Could we detect an intrinsic change in the flow of time?

[substitutematerials]

In the principle study of the Pioneer Anomaly, John Anderson and Slava Turyshev suggest a speculative explanation for the apparent deceleration of the spacecraft, as an acceleration of the clock rate used for telemetry back on earth. To be clear, this explanation has been discounted, although it was explored further in this paper. The Pioneer Anomaly is generally considered solved, being due to asymmetric thermal radiation from the probes.

My question is, if such a universal change in clock time did exist, i.e. that every subsequent second ticked by faster or slower than the one before it, how could we detect it? Can anyone imagine an Earth-based experiment? As I understand it, the effect that Anderson was proposing would be universal, effecting all clocks equally. Such an effect would be independent of special or general relativistic time dilations, occurring without any specific circumstances of motion or gravitation (although these effects would need to be subtracted from any experiment).The magnitude of the effect if it were to explain the Pioneer Anomaly, 2.9E-18 sec^-1, would exceed the uncertainty of an ordinary cesium atomic clock in a week. I'm not sure if it should be related to an observer's proper time, or cosmic time, or what coordinate system.

I'm not asking if this effect is real, I'm asking if we could make a practical experiment to detect something like it, or if it could even be logically possible for such an effect to exist.

[imatfaal]

But if it applies to everything then is it a change? You need an outside reference - and this proposal is universal so by definition there is no outside reference. An increase in gravitational potential would decrease tick rate compared to a fast clicking clock at infinite distance / zero potential BUT if your fast ticking clock is affected by the increase in gravitational potential then there is no change. This proposal would change both proper time for the observer and coordinate time of the fast ticking clock - therefore there is no actual change. Now the paper must find some way around this but I do not have time to work out what this is - but in general terms I can see no way of measuring a universal change.

[substitutematerials]

But if it applies to everything then is it a change? You need an outside reference - and this proposal is universal so by definition there is no outside reference. An increase in gravitational potential would decrease tick rate compared to a fast clicking clock at infinite distance / zero potential BUT if your fast ticking clock is affected by the increase in gravitational potential then there is no change. This proposal would change both proper time for the observer and coordinate time of the fast ticking clock - therefore there is no actual change. Now the paper must find some way around this but I do not have time to work out what this is - but in general terms I can see no way of measuring a universal change.

 

I think that's the crux of the question, how do you establish an alternate reference frame. Is it possible to compare a clock rate now, to a clock rate in the past? I believe that in the Pioneer analysis, the clock signal is sent from Earth to the probe, where it was phase-locked and then sent back to Earth, so the discrepancy would be a result of the light travel time there and back, comparing the rate of the same clock from 2 different times.

[imatfaal]

 

I think that's the crux of the question, how do you establish an alternate reference frame. Is it possible to compare a clock rate now, to a clock rate in the past? I believe that in the Pioneer analysis, the clock signal is sent from Earth to the probe, where it was phase-locked and then sent back to Earth, so the discrepancy would be a result of the light travel time there and back, comparing the rate of the same clock from 2 different times.

 

Oh that's clever. I understand know - thanks. Neat idea - the background rate of time was locked in the signal so we would have an "archaeological" time rate to compare our current rate with. Geez that is so far above my pay grade that I am getting altitude sickness even thinking about it. But I presume that as we have an pretty good alternative explanation for the acceleration (the uneven thermal emissions) then we have prima facie evidence that this time thing has not happened - otherwise we would have double sized anomaly

[substitutematerials]

 

Oh that's clever. I understand know - thanks. Neat idea - the background rate of time was locked in the signal so we would have an "archaeological" time rate to compare our current rate with. Geez that is so far above my pay grade that I am getting altitude sickness even thinking about it. But I presume that as we have an pretty good alternative explanation for the acceleration (the uneven thermal emissions) then we have prima facie evidence that this time thing has not happened - otherwise we would have double sized anomaly

Ha thanks, I like the term "archaeological" time rate. Like you say, there is nothing in the Pioneers' telemetry that isn't accounted for at this point, since they seem to have sealed the deal on the uneven thermal emisisons. Just the same, can you imagine an experiment designed to look for such an effect? The most obvious thing I can think of would be duplicate the situation of the Pioneers: Send out 2 more ballistic probes, spin-stabilized so that they are not firing thrusters, and track the doppler shift of the returned clock signal, accounting for all known forces. Special care could be taken to make sure thermal radiation from the probes is uniform in all directions. This, however, is not a cheap or speedy experiment. Could there be anyway to run a comparable test on Earth? Somehow delay a clock signal, maybe by bouncing light in an optical cavity, long enough to demonstrate such a clock drift? Figuring out that experimental design is also way over my pay grade.

