Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: timey on 13/11/2016 02:02:34
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Are the NIST 2010 ground level relativity test results exactly as relativity predicts?
The clocks in this experiment are measured by counters that are 'in' the reference frame with the clock they are measuring. The counters counting the frequency of these time dilated clocks are giving the results of relativity maths.
But doesn't relativity predict that these clocks will only be observed to be time dilated 'from' another reference frame, and will not be time dilated 'in' their own reference frame?
(Please note: All mention of rockets, space ships, or anything that does not directly pertain to the NIST 2010 relativity experiments are hereby banished from this thread.)
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Yes.
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Yes to which question Jeff?
Yes relativity predicts that a clock will be time dilated 'in' its own frame of reference?
Or...
Yes relativity predicts that a clock will only appear time dilated as viewed 'from' another frame of reference?
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But doesn't relativity predict that these clocks will only be observed to be time dilated 'from' another reference frame, and will not be time dilated 'in' their own reference frame?
The term: "Acceleration of Gravity" has an effect on the "observed" passage of time. One clock positioned at a different elevation from another will in effect, be in a different frame of reference from the other. When you suggest that these clocks are in the same reference frame, you are mistaken timey.
Why you continue to resist acknowledging this simple fact has become quite frustrating. Until you recognize this simple relationship, your error will not be reconciled.
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Are the NIST 2010 ground level relativity test results exactly as relativity predicts?
The clocks in this experiment are measured by counters that are 'in' the reference frame with the clock they are measuring. The counters counting the frequency of these time dilated clocks are giving the results of relativity maths.
But doesn't relativity predict that these clocks will only be observed to be time dilated 'from' another reference frame, and will not be time dilated 'in' their own reference frame?
(Please note: All mention of rockets, space ships, or anything that does not directly pertain to the NIST 2010 relativity experiments are hereby banished from this thread.)
In Relaitivity, when we are dealing with inertial frames of reference you will only observe time dilation if you are at rest with respect to a different frame of reference than the clock you are observing, When you are in a non-inertial frame, this is not the case, and you can measure time dilation in clocks that share your frame depending on their position in the frame. This includes linearly accelerating frames, rotating frames, and frames in a gravity field (where this test was made).
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For those who aren't familiar with the specifics of this experiment, here is the link:
https://www.nist.gov/news-events/news/2010/09/nist-pair-aluminum-atomic-clocks-reveal-einsteins-relativity-personal-scale
They used ion-trap clocks containing aluminum/aluminium ions.
By the way, timey, if NIST found a deviation from the predictions of general relativity with their new, super-accurate clocks, you can be sure they would have made a lot more noise about it (after a lot of checking - you would be brave to bet against Einstein!).
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Yes to which question Jeff?
Yes relativity predicts that a clock will be time dilated 'in' its own frame of reference?
Or...
Yes relativity predicts that a clock will only appear time dilated as viewed 'from' another frame of reference?
Neither. It was in response to the question in the title of the thread. You can choose not to believe the answer if you wish.
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Are the NIST 2010 ground level relativity test results exactly as relativity predicts?
The clocks in this experiment are measured by counters that are 'in' the reference frame with the clock they are measuring. The counters counting the frequency of these time dilated clocks are giving the results of relativity maths.
But doesn't relativity predict that these clocks will only be observed to be time dilated 'from' another reference frame, and will not be time dilated 'in' their own reference frame?
(Please note: All mention of rockets, space ships, or anything that does not directly pertain to the NIST 2010 relativity experiments are hereby banished from this thread.)
In Relaitivity, when we are dealing with inertial frames of reference you will only observe time dilation if you are at rest with respect to a different frame of reference than the clock you are observing, When you are in a non-inertial frame, this is not the case, and you can measure time dilation in clocks that share your frame depending on their position in the frame. This includes linearly accelerating frames, rotating frames, and frames in a gravity field (where this test was made).
Janus - Let us just consider the NIST moving clock experiment for now...
There is a counter 'in' the stationary clock's frame 'with' the clock counting its frequency.
We understand that the stationary clock at ground level runs at a particular frequency and the counter with that clock is confirming that this is so...
The moving clock was reported to have shown signs of time dilation at speeds as low as 36km/h.
So how was the moving clock measured?
Was there a counter 'in' the moving frame of reference, 'with' the moving clock, counting the frequency of its cycles?
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Q
" Are NIST 2010 ground relativity test results exactly as relativity predicts?"
A
"In one set of experiments, scientists raised one of the clocks by jacking up the laser table to a height one-third of a meter (about a foot) above the second clock. Sure enough, the higher clock ran at a slightly faster rate than the lower clock, exactly as predicted."
From
https://www.nist.gov/news-events/news/2010/09/nist-pair-aluminum-atomic-clocks-reveal-einsteins-relativity-personal-scale
cited earlier by Evan
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Q
" Are NIST 2010 ground relativity test results exactly as relativity predicts?"
A
"In one set of experiments, scientists raised one of the clocks by jacking up the laser table to a height one-third of a meter (about a foot) above the second clock. Sure enough, the higher clock ran at a slightly faster rate than the lower clock, exactly as predicted."
From
https://www.nist.gov/news-events/news/2010/09/nist-pair-aluminum-atomic-clocks-reveal-einsteins-relativity-personal-scale
cited earlier by Evan
For crying out loud, Boring Chemist. Do we have to keep on reiterating the blatantly obvious?
I am opening this discussion on the basis that everyone has understood the blatantly obvious, that we can progress to discussing the detail... and...
The detail I am discussing is about WHERE these observations are being observed 'from'.
P.S. I've posted that link on this forum must be a dozen times over the last 2 years, thanks.
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You could just read the experimental writeup, but if you insist on reading it here, all clocks at the same gravitational potential keep the same time if they are not moving with respect to one another. Clocks at different gravitational potentials run at different speeds, and clocks at the same gravitational potential lose synchronisation if they move relative to one another..
Obviously the only way you will know if there is a difference is if you compare one with another. It doesn't matter where or how you do the comparison because A - B = (A+X) - (B+X) regardless of the value of X. In the special case of X = 0 we are obviously observing one clock from the reference frame of the other, but even if the observer was doing aerobatics on Alpha Centauri, and A and B were in Boulder, Co., he would still see the same difference between A and B.
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I read about the experiment in the National newspapers in 2010 when it was breaking news, have read the write ups, and been thinking rather deeply about it ever since, thanks.
If the moving clock is being measured by a counter that is 'in' the clock's own reference frame, this is contradictory to the relativity remit of this clock only appearing to be time dilated from another frame of reference.
Damn it Alan - you are the one who keeps telling me that an atom doesn't know if it is moving or not...right?
And that a clock only 'appears' time dilated from another reference frame...right?
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I read about the experiment in the National newspapers in 2010 when it was breaking news, have read the write ups, and been thinking rather deeply about it ever since, thanks.
If the moving clock is being measured by a counter that is 'in' the clock's own reference frame, this is contradictory to the relativity remit of this clock only appearing to be time dilated from another frame of reference.
Damn it Alan - you are the one who keeps telling me that an atom doesn't know if it is moving or not...right?
And that a clock only 'appears' time dilated from another reference frame...right?
You really don't get it.
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Jeff - What is the point of your post above? It is saying nothing at all!
Anytime I have tried talking on this forum about an atom having a different frequency when moving relative to a stationary clock, (or when in a different gravity potential), I am being 'told' that the atom does not experience a difference in frequency, that an atom does not 'know' if it is moving or not, that the atom is actually operating at a frequency that is the same as the stationary clock, and that the 'appearance' of a difference in frequency (this being the frequency that the NIST experiment results in) is only observable 'from' another reference frame, and is 'not' observable of the moving clock to an observer 'with' the moving clock...
So again I ask - In the NIST experiment, was the counter counting the frequency of the moving clock 'in' the reference frame 'with' the moving clock?
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This reminds me of Einstein. Everyone thought the experiments results were erroneous and the theory was right. It turned out to be the opposite. But you can never be 100% sure. For example a possible problem is one way speed of light which is debatable.
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So again I ask - In the NIST experiment, was the counter counting the frequency of the moving clock 'in' the reference frame 'with' the moving clock?
And again I say it doesn't matter where the observer is in relation to either clock. All the counter was doing was measuring the difference between them, which was determined entirely and only by their relative speed and relative gravitational potential.
