# Thread: Gravitational redshift vice versa

1. ## Gravitational redshift vice versa

1) Gravitational redshift: difference in gravitational field where you are and where the source of radiation is located. Photons traveling out of the gravitation field loose energy by decrease of frequency to compensate for constant speed of light.

2) Newton's third law

3) An object in space emits light with constant changing frequency of that light towards another object with similar mass, would the change in frequency have an effect on the gravity field of the other object? Would the force created by photons be equal or would it be bigger, than if it was just constant light?

2. 3) An object in space emits light with constant changing frequency of that light towards another object with similar mass, would the change in frequency have an effect on the gravity field of the other object?
No.

You've been infected by Mazulu. Seek immediate help from your nearest competent physicist.

3. Originally Posted by AlexG
No.

You've been infected by Mazulu. Seek immediate help from your nearest competent physicist.
Alex a simple No is sufficient for me. I am asking a question, not stating anything.

I would also like others' opinions on this.

4. Individual photons redshift and blueshift because time is not absolute from place to place or from state of motion to state of motion. Photons move from place to place and from objects in one state of motion to another in perhaps an alternate state of motion, so act as a surrogate for comparing clocks in distant locations.

Nothing you do at a source can change the fate of photons already emitted, because nothing travels faster than light. Therefore a color-changing light source is in no way comparable to the red-shifting or blue-shifting of photons in flight and your analogy falls apart. The more you learn about general relativity, quantum field theory and quantum field theory in curved space time the more obvious the flaws in your physical reasoning become.

There is one particular advocate of this idea known to me, but that person has been out-of-touch with reality for as long as his writings have been known to me. Please don't emulate him.

5. Originally Posted by rpenner
Nothing you do at a source can change the fate of photons already emitted, because nothing travels faster than light. Therefore a color-changing light source is in no way comparable to the red-shifting or blue-shifting of photons in flight and your analogy falls apart.
Alright this explains to me why altering a frequency of emitted photon from source is not possible.

Are photons quantum entangled?

6. Like all objects, photons may or may not be quantum entangled.
To be quantum entangled, the requirement is that state of the objects is not a tensor product of the states of the individual objects.
Quantum physics only allows consistent world histories, but while this has been called "spooky action at a distance" that is human prejudice and intuition colliding with reality that doesn't respect crude human ideas. In quantum field theory, the simplest math that accurately describes the quantum physics of fast-moving particles like photons, even entangled photons do not propagate information or causes faster than the speed of light.
Specifically, there is no way to use quantum entanglement to change the wavelength or frequency of a photon in flight.

7. Originally Posted by rpenner
Individual photons redshift and blueshift because time is not absolute from place to place or from state of motion to state of motion. Photons move from place to place and from objects in one state of motion to another in perhaps an alternate state of motion, so act as a surrogate for comparing clocks in distant locations.

Nothing you do at a source can change the fate of photons already emitted, because nothing travels faster than light. Therefore a color-changing light source is in no way comparable to the red-shifting or blue-shifting of photons in flight and your analogy falls apart. The more you learn about general relativity, quantum field theory and quantum field theory in curved space time the more obvious the flaws in your physical reasoning become.

There is one particular advocate of this idea known to me, but that person has been out-of-touch with reality for as long as his writings have been known to me. Please don't emulate him.

My bolding/italics/underlining there. Can you tell us exactly what you mean by: "... red-shifting or blue-shifting of photons in flight ..."?

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8. Originally Posted by RealityCheck
My bolding/italics/underlining there. Can you tell us exactly what you mean by: "... red-shifting or blue-shifting of photons in flight ..."?

.
.
red-shift is for when object's wavelength increases as it moves away
blue-shift is for when object's wavelength decreases as it moves closer

9. Originally Posted by youreyes
Originally Posted by RealityCheck to rpenner
My bolding/italics/underlining there. Can you tell us exactly what you mean by: "... red-shifting or blue-shifting of photons in flight ..."?

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.

red-shift is for when object's wavelength increases as it moves away
blue-shift is for when object's wavelength decreases as it moves closer

Hi youreyes, pleased to meet you.

Thankyou for your post. Yes, objects in flight, as they emit/receive a photon, redshifts/blueshifts a photon AS it is emitted. That is 'doppler shifting' AND 'smearing' the wavelength/frequency in the case where a photon is in contact with the emiting/receiving object as the photon is being emitted/received. That wasn't what I was getting at when asking for rpenner's clarification of what he wrote there implying a photon itself is 'in flight' when blueshifting/redshifting of it occurs.

I read rpenner's statement to imply the case of a photon itself being still in transit (ie, still in free space not in contact with any object) when the 'in transit' photon itself is blueshifting/redshifting 'in free space'.

That would differ markedly from the usual photon wavelength/frequency doppler/smearing while being emitted/received by moving objects.

