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

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Offline amrit

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Graham,

“time dilatation” means only that the velocity of clock slows down.
Not as a result time running slower, because there is no time as a 4-th dimension of space.
Physical time is “ticking” if clock in space that itself is timeless.
Velocity of photon clock is equal in all inertial systems because light has same speed in all inertial systems.
More than that:
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 same construction photon clock on the surface of the earth.
Experimental data show 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. Material change clocks run included run in space only and not in time.

Experimental data shows that velocity of atom clocks change. So relativity of velocity of material change starts above photon scale.

See my last article:
http://www.fqxi.org/data/forum-attachments/Relativistic_effects_of_felative__velocity__vixra.pdf
« Last Edit: 24/05/2010 11:32:47 by amrit »
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Offline graham.d

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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.
OK

Quote
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.


No. Firstly the photon has a short path because the mirror is approaching it but then it has a long path because the front mirror is receding from it. As the plane approaches lightspeed this long path dominates and the time to get there will tend to infinity. The length contracts, but not so much that the time delay for the photon to travel in both directions gets shorter. See the maths I took the time to work out for you. The time for the photon travel is not the same in each direction.
Quote
We know that atom clock in a fast airplane ticks slower than atom clock on the earth.
Yes, and there is no contradiction as I have shown.

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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.
OK

Quote
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.


No. Firstly the photon has a short path because the mirror is approaching it but then it has a long path because the front mirror is receding from it. As the plane approaches lightspeed this long path dominates and the time to get there will tend to infinity. The length contracts, but not so much that the time delay for the photon to travel in both directions gets shorter. See the maths I took the time to work out for you. The time for the photon travel is not the same in each direction.
Quote
We know that atom clock in a fast airplane ticks slower than atom clock on the earth.


Yes, and there is no contradiction as I have shown.



Graham, in SR length is getting shorter into direction of motion. Suppose our photon clock is 5 cm long. Because of the “length contraction” our clock will shrink a bit.
So is will “tick” faster.
But we know atom clocks run slower.
So there is a mistake here. Solution is: C is constant and there is no length contraction in material universe
« Last Edit: 24/05/2010 11:41:10 by amrit »
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Offline graham.d

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Amrit you are missing the point. You have to follow the events very carefully. The light gets from the front to the back mirror quickly because the mirror is coming towards it (time t1 in the maths). But it then takes a long time to get to the front mirror which is receding from it (time t2). The sum of these two times (t1+t2) is longer, as seen from the stationary observer, than the proper time (observer on the plane). Even though the plane is Lorentz contracted the net result is still that the time is longer. You have to follow the maths carefully. If you can find an error then please point it out.

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Offline Farsight

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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.
In SR the length contraction is in the direction of motion, and in GR via the principle of equivalence it's radial. The local strength of the gravitational field indicates the rate of change of gravitational potential at this location.

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.
It's tricky to say what the proper GR treatment is. When you read the original it is different to what's in modern textbooks, and that brings us back to the conflict between interpretations again.  

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.
Einstein's interpretation was that the speed of light varies, but the modern interpretation is that it's constant. I side firmly with Einstein because IMHO this is backed up by evidence like the Shapiro delay.

You seem very definite but there seems varying opinions.
I am. Einstein started with the constant speed of light as a postulate in 1905, but in 1911 he wrote On the Influence of Gravitation on the Propagation of Light, where he gives the expression c = c0(1 + Φ/c²). Here c is varying with gravitational potential. Then in 1912 he said "On the other hand I am of the view that the principle of the constancy of the velocity of light can be maintained only insofar as one restricts oneself to spatio-temporal regions of constant gravitational potential". He repeated this in 1913 when he said this: "I arrived at the result that the velocity of light is not to be regarded as independent of the gravitational potential. Thus the principle of the constancy of the velocity of light is incompatible with the equivalence hypothesis". There it is again in 1915 when he says " the writer of these lines is of the opinion that the theory of relativity is still in need of generalization, in the sense that the principle of the constancy of the velocity of light is to be abandoned."  That’s on page 259 of Doc 21, sorry, I’m not sure what the original paper is called. He says it again in late 1915, on page 150 of Doc 30, within The Foundation of the General Theory of Relativity. Einstein says "the principle of the constancy of the velocity of light in vacuo must be modified.". He spells it out in section 22 of the 1916 book Relativity: The Special and General Theory where he says this:

"In the second place our result shows that, 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 and to which we have already frequently referred, 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. Now we might think that as a consequence of this, the special theory of relativity and with it the whole theory of relativity would be laid in the dust..."

People see the word velocity in the translations without seeing the context and without noticing that he’s repeatedly referring to “the principle” and "one of the two fundamental assumptions". That's the SR postulate, which is the constant speed of light. And it's important to note that what he actually said was in German. it was die Ausbreitungsgeschwindigkeit des Lichtes mit dem Orte variiert. It translates into the speed of light varies with the locality. The word “velocity” in the 1920 Methuen translation was the common usage, as in “high velocity bullet”, not the vector quantity that combines speed and direction. He was saying the speed varies with position, and it causes the curvilinear motion. It causes the light to follow a curved path, like a car veers when the near-side wheels encounter mud at the side of the road.

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.
I read your post. What's wrong with it is that the Lorentz contraction in SR corresponds to the radial length contraction in GR. If you say your distant observer up in space isn't moving with respect to your observer at the centre of the earth, and if both observers hold their clocks flat, there is no length change. You can then remove redshift with a single observer who leaves a light-clock in space and takes another synchronised light-clock down to the centre of the earth for a while. When he goes back up into space the clocks are no longer synchronised. So the speed must be different.    

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.
Sounds good to me graham.

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Offline amrit

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Amrit you are missing the point. You have to follow the events very carefully. The light gets from the front to the back mirror quickly because the mirror is coming towards it (time t1 in the maths). But it then takes a long time to get to the front mirror which is receding from it (time t2). The sum of these two times (t1+t2) is longer, as seen from the stationary observer, than the proper time (observer on the plane). Even though the plane is Lorentz contracted the net result is still that the time is longer. You have to follow the maths carefully. If you can find an error then please point it out.