[koti]

Wow, this is realy clever. I wonder if there would be a way to convert LIGO for this experiment.

[imatfaal]

Wow, this is realy clever. I wonder if there would be a way to convert LIGO for this experiment.

 

Cannot see how - we would need to know exactly the signal sent out and how we recieved it - LIGO is only reception. And I hope LIGO is busy getting more and more confirmation for a while yet. But we will hopefully be able to adapt LIGO to more specific tasks when the search for Gravitational waves is almost accepted to have been successfully accomplished.

 

But if we were significantly sure of our modelling of black hole merger ringdown frequencies and LIGO kept on finding that frequencies were in error, and that this error was related to transmission time then you might be on to something. Which is basically what is done with Standard Candle Super Nova and acclerated expansion

[swansont]

How would you do an experiment to detect a universal shift? All instruments and test subjects would be affected.

 

This reminds me that there is a physicist (Andrei Derevianko) who is proposing that "topological dark matter" could affect clocks, but can only be tested if there is an edge to the topology, so that different clocks see a step change at different times. If they all shifted at once, you don't measure anything.

[michel123456]

How would you do an experiment to detect a universal shift? All instruments and test subjects would be affected.

 

This reminds me that there is a physicist (Andrei Derevianko) who is proposing that "topological dark matter" could affect clocks, but can only be tested if there is an edge to the topology, so that different clocks see a step change at different times. If they all shifted at once, you don't measure anything.

At once? How could that be? That would mean universal synchronization.

[swansont]

At once? How could that be?

 

I don't know. It's not my hypothesis and I wasn't asking about or proposing a mechanism. I was asking how you could possibly measure it.

 

That would mean universal synchronization.

No, it doesn't. There's no need for the clocks to be synchronized.

[michel123456]

OK bad wording again. Forget synchronization.

 

If the phenomena doesn't happen at once, but spread over like a wave, the shifting could be observable. I think.

[swansont]

If the phenomena doesn't happen at once, but spread over like a wave, the shifting could be observable. I think.

 

 

But then is it universal?

[michel123456]

 

 

But then is it universal?

Good question.

Can a change of this kind be universal?

Or spreading at some rate? And thus local.

[Mordred]

You couldn't have a universal change at the same instant without violating the speed of information limit c.

[swansont]

You couldn't have a universal change at the same instant without violating the speed of information limit c.

 

 

If it's caused by some event, true. What if it were caused by something that happened with or right after the big bang? Tied in with expansion?

[Mordred]

Ah I see where your going with that. Your right some "hypothetical" global uniform change would not have any measurable change that would be possible to determine.

 

Not with any methodology I can think of. Any reference point would be equally affected. There would be no reference point that isn't affected equally for comparison.

[koti]

Ah I see where your going with that. Your right some "hypothetical" global uniform change would not have any measurable change that would be possible to determine.

 

Not with any methodology I can think of. Any reference point would be equally affected. There would be no reference point that isn't affected equally for comparison.

 

I don't know why but I imagined pushing a boat which I'm standing on.

 

[substitutematerials]

Don't we inherently have contact with past reference frames just through the delay of light travel time? I see the moon as it was a second ago, the sun as it was 8 minutes age, Andromeda as it was 2 million years ago, 3C 273 as it was 2 billion years ago, etc. So if time ran at a different rate 2 billion years ago, and I could observe a clock hanging out at 3C 273, it would either gain or lose seconds relative to my clock. Yes?

[swansont]

Don't we inherently have contact with past reference frames just through the delay of light travel time? I see the moon as it was a second ago, the sun as it was 8 minutes age, Andromeda as it was 2 million years ago, 3C 273 as it was 2 billion years ago, etc. So if time ran at a different rate 2 billion years ago, and I could observe a clock hanging out at 3C 273, it would either gain or lose seconds relative to my clock. Yes?