That's why I asked for rpenner's clarification as to what he meant.

Thanks again, youreyes.

RealityCheck.

PS: So, rpenner....

Did you mean to imply a case where some blueshifting/redshifting in a 'free flying photon' happens while it is still 'in transit' along the spacetime path between source/receiver?

Thanks, rpenner.

RC.

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10. Originally Posted by rpenner
Nothing you do at a source can change the fate of photons already emitted, because nothing travels faster than light. Therefore a color-changing light source is in no way comparable to the red-shifting or blue-shifting of photons in flight and your analogy falls apart.
Originally Posted by RealityCheck
Can you tell us exactly what you mean by: "... red-shifting or blue-shifting of photons in flight ..."?
As should be clear from context, I am distinguishing a source which emits light of varying frequencies as measured at the source and in the source's state of motion, from the behavior of a monochromatic source in special or general relativity where the frequency of the photons measured at the source and in the source's state of motion is distinct from the frequency of the photons measured at the receiver and in the receiver's state of motion.

For example, the CMB photons started with a thermal distribution corresponding to a temperate where hydrogen gas is ionized and today, billions of years later have a thermal distribution peaked in the microwave region. This GR effect was no where present at the source, and is effectively a change in the photon frequency "in flight."

For example, a radar gun held in the hand of a sedentary highway patrol officer sends out a pulse at frequency f to an oncoming speeding car. A dashboard-mounted radar receiver measures a frequency f' which is higher than that measured at the source. This SR effect is classically explained as a difference of motion between source and receiver but using the mechanism of GR one may construct a coordinate system where both the source and the receiver are in a state of rest and the photon's geodesic may be traced from place to place and in this case the frequency of the photon can be seen to change "in flight" -- as it is a function of place or equivalently, of affine parameter along a null geodesic.

Originally Posted by RealityCheck
Yes, objects in flight, as they emit/receive a photon, redshifts/blueshifts a photon AS it is emitted. That is 'doppler shifting' AND 'smearing' the wavelength/frequency in the case where a photon is in contact with the emiting/receiving object as the photon is being emitted/received. That wasn't what I was getting at when asking for rpenner's clarification of what he wrote there implying a photon itself is 'in flight' when blueshifting/redshifting of it occurs.
It is incorrect to attribute Doppler shifting to a phenomenon at the source or at the receiver, because such a view imbues the frequency of a photon as an absolute quantity (i.e. one independent of state of motion or position in space and time) which requires the notion of absolute time which both special and general relativity wholly reject.

Originally Posted by RealityCheck
I read rpenner's statement to imply the case of a photon itself being still in transit (ie, still in free space not in contact with any object) when the 'in transit' photon itself is blueshifting/redshifting 'in free space'.

That would differ markedly from the usual photon wavelength/frequency doppler/smearing while being emitted/received by moving objects.
Citation required that your viewpoint is "the usual" viewpoint. From the SR formulas, only relative motion between microscopic source and receivers enters into the calculation and nowhere is there an intermediate absolute frequency.

Originally Posted by RealityCheck
That's why I asked for rpenner's clarification as to what he meant.
Your smiley face may be interpreted as a mark that the former sentence is not to be read literally. I suspect your actual motivation is more closely related to your loss of posting privileges on physforum.com and your inability to rise above a pop-physics understanding of reality. If you are asserting that your knowledge of this physical subject is better than mine, then you should propose a formal debate in the appropriate sub-forum.

Originally Posted by RealityCheck
Did you mean to imply a case where some blueshifting/redshifting in a 'free flying photon' happens while it is still 'in transit' along the spacetime path between source/receiver?
I believe that is exactly the GR picture in coordinate systems where source and receivers are "places" of constant spacial coordinates. Not only does the frequency change happen in transit but it happens smoothly in transit and one may interrupt the transition at any point by inserting a second receiver in a "place" intermediate between source and receiver. In the SR picture this corresponds to inserting a second receiver, intermediate both in position and in state of motion, between the original source and receiver.

11. Originally Posted by rpenner
For example, the CMB photons started with a thermal distribution corresponding to a temperate where hydrogen gas is ionized and today, billions of years later have a thermal distribution peaked in the microwave region. This GR effect was no where present at the source, and is effectively a change in the photon frequency "in flight."
How does this explain the uniform distribution?

As mass emerged, then gravity emerged. Then, photons would alter their original frequency based on gravity.

This would indicate gravity was universally emergent in all places of the universe simultaneously.

Do you have another explanation based on GR?

12. Originally Posted by chinglu
How does this explain the uniform distribution?

As mass emerged, then gravity emerged. Then, photons would alter their original frequency based on gravity.

This would indicate gravity was universally emergent in all places of the universe simultaneously.