Graham

GPR corrections of velocity are equal for all observers.
There is no such a thing as “proper time”.
There is only a change of velocity of clock on the orbit that is valid for the observer on the orbit and for the observer on the surface of the earth.

In classical example of SR clock run slower on the fast train for the observer on the station and for the observer in the train. This is what shows experimental data.

In Relativity is relative velocity of material change and velocity of clocks and is valid for all observers.  Observer is not even necessary. Clock runs slower on the orbit without watching it.

Relativity is a very nature of the universe. Just it starts above photon size. Constancy of c point that out clearly.

Yours amrit
PS read my article on
http://www.vetrnica.net/index.php?option=com_content&view=article&id=21&Itemid=23
amrit sorli

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Offline amrit

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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.
In SR the length contraction is in the direction of motion, and in GR via the principle of equivalence it's radial. The local strength of the gravitational field indicates the rate of change of gravitational potential at this location.

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.
It's tricky to say what the proper GR treatment is. When you read the original it is different to what's in modern textbooks, and that brings us back to the conflict between interpretations again.  

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.
Einstein's interpretation was that the speed of light varies, but the modern interpretation is that it's constant. I side firmly with Einstein because IMHO this is backed up by evidence like the Shapiro delay.

You seem very definite but there seems varying opinions.
I am. Einstein started with the constant speed of light as a postulate in 1905, but in 1911 he wrote On the Influence of Gravitation on the Propagation of Light, where he gives the expression c = c0(1 + Φ/c²). Here c is varying with gravitational potential. Then in 1912 he said "On the other hand I am of the view that the principle of the constancy of the velocity of light can be maintained only insofar as one restricts oneself to spatio-temporal regions of constant gravitational potential". He repeated this in 1913 when he said this: "I arrived at the result that the velocity of light is not to be regarded as independent of the gravitational potential. Thus the principle of the constancy of the velocity of light is incompatible with the equivalence hypothesis". There it is again in 1915 when he says " the writer of these lines is of the opinion that the theory of relativity is still in need of generalization, in the sense that the principle of the constancy of the velocity of light is to be abandoned."  That’s on page 259 of Doc 21, sorry, I’m not sure what the original paper is called. He says it again in late 1915, on page 150 of Doc 30, within The Foundation of the General Theory of Relativity. Einstein says "the principle of the constancy of the velocity of light in vacuo must be modified.". He spells it out in section 22 of the 1916 book Relativity: The Special and General Theory where he says this:

"In the second place our result shows that, 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 and to which we have already frequently referred, 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. Now we might think that as a consequence of this, the special theory of relativity and with it the whole theory of relativity would be laid in the dust..."

People see the word velocity in the translations without seeing the context and without noticing that he’s repeatedly referring to “the principle” and "one of the two fundamental assumptions". That's the SR postulate, which is the constant speed of light. And it's important to note that what he actually said was in German. it was die Ausbreitungsgeschwindigkeit des Lichtes mit dem Orte variiert. It translates into the speed of light varies with the locality. The word “velocity” in the 1920 Methuen translation was the common usage, as in “high velocity bullet”, not the vector quantity that combines speed and direction. He was saying the speed varies with position, and it causes the curvilinear motion. It causes the light to follow a curved path, like a car veers when the near-side wheels encounter mud at the side of the road.

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.
I read your post. What's wrong with it is that the Lorentz contraction in SR corresponds to the radial length contraction in GR. If you say your distant observer up in space isn't moving with respect to your observer at the centre of the earth, and if both observers hold their clocks flat, there is no length change. You can then remove redshift with a single observer who leaves a light-clock in space and takes another synchronised light-clock down to the centre of the earth for a while. When he goes back up into space the clocks are no longer synchronised. So the speed must be different.    

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.
Sounds good to me graham.

Farsight gravitational red shift shows light velocity c is constant. Only frequency changes. If c is not constant connection betwen SR and GR is broken. This would be a bit to much....I do not think in Relativity there is a mistake....Relativity is perfect. The case is that there is no time there. With clocks we measure numerical order only...
http://www.vetrnica.net/index.php?option=com_content&view=article&id=21&Itemid=23
yours amrit
« Last Edit: 24/05/2010 12:38:16 by amrit »
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Offline Farsight

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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.
Noted Geezer, but remember that this is defining the second. Hertz is cycles per second, so we're finding the maximum then defining the frequency to be 9.192631770 GHz.

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 oscillation is a hyperfine transition, and electron spin-flip. The event is electromagnetic, as is the emitted light. If the gravitational potential is lower, all electromagnetic phenomena occur at a slower rate. We call it time dilation, but that rather misses the obvious fact that electromagnetic spin flips are happening slower and the emitted light is moving slower too.

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Offline Farsight

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Farsight gravitational red shift shows light velocity c is constant. Only frequency changes. If c is not constant connection betwen SR and GR is broken.
This isn't true I'm afraid, amrit. The frequency of the light isn't relevant. Start with two synchronised light clocks, leave one up in space, take the other down to the planet for a while taking care to avoid radial length contraction, then take it back up to space. The two clocks are no longer synchronised. Yes, the local speed of light is always measured to be 299,792,458 metres per second, but those two different clock readings tell you that 299,792,458 metres per second up in space is not the same as 299,792,458 metres per second down on the planet. People say the difference is because of "time dilation", but you and I know that clocks clock up motion rather than "the flow of time". Hence we know that a light clock clocks up the motion of light. Those two different readings are crystal-clear evidence that down on the planet, the light goes slower.   

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Offline amrit

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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.
Noted Geezer, but remember that this is defining the second. Hertz is cycles per second, so we're finding the maximum then defining the frequency to be 9.192631770 GHz.

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 oscillation is a hyperfine transition, and electron spin-flip. The event is electromagnetic, as is the emitted light. If the gravitational potential is lower, all electromagnetic phenomena occur at a slower rate. We call it time dilation, but that rather misses the obvious fact that electromagnetic spin flips are happening slower and the emitted light is moving slower too.

