Do atmospheric muons accelerate?

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Discussion Overview

This discussion revolves around the behavior of atmospheric muons, specifically whether they experience acceleration after their creation. Participants explore concepts related to relativistic frames of reference, the nature of muon creation, and the implications of proper acceleration versus relative motion.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants assert that muons do not accelerate from point A to B, as they maintain a constant velocity relative to the Earth's surface and atmosphere throughout their lifetime.
  • Others challenge this view by questioning the implications of "practical" velocity and proper acceleration, suggesting that the muon's rest frame indicates zero displacement, which may imply a lack of acceleration.
  • A participant argues that the muon can be considered to have been created with an initial velocity, which raises questions about the nature of its motion and whether it can be considered massless.
  • There is a discussion about the effects of electromagnetic fields and gravitational forces on the muon's acceleration, with some suggesting that these effects are negligible.
  • One participant proposes a thought experiment involving the creation of a particle at rest relative to an observer, questioning how motion would be described in different frames of reference.
  • Another participant points out that muons are typically created from the decay of pions, which carry momentum, thus affecting the muon's initial state of motion.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether muons accelerate after their creation. There are multiple competing views regarding the implications of their motion and the relevance of different frames of reference.

Contextual Notes

Participants express uncertainty about the definitions of "practical" and "essentially" in the context of muon acceleration, and the discussion includes unresolved questions about the nature of particle creation and motion in different frames.

  • #31
Joffan said:
Cosmic ray muons lose about a third of their energy due to the atmosphere - not exactly insignificant.

Wow, uh yea, the inquiry is more specific than you presume.
 
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  • #32
Joffan said:
Cosmic ray muons lose about a third of their energy due to the atmosphere - not exactly insignificant.

Although in terms of speed, that's the difference between ##.9797c## and ##.9747c##, so assuming constant speed through the atmosphere is still a pretty good approximation.
 
  • #33
Nugatory said:
Although in terms of speed, that's the difference between ##.9797c## and ##.9747c##, so assuming constant speed through the atmosphere is still a pretty good approximation.

Wow does that ever highlight the kinematics with respect to energy required to go just a little bit faster at near c velocities, or in this case the reverse.
 
  • #34
Nugatory said:
Although in terms of speed, that's the difference between ##.9797c## and ##.9747c##, so assuming constant speed through the atmosphere is still a pretty good approximation.
Interesting...
... from the Earth's viewpoint, yes... but from the muon's initial frame I would think things look very different. They still experience a massive acceleration from the opposing/onrushing atmosphere. :)
 
  • #35
Joffan said:
from the muon's initial frame I would think things look very different. They still experience a massive acceleration from the opposing/onrushing atmosphere.

They experience proper acceleration (I haven't calculated its magnitude so I don't know if it is aptly described as "massive"), but that only results in a negligible change in the velocity of the Earth in this frame (which will have the same magnitude, but opposite direction, as the the velocity of the muon in the Earth's frame). So it depends on what kind of acceleration you're talking about, proper acceleration (may be significant) or coordinate acceleration (not significant). For purposes of using an inertial frame to model what's going on, the important quantity is coordinate acceleration, which is negligible. For other purposes, proper acceleration might be more important.
 

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