The photon does have a lifespan?

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SUMMARY

The discussion confirms that photons do not have a limited lifespan, as evidenced by the oldest photons measured from the edge of the observable universe, which have traveled for billions of years and remain identical to newly generated photons. Photons are considered "dead" only when they are absorbed by an electron or positron, leading to their temporary cessation until re-emission occurs. The concept of redshift is introduced, suggesting that a photon may be deemed "dead" if its wavelength exceeds the radius of the observable universe, although this scenario has not yet occurred. Overall, the evidence supports the idea that photons can exist indefinitely in the universe.

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  • Understanding of photon behavior in quantum physics
  • Familiarity with the concept of redshift in cosmology
  • Knowledge of the observable universe's structure and limits
  • Basic principles of energy absorption and emission in atomic interactions
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artevolved
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it is born.
 
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artevolved said:
it is born.

It 'lives' until it runs into an electron or a positron, then it 'dies', to be 'reborn' again when the electron (or positron) falls back to a lower energy level and 'gives birth' to the photon.
 
The "oldest" photons we measure have come to us from the most distant edge of the "observable universe". They have traveled for billions of years. (google "observable universe") So far as we can tell those photons are identical to newly generated photons. So, the observational evidence is that there seems to be no limited lifespan of a photon.
 
Bobbywhy said:
The "oldest" photons we measure have come to us from the most distant edge of the "observable universe". They have traveled for billions of years. (google "observable universe") So far as we can tell those photons are identical to newly generated photons. So, the observational evidence is that there seems to be no limited lifespan of a photon.

I'd think a photon could be considered "dead" when it has red shifted to the point that its wavelength is greater then the radius of the observable universe. At that point we could never receive the entire wave. Granted that the universe is not old enough for that to have happened yet.
 
'As far as the photon is concerned', no time has elapsed, despite the fact that we see it as having traveled for billions of years.
 
Absorption of a photon is a question of energy, not wavelength. The two are related, of course, but I don't see how the size of the universe matters
 

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