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mysearch

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## Main Question or Discussion Point

Based on the quote below and the link to Wikipedia, I believe the implication is that gravitational redshift will occur when a photon climbs out of the gravity well, while blueshift will occur when falling into the gravity well. However, I am trying to clarify whether both time dilation and space expansion have to be taken into consideration when an observer measures the frequency or wavelength of a photon at different positions in the gravity well.

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Not sure as to what is `

If the observer is collocated with the photon source within a gravity well, does local time define the frequency and therefore the energy E=hf?

To a distant observer, far from the gravity well, time ticks faster, so would the photon, when arriving, appear to have a lower frequency and energy?

However, along the way, space would have contracted as space is said to expand in the direction of increasing gravity. Therefore, would this effect cause the wavelength to shorten?

If [tex]c=f\lambda[/tex] and [c] is constant, would the shorten wavelength not cause frequency to increase and cancel the effect of time dilation?

Clearly theory suggests that this is not the case, but then implies there is a different perception of the energy associated with the photon. Therefore, would welcome any clarification of these issues.

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Gravitational Redshift:

When a photon is emitted by a given process, for example a transition of an electron from one specific energy level to another specific level in a specific element the photon is emitted at an intrinsic frequency irrespective of where the element is located in the gravity well. Say the photon is moving upwards, then measurements made further up, by clocks with faster coordinate time make it appear as if the frequency of the photon is getting slower but the coordinate frequency (and energy) remains constant and it is the wavelength (and coordinate speed of light) that is increasing. You could view the increasing wavelength as a gravitational length contraction effect. Local observers progressively further up the gravity well see the frequency as slowing down and so to them the photon appears to be losing energy and the wavelength increasing which is consistent with the local speed of light being constant for any observer. Depends on your point of view.

Not sure as to what is `

*intrinsic`*to frequency as I would have thought frequency is subjective to an observer?

If the observer is collocated with the photon source within a gravity well, does local time define the frequency and therefore the energy E=hf?

To a distant observer, far from the gravity well, time ticks faster, so would the photon, when arriving, appear to have a lower frequency and energy?

However, along the way, space would have contracted as space is said to expand in the direction of increasing gravity. Therefore, would this effect cause the wavelength to shorten?

If [tex]c=f\lambda[/tex] and [c] is constant, would the shorten wavelength not cause frequency to increase and cancel the effect of time dilation?

Clearly theory suggests that this is not the case, but then implies there is a different perception of the energy associated with the photon. Therefore, would welcome any clarification of these issues.

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