Farsight,

I’m not expert for clocks. As far as I know atomic clock works on atom frequency. Photon clock works on photon motion in space. Difference is quite clear. I’m emotionally tuned with c as a constant. It has its own elegance this idea. As far no experiment will prove opposite I stay with it.

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Offline amrit

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Farsight gravitational red shift shows light velocity c is constant. Only frequency changes. If c is not constant connection betwen SR and GR is broken.
This isn't true I'm afraid, amrit. The frequency of the light isn't relevant. Start with two synchronised light clocks, leave one up in space, take the other down to the planet for a while taking care to avoid radial length contraction, then take it back up to space. The two clocks are no longer synchronised. Yes, the local speed of light is always measured to be 299,792,458 metres per second, but those two different clock readings tell you that 299,792,458 metres per second up in space is not the same as 299,792,458 metres per second down on the planet. People say the difference is because of "time dilation", but you and I know that clocks clock up motion rather than "the flow of time". Hence we know that a light clock clocks up the motion of light. Those two different readings are crystal-clear evidence that down on the planet, the light goes slower.  

Farsight I do not buy that.
yours amrit
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Offline graham.d

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Amrit, "proper time" has a specific definition to be just that of an observer comoving with the moving frame. Your link does not work properly by the way.

I appreciate English is not your first language, but however hard I try, I cannot understand the sense of what you are saying. Perhaps you could show me where my maths is at fault?

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Offline Farsight

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We'll have to agree to differ, amrit. Sorry I couldn't help.

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Offline graham.d

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Farsight, I understand Einstein's view on this but note he was uncomfortable with this view. And I take your point about the clocks being "flat" which I take to mean parallel to a circumference as opposed to in-line and parallel to a radius. I don't think you can conclude that this removes the difference that may occur between remote length measurements although I admit that the maths is sufficiently hard that I could not show it would produce the same quantitative result. For example you could imagine a distant observer receiving signals from the mirrors at each end of the apparatus which were set up to send beams outward exactly parallel, but because they are in a divergent field they will follow geodesics that would have them diverge such that when they reached the distant observer they would show a bigger gap between the mirrors. Now it is very hard to say that this would yield the same value as the simpler calculation for the mirrors in line, but is, nonetheless, possible. The maths to calculate this is a bit hard.

I will give this a little more thought. A tenet of GR is that the all observers should agree on the spacetime interval. I am not sure that it is necessarily possible to resolve the meaning in term of just space and just time in this case. As the modern view is, as you say, that lightspeed is constant, how would these physicist view this scenario?

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Offline imatfaal

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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.

3 coils at 90 degrees to each other would nicely (after serious number crunching) allow dilation from varying gravitational potential and dilation from relative velocities to be separated - I think...
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Offline JP

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Actually, I'm not sure that there's any contradiction between the idea that the speed of light might not seem constant over large distances and the speed of light being constant locally in a vacuum.  From what I understand of it, you can think of it like traveling on the earth.  Say it takes me 4 hours to travel from Paris to Los Angeles.  I could calculate my average speed by taking the distance between them in 3D space (which is the length straight line through the globe divided by 4 hours) or I could measure my speed at every instant as I fly around the globe and average that.  The path through the globe will be far shorter than the actual speed I was traveling.  I think it's a similar case with GR and the speed of light.  If you look at lengthy paths and just try to calculate the speed of light based on what you'd expect if space-time were flat and the light moves at c, you find that it takes longer.  However, if you look at the light at every instant, it's moving at the speed c--it just takes a curved path, so the total time is longer.

Or put another way, if you look locally enough so that you're calculating instantaneous speed, space-time is flat and SR holds.  It's when you look over large enough regions of curved space-times that you get these deviations.  (I guess even if you're comparing two flat regions--which is what this discussion is about--measurements can differ because space-time can be stretched, but not curved.  Using the rulers and clocks of one region to measure the other will also cause the speed of light to appear to be slowed.)  In fact, I think you can go further and say that if the speed of light wasn't constant locally, the geometrical interpretation of general relativity would fail.  

Is there an equally valid model that allows the speed of light to vary locally and produces identical results (at least within the regimes we've tested)?  I don't know.  

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Offline graham.d

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Paris to LA in 4 hours - I didn't think the Ramjet was flying yet!

It is interesting to think of two regions that are both essentially flat regions of Minkowski space where they have different degrees of Stretched Space-Time. There would seem to be no way of determining the degree of "Stretchedness" from inside such a region because all the physical laws would work fine in both regions. So if one region is open to investigation from the other (as in the case postulated previously) it seems odd that the observed behaviour would depend on the spacetime between the two regions. I think this is what you are saying JP. I could easily imagine that you could measure the temporal and spatial difference but it is hard to believe that these would be different depending on the route your information traveled to get to you.

I think that Farsight was alluding to the idea that the velocity of light being a tensor field (rather than a scalar field) in having different radial and tangential values in a schwartzchild metric. It still seems odd that the intervening space would affect what should be scalar measurements in flat space though. Any ideas? I may be missing some key points here.

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Offline Farsight

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Farsight, I understand Einstein's view on this but note he was uncomfortable with this view.
It's an interesting one Graham. One day when the dust has settled somebody will write an authorative narrative on the long and tortuous trail, and it will be fascinating reading.

And I take your point about the clocks being "flat" which I take to mean parallel to a circumference as opposed to in-line and parallel to a radius.
Thanks, sorry if I didn't make it clear.   

I don't think you can conclude that this removes the difference that may occur between remote length measurements although I admit that the maths is sufficiently hard that I could not show it would produce the same quantitative result.
I think you can actually, very simply. If you go along with GR radial length contraction, and Einstein, and the Occam's razor direct evidence that says the light is moving slower rather than "time runs slower", you can see it. The metre is defined as "the distance travelled by light in a complete vacuum in 1⁄299,792,458th of a second". Hence the bigger second and the slower light cancel each other out. The metre is unchanged.   

