[timey (OP)]

""no, it's because a gravitational field is equivalent to an accelerating frame of reference""

Yes, precisely... and an accelerating frame of reference (GR), and a gravitational field increasing the rate of time (ITT), can be viewed as being equivalent.  (the benefits of doing so result in a cyclic universe)

Alan, I really do not understand why you find it so difficult to grasp this simple concept:
If you are using a Doppler shift to measure a phenomenon, then the phenomenon you are measuring will be inherent with the properties of the measuring unit.
How can the gravitational shift match, ie: 'harmonise with' the created Doppler shift if it were otherwise?

[alancalverd]

""no, it's because a gravitational field is equivalent to an accelerating frame of reference""

Yes, precisely... and an accelerating frame of reference (GR), and a gravitational field increasing the rate of time (ITT), can be viewed as being equivalent.  (the benefits of doing so result in a cyclic universe)

Alan, I really do not understand why you find it so difficult to grasp this simple concept:
If you are using a Doppler shift to measure a phenomenon, then the phenomenon you are measuring will be inherent with the properties of the measuring unit.
How can the gravitational shift match, ie: 'harmonise with' the created Doppler shift if it were otherwise?

Because they are both changes in photon frequency. "will be inherent with the properties of the measuring unit." is meaningless.

G shift alters the frequency of an emitted photon, D shift alters the absorption frequency of the receiver. Suppose we both have airband transceivers. I talk to you at 120.000 MHz and your receiver is set to 120.000MHz, so you can hear me. If I  change to 120.025MHz, you can't hear anything, unless you retune your receiver to 120.025 MHz. Now I transmit at X MHz, but I don't tell you what X is, so you sweep your receiver and read the frequency Y you have set on your dial. As soon as you can hear me, you know that Y = X. All that PR did was to use very precise transmitters and receivers, where G changed the transmit frequency and D was used to sweep the receiver band.

[timey (OP)]

The man made Doppler shift in the Pound Rebka was 'not' a change in photon frequency at-all, Alan.  They created the man made Doppler shift of the emitted gamma ray in relation to the receiving atom, to cancel out the gravitational shift of the gamma ray in order that it be in the correct energy state to be absorbed by the receiving atom, as is the case in the equivalent horizontal experiment conducted without the additional man made Doppler shift.

So - What was it that the man made Doppler shift cancelled out?

The man made Doppler shift cancelled out the G shift, and the G shift that it cancelled out is gravity related, not photon related.

[alancalverd]

The man made Doppler shift in the Pound Rebka was 'not' a change in photon frequency at-all, Alan.  They created the man made Doppler shift of the emitted gamma ray in relation to the receiving atom, to cancel out the gravitational shift of the gamma ray

What is Doppler shift? What is gravitational shift? A change in the frequency of a (gamma) photon! What do we observe in cosmology? G and D shifts of photon frequencies. That is why they are called red and blue shifts!

You can call it a change in photon energy if you like, but remember that you stated that E = hf = hc/λ, so a change in energy is a change in frequency, since h is a constant.

Thanks to the equivalence principle, it doesn't matter whether you move the source or the receiver in the PR experiment, as long as you move it at the velocity v at which D shift = G shift. In the horizontal experiment δg = 0 so v = 0.

[timey (OP)]

The Doppler shift in the Pound Rebka is the man made speaker vibration of the emitted light source in relation to the motion of the receiving atom.

The gravitational shift is the change in the gravitational field gradient.

The Pound Rebka proved that the gravitational shift of the gravitational field has a frequency that can be harmonised with, and be cancelled out by a man made Doppler shift, (which was not a change in the frequency of a photon), created by speaker vibration and the motion of the receiving atom.

Why would someone call a change in the gravitational gradient, ie: gravitational shift, a change in photon energy?  The gravitational shift causes a change in photon energy, and in the case of any other particle with mass's energy, the gravitational shift causes a contrary (but not directly opposite) change in energy than it does with the photon, but you cannot describe these energy changes in the photon or any other particle as the gravitational shift itself.  The gravitational shift is the changes in the gravitational field, surely?

Edit: ...and in reply to your edit: where does this v exist in the gravitational field within a static distance?

[alancalverd]

The Doppler shift in the Pound Rebka is No. It isn't the vibration. It is caused by the vibration which at some point gave the emitter or detector a velocity such that the Doppler shift matched the gravitational shift.the man made speaker vibration of the emitted light source in relation to the motion of the receiving atom.

The gravitational shift is the change in the gravitational field gradient.NJo, it is caused by the difference in gravitational potential between the emitter and the receiver.

