Geometric Description of Relativistic Interactions
There is a fundamental difference concerning the concept of particle in Newtonian and in relativistic Physics. In Newtonian Physics a particle is a ‘thing’ which has been created once and since then exists as an absolute unit for ever. Concerning the physical quantities associated with a particle they are divided in two classes. The ones which are inherent in the structure of the particle such as mass, charge etc. and characterize the identity of the Newtonian particle and those which depend on the motion of the particle in a reference system such as velocity, linear momentum etc. Newtonian particles are assumed to interact by collisions creating larger systems. This interaction of particles happens in a way that the overall inherent quantities of the particles are conserved (i.e. mass, charge) while some of the motion dependent physical quantities such as energy, mass and linear momentum etc. are also conserved. Finally the systems consisting of many particles have additional physical quantities such as temperature, pressure etc.