Why is the anti-neutrino going against time?

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Discussion Overview

The discussion revolves around the concept of anti-neutrinos and their representation in terms of time direction, particularly focusing on why the arrow for the electron antineutrino is depicted as pointing downwards, which some participants interpret as against time. The scope includes theoretical considerations and mathematical implications related to particle physics.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant notes that the arrow for the electron antineutrino points down, suggesting it is against time, and questions the reason for this representation.
  • Another participant explains that treating an anti-particle as a regular particle moving backwards in time can yield correct mathematical results, but emphasizes that this does not imply that anti-particles are literally moving back in time.
  • A third participant asserts that the downward arrow is purely a convention, prompting further inquiry into the mathematical basis for this representation.
  • Further discussion raises questions about which equations allow for the downward arrow and whether all anti-particles are conventionally represented this way.
  • One participant suggests that the downward arrow is a logical consequence of the mathematics involved, but acknowledges that this can lead to confusion regarding the interpretation of particles and anti-particles.
  • Another participant firmly states that nothing is actually moving backwards in time, reiterating that the arrows are merely a mathematical convention.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of the downward arrow for anti-neutrinos, with some arguing it is a convention and others suggesting it has deeper implications. The discussion remains unresolved with multiple competing interpretations present.

Contextual Notes

Participants highlight the complexity of quantum field theory (QFT) and the potential for misunderstandings when interpreting Feynman diagrams and the mathematical conventions used in particle physics.

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The arrow for the electron antineutrino is pointing down which is against time, why is that?
 
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The math gives us the right answers in some problems (and this is one of them) if we treat an anti-particle as a regular particle moving backwards in time. That doesn't mean that an anti-particle is "really" a regular particle moving back in time.

Be aware that Feynman diagrams such as this one are easily misunderstood - they are not picctures of what the particles are really doing, they're a way of organizing the calculations to find the probability of various interactions.
 
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Paul Dirac said:
The arrow for the electron antineutrino is pointing down which is against time, why is that?
Purely a convention.
 
so why does the math permit the arrow pointing downwards? which equation implies that? so do all anti-particles by convention point downwards? Thanks!
 
Paul Dirac said:
so why does the math permit the arrow pointing downwards?

Its simply a logical consequence of the math. Logical consequences may have a deeper meaning, or not. Experience in this case has shown its helps sometimes, but can lead to issues if pushed too far. For example one can view an electron as a positron going backwards in time. So which is it? Is it the electron going backwards in time or is it the positron? The theory is silent about that.

Before asking questions like that you need to understand the underlying theory, including the math. And the math of QFT is no walk in the park by a long shot.

Thanks
Bill
 
Nothing is going backwards in time. The arrows are a convention for writing down the mathematics. Nothing more, nothing less.
 

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