Will a photon clock run at a different rate from an atomic clock under gravity?

  • 147 Replies
  • 46383 Views

0 Members and 1 Guest are viewing this topic.

*

Offline amrit

  • Sr. Member
  • ****
  • 103
  • Power of science is uncompromised search for truth
    • View Profile
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 of relative velocity of material change second atom clock will in 30 days “tick” faster as the atom clock on the surface for 1,23 x 10 -6 seconds.

General Theory of Relativity considers light moves through the space with constant velocity regardless upon the strength of gravitation. This implies that at the scale of the photon and below at the scale of Planck relativistic gravitational effect of relative velocity of material change does not exist.

yours amrit

Amrit, I've rephrased your title as a question to make the forum easier to navigate.  Try to do so in the future.  Thanks.  -Mod
« Last Edit: 20/05/2010 06:51:38 by JP »
amrit sorli

*

Offline Soul Surfer

  • Neilep Level Member
  • ******
  • 3345
  • keep banging the rocks together
    • View Profile
    • ian kimber's web workspace
You are thinking wrongly here.  Time always ticks at the same rate wherever you are and however you move,  so you would not notice any change.  The difference in time scales is between the two points one inside and one outside the gravitational field and/or  travelling at different speeds. so it is the distant observer who will see the clocks ticking at a different rate. and you will only notice the difference when you get back and compare your clock with that of the distant observer.
Learn, create, test and tell
evolution rules in all things
God says so!

*

Offline amrit

  • Sr. Member
  • ****
  • 103
  • Power of science is uncompromised search for truth
    • View Profile
I would not agree.
Atomic clock on the top of a high mountain runs faster than at the sea-side.
This is proved with experiment.
We will prove with experiment that for the photon clocks it is not so.
They run with the same velocity regardless to the gravity.

amrit
amrit sorli

*

Offline graham.d

  • Neilep Level Member
  • ******
  • 2208
    • View Profile
At first sight your reasoning seems sound, Amrit. It is an extension to the simple demonstration of time dilation in Special Relativity where a stationary observer is watching light bouncing between two mirrors in a moving frame. This is interesting.

Have you any theory associated with this?

*

Offline syhprum

  • Neilep Level Member
  • ******
  • 3893
    • View Profile
"General Theory of Relativity considers light moves through the space with constant velocity regardless upon the strength of gravitation"
This is true of course but when there is a gravitational field present the light takes a curved path hence the effective speed is less than if it took the direct path.
syhprum

*

Offline imatfaal

  • Neilep Level Member
  • ******
  • 2787
  • rouge moderator
    • View Profile
Amrit - a bit confused.  You are certainly right about the atomic clocks running slower due to a time dilation effect caused by gravity - but why would this time dilation effect not alter the perceived time for photon ticks as well. the speed of light will remain constant for a local observer - ie both clocks must remain in synchrony.  on the surface an observer will notice that time is slower in the mine compared to his measurement
There’s no sense in being precise when you don’t even know what you’re talking about.  John Von Neumann

At the surface, we may appear as intellects, helpful people, friendly staff or protectors of the interwebs. Deep down inside, we're all trolls. CaptainPanic @ sf.n

*

Offline graham.d

  • Neilep Level Member
  • ******
  • 2208
    • View Profile
I think that the photon clock will behave the same as the atomic clock though I do not agree with Syphrum. The maths would not work out - the bending of light would not increase the path length sufficiently. It is not the gravitational field that causes the time dilation but the gravitational potential. If you have a clock at the centre of the earth there is no significant field but the clock will be seen to run slower that one (also in no significant field) close to an observer a long way from the earth. The clock at the centre of the earth is at a much lower potential; another way to look at it is that the ticks from the clock would be redshifted in emerging from the earth's gravity to reach the distant observer.

I don't think a photon clock will behave differently but I have not reasoned out why yet. I think it is to do with not being able to time photon speed remotely. It can only be done by observing events and their intervals.

*

Offline JP

  • Neilep Level Member
  • ******
  • 3366
    • View Profile
I don't think a photon clock will behave differently but I have not reasoned out why yet. I think it is to do with not being able to time photon speed remotely. It can only be done by observing events and their intervals.

