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In relativistic doppler shift, the energy of the photon is increasing och decreasing, due to realative motion of observer vs emitter. Let say that the photon is redshiftet, does any energy dissapear? 
Doppler and enegry conservation
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SUMMARY
The discussion centers on the relativistic Doppler effect and its implications for photon energy conservation. Participants clarify that while the frequency of a photon decreases and its wavelength increases during redshift, the energy of the photon remains constant from both the emitter's and observer's perspectives. The conversation emphasizes that energy is not lost but rather perceived differently depending on the relative motion between the observer and the emitter. The concept of energy being invariant is debated, highlighting the distinction between energy measured in different reference frames.
PREREQUISITES- Understanding of relativistic physics principles
- Familiarity with the Doppler effect in light
- Knowledge of photon properties, including energy, frequency, and wavelength
- Basic grasp of reference frames in physics
- Study the relativistic Doppler effect in detail
- Explore the concept of invariant quantities in physics
- Learn about energy conservation in different inertial frames
- Investigate the relationship between frequency, wavelength, and energy in photons
Physicists, students of relativity, and anyone interested in the nuances of energy conservation in relativistic contexts.
- #2
Danger
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The energy isn't lost. While the frequency decreases, the wavelength increases. Each individual photon retains its initial energy; it just takes a 'longer path' to get here. That's a pretty lousy response. Best wait for ST or other to clear it up.
- #3
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Is this what you mean?
When the photon is emitted, its wavelength is less than the wavelength as the observer see it. The energy must have dissapeared, science the wave length is increasing. There must be a relativistic answer to this. Of course the frequency is increasing if wavelength is decreasing.. But that is not the anszer to my question i think. You must compare the initial wave length and the final wavelength.
So i guess that the answer lies in the relativisic area. According to the emitter the photon energy is constant, and according to the observer the photon energy is constant, science we can't follow a photons path. If I would make a guess. But energy is an invariant of motion.. ? That is why Iam asking.
When the photon is emitted, its wavelength is less than the wavelength as the observer see it. The energy must have dissapeared, science the wave length is increasing. There must be a relativistic answer to this. Of course the frequency is increasing if wavelength is decreasing.. But that is not the anszer to my question i think. You must compare the initial wave length and the final wavelength.
So i guess that the answer lies in the relativisic area. According to the emitter the photon energy is constant, and according to the observer the photon energy is constant, science we can't follow a photons path. If I would make a guess. But energy is an invariant of motion.. ? That is why Iam asking.
- #4
HungryChemist
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malawi_glenn said:In relativistic doppler shift, the energy of the photon is increasing och decreasing, due to realative motion of observer vs emitter. Let say that the photon is redshiftet, does any energy dissapear?
There will be difference in energy measured by emitter and receiver and that is fine. But the "change in energy" is not observed respect to emitter(and receiver). Difference in energy measured b/t two reference frame is not the same thing as the change in energy observed by one frame.
malawi_glenn said:
What makes you think Energy is invariant of motion? For one, kinetic energy is obviously a relative quantity respect to different reference frame.
- #5
Mentz114
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Energy is an invariant of force-free motion, but that energy will be measured differently from different inertial frames.
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