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Author Topic: Will a photon clock run at a different rate from an atomic clock under gravity?  (Read 45620 times)

Offline graham.d

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Can you show evidence for this slow light, Farsight. I agree with your conclusion but is it not spacial changes with gravitational potential rather than lightspeed changes? Isn't what you are saying a more classical view than a relativistic one? The view of a blackhole, from this perspective, is that light does not emerge because it can't reach escape velocity rather than it being redshifted to zero energy. Perhaps the two views are indistinguishable. Gravitational redshift is not normally thought of to result from slow light - though I seem to remember some old theory about this.
 

Offline amrit

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Amrit - I am afraid you are repeating assertions without providing anything more.  Would you care to explain how space can be timeless yet there is experimental and practical proof of time dilation through differing gravitational potential and relative velocity.  you keep on repeating that photon clocks are unvarying despite Graham's explanation under SR of why they vary - could you answer this single question.  

As an aside - I read your paper and flicked through the references; I was unable to find the quote you gave within the Eckle paper.  If, in fact, it was a paraphrase it should really not be in quotes - perhaps you could direct me towards it.
Matthew
 

Matthew there is no a single experimental data that time exist. With clocks we measure numerical order of events running in space. Gravity influences atom clocks and do not influences photon clocks. This is my answer to you.
About Eckle you find his papers on arxiv.

yours amrit
 

Offline amrit

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Amrit, (to quote from Monty Python) this is contradiction, not argument.

"Space is timeless" is meaningless unless you explain your definitions
"'Velocity' of clocks" is also not what you mean (I think).
It has everything to do with the observer and the different gravitational potential. If you were to do the maths rigorously you would find the "spacetime interval" will be the same to all observers.
The rules of the universe are what they are and not what you choose them to be, so by all means do your experiment, but you seem to have presupposed the result. But if it turned out you were right you will surprise a lot of people :-)

Space-time is timeless by the very definition of it. X4 is not time dimension, X4 is spatial too
X4 = ict ( as d = v x t)
 

Offline amrit

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We have a “photon clock” made out of two mirrors A and B. Photon is moving from A to B, back to A and so on. One traveling of the photon between A and B is a “tick” of the clock. We take two photon clocks. One photon clock is on the surface of the earth, second is 4200 meters below at the bottom of the mine shaft. Velocity of light is invariant on gravity; both of clocks will “tick” with the same velocity.
Hi amrit. I'm afraid this isn't right. The second clock runs slower than the first clock. People say the speed of light doesn't change, but it does. The reason why is simple: speed is distance over time. If we avoid radial length contraction by lying our clocks flat, the distance is the same for both clocks. However we say that time dilation has occurred for the second clock, and that the times are not the same. Speed equals distance over time, so if the distances are the same and the times aren't, the speeds aren't the same either, even though we measure them both to be 299,792,458 metres per second. There's a hidden scale-change at work here, wherein the clock goes slower not because "time goes slower", but because the light goes slower.

speed is distance over time...........No it is not
v = d/tn where tn is numerical order of event that we measure with clock
 

Offline imatfaal

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Armit

One a technical note - I have read the entire paper you referenced and could not find your quote.  Maybe I have missed it - but most academics take citations very seriously and it is important to get this simple thing right. 

I think I will leave this discussion at this point - the existence of time is so central to physics it requires more than assertion to shake my belief in it.  The mathematics and theory behind special and general relativity have been tested (including with regard to time dilation) probably more than any other theory in history. 

Good luck with developing your theories - please bear in mind my comments regarding getting your citations and references perfect.

Matthew 
 

Offline syhprum

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What is the difference between a 'Photon clock' and the resonant cavity with which we are all familiar ?.
 

Offline Farsight

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Can you show evidence for this slow light, Farsight. I agree with your conclusion but is it not spacial changes with gravitational potential rather than lightspeed changes?
The evidence is the different readings in the light clocks. In the second clock that was down the mine, the light has bounced back and forth fewer times than in the first clock. The spatial change is radial length contraction, so when you hold your clocks flat you avoid this. 

Isn't what you are saying a more classical view than a relativistic one?
No. The distinction is between Einstein's original general relativity and what's called the modern interpretation. See this article on the Baez website called is the speed of light constant?

