Particle radiation is subatomic particle accelerated to relativistic speeds by nuclear reactions. The Lagrangian formulation makes the relativistic invariance apparent. The composition of velocities is quite different in relativistic spacetime. Computer modeling is essential for quantum and relativistic physics. There are a number of equations describing relativistic particles&colon; see relativistic wave equations. Let one consider an electron in a hydrogen-like ion obeying the relativistic Dirac equation. It was the first foundation of "relativistic quantum mechanics". Postmodern philosophy shares ontological similarities with classical skeptical and relativistic belief systems. This means that phenomena such as time dilation due to relativistic effects are not simulated. Its predictions for aberration are identical to those of the relativistic theory. However, it is a simple consequence of relativistic kinematics. The second approach to the problem of accelerating relativistic particles is the isochronous cyclotron. The animations visualise the different treatments of time in the Newtonian and the relativistic descriptions. The light-second is a unit of length useful in astronomy, telecommunications and relativistic physics. This is experimentally established in many tests of relativistic energy and momentum.