I think so.  It seems to me that to compare the clocks you have to get a signal from one clock to the other.  In doing so, the signal itself is going to be distorted because it has to change from the center-of-earth coordinate frame to the far-from-earth coordinate frame, which would make the results not agree.  It would be as if you took two sheets of graph paper with different scales and gave them to two of your friends.  You ask each of them to draw a line that's 5 boxes long.  Each friend would tell you they've drawn a 5-box-long line, and only when you compare them would you be able to tell the difference.  General relativity basically tells you that your clocks are going to measure things on your local graph paper.  You have to compare them with someone else's graph paper to notice where they disagree.

Don't ask me to do the math though.... [???]
« Last Edit: 19/05/2010 15:53:30 by JP »

*

Offline amrit

  • Sr. Member
  • ****
  • 103
  • Power of science is uncompromised search for truth
    • View Profile
At first sight your reasoning seems sound, Amrit. It is an extension to the simple demonstration of time dilation in Special Relativity where a stationary observer is watching light bouncing between two mirrors in a moving frame. This is interesting.

Have you any theory associated with this?

Yes I have, see our last article published in Physics Essays:
http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PHESEM000023000002000330000001&idtype=cvips&gifs=yes&ref=no

yors amrit
amrit sorli

*

Offline amrit

  • Sr. Member
  • ****
  • 103
  • Power of science is uncompromised search for truth
    • View Profile
Amrit - a bit confused.  You are certainly right about the atomic clocks running slower due to a time dilation effect caused by gravity - but why would this time dilation effect not alter the perceived time for photon ticks as well. the speed of light will remain constant for a local observer - ie both clocks must remain in synchrony.  on the surface an observer will notice that time is slower in the mine compared to his measurement

Velocity of photon is invariant on gravity. Out of that comes that photon clock will not have relativistic gravitational effect. I got that insight dhuring 4 days of za-zen meditation.
CALTECH has such a clock. I plan to have 4 clocks, 2 atom 2 photon and do experiment next year in South Africa in Gloden Mine Shaft 4200 m deep.
If someone is interested he can join us

HERE IS PAGE OF CALTECH PHOTON CLOCK
http://www.physorg.com/news5577.html
« Last Edit: 19/05/2010 19:28:27 by amrit »
amrit sorli

*

Offline imatfaal

  • Neilep Level Member
  • ******
  • 2787
  • rouge moderator
    • View Profile

Velocity of photon is invariant on gravity. Out of that comes that photon clock will not have relativistic gravitational effect.

But the slowing of the photon clock is not premised on the concept that the speed of light has changed - quite the opposite, to the observer it is invariable.  it is time that is dilated - the passing of time has slowed.  If i have understood correctly it is not that the measuring-devices that display the passage of time are incorrect; but that the passing of time has slowed ie proper time is still displayed.

how big and expensive are these clocks?  I would have thought very...

Gonna go to caltech site now. thnks for link

Matthew
There’s no sense in being precise when you don’t even know what you’re talking about.  John Von Neumann

At the surface, we may appear as intellects, helpful people, friendly staff or protectors of the interwebs. Deep down inside, we're all trolls. CaptainPanic @ sf.n

*

Offline imatfaal

  • Neilep Level Member
  • ******
  • 2787
  • rouge moderator
    • View Profile

HERE IS PAGE OF CALTECH PHOTON CLOCK
http://www.physorg.com/news5577.html

Amrit - Sorry to write consecutive posts but I think you might have put in a dud link. 

The link you gave and the paper that the physorg paper summarises is not for a photon clock that depends of the passage of light between two mirrors!!  It is a micromechanical device that is forced into oscillation by radiation-pressure; it is an analogue of a quartz clock that is forced into oscillation by electric current but using radiation-pressure.

I must admit that I thought and still kinda think that the photon clock based on a beam of light between two mirrors was an elegant gedanken to help elucidate SR.