The Pound Rebka proved that the gravitational shift of the gravitational field has a frequency that can be harmonised with, and be cancelled out by a man made Doppler shift, (which was not a change in the frequency of a photon), created by speaker vibration and the motion of the receiving atom. Poppycock

Why would someone call a change in the gravitational gradient, ie: gravitational shift, a change in photon energy? Nobody does. Just stick to the words on the card, and don't try to add more. The gravitational shift causes a change in photon energy,no, it is a change in photon energy, caused by gravitational potential difference and in the case of any other particle with mass's energy, the gravitational shift causes a contrary (but not directly opposite) change in energy than it does with the photon,If this means anything, can you prove or explain it? but you cannot describe these energy changes in the photon or any other particle as the gravitational shift itself.  The gravitational shift is the changes in the gravitational field, surely?No, it is the shift if photon frequency caused by the change in gravitational potential

Edit: ...and in reply to your edit: where does this v exist in the gravitational field within a static distance? It is the relative velocity of source and receiver - i.e. the determinant of Doppler shift. Nothing to do with gravitation.

[timey (OP)]

Ah... Ok, I see we are having a terminology problem.  You are referring to gravitational shift as being a photon related phenomenon. ie: a photons energy and frequency being affected by changes in the gravitational field.  I am referring to gravitational shift as being a phenomenon of gravity which causes all particles to shift energy and frequency with changes in the gravitational field.  And to explain: a photons energy and frequency reduces in a decreasing gravitational field, and increases in an increasing gravitational field.  And, any particle with mass's energy and frequency increases in a decreasing gravitational field, and decreases in an increasing gravitational field.  However, this is not a truly symmetrical contrary, because the changes in a photons energy and frequency reduces or increases far more drastically with changes in the gravitational field than a particle with mass experiences...  Although there will indeed be a mathematical proportionality between these contrary phenomenon. (if only I were a mathematician)

I said: 'Edit: ...and in reply to your edit: where does this v exist in the gravitational field within a static distance?'
You said: ""It is the relative velocity of source and receiver - i.e. the determinant of Doppler shift. Nothing to do with gravitation.""

What do you mean nothing to do with gravitation???  The relative velocity of source and receiver-ie: the determinant of Doppler shift was 'used' to measure a gravitational phenomenon.  This Doppler shift was """"matched"""" by whatever it is that gravity is doing when """"gravity"""" changes energy in a gravitational gradient.  And in the Pound Rebka this gravitational gradient was """"static""""!!!  Yet a velocity of Doppler shift was """"matched"""" by the gravity (not photon) related phenomenon being measured.  I repeat, it was the gravitational field, being measured.  The Doppler shift was created in the test signal in order that the emitted gamma rays """"did not"""" shift energy, and it achieved this by """"cancelling out"""" the energy shift effect of the gravitational gradient.

Therefore, logically speaking, this velocity of Doppler shift must exist within the energy changes in the gravitational field.

[alancalverd]

velocity of Doppler shift

Try using the term "Doppler shift" instead of adding extraneous words, and it will all become clear.

I repeat, it was the gravitational field, being measured.

not at all. The gravitational potential difference was known:

Δg ≈ 0.31 x 10^-6 h

where h is height in meters above the earth's surface.

The purpose of the experiment was to measure an unknown but theoretically calculable gravitational red shift in a known field by matching it with a known Doppler shift. Good experimental science is all about measuring one unknown at a time!

[timey (OP)]

(...sigh). What was it that the 'determinant' of the Doppler shift matched, or harmonised with, and cancelled out?

Does the vibration of the speaker, or the relative motion of the receiving atom, affect the energy and frequency of the gamma ray?  No it doesn't.  The energy and frequency of the gamma ray when subjected to this determinant of Doppler shift remain unchanged by the 'gravitational potential', and are absorbed by the receiving atom because whatever it is about gravitational potential that causes light to shift in energy and frequency has been cancelled out by this determinant of Doppler shift.

So - what was it that was cancelled out by this determinant of Doppler shift in order for the gamma ray not to be gravitationally shifted in energy and frequency?

(May I politely hint to you at this juncture that I am repeating terminology that you have used yourself, which does rather render any complaint you have concerning linguistics as extraneous, and presumably you may now find yourself able to focus on the question posed within said annoying language without such distraction)

[alancalverd]

whatever it is about gravitational potential that causes light to shift in energy and frequency has been cancelled out by this determinant of Doppler shift.

Nearly correct. Let's leave out a few words, then the gravitational shift equals the Doppler shift. Easy.

Gravitational shift is the difference between emitted and received frequency caused by the difference in gravitational potential between the source and the receiver. Doppler shift is the difference between emitted and received frequency caused by the relative motion of the source and receiver.

Does the vibration of the speaker, or the relative motion of the receiving atom, affect the energy and frequency of the gamma ray?  No it doesn't.

yes it does. It alters the received frequency!
 
