One of the main objectives of research in physics is to find simple laws that
give rise to a deeper understanding and unification of diverse phenomena. A
less ambitious goal is to construct models which, in a more or less restricted
range, permit an understanding of the physical processes involved and lead
to a systematic analysis of the available experimental data while providing
insights into the complex systems being studied. A necessary condition to
reach these goals is the development of experimental instruments and methods
that give access to the relevant information needed to test these models
and guide the introduction of new concepts