Writing seems an innocent gesture. In reality it hides a decisive choice: when does "" begin? We have fixed a zero instant, an origin of times, and a zero point, an origin of positions, and only with respect to them do we measure positions.
The same physical reality — a car travelling for seconds — can be written in a thousand different ways depending on where we have planted the two markers. If I shift the origin of positions, all the values of change; if I shift the origin of times, all the values of change. Yet the motion, the real one, is always the same: the car does not know where we have put the zero.
This simple fact already contains the seed of the principle of relativity: the laws of physics must have the same form whatever marker we have chosen, provided it is an inertial reference frame. The freedom to choose the origin is not a flaw in the description, but a clue to a deep symmetry of nature.
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Topics: Cinematica Concepts: Moto uniformemente accelerato
Related exercises: Il viaggio di Carlo · Distanza di arresto (reazione e frenata) · Dimostrazione dell’equazione senza tempo