Bonn 2020 – scientific programme

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GR: Fachverband Gravitation und Relativitätstheorie

GR 14: Didactical Aspects of Relativity

GR 14.2: Invited Talk

Thursday, April 2, 2020, 17:15–18:00, H-HS IV

How Long Is Now? On the problem of accurate time measurements — •Thomas Filk — Institute of Physics, University of Freiburg, 79104 Freiburg, Germany

The eigentime in relativity depends on the world line of an object. If an object is extended or consists of several subunits (composite systems or bound states), one has to define a reference point (e.g. the center of mass) in order to assign a definite eigentime to the object. However, the eigentimes of the constituents may differ from this reference time, making an unambiguous assignment of an eigentime to the object as a whole questionable. If the object is a clock, which part defines the reading?

Even worse is the situation, when one has to assign a precise eigentime to a quantum object. Quantum objects do not follow well defined trajectories and, therefore, the assignment of an accurate eigentime is problematic. In addition, further quantum effects - superposition states of systems which serve as clocks, or the entanglement of such systems - make these assignments even more difficult.

The presentation will address and discuss some of these issues and their consequences also in the context of teaching relativity.