Do you have another explanation based on GR?
The above misstates Big Bang chronology by, I believe, on the order of 300,000 years and misstates all GUT and Big Bang cosmologies in that gravity was present at all times since at least the Planck epoch. In addition, it badly misconstrues GR as a theory that only couples curvature to mass density when pressure, energy and momentum are all relevant.

13. Double post removed by RealityCheck

14. Originally Posted by rpenner
The above misstates Big Bang chronology by, I believe, on the order of 300,000 years and misstates all GUT and Big Bang cosmologies in that gravity was present at all times since at least the Planck epoch. In addition, it badly misconstrues GR as a theory that only couples curvature to mass density when pressure, energy and momentum are all relevant.
Silly me.

Exactly how does this explain the uniform distribution of CMB under GR?

Are you claiming at the instant of the big bang that gravity was uniformly distributed?

Or, take any time period.

Are you making that claim?

15. Originally Posted by rpenner
Your smiley face may be interpreted as a mark that the former sentence is not to be read literally. I suspect your actual motivation is more closely related to your loss of posting privileges on physforum.com and your inability to rise above a pop-physics understanding of reality. If you are asserting that your knowledge of this physical subject is better than mine, then you should propose a formal debate in the appropriate sub-forum.

You sound paranoid. It was just a smiley to indicate goodwill to "youreyes" (whom I was addressing there). Please try to keep your 'personal baggage' out of this. Thanks.

Originally Posted by rpenner
As should be clear from context, I am distinguishing a source which emits light of varying frequencies as measured at the source and in the source's state of motion, from the behavior of a monochromatic source in special or general relativity where the frequency of the photons measured at the source and in the source's state of motion is distinct from the frequency of the photons measured at the receiver and in the receiver's state of motion.

The former case is self-referential 'at source'. While the latter case is 'remote-referential' between separated source and receiver. Already understood. Thanks.

Originally Posted by rpenner
For example, the CMB photons started with a thermal distribution corresponding to a temperate where hydrogen gas is ionized and today, billions of years later have a thermal distribution peaked in the microwave region. This GR effect was no where present at the source, and is effectively a change in the photon frequency "in flight."

Do you mean to say 'in flight' INTERACTIONS with other 'objects/features' during the space transit in NOT EMPTY space path? If so, then that is already known to occur, and merely involves changes due to repeated absorption and re-emissions en-route.

However, if you mean change in frequency in empty space per se due solely to spacetime transit per se unaffected by absorption/reemission en route, then would you please clarify further the actual physical mechanism/process which affects the photon frequency 'en route' all the way along the free space transit path? Thanks.

Originally Posted by rpenner
For example, a radar gun held in the hand of a sedentary highway patrol officer sends out a pulse at frequency f to an oncoming speeding car. A dashboard-mounted radar receiver measures a frequency f' which is higher than that measured at the source. This SR effect is classically explained as a difference of motion between source and receiver but using the mechanism of GR one may construct a coordinate system where both the source and the receiver are in a state of rest and the photon's geodesic may be traced from place to place and in this case the frequency of the photon can be seen to change "in flight" -- as it is a function of place or equivalently, of affine parameter along a null geodesic.

The SR construct is well observed. For example, in the Pound-Rebka experimental setup, the effect of 'dopplering' and 'smearing' due to emitter/receiver RECOIL motions during emission/receiving process itself, is 'compensated for' by giving a sharp movement to the receiver/emitter to remove the 'smearing effect' on the otherwise 'sharp' gamma ray waveform. That removes any effect due to both the 'doppler' and the 'smearing' effect during actual emission/reception, by effectively controlling for relative movement between the photonic waveform and the receiver during actual absorption process.

The GR construct is essentially an 'abstraction' which 'assumes' that the photon changed, as it were, 'in midstream' between source and detector. Please provide references where the photon is actually demonstrated to change WHILE in transit along the free-space path between 'abstractly relatively stationary' source and receiver. Thanks.

Originally Posted by rpenner
It is incorrect to attribute Doppler shifting to a phenomenon at the source or at the receiver, because such a view imbues the frequency of a photon as an absolute quantity (i.e. one independent of state of motion or position in space and time) which requires the notion of absolute time which both special and general relativity wholly reject.

Citation required that your viewpoint is "the usual" viewpoint. From the SR formulas, only relative motion between microscopic source and receivers enters into the calculation and nowhere is there an intermediate absolute frequency.

Not at all. I never claimed or implied anything, I only asked for clarification. As for the 'usual' observation, it is there in the Pound-Rebka experiment for all to look up for themselves. The photon has a frequency (as smeared/dopplered by the 'recoil' motion on the emitter/receiver. That's it. I implied or claimed nothing but that usual observation in fact. So there is nothing else to reply there.