Einstein went on to discover a more general theory of relativity which explained gravity in terms of curved spacetime, and he talked about the speed of light changing in this new theory.  In the 1920 book "Relativity: the special and general theory" he wrote: . . . "according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity [. . .] cannot claim any unlimited validity.  A curvature of rays of light can only take place when the velocity of propagation of light varies with position." Since Einstein talks of velocity (a vector quantity: speed with direction) rather than speed alone, it is not clear that he meant the speed will change, but the reference to special relativity suggests that he did mean so.  This interpretation is perfectly valid and makes good physical sense, but a more modern interpretation is that the speed of light is constant in general relativity.

The view of a blackhole, from this perspective, is that light does not emerge because it can't reach escape velocity rather than it being redshifted to zero energy. Perhaps the two views are indistinguishable. Gravitational redshift is not normally thought of to result from slow light - though I seem to remember some old theory about this.
It isn't quite like that graham. You just switch the emphasis to the coordinate speed of light, and downgrade the locally-measured 299,792,458 m/s. At the black hole event horizon the time dilation is infinite and the coordinate speed of light is zero. Hence the light doesn't emerge because it's effectively stopped. This is what's called the "Weinberg field interpretation" as opposed to the "Misner/Thorne/Wheeler" geometrical interpretation of general relativity.
 

Offline Farsight

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Amrit: atomic clocks are light clocks! See the NIST caesium fountain clock, and see http://en.wikipedia.org/wiki/Second for the definition of the second:

"Since 1967, the second has been defined to be the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom. This definition refers to a caesium atom at rest at a temperature of 0 K (absolute zero), and with appropriate corrections for gravitational time dilation."

In the NIST fountain clock, lasers and a microwave cavity are employed to cause hyperfine transitions, which are electron "spin-flips" within caesium atoms. These are electromagnetic events that emit microwaves, light in the wider sense, which is received by a detector. The detector counts incoming microwave peaks. When it gets to 9,192,631,770 we say a second has elapsed. The frequency of the light is then 9,192,631,770 Hz by definition.

Note the mention of gravitational time dilation above. If you were to take this clock and place it in a region of low gravitational potential, it would be like pressing a slow-motion button. All electromagnetic and other processes would then occur at a reduced rate, including the hyperfine transition and the motion of the light towards the detector. Again when the detectors gets to 9,192,631,770, we say a second has elapsed. But it's important to realise here that in this situation, the light is moving slower and this is why the second is bigger. We then use this second... to measure the speed of light. That's why we always measure the local speed of light in vacuo to be 299,792,458 m/s.
 

Offline Geezer

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The detector counts incoming microwave peaks. When it gets to 9,192,631,770 we say a second has elapsed. The frequency of the light is then 9,192,631,770 Hz by definition.


Actually, the detector does not count microwave peaks.

An oscillator produces microwave energy that causes the caesium to fluoresce. The detector measures the amount of fluorescence. Maximum fluorescence (photon emissions I suppose) is achieved when the microwave energy is tuned to 9.1xxx GHz. The clock makes very small adjustments to the oscillator to maintain maximum photon emission.

The clock is really comparing the natural oscillation of the caesium atom with the frequency of a microwave resonator and adjusting the resonator to match the frequency of the caesium. So, it's not really measuring a property of light at all. The caesium light output is simply used as a means to keep the resonator "in tune" with the caesium.
 

Offline graham.d

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"The spatial change is radial length contraction, so when you hold your clocks flat you avoid this." - Farsight

If you note, Farsight, I positioned both clocks in a near zero gravitational field. The only difference is gravitational potential so I am not sure how the issue of orientation is relevant. I am not sure whether is is possible to determine whether there is length change or lightspeed lowering. A proper GR treatment would simply give the result that the spacetime interval was agreed by all observers. As I said previously, the remote measurement of time intervals for light travelling has to be thought out carefully. It is necessary to define the events of emission and detection with care.

You quote Baez who says "[...] a more modern interpretation is that the speed of light is constant in general relativity", but contradict this statement, so I don't follow your reasoning. You seem very definite but there seems varying opinions. If you read my lengthy description of a local and distant observer measuring the photon clock, I would be interested to know if you see anything wrong in the reasoning.

A light pulse going around lots of coils of fibre optic might be a practical photon clock too. With enough coils the time delay can be significant and measurable with low errors.
« Last Edit: 22/05/2010 19:58:06 by graham.d »
 

Offline amrit

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RESUME

Relativistic effects of relative velocity of material change start above photon scale

Constancy of the light velocity in different inertial systems and areas of space with different gravity implies that relativistic effects of relative velocity of material change start on the scale above photon.