Many people find the twin paradox confusing because it is based on an impossible thought experiment in which two clocks magically appear in an otherwise empty universe, with a relative velocity. In any real experiment we start with two clocks in a laboratory or at least stationary and equipotential with respect to each other, and then accelerate one of them. As Einstein pointed out (but few people seem to have read his footnote!) this makes the clocks different and distinguishable as far as the experiment is concerned, so reciprocity is compromised.
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Jeff - What is the point of your post above? It is saying nothing at all!
On the contrary timey, he along with the rest of us is saying that, for what ever reason, you simply don't grasp what is blatantly obvious to those that understand relativity.
You are in error to assume that the clocks are in the same reference frame just because they may only be centimeters apart. Because the gravitational potential is different for each clock, they are not in the same frame of reference. And to repeat what many of us have pointed out: There exists no preferred frame of reference.
The only frame where both clocks are in the same frame would be one where they both reside at the same elevation and are at rest relative to each other.
It's very "elementary dear Watson".
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So again I ask - In the NIST experiment, was the counter counting the frequency of the moving clock 'in' the reference frame 'with' the moving clock?
And again I say it doesn't matter where the observer is in relation to either clock. All the counter was doing was measuring the difference between them, which was determined entirely and only by their relative speed and relative gravitational potential.
Many people find the twin paradox confusing because it is based on an impossible thought experiment in which two clocks magically appear in an otherwise empty universe, with a relative velocity. In any real experiment we start with two clocks in a laboratory or at least stationary and equipotential with respect to each other, and then accelerate one of them. As Einstein pointed out (but few people seem to have read his footnote!) this makes the clocks different and distinguishable as far as the experiment is concerned, so reciprocity is compromised.
Does this mean that I can now enter into a discussion with you about an FE57 physically having an increased frequency when located in a higher gravity potential, relative to an FE57 located in a lower gravity potential - Alan?
Edit : Ethos - Nowhere have I said the clocks are in the same reference frame, so your post is, at best, misconceived.
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But doesn't relativity predict that these clocks will only be observed to be time dilated 'from' another reference frame,
Yes
and will not be time dilated 'in' their own reference frame?
Yes, every frame sees it's own time not dilated. And in the NIST experiment, we're looking at 3 frames of reference and not just 2. #1 clock, #2 clock, and the scientific observers.
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But doesn't relativity predict that these clocks will only be observed to be time dilated 'from' another reference frame,
Yes
and will not be time dilated 'in' their own reference frame?
Yes, every frame sees it's own time not dilated. And in the NIST experiment, we're looking at 3 frames of reference and not just 2. #1 clock, #2 clock, and the scientific observers.
Sorry Ethos, but we just got through to the fact that NIST experimenters are recording the frequency of the clocks in the clocks own reference frames.
Can you spot the difference?
Because this means that although the observer in the frame with the clock will experience his clock as normal, his clock 'is' time dilated...
(...and this fact has a bearing on my longstanding discussion with Alan concerning Pound Rebka.)
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But doesn't relativity predict that these clocks will only be observed to be time dilated 'from' another reference frame, and will not be time dilated 'in' their own reference frame?
relativity predicts that frequencies/clocks will be observed to be time dilated when measured relative to another frame
I am quite prepared to accept that in your extensive reading of these experiments you have spotted something everyone else has missed. A comprehensive write up of the NIST 2010 experiment was in Science VOL 329, 24 Sept 2010, could you please quote the sections that you believe indicate that the measurements were not compared with the other frame. I have reread it and everything I read says the measurements were comparative via the fibre optic cable, where have I missed it?
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Does this mean that I can now enter into a discussion with you about an FE57 physically having an increased frequency when located in a higher gravity potential, relative to an FE57 located in a lower gravity potential - Alan?
You can try, but to save time you can predict my answer by looking at the gravitational blue shift equation.
I suspect your use of "physically" denotes a yearning for an absolute reference frame. Some commentators have tried to reconcile relativistic and newtonian physics by reference to the fixed stars, but it turns out the buggers aren't fixed anyway, so it's better to stick with what we know: the observed frequency of a clock or a photon depends on the relative gravitational potential of the source and the observer.
KISALC!
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Alan that is all very well but looking at the gravitational shift equation does not provide me with the answer that I am seeking from you.
To continue the discussion - does the atom at elevation have a higher frequency relative to the same atom at lower elevation, or not?
Yes, or no?
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Colin - yes the clocks were connected to a computer via fibre optic cables, but the counter counting the frequency of the clock is in the reference frame with the clock who's frequency its counting. The information is then sent down the cable to the computer and the computer is the comparison point between the information received from both clocks.
So because the counter is reading a frequency change from within the clocks own reference frame, the clock is appearing time dilated 'in' its own reference frame, rather than 'only' being time dilated as seen 'from' another reference frame.
(When we start talking about light being emitted from an atom in its own frame of reference, versus already emitted light arriving from another frame of reference into the frame of reference of the observer, you may understand why this NIST observation is important.)
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Colin - just a foot note. I am quite prepared for some tech savvy person to tell me that the counter was not 'in' the reference frame with the clock it was counting, but actually located in the other clocks reference frame. And that the other clock in frame A was responsible for measuring the clock in the frame B, and visa versa...
But I have read no evidence of this having been the case, and why would the experimenters 'not' place the counter 'in' the reference frame with the clock they are measuring? The only reason not to do so, would be because having done so already did not produce relativity results, and this fact would have definitely been made much mention of... correct?
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Alan that is all very well but looking at the gravitational shift equation does not provide me with the answer that I am seeking from you.
To continue the discussion - does the atom at elevation have a higher frequency relative to the same atom at lower elevation, or not?
Yes, or no?
Since that is what all the measurements tell us, and the theory predicts, obviously yes, but only if by "atom" you mean "clock" or "source". You would make more rapid progress by using the same words as everyone else.
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why would the experimenters 'not' place the counter 'in' the reference frame with the clock they are measuring?
I suggest that you look up what an ion trap clock is: https://en.wikipedia.org/wiki/Quantum_clock
These aluminum ion clocks were the most accurate that had been built up to that date. It was not possible to measure the rate of one clock (eg with a cesium fountain atomic clock), and measure the rate of the second clock, then compare the rates.
As a "rule of thumb", the accuracy of your measuring device should be at least 10x more accurate than the precision that you wish to measure; a cesium fountain clock is just not accurate enough to measure the rate of an aluminum ion clock.
So what they did was to compare the frequency of light emitted by one ion with the frequency of light emitted by the other ion. This achieves a direct measurement of the difference in clock rates without needing two other (more accurate) clocks to discover the absolute rate of each clock.
This is what is needed to confirm gravitational time dilation - a comparison of the rate of two clocks at different heights, which they achieved via the optical fiber.
The only reason not to do so, would be because having done so already did not produce relativity results, and this fact would have definitely been made much mention of... correct?
No. The reason is that there were no other clocks on Earth at the time accurate enough to compare the rates of aluminum ion clocks.
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Evan - I have read extensively about the quantum clock. I will read the link at some point in the future, as have very limited internet access at mo, but off the top of my head, I recall that the quantum clock although superior in precision is somewhat unreliable, and has to be used in tandem with a cesium atomic clock to be of any service.
This does not however detract from the fact that the NIST measurements were taken from within the measured clocks reference frame, whereby the information from both clocks was sent to the computer for comparison.
Why otherwise would the headlines have been:
"Einstein's relativity proven to be a real effect. You really will age faster if you live at the top of a high rise building, than your downstairs neighbour will age living on the ground floor"
...?
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Alan that is all very well but looking at the gravitational shift equation does not provide me with the answer that I am seeking from you.
To continue the discussion - does the atom at elevation have a higher frequency relative to the same atom at lower elevation, or not?
Yes, or no?
Since that is what all the measurements tell us, and the theory predicts, obviously yes, but only if by "atom" you mean "clock" or "source". You would make more rapid progress by using the same words as everyone else.
So Alan - are you saying that the clock, or the source, physically has a higher frequency at elevation, relative to an identical clock, or source on the ground?
And that a clock or source moving at 36km/h physically has a lower frequency relative to the stationary clock, or source?
