Title: "Motion and Relativity"

In this talk I present an outline of the problem of motion in General Relativity. After a moderate survey on the existing literature I focus on the motion of a test particle and discuss one of the established approximation schemes in more detail. A (very) short outlook on alternative gravity theories and the cosmological model building process will be provided.
"Die Tatsache, dass die Materie unter dem Einfluss eines aeusseren Feldes Kraeften unterworfen ist, erscheint dem experimentierenden Physiker als etwas ausserordentlich Natuerliches und Selbstverstaendliches, - fuer den Theoretiker bildet sie eine harte Nuss." C. Lanczos, Physikal. Zeit. 28 (1927) 723
"The fact that matter is subject to forces under the influence of an external field appears to be natural and self-evident for an experimental physicist, but is a hard nut for the theoretician to crack."