Special Theory of Relativity and General Theory of Relativity considers light moves through the space with constant velocity regardless upon the velocity of inertial system and strength of gravitation. This implies that at the scale of the photon and below at the scale of Planck relativistic effects of relative velocity of material change does not exist. Here is proposed that in all inertial systems velocity of a photon clock is unchanged. Change of gravity does not effect velocity of a photon clock as it effect velocity of an atom clock. Changes of atomic clocks are well known and calculated by Relativity in the Global Positioning System.

We have a “photon clock” made out of two mirrors A and B. Photon is moving from A to B, back to A and so on. One traveling of the photon between A and B is a “tick” of the clock. We take two photon clocks. One photon clock is on the surface of the earth, second is 4200 meters below at the bottom of the mine shaft. Velocity of light is invariant on gravity; both of clocks will “tick” with the same velocity.
We take two atomic clocks. One clock we put beside photon clock on the surface and second beside clock that is 4200 meters deep. According to the relativistic gravitational effect second atom clock will in 30 days “tick” faster as the atom clock on the surface for.

Photon clock will also have unchanged velocity in all different inertial systems, because velocity of light is equal in all different inertial systems. Similar experiment with 2 atom clocks an 2 photon clocks can be carried out by putting one atomic and one photon clock in the orbit station and one atom clock and one photon clock on the surface of the earth.

Special Relativity SR is postulated on constancy of light velocity. Equality of inertial and gravitational mass is connecting SR and General Relativity GR. Discussing on possibility that gravity infects velocity of light put under question relatedness of SR and GR. Gravitational red shift shows that gravity influences only frequency and not velocity of light. This means that “thought experiment” with photonic clock is correct: Velocity of photonic clock is invariant on gravity. In stronger gravity photon moving between mirror A and B change only frequency and not velocity. And this means that relativity gravitational effect of relative velocity of material change starts above photon scale.

Planck Clock
In this “Gedanken experiment” we use a photon clock that is made out of two mirrors that are on the distance of Planck. Photon moves from one to other mirror into a Planck time. This is so called “Planck clock”. Planck time is a fundament al unit to measure numerical order of material change i.e. motion in a timeless space. “Length dilatation” and “time dilatation” do not work on the Planck clock. Planck distance can not be smaller as it is. Planck distance is a fundamental constant invariant on the “length dilatation”. So by the “Planck clock” there is also no “time dilatation. Length dilatation and time dilatation exist above scale of the photon.

Invariance of light velocity excludes existence of relativistic effects of relative velocity of material change at the photon scale. Experiment with photon clocks and atomic clocks will give us more experimental data.
 

Offline Geezer

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I'm probably missing something here, but velocity is a measurement of distance in time. Surely any measurement of velocity is therefore determined by the time local to that distance?

This does not appear to contradict the constant speed of light. In fact, if photons did not "observe" local time, would not the speed of light vary?
 

Offline amrit

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photon moves in space only and not in time
c = Planck distance / Planck time
Planck time is a fundamental unit for measuring numerical order  of material change i.e. motion
Space-time is timeless, space-time is 4D.
see more in my article published in Physics Essays in last issue.
 

Offline Geezer

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photon moves in space only and not in time

Relative to the photon I think that is true. Relative to us the photon does take time, therefore we observe velocity and we can confirm this experimentally in many different ways.
 

Offline amrit

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By photon clock “time dilatation” is in contradiction with “length contraction”
   We have a photon clock in a fast airplane.  Mirrors are fixed in a way that photon moves along the direction of motion of the airplane. Distance between the mirrors is shortened by the length contraction. Because of the shorter distance between mirrors a path for the photon is shorter and so photon clock on the airplane “ticks” faster than photon clock on the surface of the earth. We know that atom clock in a fast airplane ticks slower than atom clock on the earth. Solution of this contradiction is in a preposition that photon clock in the airplane do not shorten. “Length contraction” is only a mathematical calculation that has no correspondence to the physical world. “Time dilatation” has also no correspondence in the physical world. What really happens by time dilatation is that velocity of material change velocity of clocks including slows down. Clocks run in space only and not in time
 

Offline amrit

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photon moves in space only and not in time

Relative to the photon I think that is true. Relative to us the photon does take time, therefore we observe velocity and we can confirm this experimentally in many different ways.

