Discussion Overview
The discussion centers around a question raised by Feynman regarding the apparent discrepancy between action and reaction in the context of charged particles moving at right angles, as illustrated in Figure 26-2 of his lectures. Participants explore the implications of this observation on momentum conservation within electromagnetic fields.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- One participant inquires about the current understanding of Feynman's statement that "action is not equal to reaction" in the context of charged particles moving orthogonally.
- Another participant references Section 27-6, explaining that the forces on two charged particles do not balance, leading to a change in net momentum, which is not conserved unless the momentum of the electromagnetic field is also considered.
- Some participants suggest that the situation may be analogous to the Feynman Disk, indicating a search for similar examples or analogies.
- One participant discusses the implications of the fourth Maxwell's equation, asserting that including the contribution of a changing electric field leads to a situation where action equals reaction when considering the system of charges and fields together.
- Another participant reiterates that the action will be equal to the reaction when the field momentum is included, emphasizing the need to consider the entire system rather than just the charges.
- A later reply acknowledges a previous error in explanation, indicating ongoing refinement of ideas within the discussion.
Areas of Agreement / Disagreement
Participants express differing views on the implications of Feynman's statement, with some agreeing that including field momentum resolves the issue of action and reaction, while others remain uncertain about the completeness of this explanation. The discussion does not reach a consensus.
Contextual Notes
Participants note the complexity of momentum conservation in electromagnetic fields and the necessity of considering both particle and field contributions, but do not resolve the underlying assumptions or implications of these points.