If we can agree that the clock, or source being measured is physically different than the clock, or source that the measured clock is being held relative to, then the purpose of this discussion has been achieved, and I would then wish to talk to you about the source and receiver of the Pound Rebka experiment.
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This does not however detract from the fact that the NIST measurements were taken from within the measured clocks reference frame, whereby the information from both clocks was sent to the computer for comparison.
Normally measurements are taken from one frame relative to another, however If you have access to the clocks in both frames then you can compare measurements taken in one frame with measurements taken in the other. In that case it doesn't matter if a measurement is taken within the measured clock's reference frame. If you read the article you will see at the bottom of the 2nd page it says "The two Al+ optical clocks were located in separate laboratories and were compared by transmitting the stable clock signal through a 75-m length of phase-stabilized optical fiber."
Comparison is all that is required.
If we can agree that the clock, or source being measured is physically different than the clock, or source that the measured clock is being held relative to, then the purpose of this discussion has been achieved,
Can you define what you mean by "physically different"?
To me the way you have worded this makes little sense as clearly the 2 clocks are different clocks! So, no matter what the answer I can't see how the purpose of the discussion could be achieved by agreeing your statement. Please enlighten me.
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Colin - I simply wish to get to a solid position where I may speak about the source and receiver of the Pound Rebka in comparison to the NIST experiments measuring the clock/source 'in' its own frame of reference.
If an FE57 has a higher frequency at elevation it will emit a higher frequency photon... If we can get past this stage of the discussion, then we can go on to talk about how that already emitted photon is observed when it reaches the grounds frame of reference.
(I could make another thread for the Pound Rebka discussion, should you prefer)
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Try this.
Frequency is the number of events occurring in one second.
Place a source (something producing the events) at A and a clock (something that defines a second) at B. The only definition and measure of the frequency of A is the number of A ticks received per B tick.
If the source and clock are identical mechanisms then relativity predicts, and we find in practice, that f(A) = f(B) if they are in the same reference frame, f(A) > f(B) if A is at a higher gravitational potential and f(A) < f(B) if we accelerate A and then keep it moving at a constant speed relative to B .
The dilatation at constant speed arises from SR and dilatation under grav potential arises from GR. The key word is RELATIVITY because frequency is only defined as and by the RELATION between source and clock.
That's all there is to it.
Now in the case of an atomic source/clock, the underlying phenomenon is independent of gravitation, acceleration or speed (unlike a pendulum or even an escapement clock), so whilst the SR phenomenon is simply explained by the (observed) constancy of c, the GR phenomenon requires also that gravitation distorts the spacetime continuum.
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The ball and spring model clearly doesn't determine the energy of the spin-spin hyperfine interaction of a cesium clock, or a nuclear photon in mossbauer experiments, yet both sources give exactly the same result as the ion-resonance mercury and aluminum clocks used in the more recent determinations of frequency shift.
And if anyone is still interested in mechanical clocks, don't forget that the frequency of a pendulum is
f = sqrt(g/L) / 2.pi, so instead of speeding up, a pendulum clock at altitude slows down to a complete stop when g = 0 in deep space.
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Colin - I simply wish to get to a solid position where I may speak about the source and receiver of the Pound Rebka in comparison to the NIST experiments measuring the clock/source 'in' its own frame of reference.
Since they give exactly the same result, what is there to discuss?
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To say so, there would be very little point in discussing anything other than a scenario producing relativity results...
But where are these relativity results supposed to be being viewed from?
...Because light that is travelling from one reference frame to another can only be viewed by the reference frame that it has traveled to as being the frequency that it has become when it got there... (light can only be observed when it reaches the observer)
So - looking at the emitting source of the Pound Rebka at top of tower - are the blue shift mathematics describing an increase in frequency of the photon, as per how the photon is observed 'in' the ground reference frame?
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Yes.
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...and does the blue shift equation take into account that the source will be emitting a higher frequency photon in the top of tower frame of reference, than it will in the bottom of tower frame of reference?
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The blue shift equation applies to all sources and observers and has been confirmed by experiment. It predicts what an observer will see if he is at a different gravitational potential from the source.
What don't you understand? We've been through all this umpteen times!
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Alan - I am literally begging you now... Please follow cause and effect mechanics.
A clock at the top of the tower is emitting at a higher frequency than the clock at bottom of tower, and NIST have measured these time dilation effects actually 'in' the reference frame of the clock to be a real and physical difference...
Therefore the emitting source of the Pound Rebka at top of tower will also be emitting at a higher frequency at top of tower relative to the same source at bottom of tower.
The NIST results are matching the gravitational blue shift equations for the emission of a photon 'in' top of tower frame of reference - but the gravitational blue shift equation is calculating these results for a photon having arrived 'in' the bottom of tower frame of reference.
Can you not spot the difference?
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NIST have measured these time dilation effects actually 'in' the reference frame of the clock to be a real and physical difference...
No they haven't, because there is no effect within a single reference frame. If A and B are at the same grav potential and not moving with respect to one another, f(A) = f(B). All they have done is to compare two clocks in the same and different reference frames, and shown that the relativistic equations are correct.
The effect is blue shift. The cause is gravitational potential difference.
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No - Alan, we have been through all of this. NIST did not compare clocks that were in the same reference frame. They compared clocks that were in different gravity potentials, or moving relatively.
The experimenters measured each clock in the clock's own reference frame via a frequency counter that is part of the clocks mechanics, that sends the count via fibre optic cable to a computer for comparison.
The headlines read that Einstein's relativity had been proven on a personal scale. That a person really would age faster if they live top of a high rise, than their neighbour will on ground floor. (albeit by a miniscule amount)
I am continuing this discussion based on there being an actual physical difference between clocks in different gravity potentials, and that by remit of the equivalence principle, that which holds for the clock, holds for all atoms.
So - to try again...
Do the emissions of a clock 'in' the top of tower frame of reference match the gravitational blue shift equation?
Do the emissions (gamma rays) of the Pound Rebka source emitted 'from' top of tower match the gravitational blue shift equation when arrived 'in' bottom of tower frame of reference?
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How do you define frequency? Then how do you measure it?
Do the emissions of a clock 'in' the top of tower frame of reference match the gravitational blue shift equation?
Do the emissions (gamma rays) of the Pound Rebka source emitted 'from' top of tower match the gravitational blue shift equation when arrived 'in' bottom of tower frame of reference?
Yes, yes. As you well know.
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The experimenters measured each clock in the clock's own reference frame via a frequency counter that is part of the clocks mechanics, that sends the count via fibre optic cable to a computer for comparison.
There is no frequency counter in the clock mechanism, you must have misread something. Reread Alan's comment:
How do you define frequency? Then how do you measure it?
The frequency from the oscillator will contain some jitter so will be passed through a stabiliser and will be converted to a sqare wave to make comparison easier. It is this stabilised clock pulse which is used for comparison down the fibre - see my post #28.
The oscillator is free running, ie without any external clock reference, so if there were a frequency counter on board it would not return a value different from that which it would measure at the lower level. I explained in my simplified example why this is so.
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How do you define frequency? Then how do you measure it?
Do the emissions of a clock 'in' the top of tower frame of reference match the gravitational blue shift equation?
Do the emissions (gamma rays) of the Pound Rebka source emitted 'from' top of tower match the gravitational blue shift equation when arrived 'in' bottom of tower frame of reference?
Yes, yes. As you well know.
Frequency is defined as per how many cycles per standard second.
The standard second is defined as a 1 part duration of 86400 durations that make up the duration of 1 complete rotation of planet Earth.
(Edit: Colin the point is that whatever is counting the clock is doing so 'in' the clocks reference frame 'with' the clock, and that this info is being sent to computer by the cable. The gathering of the information 'itself' is NOT reliant on a light pulse beacon travelling between the reference frames for observational comparison.)
So - the clock is following the gravitational blue shift equation for light emitted 'in' the top of tower frame of reference relative to the bottom of tower frame of reference. We know the clock is emitting higher frequency photons 'in' the top of tower frame of reference... because a fibre optic cable is sending the information from the counter 'in' the clocks reference frame to the computer for comparison...
Let us hypothetically now observe the cesium atoms emissions emitted 'in' the top of tower frame of reference 'from' the bottom of tower frame of reference.
These light emissions must now travel to bottom of tower frame of reference to be observed, as do the gamma ray emissions from the Pound Rebka source.