For example you could imagine a distant observer receiving signals from the mirrors at each end of the apparatus which were set up to send beams outward exactly parallel, but because they are in a divergent field they will follow geodesics that would have them diverge such that when they reached the distant observer they would show a bigger gap between the mirrors. Now it is very hard to say that this would yield the same value as the simpler calculation for the mirrors in line, but is, nonetheless, possible. The maths to calculate this is a bit hard.
Sorry, I'm not keen on this because it seems to go against the grain of general relativity regardless of which interpretation one prefers. 

I will give this a little more thought. A tenet of GR is that the all observers should agree on the spacetime interval. I am not sure that it is necessarily possible to resolve the meaning in term of just space and just time in this case. As the modern view is, as you say, that lightspeed is constant, how would these physicist view this scenario?
I'm not sure graham. But I'd say that to fix the speed of light as an absolute constant, one has to elevate time to something above and beyond the experimental and observational evidence, and say "time runs slower". The trouble is, when you look at a clock, you don't see time running at all. All you see is cogs moving, or a crystal oscillating, or a caesium atom oscillating, or light moving. It always comes down to motion one way or another. Clocks clock up motion, that's all they ever do, that's why in The Foundation of the General Theory of relativity Einstein gave us the equations of motion. And when the clock runs slower, it isn't really time running slower, it's the motion going slower. Have a google on "Farsight" and "Time Explained" for my take on this.

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Offline Farsight

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..I think that Farsight was alluding to the idea that the velocity of light being a tensor field (rather than a scalar field) in having different radial and tangential values in a schwartzchild metric.
I wasn't, I was just trying to keep things simple and focus on what we actually observe, which is two different readings from two identical parallel-mirror light-clocks at different locations where the gμv gravitational potential is different. 

It still seems odd that the intervening space would affect what should be scalar measurements in flat space though. Any ideas? I may be missing some key points here.
The intervening space isn't relevant. You could run the clocks for years and see the discrepancy grow ever larger. Redshift and signal time becomes increasingly inconsequential. Like you say, the spacetime is flat at both locations. There is no discernible curvature out in space or at the centre of the earth, because there is no detectable gμv gradient. The different measurements are because the space itself is different at those two locations.

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Offline Geezer

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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.
Noted Geezer, but remember that this is defining the second. Hertz is cycles per second, so we're finding the maximum then defining the frequency to be 9.192631770 GHz.

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 oscillation is a hyperfine transition, and electron spin-flip. The event is electromagnetic, as is the emitted light. If the gravitational potential is lower, all electromagnetic phenomena occur at a slower rate. We call it time dilation, but that rather misses the obvious fact that electromagnetic spin flips are happening slower and the emitted light is moving slower too.

Er, well the second is defined as the interval for a certain number of the atomic events. The number was chosen to line up with more traditional definitions for the second. As you point out, the fundamental "tick" is an electromagnetic event with the atom.

The light output could be delayed in a very variable fashion, but it would have no effect on the frequency of the microwave resonator. The light output is only sampled periodically to make very infrequent and very minute adjustments to the frequency of the microwave resonator. I believe the detector only responds to the number of photons that reach it. I'm not sure how they know to adjust up or down because I would assume that the light output will diminish if the resonator is slow or fast relative to the caesium events.

Being pedantic, you can't really say that the events are happening at a "slower rate", because that seems to suggest that time itself is invariant.
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Offline graham.d

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Both spaces are flat Minkowski space and I think we are assuming that the physical laws are the same, as measured locally, at each location and that it would be expected that the gravitational potential is purely relative and has no meaning in absolute terms. Are these correct assumptions to work with? If, then, the only difference is that space is "stretched" more in one region than the other then this "scaling" must apply to (x,y,x,-ct) equally mustn't it? If not what coordinate transformation would apply? In SR the basis for the Lorentz transformation is the constancy of c to all observers. Is the only effect of gravitational potential (Φ) that c is a function of Φ and that this would be the basis of any coordinate transformation?

This seems reasonable but is it all consistent with observation or gedanken experiments?

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Offline JP

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Paris to LA in 4 hours - I didn't think the Ramjet was flying yet!

Heh.  I'm riding in my photon jet.  It would be faster, but it slowed down a bit because it's so close to the earth.
 [;)]

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Offline Geezer

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Heh.  I'm riding in my photon jet.  It would be faster, but it slowed down a bit because it's so close to the earth.
 [;)]


Yes, but I'm sure you'll arrive in no time at all.
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Offline amrit

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Amrit, "proper time" has a specific definition to be just that of an observer comoving with the moving frame. Your link does not work properly by the way.

I appreciate English is not your first language, but however hard I try, I cannot understand the sense of what you are saying. Perhaps you could show me where my maths is at fault?

Graham with your math all is fine. Just be aware clocks tick in space only and not in time. Time dilatation means that clocks run slower in a timeless space. You think in math terms, think in physical terms and you will discover universe is timeless. In the universe there is only motion, time belongs to the mind. Time is a mind frame through which we experience motion, read ma article below:
http://www.vetrnica.net/index.php?option=com_content&view=article&id=21&Itemid=23
yours amrit
amrit sorli

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Offline Geezer

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In the universe there is only motion, time belongs to the mind. Time is a mind frame through which we experience motion, read ma article below:

Amrit,

I have tried to persuade the molecules that make up my body that time is only a state of mind, but they won't listen.

Isn't it high time we move this topic to New Theories?

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Offline amrit

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NO. This is not new theory. This is about right understanding of SR. We live in space only. X4 is not time, X4 is spatial too.

PS
missing understanding is that in SR velocity of clocks in all inertial systems is invariant of the observers. Observer has no influence on velocity of clocks. Clocks run with the same velocity for all observers.
amrit sorli

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Offline Geezer

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Clocks run with the same velocity for all observers.

Yes. I completely agree with you there. As I see it, all things are affected by their local time. That means everything from subatomic events to fancy atomic clocks have to obey local time. Consequently, any observation of velocity (which can only be expressed in terms of time) will be the same for all observers.
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Offline JP

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Clocks run with the same velocity for all observers.

