Theoretical Physics of Time
A rigorous and progressive itinerary from high school to the open questions of the doctorate. Learn to calculate, question, and distinguish confirmed physics from speculation.
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Movement, slopes and possible worlds
Read a position-time graph as a physical history and not as a trajectory drawing.
When finished you will be able
- Interpret slopes as speeds
- Distinguish temporal graph and spatial trajectory
- Detect impossible or discontinuous movements
6 min main tour
This time covers essential reading and self-assessment. Derivations, exercises and research tasks are optional extensions and are not included in the estimate.
- Guided reading3 min
- essential example1 min
- Self-assessment2 min
The graph is not the way
In a position–time diagram, the horizontal axis represents the clock reading. An inclined line does not mean that the object ascends a ramp: it means that it changes position at a constant rate. The slope contains the velocity and the curvature reveals acceleration.
Limits of a classical description
Newtonian mechanics allows us to idealize instantaneous changes, but no material object can jump from one position to another without covering the interval. Relativity will add a deeper limit: no local signal carries information above c.
Models and data
A model can interpolate measurements without being a complete photograph of reality. Always ask what was measured, from what reference system and what uncertainty the points have.
Average speed
The slope between two points summarizes the displacement per unit of time.
A probe goes from x=20 km to x=140 km between t=10 s and t=70 s: vm=2 km/s.
You try
Draw a story with 4 minutes at rest, 3 minutes moving away at a constant speed, and 2 minutes returning faster. Identify slope changes.
See guidance and solution
First horizontal section; second straight section with positive slope; third section with negative slope and higher module. The final position depends on the temporal area of each speed.
In a position-time graph, a horizontal section indicates…
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