To quote from your favorite Wikipedia entry

 

Pound and Rebka countered the gravitational blueshift by moving the emitter away from the receiver, thus generating a relativistic Doppler redshift

That's all there is to it.

[timey (OP)]

And...also quoting from my favourite wiki link:

""This experiment is based on the principle that when an atom transitions from an excited state to a ground state, it emits a photon with a characteristic frequency and energy. Conversely, when an atom of the same species, in its ground state, encounters a photon with the same characteristic frequency and energy, it will absorb the photon and transition to the excited state. If the photon's frequency and energy is different by even a small amount, the atom cannot absorb it (this is the basis of quantum mechanics). When the photon travels through a gravitational field, its frequency, as well as its energy, will change due to the gravitational redshift. As a result, the receiving atom cannot absorb it. But if the emitting atom moves with just the right speed relative to the receiving atom the resulting Doppler shift cancels out the gravitational shift and the receiving atom can now absorb the photon. The "right" relative speed of the atoms is therefore a measure of the gravitational shift.""

Yes we can see that the determinate of the Doppler shift is a measure of what the gravitational shift of the gamma ray would have been, had it shifted energy and frequency.  But again I ask you, 'what' in the gravitational shift was 'cancelled out' in order for the gamma ray's energy and frequency 'not' to be shifted in the gravitational gradient?

[alancalverd]

First, get rid of the unnecessary words you have added.

Yes we can see that the determinate of the Doppler shift is a measure of what the gravitational shift of the gamma ray would have been, had it shifted energy and frequency.

Now look at the physics. The frequency did indeed shift, exactly as predicted......

 

But again I ask you, 'what' in the gravitational shift was 'cancelled out' in order for the gamma ray's energy and frequency 'not' to be shifted in the gravitational gradient?

.....then they added a Doppler shift of equal and opposite magnitude, so that the received frequency was the same as the emitted frequency. What's the problem?

Think about a simple Doppler shift. A train is coming towards you. Its whistle emits an A at 440Hz. (How do we know the frequency? Because it's written on the whistle and I tuned it.) But because it is travelling towards you at 20 meters/second over the ground, you hear the note as

440 x (1 + v/c) = 440 x (1 + 20/340) = 466 Hz = A#  (note c here is the speed of sound, 340 m/s,  not light!)

So being a sensible person, you get in your car and drive away from the train at a ground speed of 50 m/s, so now your relative speed is -30 m/s and you hear

440  x (1 - 30/340) = 401 Hz (a bit sharp of G)

Having perfect pitch, you slow down until you hear an A. What speed are you travelling? It must be 20 m/s, to exactly cancel the Doppler shift from the train's movement. It's a dangerous way of measuring the speed of a train, but you gotta admit it works!

How does this fit with the PR experiment? Instead of a moving train, they used the gravitational gradient to produce the initial frequency shift. And of course c was the speed of light, not sound. That's all there was to it! 

Rule 1 of physics: don't go looking for complications.   

[jeffreyH]

**sigh** That timey eh? If you have to explain once you have to explain a Million times! Brain not in gear girl?

[timey (OP)]

**sigh** That timey eh? If you have to explain once you have to explain a Million times! Brain not in gear girl?

Agreed wholeheartedly Jeff!  It is absolutely ridiculous how many times I am having to explain this incredibly simple concept.

[timey (OP)]

Quote from: timey on Today at 22:05:37
Yes we can see that the determinate of the Doppler shift is a measure of what the gravitational shift of the gamma ray would have been, had it shifted energy and frequency.
Now look at the physics. The frequency did indeed shift, exactly as predicted......

Yes the frequency shifted before they added the Doppler shift. Edit: and the gamma rays were not absorbed by the receiving atom.

[timey (OP)]

Quote
But again I ask you, 'what' in the gravitational shift was 'cancelled out' in order for the gamma ray's energy and frequency 'not' to be shifted in the gravitational gradient?

.....then they added a Doppler shift of equal and opposite magnitude, so that the received frequency was the same as the emitted frequency. What's the problem?

...and then the gamma ray's frequency did not shift.  Edit: and the gamma rays were absorbed by the receiving atom.

[timey (OP)]

You cannot change the energy or frequency of a gamma ray by shaking its emitter source via a speaker cone vibration, or by movement of the receiving atom, when conducting an equivalent horizontal experiment...  And you cannot change the energy or  frequency of an emitted photon by shaking its emitter source, or by the movement of the receiving atom, in the vertical experiment either!  Although there is indeed a case for the receiving atom having changed its energy as it moves through changes in the gravitational field towards the emitted photon.  However, as you yourself have previously pointed out to me somewhere else, the receiving atom will have travelled a minimal distance in relation to the distance travelled by the photon.

