Göttingen 2025 – wissenschaftliches Programm

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MP: Fachverband Theoretische und Mathematische Grundlagen der Physik

MP 12: Concepts of Physics

MP 12.2: Vortrag

Donnerstag, 3. April 2025, 16:35–16:55, ZHG002

What physically characterizes the present? — •Matthias Kölbel and Werner Ahrendt — welträtsel.org

Albert Einstein was convinced that time is what you measure by a clock. According to him, the concept of 'now' has no place in physics. In fact, the physical theories available to date do not provide a comprehensive explanation why time flows and what characterizes the present in the flow of time. The phenomenon of time continues to puzzle physicists and philosophers alike.

We try to solve part of this puzzle by finding out what could physically characterize the present. To do this, we conduct a thought experiment, a modified version of the well-known twin paradox. Our thought experiment suggests that the flow of time is associated with a relative change in the magnitude of the physical quantity known as action, which occurs in the same way for all physical objects.

This consideration has several interesting consequences: Firstly, it becomes understandable why all laws of motion in physics can be derived from the principle of least action. Secondly, it leads to the unexpected conclusion that the redshift of light from distant galaxies is not due to an expansion of space, as usually assumed, but is rather due to the age of the light.

To test our hypothesis and its consequences, we propose a key experiment.

Keywords: fundamental physics; flow of time; twin paradox; principle of least action; cosmological red shift