 

 

How are you getting a clock signal from the photons? We already know the light will be redshifted from the expansion, but time requires counting the oscillations in some way. How is one doing that counting?

[Strange]

I am told (by people I trust understand these things) that it is quite possible to change the coordinate system used to describe the universe so that there is no expansion but a change in time: thus red-shifted photons are not "stretched" (or lower energy, if you prefer) but were ticking at a slower rate.

 

No one uses this coordinate system because it has no advantages and is more complex (the speed of light is not constant, for example). And, for most people, it is less intuitive than the normal coordinate choice.

[substitutematerials]

I am told (by people I trust understand these things) that it is quite possible to change the coordinate system used to describe the universe so that there is no expansion but a change in time: thus red-shifted photons are not "stretched" (or lower energy, if you prefer) but were ticking at a slower rate.

 

No one uses this coordinate system because it has no advantages and is more complex (the speed of light is not constant, for example). And, for most people, it is less intuitive than the normal coordinate choice.

 

I have wondered if such an equivalence could be made. I know that time dilation is factored into type 1A supernova analysis at high redshifts, for instance. Also, it perks my interest that the Hubble parameter, 71 km/s/mpc, is more properly written as 2.27E-18 sec^-1, since there are units of distance in the numerator and denominator. This number is quite close to what the Pioneers displayed if you interpret the anomaly as a clock acceleration, 2.9E-18 sec^-1. Just sayin...

Pulling back from grandiose speculation, I still wonder if an experiment on Earth could be conducted, under the assumption that light travel delay puts us in contact with past clocks. Koti suggested LIGO, which seems to me to have some promise, although not as it is configured to detect gravitational waves.

 

Wow, this is realy clever. I wonder if there would be a way to convert LIGO for this experiment.

Here's my attempt at the numbers:

The 4 km beam path is traversed 280 times by the lasers, giving a complete travel distance of 1120 km, and thus a .0037 second light delay. If the entire Pioneer Anomaly (2.9E-18) was attributed to a clock acceleration, we can check to see if LIGO is sensitive enough to see it. If we encoded a synchronized clock signal onto the 2 lasers, and one of them bypassed the long beam path, while the other one traversed it, the one that made the long journey should be behind a greater amount than could be attributed strictly to it's light delay. The actual time lost would be 1/2at^2 assuming a constant clock acceleration, so 1.985E-23 seconds. This is well below the 10^-18 accuracy of the best clocks I could find reference to, so it doesn't seem like it would work. You'd need to increase the travel time to an entire second to get to a 1:1 signal to noise ratio, or 75,000 bounces down the beam path. I have no idea if this is possible. Alternately I wonder if you would even need a clock signal. If there is an equivalence of redshift/clock acceleration such as Strange mentioned, the wavelength of the laser light would have to change with the clock change, right? So you could use the interferometer setup already there. I can't quite grasp how to estimate this degree of accuracy, but if it's just c(delta(t)), then it would be 5.95E-15 meters for the regular beam path, or the same order of magnitude as the width of a proton. Popular accounts of LIGO indicate that it can detect changes of 1/10,000th the width of a proton. Which is bonkers, by the way. But so if this is right, a change of clock time would manifest as a change in interference between the 2 beams, one on a short path, one on a long. It does seem a bit far fetched to me to imagine that this effect would not have been observed by now, in one way or another. What do you think?

[Strange]

It seems it would, in principle, be possible for LIGO to compare the reflected beam with an unreflected beam (i.e. straight out of the laser). If there were a difference in time, then it would appear as a slow drifting in and out of phase. I don't know if the system could be configured to do this, if they do this as part of their testing, if they might be interested in trying it during a maintenance period or ...