Matthew
There’s no sense in being precise when you don’t even know what you’re talking about.  John Von Neumann

At the surface, we may appear as intellects, helpful people, friendly staff or protectors of the interwebs. Deep down inside, we're all trolls. CaptainPanic @ sf.n

*

Offline amrit

  • Sr. Member
  • ****
  • 103
  • Power of science is uncompromised search for truth
    • View Profile
Matthew

you think it is possible to make a real Photon Clock with two mirrors ?
If yes, than we will do an interesting experiment.

yours amrit
amrit sorli

*

Offline imatfaal

  • Neilep Level Member
  • ******
  • 2787
  • rouge moderator
    • View Profile
Matthew

you think it is possible to make a real Photon Clock with two mirrors ?
If yes, than we will do an interesting experiment.

yours amrit

Amrit - No I don't think it is possible , I think it is a Gedankenexperiment; ie a thought experiment to help people to get their heads around SR.  On top of that I think your concept that photon clock (if it existed) would be unaffected by gravitational potential time dilation is incorrect.  I must admit I have grave doubts about your initial statements; they challenge very profound and important ideas - and I do not think you have backed them up enough yet.

Matthew
There’s no sense in being precise when you don’t even know what you’re talking about.  John Von Neumann

At the surface, we may appear as intellects, helpful people, friendly staff or protectors of the interwebs. Deep down inside, we're all trolls. CaptainPanic @ sf.n

*

Offline amrit

  • Sr. Member
  • ****
  • 103
  • Power of science is uncompromised search for truth
    • View Profile
Mathew is interesting link where Einstein discuss the subject:
http://www.relativitybook.com/resources/Einstein_gravity.html
important to know he never talks about fourth coordinate X4 as time,
he presented as X4 = ict.

A ) if light velocity is constant than photon clock "ticks" with equal velocity regardless gravity
B ) if light velocity is influenced by gravity change than photon clock "ticks" with different velocity in different gravity
What you think is real ?

We all agree that c = frequency •  vawe lenght
by gravitational red shift frequency goes down and vawe lenght goes up. For me this shows gravity does not influences velocity of light, A is real B is wrong.

yours amrit
« Last Edit: 21/05/2010 01:18:51 by amrit »
amrit sorli

*

Offline JP

  • Neilep Level Member
  • ******
  • 3366
    • View Profile
He did that to make all the coordinates have the same units so that you can use (x1,x2,x3,x4) as a four-vector...

*

Offline amrit

  • Sr. Member
  • ****
  • 103
  • Power of science is uncompromised search for truth
    • View Profile
SR is postulated on constancy of light velocity.
Equality of inertial and gravitational mass is connecting SR and 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.
amrit sorli

*

Offline JP

  • Neilep Level Member
  • ******
  • 3366
    • View Profile
Gravity effects space and time.  This is why it can cause disagreement between your photon clocks at the center of the earth and in deep space.  Gravity doesn't have to effect the velocity of light in order to cause the clocks to disagree, since it effects the spatial distance between them.  Are you arguing that the clocks at the center of the earth and in deep space will agree perfectly when you compare them?

*

Offline graham.d

  • Neilep Level Member
  • ******
  • 2208
    • View Profile
A proper treatment should use GR but here is my reasoning; as I said before it is importent to understand what is meant by measuring times and lengths - you should really measure events and intervals as these would be invariant. Please bear with this lengthy description.

I prefer to use two observers - one at a long distance from the earth and another at the centre of the earth (ignoring practical difficulties that do not change the gedanken experiment). The reason is that neither will be in a gravitational field (or at least not one that cannot be made arbitrarily small) but the one at the earth's centre is at a lower gravitational potential.

The photon clock is constructed of two miirors spaced apart by a distance "x" so that a "tick" would be 2x/c long. In taking such a clock to the centre of the earth you, as a local observer, would not see any change in its behaviour. The mirrors will be the same distance apart however measured with any method you would have locally and the ticks would appear at the same time interval as when you constructed it (using measuring sticks, other clocks etc).