We know that the frequency of the clocks emissions is already matching the blue shift equation as emitted 'in' top of tower frame of reference relative to the clock in the ground frame of reference - so after these higher frequency (relative to ground frame clock) photons emitted from the elevated clock reach the ground, what are the frequency of these photons ***now*** 'in' the ground frame of reference?
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Frequency is defined as per how many cycles per standard second.
The standard second is defined as a 1 part duration of 86400 durations that make up the duration of 1 complete rotation of planet Earth.
No!!!!!
One second is the time that elapses during 9,192,631,770 (9.192631770 x 10 9 ) cycles of the radiation produced by the transition between two levels of the cesium 133 atom.
So if you measure frequency by comparing a stable oscillator with a standard clock, you will get the same value anywhere if they are in the same reference frame, and a different value if they are in different reference frames. Which is exactly what we see when we launch GPS satellites.*
Whilst the cesium clock is the world legal standard, it isn't the most sensitive device for measuring small changes in spacetime: the aluminum ion clock runs at a much higher (optical rather than microwave) frequency so you get more cycles to compare in a given time, and it's more robust than a mossbauer rig.
*interestingly, I understand that a circular orbit at around 9500 km gives an exact balance between GR and SR frequency shifts, so at some point in the launch the two clocks will resynchronise. You could even monitor progress on a Lissajous scope, but it's a horribly slow and complicated form of altimeter.
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Colin the point is that whatever is counting the clock is doing so 'in' the clocks reference frame 'with' the clock, and that this info is being sent to computer by the cable.
Nothing is doing the counting. Re read the article I quoted, what is referred to as the clock signal is the frequency output from the oscillators which can be compared directly without actually counting or measuring the frequency.
Consider the oscillator outputs as square waves, upper and lower, these pulses represent the 'ticking' of the Al ion:
___ ___ ___
|. | |. | |. |
--- --- --- ---
______ ______ ______
|. |. |. | |. |
--- ------ ------- ------
As you can see the upper frequency is higher than the lower. These can be fed via the fibre directly into a comparator which will give you the frequency difference using the lower frequency as a reference without having to measure either frequency. This will give you a fractional difference which is dimensionless and can be uses in the relativity formulae. Reread the detailed description in the science writeup and you will see that this is what they are doing.
Also, read Alan's post above it important to understand this.
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Why does the frequency of a cesium atom define a standard second Alan?
The duration of a standard second is defined by historical time keeping based on a second being a division of the duration it takes for the planet to complete 1 full rotation of planet Earth. There is nothing magical, nor special about the duration of a standard second, other than the fact that we measure the durations of all events against it. Just so happens that the cesium atom resonates at a given frequency, when excited by a certain microwave frequency, that we can use to more precisely measure a period of a duration. And the given frequency of the cesium 133 is the standard duration of a period by which a second second is standardised.
Your other commentary is interesting, but you do not answer the question relevant to the discussion...
The cesium atom does not operate at the same frequency at elevation, it has a higher frequency of cycles relative to the lower clock. So no, you cannot say that the cesium atom is operating at the same frequency in all reference frames and only appears to have a higher frequency when observed from the lower frame, or visa versa.
NIST have recorded the frequency of the clocks in their own frames, 1 operating at the frequency we have set as standard, and the higher clock operating at an increased frequency that is said to be synonymous to a second that is shorter than the standard second. The two states of the clock are ground state, and emitting photons state. The atoms are thrown upwards through a microwave beam, are excited by this microwave beam, emit a photon in this excited state, and fall back to the bottom of the chamber. The difference in gravity potential, ie: increase in gravity potential energy, is increasing the frequency of the elevated atoms emissions. (note: A cesium atomic clock could be much more precise but for the fact of its own dimensions. The chamber is 3 feet tall, and the microwave beam exciting the atoms could be more finely tuned except for the fact that the atoms experience time dilation effects within the elevations of the 3 foot chamber itself. Hence the ion trap clock, which runs at a much higher frequency for more precision, but is not as reliable as the cesium atomic clock and must be used in tandem with the cesium atomic clock to be of any service.)
Never mind the length of second for mo. Just looking at the increased frequency of the elevated cesium atom - the photons (cesium fountain) the clock is emitting at this elevation are of a higher frequency, relative to the lower clock... correct?
Colin - those signals are being sent from the clock to the computer for comparison. There is NO reliance on an observation of a light pulse beacon from one reference frame to another to determine frequency. When observing light that has been emitted 'in' 1 reference frame 'from' another, one can only view that light when it arrives in the observers frame, and this will be an observation of what the frequency of the light 'is' in the observers frame, not an observation of what frequency that light 'was' in the reference frame it was emitted from.
These are the only considerations at foot here. Oscillators, counters, square waves, whatever - the fibre optic cable does not change the information of the clock sent from the clocks reference frame to the computer.
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The cesium atom does not operate at the same frequency at elevation, it has a higher frequency of cycles relative to the lower clock. So no, you cannot say that the cesium atom is operating at the same frequency in all reference frames and only appears to have a higher frequency when observed from the lower frame, or visa versa.
Suppose you are at ground floor. If you measure a piece of paper with a stick you get 10 by 10 sticks for example. This means the paper is 10x10 in your reference frame. If you go higer at first floor, you measure the paper and you get 10x10 stick again. In your reference frame the paper still measures 10x10 sticks. You can even define a centimeter being the length of that stick. But you now, that, because of the gravity effect, the paper at the first floor is bigger. It is only when you compare the paper from a different reference frame you notice the difference. In the case if clocks the same thing happens. You define a second based on say 1G osciclations. No matter how fast is ticking you still say a second is 1G osciclations. Only when you compare the clocks from different frames of reference you realize their frequency was not the same.
Yes, the difference in rates is real not an apparent, only it is impossible to detect an absolute value or even a change if everything arround is changing the same way.
A convincing way to do the experiment is to leave the clocks count on their own for a longer period, then compare the results. But even if you measure realtime a tiny difference will always be measured when sendig signals to the comparator.
These things happen because space is a dynamic real thing, like living inside a material witn regions of different built-in stress . The space geometry is not homogeneous and also it changes with time hence we het curved spacetime geometry.
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Why does the frequency of a cesium atom define a standard second Alan?
for the same reason that King Edward II's arm defines the standard yard: because we say so!
The duration of a standard second is defined by historical time keeping based on a second being a division of the duration it takes for the planet to complete 1 full rotation of planet Earth.
In the words of Henry Ford, history is bunk. The earth does not keep precise time and is useless as a clock, even for agriculture (which is why we have leap years and leap seconds).
The cesium atom does not operate at the same frequency at elevation, it has a higher frequency of cycles relative to the lower clock. So no, you cannot say that the cesium atom is operating at the same frequency in all reference frames and only appears to have a higher frequency when observed from the lower frame, or visa versa.
which is why I didn't say it.
NIST have recorded the frequency of the clocks in their own frames, 1 operating at the frequency we have set as standard, and the higher clock operating at an increased frequency that is said to be synonymous to a second that is shorter than the standard second.
nobody said that, because it isn't true. If you measure the frequency of a stable oscillator by comparison with a clock in the same reference frame, it will always be the same. If you compare it with a clock in a different frame, it will be different.
Never mind the length of second for mo. Just looking at the increased frequency of the elevated cesium atom - the photons (cesium fountain) the clock is emitting at this elevation are of a higher frequency, relative to the lower clock... correct?
It has been so for as long as anyone cares to remember. Why do you keep repeating it?
Colin - those signals are being sent from the clock to the computer for comparison. There is NO reliance on an observation of a light pulse beacon from one reference frame to another to determine frequency.
Of copurse trhere is. How else can you measure or compare frequency? When observing light that has been emitted 'in' 1 reference frame 'from' another, one can only view that light when it arrives in the observers frame, and this will be an observation of what the frequency of the light 'is' in the observers frame, not an observation of what frequency that light 'was' in the reference frame it was emitted from.
Don't confuse the energy of the photons with the period between them. Not that it matters, because both are equally subject to GR shift.
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The fibre optic cable does not change the information of the clock sent from the clocks reference frame to the computer.
Who said it does? Certainly not me.
I was merely pointing out that it is not necessary to have a frequency counter in order to measure a frequency difference.
It seems to me that you were saying that if the ion clocks at different heights contain frequency counters such that they measure the frequency in their respective frame, then the NIST experiment is flawed.
