fundamental physics in space
Physical theories are structured in a hierarchical fashion. A theory is regarded as fundamental if it formulates basic principles of almost universal applicability, the explanatory power of which covers significant classes of physical phenomena. Examples are Quantum Theory, Special Relativity, and General Relativity. Each of these theories introduces one parameter: Planck's constant, the velocity of light, and the gravitational constant respectively. These are believed to be fundamental constants of Nature.
It is the aim of the Fundamental Physics in Space section to draw conclusions regarding these general principles from all sorts of earthbound as well as space experiments.
The main motivation for this emerges from the partial incompatibilities between various fundamental theories. There is certainly no real tension between Special and General Relativity, since the former can be seen as a special case of the latter in the limit of vanishing gravitational forces. Also, Special Relativity and Quantum Theory have been combined into what is known as Relativistic Quantum Field Theory, which underlies all of theoretical elementary particle physics. On the other hand, real problems arise between Quantum Theory and General Relativity, which seem to rest on mutually incompatible assumptions. It can fairly be said that the unification of these theories presents the single most outstanding challenge in fundamental physics today. Our aim at the Fundamental Physics in Space department is to seek guidance for further progress by incorporating results from earthbound and space experiments that make use of technologies with highest state-of-the-art accuracy.
One of our main interests concerns tests of the universality of free fall, the so called "Weak Equivalence Principle", or short "WEP". This principle lies at the heart of General Relativity since it allows to interpret the inertial and gravitational forces entirely in terms of the geometry of space and time. In particular, we analyse satellite missions where anomalies already were or could be detected in the future, which may be related to unknown gravitational effects. In that context, various consequences of the basic equations of General Relativity concerning the precise nature of gravitational fields and motions in them are worked out. We also consider theories describing small violations of Special and General Relativity. In the quantum optics research area macroscopic quantum objects are studied in free fall, which will be used in future to realize atom interferometry and a further test of the WEP. More theoretical studies concern the influence of gravitational fields on the motion of matter waves. All this results in many experimental activities, either by performing experiments under the condition of weightlessness in the drop tower or in satellites, or by investigations of satellite dynamics.