To a distant observer though, you and your clock have moved to a lower gravitational potential. The ticks from your clock (and any other clock) will be redshifted and running slow compared with his clocks. The apparent conundrum is why, if the velocity of light is the same to all observers, should the ticks from the photon clock be slow? The answer is (I think) that, at the lower potential, lengths (as measured by the distant observer) are larger so the mirrors are further apart. It is importent to understand how a distant observer would measure lengths and this is fundamental in solving even some apparent paradoxes in Special Relativity. The distant observer could measure the mirror spacing by sending a light pulse that partially reflects of the back of the first mirror (closest to him) but also passes by and reflects of the front face of the second mirror (furthest away from him). He would receive, some time later, two pulses with a time interval between them. This time interval (at the centre of the earth) would be the same as the tick time, but it would also be redshifted in returning to the distant observer. Like the tick, he would see that the gravitational potential gradient would have stretched the measured time to 2x'/c. This is interpreted exactly in the way that Lorentz contraction in SR is defined. It is the only way a distant observer can measure distances and lengths. The mirror spacing is larger to the distant observer.

The correct and more rigorous treatment would use GR and intervals in space-time but is mathematically challenging - at least for me.
« Last Edit: 21/05/2010 08:58:41 by graham.d »

*

Offline imatfaal

  • Neilep Level Member
  • ******
  • 2787
  • rouge moderator
    • View Profile
Amrit - I realise from your paper and other points you have made that you are trying to investigate new concepts of time - but in order to do this you are advancing arguments and quoting sources that explicitly require an engagement with the effet of gravity on space and time; and you seem to be avoiding this.  Your photon clocks will disagree for reasons that JP and Graham mentioned above.

With regards to your link of Einstein's notes - please read the final few paragraphs of section 3 and advise how this does not compromise your entire argument.  you will note that in the argument Einstein does not define 4th dimnsion attributes at all but talks of three-dimensional frames of reference in either uniform acceleration or homogeneous gravitational field.

in order to prove your points you must deal with observed and theoretical predicted time dilation and with spacial distortion (as described very clearly by Graham above) - which you have not done so far.

Matthew
There’s no sense in being precise when you don’t even know what you’re talking about.  John Von Neumann

At the surface, we may appear as intellects, helpful people, friendly staff or protectors of the interwebs. Deep down inside, we're all trolls. CaptainPanic @ sf.n

*

Offline amrit

  • Sr. Member
  • ****
  • 103
  • Power of science is uncompromised search for truth
    • View Profile
Amrit - I realise from your paper and other points you have made that you are trying to investigate new concepts of time - but in order to do this you are advancing arguments and quoting sources that explicitly require an engagement with the effet of gravity on space and time; and you seem to be avoiding this.  Your photon clocks will disagree for reasons that JP and Graham mentioned above.

With regards to your link of Einstein's notes - please read the final few paragraphs of section 3 and advise how this does not compromise your entire argument.  you will note that in the argument Einstein does not define 4th dimnsion attributes at all but talks of three-dimensional frames of reference in either uniform acceleration or homogeneous gravitational field.

in order to prove your points you must deal with observed and theoretical predicted time dilation and with spacial distortion (as described very clearly by Graham above) - which you have not done so far.

Matthew

Matthew space is timeless.
With clocks we measure numeric order of material change i.e. motion running in space.
Fundamental unit of numeric order is Planck Time.
Velocity of atomic clocks depends on gravity.
Velocity of photon clocks is independent on gravity as C is constant.
This has nothing to do with close or distant observer.
Such are rules of the universe, we observe it or not.
http://www.vetrnica.net/index.php?option=com_content&view=article&id=21&Itemid=23
yours amrit
amrit sorli

*

Offline amrit

  • Sr. Member
  • ****
  • 103
  • Power of science is uncompromised search for truth
    • View Profile
Gravity effects space and time.  This is why it can cause disagreement between your photon clocks at the center of the earth and in deep space.  Gravity doesn't have to effect the velocity of light in order to cause the clocks to disagree, since it effects the spatial distance between them.  Are you arguing that the clocks at the center of the earth and in deep space will agree perfectly when you compare them?

as C is invariant on inertial system and gravity, velocity of photon clocks is the same in the whole universe
velocity of atom clocks is not the same.....we know why and when
amrit sorli

*

Offline graham.d

  • Neilep Level Member
  • ******
  • 2208
    • View Profile
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 :-)

*

Offline imatfaal

  • Neilep Level Member
  • ******
  • 2787
  • rouge moderator
    • View Profile
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
 
There’s no sense in being precise when you don’t even know what you’re talking about.  John Von Neumann

At the surface, we may appear as intellects, helpful people, friendly staff or protectors of the interwebs. Deep down inside, we're all trolls. CaptainPanic @ sf.n

*

Offline Farsight

  • Sr. Member
  • ****
  • 396
    • View Profile
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.