In this I agree with you, but not for the reasons you give, but for the simple fact that the experiment would have shown no difference between the frequencies of the clocks at different heights, nor the moving clocks.
Colin - those signals are being sent from the clock to the computer for comparison. ........one can only view that light when it arrives in the observers frame, and this will be an observation of what the frequency of the light 'is' in the observers frame, not an observation of what frequency that light 'was' in the reference frame it was emitted from.
Ah, I see you still haven't worked out why the height of the computer is irrelevant (other than the fact that it has to be within the 75m fibre length). Read the article again and follow the methodology and it soon becomes obvious.
Hint: 100,000s of measurements were made of the tick rates with both clocks in the lower position. Bear in mind that they are not looking for absolute frequency measurements just δf/f0, see equations 1, 2 and 3.
EDIT: just noticed that Alan has responded while I was typing this, he gives you additional hints in his last 2 comments - actually to be fair he's given it away!
Hence the ion trap clock, which runs at a much higher frequency for more precision, but is not as reliable as the cesium atomic clock and must be used in tandem with the cesium atomic clock to be of any service.
Not in this case. If you read the article you will see that in the Al clock they used logic ions of Be and Mg which not only give a very high Q factor but have better frequency uncertainties than Cs fountain.
Are you sure you've read this article?
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Alan - the only significance a standard second has in this discussion is that events are measured against it, including the frequency of anything. No the planets rotation is not precisely regular. The frequency of the cesium atom is more regular. Therefore modern science uses the cesium atom to measure this set duration of a period more precisely. End of story!
When a cesium clock is running at the frequency of a standard second, the clock is being measured how?
Is it being measured via a method that counts the frequency of the cesium atom?
The answer to this question is yes. The information is being transfered into square waves and sent to the computer...
How is the clock in elevation being measured?
Is it being measured via a method that counts the frequency of the cesium atom?
The answer to this question is yes. The information is being transferred to square waves and sent to the computer...
The results of these measurements match the blue shift equation.
Now listen very carefully!
Taking just 1 cesium atom, at the same elevation as the clock, and exciting the atom to produce a photon that we are now going to observe 'from' the ground frame of reference, we must remember that unlike the readings from the clocks, the photon will only be observable 'in' the ground frame of reference 'when' it gets there...
This photon will have been blue shifted on its way to the ground frame of reference.
What frequency will it be?
Colin - I have not read that article you posted. It is a PDF, and I cannot read them on this phone. When the experiment hit the news, I read that the computer took readings from the moving clock at intervals. I read that the upper clock and lower clock were connected to a computer. I did not read how a light pulse is arriving at the computer having been gravitationally blue shifted, or Doppler shifted.
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If you think that I don't understand that your viewpoint is that in comparing the upper clock to the lower clock, the upper clock has more cycles per second than the lower clock, so in saying that a second is shorter in the upper frame, you are taking the stand that where there is a shorter second that the cesium atom is still operating at the same frequency of cycles that it will be operating at as per the lower clock, but in a shorter amount of time.
And in principal I am not disagreeing here. If you shorten a standard second proportionally to the extra cycles of the higher frequency, the number of cycles per shorter second will be the same number of cycles per shorter second. This being the exact equivalent of the amount of cycles the lower clock has per standard second...
I am of the understanding that physics is calculating an atom at elevation as emitting the same frequency of photon at elevation as it does on the ground.
I'm just taking the viewpoint that as far as calculating the universe goes, it is much more useful to view the situation as the cesium atom having a higher frequency in its elevated frame of reference held relative to the frequency a cesium atom has as per the standard second.
This being because light emitted from the atom at elevation is 'now' being calculated as emitted photons of a higher frequency, and this difference might well have a huge bearing on the interpretation of the Pound Rebka results.
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You can define a second based on a cessium clock if that is the most accurate thing you have. Time we measure is not absolute, although I feel it is possible an absolute time to exist but its no way to define it. Speed of light (more precisely speed of causality which is equal to speed of light in vacuum) is absolute. You define its magnitude once and it stays like that forever everywhere.
How would you define a standard unit of time or second ?
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Nobody is "calculating" anything about the frequency of the emitter. Whether it is a nuclear photon or a hyperfine spin-spin transition, all that matters is that the energy of the defining phenomenon is not dependent on gravitational potential (which is why we can't use a pendulum clock). If it was, then the energy would be orientation-dependent in a high-g field, and there is no evidence that it is (line broadening between the sun and Vega is a temperature and pressure phenomenon).
Since the initiating phenomenon is not g-dependent, but the received frequency is, the explanation can only be that time is g-dependent. This is convenient because it means we can predict the gravitational shift of all clocks, regardless of their mechanism (except pendulum clocks) as being exactly the same for any given gravitational potential. And to nobody's surprise (except for those who think the mechanism ought to be g-dependent) that's exactly what Pound & Rebka, NIST, GPS and everyone else finds by experiment, using mossbauer, rubidium, aluminum, cesium and mercury clocks, all with different initiating phenomena.
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For cosmological purposes an absolute time theory can be thought. Time will be what we feel like it is. We have the intuition it is absolute. Defining time absolute will make speed of light variable. When studying twins paradox we will say one the time passed was the same for both. One of the twins will apear as younger and we will say, it is the consequence of the speed of light that slowed down in the rocket.
This theory will require a protocol in relation to GR. Energy wise we might get into more trubble.
Clocks we use now will not indicate time anymore. Time will have to be deduced.
Timey, I think this is the time you are talking about.
Speed of light as constant has the advantage that it can apear as constant when measured using our clocks everywhere and can be thought as absolute also explains biological aging but it is in contradiction with our intuition, that is the drawback.
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Colin - I have not read that article you posted. It is a PDF, and I cannot read them on this phone. When the experiment hit the news, I read that the computer took readings from the moving clock at intervals. I read that the upper clock and lower clock were connected to a computer. I did not read how a light pulse is arriving at the computer having been gravitationally blue shifted, or Doppler shifted.
I assumed your statement that you had read everything on the NIST experiment meant you have also read the Science article which was also on the NIST site at the time. Problem with press releases is they are not informative on detail and often take shortcuts in description because they cater for a wider audience. Most people would be confused by reference to blue or red shift (not Doppler) and those who aren't will easily work out that it doesn't matter. They will also use clock to describe the oscillator (as we all do) but to many people this includes a counter and display which isn't part of this 'clock' - even you assumed there was a frequency counter!
In my post I said you are not trying to measure actual frequencies, in fact it doesn't matter whether you are comparing relative to premoved or or just measuring, there is a height difference between measuring point and the measured frame which changes.
In the case of the moving clock the height didn't change so you wouldn't expect measured frequencies to differ unless due to motion.
PS There is no Doppler Shift because the upper clock had been moved to its new height when the second set of measurements were taken.
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Nobody is "calculating" anything about the frequency of the emitter. Whether it is a nuclear photon or a hyperfine spin-spin transition, all that matters is that the energy of the defining phenomenon is not dependent on gravitational potential (which is why we can't use a pendulum clock). If it was, then the energy would be orientation-dependent in a high-g field, and there is no evidence that it is (line broadening between the sun and Vega is a temperature and pressure phenomenon).
Since the initiating phenomenon is not g-dependent, but the received frequency is, the explanation can only be that time is g-dependent. This is convenient because it means we can predict the gravitational shift of all clocks, regardless of their mechanism (except pendulum clocks) as being exactly the same for any given gravitational potential. And to nobody's surprise (except for those who think the mechanism ought to be g-dependent) that's exactly what Pound & Rebka, NIST, GPS and everyone else finds by experiment, using mossbauer, rubidium, aluminum, cesium and mercury clocks, all with different initiating phenomena.
Yes - you are correct, nobody is calculating any of these atoms observed as increased in frequency at elevation, as being increased in energy...
Why not? All atoms will be increased in energy by the same proportionality and the equivalence principle is upheld.