No motion of photon is timeless, photon moves only in space. With clocks we measure numerical order of motion.
 

Offline amrit

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Let’s take a photon that is moving on the distance d  between point A and point B of space. Distance  d is composed out of Planck distances dp1 + dp2 + dp3....dpn. The smallest distance a photon can pass on the way from A to B is dp . A unit of numerical order of photon motion from  dp1 to dp2  is the Planck time tp . The photon moves exclusively in space and not in time. The photon position dp1  is “before” position dp2  in a sense that the numerical order  n is “before” n+1 . Equivalently as the natural number 1 is “before” the natural number 2. Numerical order of material change is measured with the “ticking” of a clock where t0  represents the beginning of measurement, and  tn the end of measurement. Velocity v of a material change is derived from its numerical order:
v = d/tn. Frequency of material change is derived from its numerical order: Frequency = 1/tn
 

Offline graham.d

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Amrit, this is just special relativity and there is no contradiction here. You are making a mistake in your calculations. You MUST measure time between events. The time of flight for the photon, from the perspective of the stationary observer, is not the same in each direction. If you imagine the photon is emitted (event 1) opposite to the motion direction from the front mirror, it reaches the back mirror more quickly because the back mirror is moving towards it. Work out the time to reach that mirror (event 2). After reflection it now has further to go to reach the front mirror which is receding from it. Work out the time it takes to get there (event 3). You will see that, from the perspective of the observer the time from event 1 to event 2 is shorter than event 2 to event 3. The total time is the sum of the two intervals. I am not going to do the maths here but it works out to be the 2 x the Lorentz contracted distance between the mirrors divided by the speed of light. This is exactly as SR predicts.

Nearly all apparant paradoxes in SR are because this sort of mistake is made, including the famous twin paradox.
 

Offline graham.d

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Amrit, I thought I would show the maths anyway:

Let t1 be the first interval and t2 the second interval

c.t1 = d' - v.t1, c.t2 = d' + v.t2    where d' is the Lorentz Contracted mirror spacing

Hence t1 + t2 = d'/(c+v) + d'/(c-v)

              = (2d/c).[1/(1-v²/c²)]


Substituting the Lorentz contraction value for d'

d' = d.√(1-v²/c²)
where d is the proper mirror spacing gives

t1 + t2 = (2d/c).[1/√(1-v²/c²)]

Which shows that the stationary observer sees the photon clock running slow by the anount given by the cusomary time dilation equation.

 

Offline amrit

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yes Graham, here is the point. What mathematic shows in not in accordance with experimental data. Light velocity is invariant on inertial system.
This simply means there is no length contraction in physical world.
Velocity of photon clock is invariant on inertial system as is case with C.

 

Offline Murchie85

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Isn't relativity and time dialation tested every single time we put a satellite into orbit and the fact the two actual clocks or time settings are adjusted to compensate for this?
 

Offline JP

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Hi Amrit,

It sounds like what you're claiming is that special relativity as it's usually formulated has errors.  If that's the case, it's a new theory rather than mainstream physics.  Do you mind posting about it further in the New Theories section of the board?  

Thanks,

JP (moderator)
 

Offline amrit

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Isn't relativity and time dialation tested every single time we put a satellite into orbit and the fact the two actual clocks or time settings are adjusted to compensate for this?

Yes different velocity of clocks is measured, not time. Space is timeless, space is not 3D + T, space is 4D, see my article on
http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PHESEM000023000002000330000001&idtype=cvips&gifs=yes&ref=no
 

Offline amrit

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Hi Amrit,

It sounds like what you're claiming is that special relativity as it's usually formulated has errors.  If that's the case, it's a new theory rather than mainstream physics.  Do you mind posting about it further in the New Theories section of the board?  

Thanks,

JP (moderator)

SR has no errors, X4 is not temporal, X4 is spatial too by the math formalism X4 = ict X4 is spatial distance ( d = v x t )where t means "tick" of clock in space that is timeless.
« Last Edit: 24/05/2010 11:08:55 by amrit »
 

Offline graham.d

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Amrit, the maths I used is based on Special Relativity and assumes lightspeed is invariant. You may argue your point regarding gravitational effects but Special Relativity is extremely well accepted and has yet to be contradicted by any experiment. In fact the concept of the photon clock is used in many undergraduate text books as a way of demonstrating how the invariance of lightspeed leads to the conclusion that there IS time dilation and Lorentz contraction.
 

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