*

Offline graham.d

  • Neilep Level Member
  • ******
  • 2208
    • View Profile
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

  • Sr. Member
  • ****
  • 103
  • Power of science is uncompromised search for truth
    • View Profile
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
amrit sorli

*

Offline amrit

  • Sr. Member
  • ****
  • 103
  • Power of science is uncompromised search for truth
    • View Profile
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)
amrit sorli

*

Offline amrit

  • Sr. Member
  • ****
  • 103
  • Power of science is uncompromised search for truth
    • View Profile
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
amrit sorli

*

Offline imatfaal

  • Neilep Level Member
  • ******
  • 2787
  • rouge moderator
    • View Profile
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 
There’s no sense in being precise when you don’t even know what you’re talking about.  John Von Neumann

At the surface, we may appear as intellects, helpful people, friendly staff or protectors of the interwebs. Deep down inside, we're all trolls. CaptainPanic @ sf.n

*

Offline syhprum

  • Neilep Level Member
  • ******
  • 3893
    • View Profile
What is the difference between a 'Photon clock' and the resonant cavity with which we are all familiar ?.
syhprum

*

Offline Farsight

  • Sr. Member
  • ****
  • 396
    • View Profile
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

  • Sr. Member
  • ****
  • 396
    • View Profile
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

  • Neilep Level Member
  • ******
  • 8328
  • "Vive la résistance!"
    • View Profile
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.
There ain'ta no sanity clause, and there ain'ta no centrifugal force æther.

*

Offline graham.d

  • Neilep Level Member
  • ******
  • 2208
    • View Profile
"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

  • Sr. Member
  • ****
  • 103
  • Power of science is uncompromised search for truth
    • View Profile
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.
amrit sorli

*

Offline Geezer

  • Neilep Level Member
  • ******
  • 8328
  • "Vive la résistance!"
    • View Profile
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?
There ain'ta no sanity clause, and there ain'ta no centrifugal force æther.

*

Offline amrit

  • Sr. Member
  • ****
  • 103
  • Power of science is uncompromised search for truth
    • View Profile
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.
amrit sorli

*

Offline Geezer

  • Neilep Level Member
  • ******
  • 8328
  • "Vive la résistance!"
    • View Profile
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.
There ain'ta no sanity clause, and there ain'ta no centrifugal force æther.

*

Offline amrit

  • Sr. Member
  • ****
  • 103
  • Power of science is uncompromised search for truth
    • View Profile
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
amrit sorli

*

Offline amrit

  • Sr. Member
  • ****
  • 103
  • Power of science is uncompromised search for truth
    • View Profile
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.
amrit sorli

*

Offline amrit

  • Sr. Member
  • ****
  • 103
  • Power of science is uncompromised search for truth
    • View Profile
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
amrit sorli

*

Offline graham.d

  • Neilep Level Member
  • ******
  • 2208
    • View Profile
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

  • Neilep Level Member
  • ******
  • 2208
    • View Profile
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

  • Sr. Member
  • ****
  • 103
  • Power of science is uncompromised search for truth
    • View Profile
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.

amrit sorli

*

Offline Murchie85

  • Sr. Member
  • ****
  • 124
    • View Profile
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

  • Neilep Level Member
  • ******
  • 3366
    • View Profile
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

  • Sr. Member
  • ****
  • 103
  • Power of science is uncompromised search for truth
    • View Profile
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
amrit sorli

*

Offline amrit

  • Sr. Member
  • ****
  • 103
  • Power of science is uncompromised search for truth
    • View Profile
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 »
amrit sorli

*

Offline graham.d

  • Neilep Level Member
  • ******
  • 2208
    • View Profile
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.