A gamma ray emitted on the vertical Mossbauer experiment will be emitted at a higher frequency and energy at elevation than a gamma ray emitted on the ground. It will be of the 'wrong' energy to be received by the receiver on the ground. Add in a recoil motion, synonymous to the recoil motion that placing the atom in the crystal lattice has eliminated, or a forward motion (that according to NIST results will reduce the frequency of a clock), then the energy of the emitted photon will be reduced. (this would require one to view the kinetic energy, relativistic mass calculation of light alternatively)
By my reckoning, if one were to view events as so and make the correct calculations, that the value of how g is affecting the gravitational shift of light will be different, and very interesting... (and match with relativity results)
Nilak - I am reading your posts... I don't have access to my own internet connection at mo, so am having to stay strictly on point with the purpose of the discussion. I am not saying the speed of light is variable. If the conversation takes the direction I intend, the subject will be being discussed presently.
Colin - I read everything available at the time, but that was 6 years ago. My point is that an observation of light travelling through a gravitational change, and an atom emitting a photon at a different gravity potential are different. Light can only be viewed 'in' the frame of observation, no matter where it comes from. The clock emitting photons is being read by a computer. The info travelling that fibre optic cable from the clock, does not 'change' on its way to the computer.
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Nilak - I am reading your posts... I don't have access to my own internet connection at mo, so am having to stay strictly on point with the purpose of the discussion. I am not saying the speed of light is variable. If the conversation takes the direction I intend, the subject will be being discussed presently.
Thanks,
I don't think this is off topic. If you say, a clock cycle, like a rotation of a hand doesn't measure a second anywhere you place it, it means speed of light is variable. Speed of light is constant in the theory of GR. You can construct a theory where speed of light is not constant, no problem. It is a matter of preference, but clocks we have now, won't measure time anymore, they will measure the speed of light (defined as variable). You will need different clocks to measure time.
In GR the clocks we use measure time. Clocks defined in GR are perfect. It is the definition of time. Perfect clocks don't exist in real life but still we have enough accuracy to test GR.
Time was already defined when we invented clocks (planetary clocks roughly measure the same time but they are not accurate).
We couldn't have defined time otherwise, because those were the clocks we had available and also, because when time was defined we didn't know, time we defined could change.
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No you are not off topic as such, just ahead of topic...
GR keeps the speed of light constant by rendering distance as variable... It is actually possible to have a constant speed of light and keep distance constant in the face of an additional gravitational time dilation that runs counter directional to GR time dilation for reference frames of empty space in relation to M. This rendering GR gravitational time dilation an m near M phenomenon...
But as said, this is well ahead of topic... For the present we are looking at the frequency of atom's in elevation physically having a higher energy relative to atoms in a lower gravity potential, and emitting higher energy photons relative to the photons they would emit in a lower gravity potential.
P.S. It is a documented fact that physics does not actually have a comprehensive theory of time.
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Colin - I read everything available at the time, but that was 6 years ago.
The Science article was 2010, 6 yrs ago. It triggered the press releases.
The info travelling that fibre optic cable from the clock, does not 'change' on its way to the computer.
Again I am not saying the fibre optic makes any changes to the info or light.
My point is that an observation of light travelling through a gravitational change, and an atom emitting a photon at a different gravity potential are different. Light can only be viewed 'in' the frame of observation, no matter where it comes from. The clock emitting photons is being read by a computer.
I don't really understand what point you are making here, but the point I am making is that the height of the comparator/computer makes no difference to the result.
Just so we have common understanding (in no way trying to teach you relativity):
Both oscillators - we'll call them clocks - start at the same gravitational potential (GP).
The light from each enters a fibre optic at that GP and thus its frequency is as measured in that local time. The fibres are then routed to a comparator/computer which we will assume is at a different GP so the light exits the fibre at the local time at this height, this means that a measurement at this height will be different from one taken at the height of the clocks. If we wanted to measure the frequency at this height the computer would need its own atomic clock, but no worries one of the fibres carries light from the clock which will not move in height, so we can compare the two signals - which are still the same, but shifted.
So now we have a reference against which to measure the clock which is now moved in height relative to the computer, and the height it moves will define the change in GP and hence the change in frequency measured at the computer's height, and match the predictions of GR. Note, this change in GP is the same as between fixed clock and raised clock, so all is consistent.
Now, if you imagine varying the height of the computer you can see that the % difference in frequency will remain the same, so height of computer is irrelevant to these discussions.
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Colin - I do not understand why you think that I thought the gravity potential of the reference frame of the computer was relevant. I gave indication that it was irrelevant posts ago when I stated the computer in another room entirely, at an unspecified, and possibly different height.
I thought you said the frequency of the clock was translated to square wave to be transmitted via the fibre optic cable...
The point I'm making:
The information of the square wave will not be changed by its transit to the computer via the cable.
Light emitted by the elevated clock, ***as seen from*** the lower clock, cannot be viewed by the lower frame ***until it gets there***, and ***will be changed*** in frequency during its transit from the upper frame to the lower frame.
Do you understand the difference?
Edit: I didn't mean that the info wasn't available 6 years ago - I read the info 6 years ago is what I meant.
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I gave indication that it was irrelevant posts ago when I stated the computer in another room entirely, at an unspecified, and possibly different height.
OK that's good, but at least from the description I gave of the computer comparator process you can see that the measurement does not take place using a counter in the reference frame of the clock. Can we agree that?
The information of the square wave will not be changed by its transit to the computer via the cable.
Light emitted by the elevated clock, ***as seen from*** the lower clock, cannot be viewed by the lower frame ***until it gets there***, and ***will be changed*** in frequency during its transit from the upper frame to the lower frame.
Do you understand the difference?
Not really, we need to be clearer on what you are asking/stating. So let's try and clarify some points.
If we pass light down a fibre, the fibre (in the context of relativity) does not change the frequency of that light as I stated before.
We agree that light enters the fibre at one GP (upper frame) and exits at a different GP (lower frame), so because the passage of time is different for each of these GPs then we will measure a difference in frequency e.g. At the computer or lower clock, whichever we choose. Agreed?
However, as the light passes down the fibre it passes through intermediate GPs so if we tap the fibre at any point we would be able to measure an intermediate frequency. So the frequency of the light progressively changes as it passes through the cable.
This is exactly the same as if you shone light from the top of the tower in Pound Rebka.
So, in the light 😊 of the above, can you rephrase your question.
PS square wave was used as an example of how clock signals are processed. We can just refer to light, signal or ticks, whichever you prefer.
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Colin - you have just said that the height, location, gravity potential, etc, of the computer is irrelevant.
So why do you think that the signal from the clock being sent to the computer is changed by its transit through the fibre optic cable?
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Colin - you have just said that the height, location, gravity potential, etc, of the computer is irrelevant.
So why do you think that the signal from the clock being sent to the computer is changed by its transit through the fibre optic cable?
Did you read my posts #58 and 60? Or did you not understand them?
As I have said before it is not the transit through the cable that changes the clock ticks but that the difference in GP, hence time zone/frame, between the input frame and the output frame that changes the measurement.
Why do you think it can't change?
Also, if you do happen to read #58 you will see that I make it clear that the clock over the fibre is measured at each end according to its local time zone/frame and that these measurements differ.
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Colin - I have read and understood your posts, thanks.
a) You are telling me that the location and elevation of the computer are irrelevant...
...and...
b) You are telling me that the difference in gravity potential between the clock and the computer is relevant.
This is contradictory information - so which one is it please?
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Colin - I have read and understood your posts, thanks.
Your next question indicates quite clearly that you did not understand.
a) You are telling me that the location and elevation of the computer are irrelevant...
...and...
b) You are telling me that the difference in gravity potential between the clock and the computer is relevant.
This is contradictory information - so which one is it please?
It is not contradictory, it is not either or, both are true - if by relevant you mean there is a difference in frequency measured at clock and computer, but notice how it cancels out.
If you do not understand my explanation try rereading Alan's explanation, which is another you might not have understood first time round:
Obviously the only way you will know if there is a difference is if you compare one with another. It doesn't matter where or how you do the comparison because A - B = (A+X) - (B+X) regardless of the value of X. In the special case of X = 0 we are obviously observing one clock from the reference frame of the other, but even if the observer was doing aerobatics on Alpha Centauri, and A and B were in Boulder, Co., he would still see the same difference between A and B.
If you are still confused about the fibre imagine a long tube, silvered on the inside running from top of P-R tower to bottom. Light shon down that tube will be blue shifted, an optical fibre is little more than a silvered tube.
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OK, well since your understanding is so much greater than mine:
Where in the NIST data did they say they were measuring the reference frame of the computer?