Yes. I completely agree with you there. As I see it, all things are affected by their local time. That means everything from subatomic events to fancy atomic clocks have to obey local time. Consequently, any observation of velocity (which can only be expressed in terms of time) will be the same for all observers.

I'm going to disagree just to be difficult.  But seriously, clocks don't measure velocity.  The "velocity of a clock" is how fast it goes when you throw it.  Clocks measure time.  If clocks only measured velocity, they couldn't count time, since velocity only tells you the ratio of distance to time.  You need a value for distance and for velocity to get time.  That's how light clocks work: by knowing the distance between the mirrors and using the known value of the speed of light. 

That's also why this theory doesn't agree with special relativity.  The velocity of light might be constant for all clocks, but their distance measurements don't agree, so they can't possibly tick at the same speed.

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Offline Geezer

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I'm going to disagree just to be difficult.  But seriously, clocks don't measure velocity.  The "velocity of a clock" is how fast it goes when you throw it.  Clocks measure time.

Far be it from me to disagree with someone who obviously knows what they are talking about, but clocks don't measure time. The only thing that clocks do is count events. The events may be determined by time, but I'm not sure that's quite the same thing as saying that clocks measure time.

Time measures clocks might be a better way to look at it.
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Offline JP

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I'm going to disagree just to be difficult.  But seriously, clocks don't measure velocity.  The "velocity of a clock" is how fast it goes when you throw it.  Clocks measure time.

Far be it from me to disagree with someone who obviously knows what they are talking about, but clocks don't measure time. The only thing that clocks do is count events. The events may be determined by time, but I'm not sure that's quite the same thing as saying that clocks measure time.

Time measures clocks might be a better way to look at it.

This is somewhat speculative, since I'm not a relativity expert:

I guess maybe since we're stuck using the language of special relativity here, maybe the best any device can do is to measure the interval between two events?  (The interval being Δx2-Δt2, where Δx is the spatial separation of the events and Δt is their temporal separation [with c=1]).  You can then get time by relating this interval to physical processes.  If your clock is using a cesium atom at rest, Δx=0, so your measurement of a "tick" is directly getting time out.  If your clock is a light clock, then you're measuring an interval which includes both a Δx and a Δt (I suspect you need to calculate two intervals: one in each direction, as graham.d did).  That's why you need to also use the fact that light speed is constant--which tells you that the interval between the events is zero, which in turn lets you calculate the time of a second from the distance between mirrors. 

---------------------------------
Now that I'm done confusing myself, this part is my real point:

The point I was trying to get across is that clocks spit out "time" as an answer, no matter what they're using as input.  Velocity isn't enough information on its own to give you time as an answer--you need to know a distance measurement as well, which is why you will still get time dilation in a photon clock even with a constant speed of light.

I guess a good question is whether or not a "good" clock (meaning one that measures local time accurately) is in practice any different than measuring time itself.  I don't know the answer, but I've been assuming that it isn't.

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Offline Farsight

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Er, well the second is defined as the interval for a certain number of the atomic events. The number was chosen to line up with more traditional definitions for the second. As you point out, the fundamental "tick" is an electromagnetic event with the atom.
And if the space is different, the underlying motion associated with this event is slower. It's a spin-flip, the electron is turning over. You can get a feel for this by stretching an eleastic band over your finger and thumb. Stick a pencil in, and turn the pencil over 180 degrees tensioning the elastic, then let go. It vibrates back and forth.   

The light output could be delayed in a very variable fashion, but it would have no effect on the frequency of the microwave resonator. The light output is only sampled periodically to make very infrequent and very minute adjustments to the frequency of the microwave resonator. I believe the detector only responds to the number of photons that reach it. I'm not sure how they know to adjust up or down because I would assume that the light output will diminish if the resonator is slow or fast relative to the caesium events.
It makes no odds, electromagnetic phenomena propagate at a slower rate in a region of lower gravitational potential.

Being pedantic, you can't really say that the events are happening at a "slower rate", because that seems to suggest that time itself is invariant.
Things move slower, that's all. When the motion is cyclic like the spin-flip, we call the result an event.

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Offline Farsight

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Both spaces are flat Minkowski space and I think we are assuming that the physical laws are the same, as measured locally, at each location and that it would be expected that the gravitational potential is purely relative and has no meaning in absolute terms. Are these correct assumptions to work with?
Yes, both spaces are flat and local physical laws are the same. But whilst that  gravitational potential is relative, it does have an absolute meaning. It's saying something pretty fundamental about the nature of space at that location, and relative measurements tell you that the difference between locations is very real.   

If, then, the only difference is that space is "stretched" more in one region than the other then this "scaling" must apply to (x,y,x,-ct) equally mustn't it? If not what coordinate transformation would apply?
I wouldn't say space is "stretched". Instead it's "squashed" in the radial direction, and we're trying to set that aside to make it clear that the -ct term has changed. The best colloquial term I can find is that space is "stronger" in a region of lower gravitational potential.

In SR the basis for the Lorentz transformation is the constancy of c to all observers. Is the only effect of gravitational potential (Φ) that c is a function of Φ and that this would be the basis of any coordinate transformation?
Not quite, because of the radial length contraction that equates to the SR length contraction. The effect of gravitational potential on c is the one to home in on. 

This seems reasonable but is it all consistent with observation or gedanken experiments?
Yes, absolutely. Clocks run slower, even light clocks, along with all physical processes. We have the GPS clock adjustment, and it's the Shapiro Delay. The time component of this is the most important, more important than any path change. 