 

(I am fairly sure experiments like this have been done - e.g. interferometers with different length arms - but probably not with the sensitivity that could be achieved with something like LIGO)

[koti]

 

Here's my attempt at the numbers:

The 4 km beam path is traversed 280 times by the lasers, giving a complete travel distance of 1120 km, and thus a .0037 second light delay. If the entire Pioneer Anomaly (2.9E-18) was attributed to a clock acceleration, we can check to see if LIGO is sensitive enough to see it. If we encoded a synchronized clock signal onto the 2 lasers, and one of them bypassed the long beam path, while the other one traversed it, the one that made the long journey should be behind a greater amount than could be attributed strictly to it's light delay. The actual time lost would be 1/2at^2 assuming a constant clock acceleration, so 1.985E-23 seconds. This is well below the 10^-18 accuracy of the best clocks I could find reference to, so it doesn't seem like it would work. You'd need to increase the travel time to an entire second to get to a 1:1 signal to noise ratio, or 75,000 bounces down the beam path. I have no idea if this is possible. Alternately I wonder if you would even need a clock signal. If there is an equivalence of redshift/clock acceleration such as Strange mentioned, the wavelength of the laser light would have to change with the clock change, right? So you could use the interferometer setup already there. I can't quite grasp how to estimate this degree of accuracy, but if it's just c(delta(t)), then it would be 5.95E-15 meters for the regular beam path, or the same order of magnitude as the width of a proton. Popular accounts of LIGO indicate that it can detect changes of 1/10,000th the width of a proton. Which is bonkers, by the way. But so if this is right, a change of clock time would manifest as a change in interference between the 2 beams, one on a short path, one on a long. It does seem a bit far fetched to me to imagine that this effect would not have been observed by now, in one way or another. What do you think?

 

 

This is well beyond my pay grade. I think Swansont is the most qualified to answer this.

[swansont]

 

Here's my attempt at the numbers:

The 4 km beam path is traversed 280 times by the lasers, giving a complete travel distance of 1120 km, and thus a .0037 second light delay. If the entire Pioneer Anomaly (2.9E-18) was attributed to a clock acceleration, we can check to see if LIGO is sensitive enough to see it. If we encoded a synchronized clock signal onto the 2 lasers, and one of them bypassed the long beam path, while the other one traversed it, the one that made the long journey should be behind a greater amount than could be attributed strictly to it's light delay. The actual time lost would be 1/2at^2 assuming a constant clock acceleration, so 1.985E-23 seconds. This is well below the 10^-18 accuracy of the best clocks I could find reference to, so it doesn't seem like it would work. You'd need to increase the travel time to an entire second to get to a 1:1 signal to noise ratio, or 75,000 bounces down the beam path. I have no idea if this is possible. Alternately I wonder if you would even need a clock signal. If there is an equivalence of redshift/clock acceleration such as Strange mentioned, the wavelength of the laser light would have to change with the clock change, right? So you could use the interferometer setup already there. I can't quite grasp how to estimate this degree of accuracy, but if it's just c(delta(t)), then it would be 5.95E-15 meters for the regular beam path, or the same order of magnitude as the width of a proton. Popular accounts of LIGO indicate that it can detect changes of 1/10,000th the width of a proton. Which is bonkers, by the way. But so if this is right, a change of clock time would manifest as a change in interference between the 2 beams, one on a short path, one on a long. It does seem a bit far fetched to me to imagine that this effect would not have been observed by now, in one way or another. What do you think?

 

 

 

The clock drift in this scenario (as I am understanding it) is affected by distance, and therefore has a time component, not by time in the same location. Interfering two lasers with a several km path delay is trivial to attempt in fiber (and increases the time delay by ~50%, owing to the index of refraction slowing the light), though you run into problems with the coherence of the beams at some point*. LIGO was comparing beams that had traversed nominally the same distance, so AFAIK they didn't have that problem. They also went to great lengths to stabilize the system to reduce noise. Typical table-top systems allow you to measure a small fraction of a fringe. So if you're doing this with a 1 micron laser, measuring a fringe shift of a couple parts in 10^8 to get you to your 5.95E-15 meters sounds pretty hard.

 

*~10 km requires a laser linewidth of ~10 kHz. So 1000 km will require 100 Hz.

[michel123456]

I am told (by people I trust understand these things) that it is quite possible to change the coordinate system used to describe the universe so that there is no expansion but a change in time: thus red-shifted photons are not "stretched" (or lower energy, if you prefer) but were ticking at a slower rate.

 

No one uses this coordinate system because it has no advantages and is more complex (the speed of light is not constant, for example). And, for most people, it is less intuitive than the normal coordinate choice.

Oh. Do you mean the expansion of Space can be translated into a change in Time, and vice-versa?

Edited October 20, 2016 by michel123456