If the experimenters were not measuring the reference frame of the computer, then why is the gravity potential difference between the clock and the computer relevant?
Also...
How does a cesium fountain send its photons down a fibre optic cable?
...as a cesium fountain is unlikely to be sending its photons along a cable, exactly which light from the clock is being sent along the cable?
And if it is not photons being sent along the cable, what exactly is the signal that is being sent?
(I noticed that Evan posted somewhere about there being an inherent time delay for information being transited by cable. Are you sure that you are not mixing up the inherent time delays associated with the slowing of transiting information via cable, with the time dilation/difference in gravity potential considerations that the computer is comparing of 2 clocks placed elsewhere in designated reference frames, Colin?)
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Heh, you don't need to be a 'rocket scientist' to ponder that question, do you?
It works for me and it works for you :)
And you're perfectly correct in defining 'time' as not being 'time dilated' locally, aka using your wrist watch.
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why that is, is also the reason why we are able to define 'c', and 'constants'.
Without that assumption, physics will have a really hard 'time' defining itself :)
Prove it wrong
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OK, well since your understanding is so much greater than mine:
Where in the NIST data did they say they were measuring the reference frame of the computer?
Nowhere.The statement is meanigless.
If the experimenters were not measuring the reference frame of the computer, then why is the gravity potential difference between the clock and the computer relevant?
It isn't.
How does a cesium fountain send its photons down a fibre optic cable?
...as a cesium fountain is unlikely to be sending its photons along a cable, exactly which light from the clock is being sent along the cable?
Same way as everyone else uses fiber optics. Clock pulses operate a LED at the transmitter end, stimulating a photodiode at the receiver.
(I noticed that Evan posted somewhere about there being an inherent time delay for information being transited by cable. Are you sure that you are not mixing up the inherent time delays associated with the slowing of transiting information via cable, with the time dilation/difference in gravity potential considerations that the computer is comparing of 2 clocks placed elsewhere in designated reference frames, Colin?)
The delay is irrelevant. They aren't measuring Zulu time, just comparing the tick rates from two clocks.
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OK, well since your understanding is so much greater than mine
No, that's not it at all. We are just trying to help you understand what is happening. Come on, this is not above your pay grade, you are smart enough to work this through but it does need a degree of concentration and that appears to be lacking recently. I know times are stressful, but we post stuff and it's as if it hasn't registered, almost as if you haven't bothered to think about it. We will understand if you need time out to sort stuff. OK?
Where in the NIST data did they say they were measuring the reference frame of the computer?
If the experimenters were not measuring the reference frame of the computer, then why is the gravity potential difference between the clock and the computer relevant?
They weren't measuring the reference frame of the computer and the gravity potential difference between clock and computer is not relevant.
As I said before, some thing don't need mentioning because they would confuse folks who don't know and those who do know would consider it teaching egg sucking. This is particularly true of the use of the computer and its reference frame as it cancels out so is not used in any calculations so would not be mentioned.
The GP between computer and clock is not relevant to the final result, but you had an issue with what was being measured from where (in particular whether measurements were being made within the clock frame), and whether the fibre influenced the result, so I included a detailed examination of what can actually happen in a comparator/computer, just for clarification. You could just as easily have relied on Alan's post to explain in maths.
How does a cesium fountain send its photons down a fibre optic cable?
What Cesium fountain???
This is a typical example of what I was talking about. A number of posts from us that appear not to have registered:
They used ion-trap clocks containing aluminum/aluminium ions.
By the way, timey, if NIST found a deviation from the predictions of general relativity with their new, super-accurate clocks, you can be sure they would have made a lot more noise about it (after a lot of checking - you would be brave to bet against Einstein!).
my bold
These aluminum ion clocks were the most accurate that had been built up to that date. It was not possible to measure the rate of one clock (eg with a cesium fountain atomic clock), and measure the rate of the second clock, then compare the rates.
... a cesium fountain clock is just not accurate enough to measure the rate of an aluminum ion clock.
So what they did was to compare the frequency of light emitted by one ion with the frequency of light emitted by the other ion.
This is what is needed to confirm gravitational time dilation - a comparison of the rate of two clocks at different heights, which they achieved via the optical fiber.
If you read the article you will see at the bottom of the 2nd page it says "The two Al+ optical clocks were located in separate laboratories and were compared by transmitting the stable clock signal through a 75-m length of phase-stabilized optical fiber."
Comparison is all that is required.
Note: the article here is the Science article you say you read in 2010.
Whilst the cesium clock is the world legal standard, it isn't the most sensitive device for measuring small changes in spacetime: the aluminum ion clock runs at a much higher (optical rather than microwave) frequency so you get more cycles to compare in a given time, and it's more robust than a mossbauer rig.
So, I have to ask whether there is any point us posting the fact that these are Al optical clocks if you are going to persistently ignore what we say and insist that they are Cesium microwave clocks.
You don't want to believe anything we say so why should we bother?
What frustrates me is that although I don't agree with all your ideas I feel that any nuggets you have are getting lost. Judging by the emails I have had it is clear that the topics you have posted in this section have not enhanced your credibility nor the credibility of your ideas. And that is sad.
(I noticed that Evan posted somewhere about there being an inherent time delay for information being transited by cable. Are you sure that you are not mixing up the inherent time delays associated with the slowing of transiting information via cable, with the time dilation/difference in gravity potential considerations that the computer is comparing of 2 clocks placed elsewhere in designated reference frames, Colin?)
Time delays are inherent in everything to do with transmission, but do not contribute to red/blue shifts. Think about the discussions with the Box regarding the 8min delay on light from the Sun, redshift is a separate phenomenon.
We are willing to help you tune and clean up your ideas, but it can't be one sided, and you certainly can't build any theory on false premises.
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OK, well since your understanding is so much greater than mine:
Where in the NIST data did they say they were measuring the reference frame of the computer?
Nowhere.The statement is meanigless.
If the experimenters were not measuring the reference frame of the computer, then why is the gravity potential difference between the clock and the computer relevant?
It isn't.
How does a cesium fountain send its photons down a fibre optic cable?
...as a cesium fountain is unlikely to be sending its photons along a cable, exactly which light from the clock is being sent along the cable?
Same way as everyone else uses fiber optics. Clock pulses operate a LED at the transmitter end, stimulating a photodiode at the receiver.
(I noticed that Evan posted somewhere about there being an inherent time delay for information being transited by cable. Are you sure that you are not mixing up the inherent time delays associated with the slowing of transiting information via cable, with the time dilation/difference in gravity potential considerations that the computer is comparing of 2 clocks placed elsewhere in designated reference frames, Colin?)
The delay is irrelevant. They aren't measuring Zulu time, just comparing the tick rates from two clocks.
Alan - thankyou!
...but for all those people sending Colin emails, can we please just clarify:
The tick rate of the clock being measured is generated in the reference frame of the clock by the clock.
This rate of tick is then sent to the computer as an exact replication of the rate of tick that the clock is generating in its reference frame...?
If we can all agree that this is the case, then we can go on to look at how an observation of light generated in another reference frame of differing potential from the observation frame, 'will' be changed by it's transit to the frame it is being observed from...
...Light can only be observed when it reaches the observers frame!
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Keep it simple. Clock A ticks. Clock B ticks. We measure the difference f(A) - f(B) in received tick rate.
We know the clocks are effectively identical because f(A) = f(B) when they are at the same gravitational potential.
If we raise A or lower B, we find f(A) > f(B), exactly as predicted by GR.
If we accelerate A so it is moving at a constant speed relative to B, we find f(A) < f(B), exactly as predicted by SR.
So in answer to Are NIST 2010 ground relativity test results exactly as relativity predicts?
is "yes".
But you knew that already, because that's what the NIST paper said.
What a waste of life!
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But does Relativity predict that the FE57 of the Mossbauer effect will be emitting a higher frequency photon at the top of tower relative to the FE57 at the bottom of the tower will?
...and are the equations of this experiment taking this factor into consideration?
If the answer to these 2 questions is 'yes' Alan, then yup, you are right. Waste of life!
But the answer to both of these questions is actually 'no', isn't it?
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But does Relativity predict that the FE57 of the Mossbauer effect will be emitting a higher frequency photon at the top of tower relative to the FE57 at the bottom of the tower will?
What is you reference point? Where are you taking these measurements? If you can't answer this then you are using fantasy physics.