Edit: Amrit is correct when he says this is not a new theory. The concept that "time is change" goes back to Aristotle, it resurfaced as Presentism in 1908, and was only fully appreciated by Godel and Einstein in 1949. And I'm afraid clocks don't measure time. What they actually measure is motion. This might be cyclical motion such as the turning of a cog or the vibration of a crystal or an electron bond, and we might label these cyclical motions as events. But the important thing to grasp is if that motion goes slower, the clock goes slower. It's not time going slower, it's motion. And that motion is through space. When you "stop the clock" or "freeze the frame" what you're actually stopping is motion. I've written an essay called "Time Explained" to flesh out the details of all this, but people consider this sort of thing to be "New Theories". That's because it's not in line with the common current concept of time as something that flows and that we travel through. It isn't, and we don't. There is absolutely no scientific evidence to back up this common concept of time, none whatsoever.
« Last Edit: 25/05/2010 11:39:24 by Farsight »

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Offline graham.d

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"Yes, both spaces are flat and local physical laws are the same. But whilst that  gravitational potential is relative, it does have an absolute meaning. It's saying something pretty fundamental about the nature of space at that location, and relative measurements tell you that the difference between locations is very real." - Farsight

This is what I was getting at but I have not really thought it through yet. Unfortunately I have to work too :-) If Gravitational Potential has an absolute range, then there must come a point where the this should be detectable within the spacetime region itself - like a BH singularity for example. It is unusual in nature to find brickwall phenomena where there is no effect of a parameter but when it reaches a certain value there is a dramatic change. Though, come to think of it, it may be that the assumption of flatness may start to be invalid, covering a smaller and smaller region, as the potential gets lower. Then this would be noticeable. Though this would depend on whether this changed faster than the the space compression.

The radial direction for the sqashing of space would presumably not be important if we could assume that the spacetime region was sufficiently flat (a small enough volume for example). I'm trying to stick with a Minkowski metric rather than a Schwartzchild metric - but maybe this cannot be done. Going back to the mirror spacing, this would mean the mirror spacing would be smaller as viwed by a distant observer at a higher potential. This would then mean that that c would have to change (be slower) with a higher order than the space compression to produce the gravitational time dilation. Have you a web reference that gives the coordinate tranformation that should be applied for a change in Gravitational Potential? It should take these effects into account.
« Last Edit: 25/05/2010 12:14:20 by graham.d »

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Offline Farsight

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There is a "brick wall" phenomenum, graham - at the event horizon of a black hole. The coordinate speed of light at the event horozon is zero according to all observers in the universe at large, and the radial length contraction is total. This is the Schwartzchild metric, where the singularity is at the event horizon "surface", rather than at a point in the centre.

No, I'm afraid I don't have a web reference for a coordinate tranformation that should be applied for a change in gravitational potential. This: http://casa.colorado.edu/~ajsh/schwp.html isn't bad, but the problem is that if light has stopped you don't actually have a coordinate system any more. All measurements take a finite time in your proper time, but forever as far as the rest of the universe is concerned, so those measurements are never actually made.

This is quite a good article too: http://www.mathpages.com/rr/s7-02/7-02.htm. The author doesn't agree with me, but he does mention the Weinberg field interpretation, which is what I'm talking about here.

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Offline graham.d

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Thanks, I'll take a look when time permits. I was referring to a coordinate transformation before the limit of a singularity although if it doesn't include that, it is incomplete. In any case, my point was to see whether the approach of the singularity was detectable (before the singularity was reached) from inside the spacetime region that was being "compressed". Having thought about it, I think not. I mentioned before that it may be increasingly difficult to have a region of approximately flat space approaching such a condition, and this would be detectable. This is analogous to increasing tidal forces when approaching a BH however, a sufficiently huge BH would allow crossing of such a horizon without noticeable tidal forces (i.e. local space is reasonably flat). To take this analogy further, does this mean the gravitational potential has gone negative? I appreciate this would have no meaning to the outside observer any more than the state of anything crossing a BH event horizon.

Mathpages are generally excellent - I don't know why I didn't look there anyway. I will take a look. Thanks.

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Offline Geezer

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Er, well the second is defined as the interval for a certain number of the atomic events. The number was chosen to line up with more traditional definitions for the second. As you point out, the fundamental "tick" is an electromagnetic event with the atom.
And if the space is different, the underlying motion associated with this event is slower. It's a spin-flip, the electron is turning over. You can get a feel for this by stretching an eleastic band over your finger and thumb. Stick a pencil in, and turn the pencil over 180 degrees tensioning the elastic, then let go. It vibrates back and forth.   

The light output could be delayed in a very variable fashion, but it would have no effect on the frequency of the microwave resonator. The light output is only sampled periodically to make very infrequent and very minute adjustments to the frequency of the microwave resonator. I believe the detector only responds to the number of photons that reach it. I'm not sure how they know to adjust up or down because I would assume that the light output will diminish if the resonator is slow or fast relative to the caesium events.
It makes no odds, electromagnetic phenomena propagate at a slower rate in a region of lower gravitational potential.

Being pedantic, you can't really say that the events are happening at a "slower rate", because that seems to suggest that time itself is invariant.
Things move slower, that's all. When the motion is cyclic like the spin-flip, we call the result an event.

LOL - it's not really "slower". If we are measuring time by counting atomic events, we always observe the same number of atomic events for a particular amount of time. My point is that we have to be very careful when we use measures that are a function of time.
There ain'ta no sanity clause, and there ain'ta no centrifugal force æther.

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Offline Geezer

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I guess a good question is whether or not a "good" clock (meaning one that measures local time accurately) is in practice any different than measuring time itself.  I don't know the answer, but I've been assuming that it isn't.

JP - I think that any clock is actually measuring the passage of time in its locality. And clocks can include anything from atomic activity, chemical processes, large pendulums and rotating orbs. I think our intution suggests there is some sort of absolute time, even though science tells us it's not so.

We sense the the passage of time is smooth, but if it was in fact quite jittery I think it would be impossible to detect that it actually was jittery without some sort of absolute timing device which was independent of local time (which I think is impossible!)

I'm going to have to lie down for a bit now  [;D]
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Offline amrit

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Time does not run on its own. There is no passage of time.
Time dilatations means exactly that clock run slower.
Not because of time run slower.
There is no physical time behind run of a clock.
Clock run in a timeless space.
amrit sorli

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Offline Farsight

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..In any case, my point was to see whether the approach of the singularity was detectable (before the singularity was reached) from inside the spacetime region that was being "compressed". Having thought about it, I think not.
You certainly won't observe the time dilation or the  length contraction locally, but there actually be a way to find out that things are changing by measuring the fine structure constant. Search the internet for "tests of Lorentz invariance" to read about other ideas for this. I'm all for relativity, but I wouldn't rule out some subtle breach here.

