Redshift effect And photon energy loss

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Discussion Overview

The discussion centers on the phenomenon of redshift in photons as they travel from stars and other light sources. Participants explore the concepts of energy loss in relation to redshift, questioning how and if photons lose energy during this process, and the implications of different observers measuring varying energies.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant expresses confusion regarding the energy loss of photons during redshift and seeks clarification on how this occurs and where the energy goes.
  • Another participant asserts that photons do not lose energy; rather, different observers measure different energies, referencing a link for further information.
  • A later reply highlights the distinction between redshift due to speed and gravitational redshift, noting historical perspectives from Einstein on energy transfer and frequency changes in radiation.
  • The same reply mentions Einstein's prediction of gravitational redshift, suggesting that light emitted from massive stars appears at lower frequencies, which could imply a form of energy consideration without actual loss during travel through vacuum.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether photons lose energy during redshift. There are competing views regarding the interpretation of energy loss, with some asserting that it is a matter of measurement rather than actual energy loss.

Contextual Notes

The discussion includes references to historical interpretations and varying perspectives on redshift, particularly regarding the effects of speed and gravity. There are unresolved aspects concerning the definitions and implications of energy loss in the context of redshift.

ujellytek
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I've been searching around the web to figure out why photons shift towards the longer wavelengths as they travel from stars and other light sources but I haven't figured out why they loose energy as they travel ( and after reading some web pages I was told that they don't even loose the energy as they travel) so essentially I'm all confused on this topic. Here are my questions. How do photons loose the energy in the red shift effect? Where does that energy lost go?
 
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ujellytek said:
I've been searching around the web to figure out why photons shift towards the longer wavelengths as they travel from stars and other light sources but I haven't figured out why they loose energy as they travel ( and after reading some web pages I was told that they don't even loose the energy as they travel) so essentially I'm all confused on this topic. Here are my questions. How do photons loose the energy in the red shift effect? Where does that energy lost go?
It's not clear if you talk about redshift due to speed or due to gravitation; you already got an answer about the effect of speed, and the discussion in the link is a good primer for the effect of gravitation.

Concerning gravitation there is some disagreement, in part perhaps due to Einstein who in 1911 suggested that radiation can loose energy in transfer, but in that same paper clarified that radiation cannot change frequency on its travel through vacuum - and without a change in frequency there is also no "lost energy". That second consideration fits neatly with the reference about speed that Bill gave and leads to consistent descriptions.
For example Einstein predicted the gravitational redshift effect of light from stars because it is emitted at lower frequencies:

"Thus the clock goes more slowly if set up in the neighbourhood of ponderable masses. From this it follows that the spectral lines of light reaching us from the surface of large stars must appear displaced towards the red end of the spectrum."
- p.198, Foundation of General Relativity, 1916. http://web.archive.org/web/20060829045130/http://www.Alberteinstein.info/gallery/gtext3.html
 
Last edited:
Alright thanks guys. You guys have given me enough info , thanks.
 

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