Lifespan of a Photon: Debunking the Myth of Time Travel

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SUMMARY

The discussion clarifies that photons move along null worldlines in spacetime, which is a fundamental concept in General Relativity and Quantum Electrodynamics (QED). Contrary to popular misconceptions, photons do not have a defined trajectory as classical particles do, and their long lifespan is not due to their movement through space rather than time. Instead, the stability of photons is attributed to the absence of decay pathways that conserve fundamental physical laws. The standard model of particle physics asserts that photons are massless and do not decay, although theoretical calculations suggest a potential but extremely long lifespan under specific conditions.

PREREQUISITES
  • Understanding of General Relativity and its concepts of spacetime and null worldlines.
  • Familiarity with Quantum Electrodynamics (QED) and the nature of photons.
  • Knowledge of classical electrodynamics and electromagnetic waves.
  • Basic grasp of the standard model of particle physics and conservation laws.
NEXT STEPS
  • Study General Relativity and the concept of null worldlines in detail.
  • Explore Quantum Electrodynamics (QED) and its implications for particle behavior.
  • Read about classical electrodynamics and the properties of electromagnetic waves.
  • Investigate the standard model of particle physics, focusing on massless particles and decay processes.
USEFUL FOR

Students and professionals in physics, particularly those interested in quantum mechanics, general relativity, and the fundamental nature of light and particles. This discussion is also beneficial for anyone seeking to deepen their understanding of the complexities surrounding photons and their behavior in the universe.

  • #31
rolnor said:
This is bullying, not nessecary and not science
No, no, it's not meant as bullying at all. Over the years at PF we have come to understand how important it is to tune the level of responses to the level of understanding of the OP asking the question. That is why in many of our technical PF forums we use the prefix system on the thread title, to better help responders know how to respond to the OP's question.
 
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  • #32
rolnor said:
This is bullying, not nessecary and not science
OK, so what level do you want an answer? Graduate level texts have been suggested. Is this an adequate answer? If not, what do you want instead?

Lack of mental telepathy is not the same as bullying.
 
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  • #33
I am grateful for all answers that help me understand this matter. One comment seemed unecessary. Maybe I missinterpreted the intention.
 
  • #34
vanhees71 said:
It's not ignorance! It's just that relativistic QFT is a quite difficult subject, and it's impossible to understand it without the adequate math. In addition it's also not fully established from a strict mathematical point of view. It needs time to learn all this. For me the most concise introductory treatment is given in

S. Coleman, Lectures of Sidney Coleman on Quantum Field
Theory, World Scientific Publishing Co. Pte. Ltd., Hackensack
(2018), https://doi.org/10.1142/9371

Large parts of this book is also freely available from the arXiv:

https://arxiv.org/abs/1110.5013

More details, particularly the emphasis of the importance of the microcausality constraints can be found in the 3-volume textbook series by Weinberg, Quantum Theory of Fields.

Complementary to that is

A. Duncan, The conceptual framework of quantum field
theory, Oxford University Press, Oxford (2012).
Thanx a lot now I have some reading to do.
 
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