Discussion Overview
The discussion centers around the concept of the relativistic definition of action, particularly in relation to a beam of light. Participants explore the implications of this definition and its relationship to the Lagrangian density derived from Maxwell's equations, questioning the significance of the numeric value of action in this context.
Discussion Character
- Debate/contested
- Technical explanation
- Conceptual clarification
Main Points Raised
- One participant questions whether the action for a beam of light is always zero under the relativistic definition of action.
- Another participant challenges the clarity of the term "RELATIVISTIC definition of Action" and suggests looking into textbooks for further understanding.
- A different participant raises a philosophical point about the numeric value of action and its meaning.
- One participant states that the Lagrangian density for the electromagnetic (EM) field can be derived from Maxwell's equations and notes that for an EM plane wave, the Lagrangian density could be zero.
- A follow-up question is posed regarding the impact of adding a constant to the Lagrangian on the equations of motion, implying that it may not matter.
- Another participant clarifies that Maxwell's equations can be viewed as the Euler-Lagrange equations for the EM field Lagrangian and emphasizes the Lorentz invariance of these equations.
Areas of Agreement / Disagreement
Participants express differing views on the significance of the action's numeric value and whether it holds any meaning, indicating that multiple competing perspectives remain without consensus.
Contextual Notes
There are unresolved questions regarding the assumptions behind the relativistic definition of action and the implications of the Lagrangian density being zero for an EM plane wave.