Computer-Modeling of Stars

A human being experiences his immediate environment on the scale of meters, seconds and grams. These are also the natural scales of his actions. Thus, as soon as he starts to explore the laws of physics, he can easily move around masses at the scale of grams, objects on the scale of meters and perform experiments on the scale of seconds. On these scales, the experimentator has full control on the setup of an experiment and direct access to all degrees of freedom during the evolution of the experiment. This direct access is lost in experiments that explore the physics on scales that are many orders of magnitude smaller. The experimentator still has full control on the setup, for example, by putting a specific target into a properly designed accelerator beam. But the measurements are then limited to the far field, where only a superposition of the effects of the microscopic physics becomes detectable. The large number of degrees of freedom that may be present in the microscopic physics must be explored by clever variations of the experimental setup. Most astronomical observations are obviously also taken from the far field, because the distance to the observed source is so much larger than the length scale of the source. Hence, many degrees of freedom of the dynamics on the length scale of the source are only indirectly accessible for the observer. Moreover, it is not possible to efficiently manipulate and prepare matter outside the solar system in order to produce systematic variations in the setup as in terrestrial experiments.