ABSTRACT
The Newtonian, classical mass of a particle system suggests the introduction of barycentric coordinates into Euclidean geometry. In full analogy, the Einsteinian, relativistic mass of a particle system suggests the introduction of barycentric coordinates into hyperbolic geometry, where they are called gyrobarycentric coordinates. The relativistic mass, which is velocity dependent [135], thus meets hyperbolic geometry in the context of gyrobarycentric coordinates, just as the classical mass meets Euclidean geometry in the context of barycentric coordinates.
