Space and time play a special role in all physical theories, because they are implicitly assumed in all physical theories. Physical theories can only be applied in practice if we know what 'here' and 'now' mean.

We want to leave behind the container theory of space and time on which physical theories have been based up to now. To do this, we need to unveil two great mysteries: What characterizes the present as “now”? And what drives the flow of time? In order to get closer to an answer to these questions, we want to conduct a thought experiment.

What is "time"? This question not only moved the church father Augustine, but is still a fundamental question for our understanding of the world today.

The modern mathematical description of physics focuses on symmetries. Physical theories are considered beautiful because of their symmetries. What are these symmetries and where do they come from?

Classical mechanics is based on the everyday understanding of space and time that everyone can observe. According to it, space and time form the stage of world events, where space is three-dimensional, homogeneous, and isotropic in all directions. Time is one-dimensional and progresses uniformly.

In the common narrative of the history of science, one finds the story that classical mechanics was replaced by Einstein's theory of relativity and is contained in the theory of relativity as a special case for small velocities. On closer inspection, however, this narrative is not quite right.

Die relativistische Mechanik lässt sich mittels eines vierdimensionalen Energie-Vektors reformulieren, sodass analog zur klassischen Mechanik sowohl gleichförmige als auch beschleunigte Bewegungen mit dem gleichen mathematischen Formalismus beschrieben werden können.

Theoretical physicists use Hamilton's principle, according to which the effect always takes an extreme value, to derive the laws of motion. Richard Feynman applied this principle to quantum field theories using the path integral method, according to which a particle takes all possible paths, with each path weighted by its effect and integrated over all paths. But how can this fundamental role of the physical quantity “effect” be explained?

The aim is to test whether the cosmological redshift is due to the relative movement of the light source, distance or to the age of the light. If it were an age-dependent effect, the cosmological assumption of an expanding universe would have to be reconsidered.