Originally Posted by rpenner
I believe that is exactly the GR picture in coordinate systems where source and receivers are "places" of constant spacial coordinates. Not only does the frequency change happen in transit but it happens smoothly in transit and one may interrupt the transition at any point by inserting a second receiver in a "place" intermediate between source and receiver. In the SR picture this corresponds to inserting a second receiver, intermediate both in position and in state of motion, between the original source and receiver.

"I believe"? You are not sure?

Anyhow, trivial in both cases. Photon travel between ANY emitter/receiver combination will suffice. Any 'intermediate receiver' will merely change the position/state of the receiver compared to any other receiver further along the projected path. It still does not demonstrate that the photon actually changed in flight per se, but that the 'receptor' position/state is changed if one uses another 'intermediate' receptor instead of the original intended receptor in ITS position/state. None of that actually demonstrates that the change happens 'in-flight'; only upon reception and its inherent position/state compared to any other potential receptor, and their overall respective positions/states relative to the initial source's position/state. So was there anything you wished to illustrate by that 'exercise'?

Thanks for your post in reply. I look forward to your further post. I will be back tomorrow if I can.

In closing, the following is just a 'smiley', nothing more sinister than that. OK? Cheers!

RealityCheck.

16. Originally Posted by RealityCheck
The GR construct is essentially an 'abstraction' which 'assumes'
There is no "assumption", just your misunderstanding of the GR explanation.

The photon has a frequency (as smeared/dopplered by the 'recoil'
There is no "smearing", by the recoil or by anything else.

17. Originally Posted by Tach
There is no "smearing", by the recoil or by anything else.
He's right, RC. I have no idea why but he even wrote a paper on it.

http://en.wikipedia.org/wiki/M%C3%B6...r_spectroscopy

18. Originally Posted by Trooper
He's right, RC. I have no idea why but he even wrote a paper on it.

http://en.wikipedia.org/wiki/M%C3%B6...r_spectroscopy
Hi, NA.

...During Mössbauer absorption spectroscopy, the source is accelerated through a range of velocities using a linear motor to produce a Doppler effect and scan the gamma ray energy through a given range. A typical range of velocities for 57Fe, for example, may be ±11 mm/s (1 mm/s = 48.075 neV).[2][3]
In the resulting spectra, gamma ray intensity is plotted as a function of the source velocity. At velocities corresponding to the resonant energy levels of the sample, a fraction of the gamma rays are absorbed, resulting in a drop in the measured intensity and a corresponding dip in the spectrum. The number, positions, and intensities of the dips (also called peaks; dips in transmitted intensity are peaks in absorbance) provide information about the chemical environment of the absorbing nuclei and can be used to characterize the sample.
That is the sort of Dopplering/Smearing of the emitted gamma ray waveforms I was alluding to.

Note that it is THE SOURCE-PHOTON RELATIONSHIP DURING EMISSION PROCESS that determines the waveform emitted, even before any free space transit to receiver is involved.

That is what I was pointing out. That the waveform is determined AT SOURCE and MODIFIED by SOURCE MOTION with respect to emission process DURING EMISSION and no 'receiver' is yet involved at that 'stage' of determination of waveform.

Cheers!

RealityCheck.

19. Originally Posted by Tach
There is no "assumption", just your misunderstanding of the GR explanation.
I already asked rpenner to supply evidence to support his (now also your) claim on this, as follows (in bold)...

Originally Posted by RealityCheck to rpenner
The GR construct is essentially an 'abstraction' which 'assumes' that the photon changed, as it were, 'in midstream' between source and detector. Please provide references where the photon is actually demonstrated to change WHILE in transit along the free-space path between 'abstractly relatively stationary' source and receiver. Thanks.

That was the GR 'abstraction/assumption' interpretation posted by rpenner in reply to my request for clarification of his statement. So, please, if YOU can provide what he has not been able to do so far in support of his claim, then please by all means feel free to do so for him now. Thanks.

Originally Posted by Tach
There is no "smearing", by the recoil or by anything else.
I just posted on this aspect to NA. Please read what I quoted there from the referenced link.

As the quote tells, the INITIAL SR 'Doppler/smearing' effect on the photonic waveform determination occurs AT SOURCE as a function of the SOURCE MOTION DURING EMISSION, totally independent of any 'absorption' process/differences involved at a remote receiver AFTERWARDS. Thanks.

RealityCheck.

20. Originally Posted by chinglu
Silly me.

Exactly how does this explain the uniform distribution of CMB under GR?

Are you claiming at the instant of the big bang that gravity was uniformly distributed?

Or, take any time period.

Are you making that claim?
So what does GR have to do with the CMBR other than mapping the expansion of the universe to the last scattering surface? Explain that to me. Maybe you have another clueless experiment to run by us. Your other question needs to be asked when you get your clown shoe out of your mouth.

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