I mentioned before that it may be increasingly difficult to have a region of approximately flat space approaching such a condition, and this would be detectable. This is analogous to increasing tidal forces when approaching a BH however, a sufficiently huge BH would allow crossing of such a horizon without noticeable tidal forces (i.e. local space is reasonably flat). To take this analogy further, does this mean the gravitational potential has gone negative? I appreciate this would have no meaning to the outside observer any more than the state of anything crossing a BH event horizon.
I don't see how a gravitational potential can go negative. The gradient in gravitational potential is "why things fall down". If there's no gradient at all, things don't fall down. If the gradient is uniform you still fall down, but there's no tidal force. There's only a tidal force when the gradient changes say between your head and your feet. There's a gradient in the gradient, as it were.

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Offline Farsight

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LOL - it's not really "slower". If we are measuring time by counting atomic events, we always observe the same number of atomic events for a particular amount of time. My point is that we have to be very careful when we use measures that are a function of time.
It really is slower, Geezer. If you could actually film those atomic events at the different locations then put them up on a split screen, you'd see it. And the definition of the second is the other way round. The number of atomic events defines the second. It increases with reducing gravitational potential because the motion underlying the events is slower. Amrit is right. Time doesn't "run" and it doesn't "pass". When a clock goes slower it's because things move slower. Godel and Einstein really did work this out in 1949.

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Offline Geezer

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LOL - it's not really "slower". If we are measuring time by counting atomic events, we always observe the same number of atomic events for a particular amount of time. My point is that we have to be very careful when we use measures that are a function of time.
It really is slower, Geezer. If you could actually film those atomic events at the different locations then put them up on a split screen, you'd see it. And the definition of the second is the other way round. The number of atomic events defines the second. It increases with reducing gravitational potential because the motion underlying the events is slower. Amrit is right. Time doesn't "run" and it doesn't "pass". When a clock goes slower it's because things move slower. Godel and Einstein really did work this out in 1949.

OK - I'll admit I'm being pedantic, but I think it's important to precise when we talk about time.

I don't think we can really use the terms "slower" or "faster" because speed is a function of time, so there is no difference in speed. There is no "absolute" time, so when you say "slower", I think you really mean that the count of observed events at different locations can differ (assuming we have some method to observe or record those events.)
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Offline graham.d

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"I don't see how a gravitational potential can go negative. The gradient in gravitational potential is "why things fall down". If there's no gradient at all, things don't fall down. If the gradient is uniform you still fall down, but there's no tidal force. " - Farsight

I do understand this Farsight but linearity in potential, in itself, does not preclude a negative value. You can have linearity in Potential from + to - infinity with respect to an arbtrary spacial measure (say r) and its differential with respect to r would be a constant. It is also obvious that it would be the second derivative that would result in tidal forces.

My point was simply that someone can pass through a BH event horizon and there would be no specific local measurement to mark that event providing the BH were large enough to minimise destructive tidal forces. But what would be their Gravitational Potential? There is no doubt that it would continue to fall as they moved toward the BH centre. From a distant observer's perspective they would have zero GP as they reach the EH but that time dilation would infinitely delay the event. In this sense negative GP values are "cosmically censored". From the perspective of the person crossing a BH EH, I guess it would not be the first thing on his mind. I'm never sure what he would see though there are some interesting simulations and animations on the web. Perhaps he should see the distant observer having infinite GP.

Anyway, this is not so profound as I first thought and is not leading to any great insight. It does suggest that GP would depend on from whose perspective it is being measured and that the scale can slide so as to define the zero value at (say) an EH.

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Offline amrit

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LOL - it's not really "slower". If we are measuring time by counting atomic events, we always observe the same number of atomic events for a particular amount of time. My point is that we have to be very careful when we use measures that are a function of time.
It really is slower, Geezer. If you could actually film those atomic events at the different locations then put them up on a split screen, you'd see it. And the definition of the second is the other way round. The number of atomic events defines the second. It increases with reducing gravitational potential because the motion underlying the events is slower. Amrit is right. Time doesn't "run" and it doesn't "pass". When a clock goes slower it's because things move slower. Godel and Einstein really did work this out in 1949.

OK - I'll admit I'm being pedantic, but I think it's important to precise when we talk about time.

I don't think we can really use the terms "slower" or "faster" because speed is a function of time, so there is no difference in speed. There is no "absolute" time, so when you say "slower", I think you really mean that the count of observed events at different locations can differ (assuming we have some method to observe or record those events.)

speed is not function of time, speed is a function of motion that run in space (and not in time)
ve measure speed with clocks

v = d/tn  where tn is a last "tick" of clock.
amrit sorli

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Offline JP

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speed is not function of time, speed is a function of motion that run in space (and not in time)
ve measure speed with clocks

v = d/tn  where tn is a last "tick" of clock.

I disagree.  Everything I've ever learned in mainstream physics on the subject says that speed a ratio of change in position to change in time.  Classically speaking, speed=dx/dt (dx distance moved in a short time, dt).  Do you have a source for your claim?

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Offline amrit

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speed is not function of time, speed is a function of motion that run in space (and not in time)
ve measure speed with clocks

v = d/tn  where tn is a last "tick" of clock.

I disagree.  Everything I've ever learned in mainstream physics on the subject says that speed a ratio of change in position to change in time.  Classically speaking, speed=dx/dt (dx distance moved in a short time, dt).  Do you have a source for your claim?