The only means of change in the energy and frequency of an emitted photon is via the changes in a gravitational field.  You yourself have previously pointed out to me elsewhere (to my agreement), that an already emitted photon cannot gain or lose energy via any means other than changes in the gravitational field.

So when the measure of the frequency that the gamma ray would have changed to is determined, ( ie: the 'measure of' (is that aloud?) the Doppler shift created by this shaking of the light source emitter in relation to the movement of the receiving atom), 'where' does the phenomenon/frequency that it 'matches', 'resonates' or 'harmonises with' exist?

This being my problem, because far as I can tell Alan, within the physical definition of 'match', 'resonate' or 'harmonise', at the very least 2 aspects are required for the function.  ie: to re-instate your radio frequency analogy, 2 transmitter/receivers would be necessary in order to tune into the same frequency.

The emitted gamma ray, no matter what you do with it, cannot match, resonate or harmonise with anything of its own self and change a phenomenon that is caused by changes in the gravitational field.  It has to be 'something' in the gravitational field that the Doppler shift created matches and cancels out.

[alancalverd]

A teacher is someone who takes a subject he understands and phrases it in words a pupil can understand. An educationalist is someone who takes a subject he doesn't understand and rephrases it until nobody can.

Like when you add words to a perfectly simple statement such as

"Gravitational shift is the difference between emitted and received frequency caused by the difference in gravitational potential between the source and the receiver. Doppler shift is the difference between emitted and received frequency caused by the relative motion of the source and receiver."

until you can't understand it.

I suspect you are a covert educationalist. Or a New Age troll, injecting mystery where others seek simplicity. I enjoy matching, resonating and harmonising, but with girlfriends and musicians, not photons.

One last try. For chrissake (or at least your own) delete "energy and frequency". The speed of a photon is constant so the only thing that can change is its frequency as seen by a receiver. So let's talk about frequency.

If a Mossbauer photon is redshifted because it has come from a gravitational potential well, it will arrive at the detector with a lower frequency than expected, so it won't be absorbed. Now if we move the detector towards the source, we are adding a Doppler shift to the received frequency and at some critical velocity the D shift will be equal and opposite to the G shift, and the photon will be absorbed.

If, in the PR experiment, the source is at the top of the tower, the photon will be blueshifted by the time it reaches the bottom, so you have to move the detector away from the source, thus subtracting the D shift from the G shift.

In the horizontal case, there is no gravitational potential difference between source and receiver, so there must be absolutely no relative movement if the photon is to be absorbed.

The power of the Mossbauer effect is that the receiver bandwidth is very, very, very narrow, so you can measure small G shifts (as from a few meters vertical separation) with quite small D shifts (as from a loudspeaker movement).

[timey (OP)]

Yes Alan - yawn.  And what is causing the photon to G-shift?  Is it the 'extra relative motion" that is causing the G shift?

Adding extra relative motion to a photons speed aye?  In a static distance of gravitational gradient aye?  Speed of light is 'constant' aye?

When the photon does suffer the gravitational shift in the Pound Rebka, before they added the Doppler shift that cancels the effect, either the photon is moving 'slower' for a 'reason' or the speed of light is 'not' constant, because the extra motion added by the Doppler shift that cancelled the effect has no extra 'distance' to exist in.

My theory says that the extra relative motion that the Pound Rebka measured as the G shift via the Doppler shift is caused by the photon moving through a slower rate of time in the weaker gravitational field.

On a more personal note, I'm becoming quite concerned Alan that you have picked up a touch of Simon Cowell from somewhere...  Far more dangerous than an STD and just as embarrassing, I've read that self diagnosis in these cases is nigh impossible.  So - as your sworn friend and internet buddy Alan, I feel it my social duty to inform you, that you may have your condition attended ASAP before it causes you any permanent damage.

[alancalverd]

And what is causing the photon to G-shift?

I can do no better than quote Wikipedia

In astrophysics, gravitational redshift or Einstein shift is the process by which electromagnetic radiation originating from a source that is in a gravitational field is reduced in frequency, or redshifted, when observed in a region of a weaker gravitational field. This is a direct result of gravitational time dilation - as one moves away from a source of gravitational field, the rate at which time passes is increased relative to the case when one is near the source. As frequency is inverse of time (specifically, time required for completing one wave oscillation), frequency of the electromagnetic radiation is reduced in an area of a lower gravitational field.

which, if I understand your jargon, is exactly the opposite of

My theory says that the extra relative motion that the Pound Rebka measured as the G shift via the Doppler shift is caused by the photon moving through a slower rate of time in the weaker gravitational field.

though you might like to tell us what the words in purple mean to you.