“…For Euclidean relational particle mechanics, these are P = N I=1 p I = 0 (zero total momentum for the model universe) and L = N I=1 q I × p I = 0 (zero total momentum for the model universe), while similarity relational particle mechanics has these again alongside D = N I=1 q I · p I = 0. By analogy with Example 3 below, relational particle mechanics are additionally useful models [31,32,33,34,27,17,18,35,36,37,38,28,24] for the Problem of Time in Quantum Gravity [32,39] and other issues of interest in Quantum Cosmology [40,41,42]. Example 2B) Relational particle mechanics can be cast in reduced form in spatial dimension 1 or 2.…”