Yes now we will change this idea as there is no experimental data for it. Nothing happens in time as time is a mind frame through which we experience motion in space.
amrit sorli

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Offline Farsight

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I disagree. Everything I've ever learned in mainstream physics on the subject says that speed [is] a ratio of change in position to change in time.
There no easy way to say this, JP, but it has to be said: everything you've ever learned on the subject is wrong. It sounds awful I know, but look to the evidence. What we actually see is space and motion through it. We don't see time flowing or any travel through time. The motion is through space. So motion gains precedence over time. Time is reduced to a cumulative measure of local motion, such as the motion of light or caesium spin-flips. For a reference, see A World Without Time: The Forgotten Legacy of Godel and Einstein. Godel and Einstein worked it out in 1949: you don't need time to have motion, you need motion to have time.

Amrit is right. Shame he's wrong about that photon clock, but hey-ho. Hi amrit!

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Offline Geezer

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speed is not function of time, speed is a function of motion that run in space (and not in time)
ve measure speed with clocks

v = d/tn  where tn is a last "tick" of clock.

I disagree.  Everything I've ever learned in mainstream physics on the subject says that speed a ratio of change in position to change in time.  Classically speaking, speed=dx/dt (dx distance moved in a short time, dt).  Do you have a source for your claim?

Yes now we will change this idea as there is no experimental data for it. Nothing happens in time as time is a mind frame through which we experience motion in space.

JP is providing the accepted definition for speed. If you remove time from the definition, I think you are referring to something other than speed. To avoid confusion you should probably use a different name for whatever it is you are referring to.

Mind you, it would be good if you are correct, because, if you are, it means I'm not really getting older. I just think I'm getting older as I move around in space  [;D]
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Offline JP

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I disagree. Everything I've ever learned in mainstream physics on the subject says that speed [is] a ratio of change in position to change in time.
There no easy way to say this, JP, but it has to be said: everything you've ever learned on the subject is wrong. It sounds awful I know, but look to the evidence. What we actually see is space and motion through it. We don't see time flowing or any travel through time. The motion is through space. So motion gains precedence over time. Time is reduced to a cumulative measure of local motion, such as the motion of light or caesium spin-flips. For a reference, see A World Without Time: The Forgotten Legacy of Godel and Einstein. Godel and Einstein worked it out in 1949: you don't need time to have motion, you need motion to have time.

Amrit is right. Shame he's wrong about that photon clock, but hey-ho. Hi amrit!

I did a bit of poking around to find out what Godel actually did, scientifically.  What Godel did, it seems, was to work out solutions to Einstein's field equations that show that an object moving normally through the universe (i.e. on time-like paths) could go back in time. 

Does this cause problems with physics in our universe?  Almost certainly not, since Godel's universes are not our universe.  It might have philosophical implications about time being a "special" dimension. 

At any rate, back to your post.  I disagree with the conclusions you're drawing.  We certainly don't see "space and motion through it."  What we "see" (and how GR describes the universe) is paths in space-time.  What we locally define as velocity is a measurement of the slope between the space and time components of that path at any point.  Since these paths are geometrical objects, what you can physically measure are distances.  From these distances you can derive slopes.  Therefore, time is a fundamental quantity (it's a measure of "distance") and speed is a derived quantity (it's a measure of slope, or a ratio of "distances.")

Can you provide any scientific evidence to the contrary?

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Offline amrit

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I disagree. Everything I've ever learned in mainstream physics on the subject says that speed [is] a ratio of change in position to change in time.
There no easy way to say this, JP, but it has to be said: everything you've ever learned on the subject is wrong. It sounds awful I know, but look to the evidence. What we actually see is space and motion through it. We don't see time flowing or any travel through time. The motion is through space. So motion gains precedence over time. Time is reduced to a cumulative measure of local motion, such as the motion of light or caesium spin-flips. For a reference, see A World Without Time: The Forgotten Legacy of Godel and Einstein. Godel and Einstein worked it out in 1949: you don't need time to have motion, you need motion to have time.

Amrit is right. Shame he's wrong about that photon clock, but hey-ho. Hi amrit!

Yes this picture here on the first page how mirrors are moving and so photon has longer way and photon clock ticks slower is ridiculous.
Mora than that: when you move mirrors that atom run between them along the direction of the fast aircraft motion that photon clock should shrink and so “tick” faster what is contrary to SR
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I disagree. Everything I've ever learned in mainstream physics on the subject says that speed [is] a ratio of change in position to change in time.
There no easy way to say this, JP, but it has to be said: everything you've ever learned on the subject is wrong. It sounds awful I know, but look to the evidence. What we actually see is space and motion through it. We don't see time flowing or any travel through time. The motion is through space. So motion gains precedence over time. Time is reduced to a cumulative measure of local motion, such as the motion of light or caesium spin-flips. For a reference, see A World Without Time: The Forgotten Legacy of Godel and Einstein. Godel and Einstein worked it out in 1949: you don't need time to have motion, you need motion to have time.

Amrit is right. Shame he's wrong about that photon clock, but hey-ho. Hi amrit!

I did a bit of poking around to find out what Godel actually did, scientifically.  What Godel did, it seems, was to work out solutions to Einstein's field equations that show that an object moving normally through the universe (i.e. on time-like paths) could go back in time. 

Does this cause problems with physics in our universe?  Almost certainly not, since Godel's universes are not our universe.  It might have philosophical implications about time being a "special" dimension. 

At any rate, back to your post.  I disagree with the conclusions you're drawing.  We certainly don't see "space and motion through it."  What we "see" (and how GR describes the universe) is paths in space-time.  What we locally define as velocity is a measurement of the slope between the space and time components of that path at any point.  Since these paths are geometrical objects, what you can physically measure are distances.  From these distances you can derive slopes.  Therefore, time is a fundamental quantity (it's a measure of "distance") and speed is a derived quantity (it's a measure of slope, or a ratio of "distances.")

Can you provide any scientific evidence to the contrary?

There is no time in the universe. Photon (and all other motions) moves in space only. With clocks we measure numerical order of motion.
Never until know time was measured or observed as motion is observed and experienced. We measure with clocks motion and not time. Time is in the mind, we experience motion in time "past-present-future" that is a mind creation. Universe is without time as predicted by Einstein and Godel. See my post "Block Universe" in new theories.
« Last Edit: 27/05/2010 07:32:30 by amrit »
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