notion of centre of mass, motion equations (and their numerical solution for a
system of multiple bodies), and change of referential is introduced. The
discussion is done based on conceptual and real world examples, using the solar
system. Consequently, through the use of simple "do it yourself" methods and
basic equations, students can debate complex motions, and have a wider and
potentially effective understanding of physics.