...and are the equations of this experiment taking this factor into consideration?
If the answer to these 2 questions is 'yes' Alan, then yup, you are right. Waste of life!
But the answer to both of these questions is actually 'no', isn't it?
How do you arrive at that conclusion? Have you replicated the experiment and analysed the data?
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Is there something wrong with your brains?
...A clock is blue shifted in elevation relative to the lower clock...
...Light emitted by an atom at elevation is observed as blue shifted in the lower frame relative to the elevated frame...
The difference in the mechanics of these phenomenon is staring you all straight in the face. I don't know what's with you all. Are you blind?
Anyway, if there is anyone out there who cann see this difference:
The clock in elevation is emitting a higher frequency light relative to the lower frame. The difference in frequency between the lower clock and the elevated clock matches the blue shift equation with the higher frequency being observed of the elevated clock.
Does the emitting atom of the Pound Rebka also emit higher frequency gamma rays at top of tower relative to the gamma rays this atom will emit at bottom of tower?
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Is there something wrong with your brains?
Comments like this border on the insulting timey, and for the most part, the entries posted by the membership involved in this thread have been accommodating. If you wish to continue with these condescending remarks, you can expect only grief and little help from those you so readily disparage. We recognize your frustration, needless to say, you should also recognize ours!
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But does Relativity predict that the FE57 of the Mossbauer effect will be emitting a higher frequency photon at the top of tower relative to the FE57 at the bottom of the tower will?
...and are the equations of this experiment taking this factor into consideration?
Relativity predicts that the photon received at the lower gravitational potential will have a higher energy than one emitted by the same process at the lower potential. And thus it was, is, and probably ever shall be, world without end, for ever and ever, amen.
The gravitational blueshift equation is, boringly, exactly the same for all phenomena, and appears to give the correct answer every damn time.
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Poster:
"I've got a new cyclic model of the universe, can someone help me with the maths?'
Physicist:
"Would you like some help understanding relativity?
*
Ethos -
I am not asking questions because I do not know the answers to them.
I do not need to have the difference between a cesium atomic clock and an ion trap clock explained, nor the fact that the ion trap quantum clock must be run in tandem with the more reliable cesium atomic clock, as I explained many posts ago.
I do not need the fact of the potential of the computers reference frame being irrelevant explained to me.
Nor do I need to be told that if one tapped into the fibre optic cable, that there would be different stages of gravity potential in the cable... (That would be true of a vertically aligned cable, but the fact would have no bearing on a tick rate being transmitted through the cable. If it did then the reference frame of the computer would be highly relevant)
People accuse me of not reading their posts... It would seem to me that they have not read mine.
Yes - the NIST results are relativity results...
...The upper clock is blue shifted.
Yes - the Pound Rebka results are Relativity results...
...The gamma ray arriving from the upper frame is blue shifted when it arrives in the lower frame.
NIST = upper frame blue shifted
Pound Rebka = lower frame blue shifted.
I don't whine when the people here insult me, which they do, either directly in words or by patronisation...
Instead of your whining here like this - not even in defence of yourself, but on other peoples behalf - why don't you just answer the question:
Do the Pound Rebka maths take into account that the emitting source will be blue shifted at top of tower relative to the same emitting source, (or more pertinently, we can describe this as the receiver) at bottom of tower, or not?
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Timey,
If two persons have contradictory opinions about something, one of them will think like the other need to study some more to understant the phenomenon. Obviously, the other will think the same way. It is like in the twins paradox. At the end of the journey the aging is revealed. If we extend this, it doesn't matter how many people are on each side, eventually they could all agree about one side or another.
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The blue/red shift is a property of a boson and they travel straight at constant speed.
The clocks that measure time are made of atoms . It doesn't matter the path they describe but they are more complex. The process within them are not confined on a single axis, plus they can have different velocities bellow c.
This means that cloks tick rates do not follow the same rules as light.
You are judging them the same way.
If the clock postulate holds, tick rates will only varry because of tangential velocities difference.
Clocks rates can be sent as pulses. If the comparator is midway between the clocks, what happens to the distance between two pulses as they travel downwards ? What do you think ?
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But does Relativity predict that the FE57 of the Mossbauer effect will be emitting a higher frequency photon at the top of tower relative to the FE57 at the bottom of the tower will?
...and are the equations of this experiment taking this factor into consideration?
Relativity predicts that the photon received at the lower gravitational potential will have a higher energy than one emitted by the same process at the lower potential. And thus it was, is, and probably ever shall be, world without end, for ever and ever, amen.
The gravitational blueshift equation is, boringly, exactly the same for all phenomena, and appears to give the correct answer every damn time.
Do the Pound Rebka maths take into account that the emitting source will be blue shifted at top of tower relative to same emitting source, (which can be more pertinently described as the receiver), at bottom of tower, or not?
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Except that you cannot describe a receiver as a source, pertinently or otherwise, the answer is yes.
Poster:
"I've got a new cyclic model of the universe, can someone help me with the maths?'
Physicist:
"never mind the maths, what are your underpinning assumptions and testable predictions?"
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Just to be absolutely sure that you have answered the question Alan...
Do the maths of the Pound Rebka, in relation to the Mossbauer effect, take into account that the emitting source is blue shifted at top of tower relative to the frequency the same source would be emitting at when located at bottom of tower?
Because I'm pretty sure (but I could be wrong) that Relativity does 'not' predict that atoms have higher energy, or emit higher energy photons at elevation, relative to the energy they have, or the photons they emit in a lower gravity potential.
I'm pretty sure that Relativity does predict that an observation of light arriving from an elevated frame of reference will be blue shifted from the perspective of an observer in the lower frame. This being because the observer can only observe light when it arrives in his own frame of reference... But nowhere did I read that an atom would have a blue shifted frequency at elevation relative to that which it would have in a lower frame of reference.
(I've told you my theory and its predictions. You said show me the physics)
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You are almost absolutely correct. To be pedantic, the photon is blue shifted "from", not "at" the top of the tower.
The stuff you say you never read, is nonsense, which is why you never read it.
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You are almost absolutely correct. To be pedantic, the photon is blue shifted "from", not "at" the top of the tower.
The stuff you say you never read, is nonsense, which is why you never read it.
But the clock IS blue shifted 'at' elevation... (this has been the whole point of the thread)
Why does physics think that the gamma ray source will 'not' be blue shifted at top of tower?
(It may be that Relativity didn't predict that atoms are blue shifted in elevation, but it is most certainly not nonsense that they are because it is proven by the NIST experiment... And if a cesium atom is blue shifted at elevation, a gamma ray source will be as well.)
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If two persons have contradictory opinions about something, one of them will think like the other need to study some more to understant the phenomenon. Obviously, the other will think the same way.
But the clock IS blue shifted 'at' elevation... (this has been the whole point of the thread)
Not from our point of view. We were trying to convince you that it isn't blue shifted 'at elevation'.
Why does physics think that the gamma ray source will 'not' be blue shifted at top of tower?
Sorry, I'm not going to fall into the trap of trying to explain again. You asked me not to and it seems to irritate you when I do.
(It may be that Relativity didn't predict that atoms are blue shifted in elevation, but it is most certainly not nonsense that they are because it is proven by the NIST experiment... And if a cesium atom is blue shifted at elevation, a gamma ray source will be as well.)
NIST did not prove this. The Al ion was not blue shifted in its frame at elevation.
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You are almost absolutely correct. To be pedantic, the photon is blue shifted "from", not "at" the top of the tower.
While some may view this point as "pedant"or trivial, the designation of "from", not "at" is the very problem one of us has regarding their view about the accuracy of relativity.
The stuff you say you never read, is nonsense, which is why you never read it.
And is also the reason they resist considering the difference between "from" and "at" when forming their rationalizations about that accuracy.
As usual, Alan is direct, correct, and efficient with his answers.
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For the umpteenth time, all the clocks and gamma sources that have been used to test GR and SR have given exactly the same result, yet they all generate their signals by different mechanisms, none of which is determined by the local gravitational potential.
Relativistic effects are exactly that: effects due to the relative gravitational potential and/or speed of source and receiver.
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Damn timey :)
You made us run, didn't you
The truth is simple.
you're the one measuring
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Now, what you need to prove is that those measurements doesn't fit.
Can you?