Redefining time

Apr 30, 2012
This is a map of Germany showing the path of the 920-kilometer-long optical fiber link from Max Planck Institute of Quantum Optics to the Federal Institute of Physical and Technical Affairs. The red houses represent amplifier stations. Credit: Stefan Droste, Max Planck Institute of Quantum Optics

Atomic clocks based on the oscillations of a cesium atom keep amazingly steady time and also define the precise length of a second. But cesium clocks are no longer the most accurate. That title has been transferred to an optical clock housed at the U.S. National Institute of Standards and Technology (NIST) in Boulder, Colo. that can keep time to within 1 second in 3.7 billion years. Before this newfound precision can redefine the second, or lead to new applications like ultra-precise navigation, the system used to communicate time around the globe will need an upgrade. Recently scientists from the Max Planck Institute of Quantum Optics, in the south of Germany, and the Federal Institute of Physical and Technical Affairs in the north have taken a first step along that path, successfully sending a highly accurate clock signal across the many hundreds of kilometers of countryside that separate their two institutions.

The researchers will present their finding at Conference on Lasers and Electro Optics (CLEO: 2012), taking place May 6 -11 in San Jose, Calif.

"Over the last decade a new kind of frequency standard has been developed that is based on optical transitions, the so-called optical clock," says Stefan Droste, a researcher at the Max Planck Institute of . The NIST optical clock, for example, is more than one hundred times more accurate than the cesium clock that serves as the United States' primary time standard.

Extremely precise time keeping—and the ability to communicate the world standard across long distances—is vital to myriad applications, including in navigation, international commerce, seismology, and fundamental quantum physics. Unfortunately, the satellite-based links currently used to communicate that standard are not up to the task of transmitting such a stable signal, so the second retains its less precise measure. Optical fiber links could work better, but had previously been tested only over short distances, such as those separating buildings on the same campus or within the same urban area.

"The average distance between institutes that operate frequency standards in Europe is on the order of a few thousand kilometers," notes Droste. "Spanning these great distances with an optical link is challenging not only because of the additional degradation of the transferred signal, but also because multiple signal conditioning stations need to be installed and operated continuously along the link path." Droste and his colleagues were able to overcome the challenges by installing nine signal amplifiers along a 920-kilometer-long fiber link. They successfully transferred a frequency signal with more than 10 times the accuracy than would be required for today's most precise optical clocks.

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More information: www.cleoconference.org

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kaasinees
0.3 / 5 (28) Apr 30, 2012
Let me geuss they need the exact length of the optical path which they calculated with kilometers.

Than it is as accurate as the kilometer is which is not more accurate than a cesium clock.

Am i wrong here? What is the formula they used?
Argiod
2.5 / 5 (8) Apr 30, 2012
That is so three nanoseconds ago...
Dichotomy
1 / 5 (4) Apr 30, 2012
This ought to be interesting. The theory of relativity with time dialation was tested using atomic clocks, but I don't think those doing the experiments took into account the difference gravity would have on the oscillations of the cesium atom. As a result the findings used to "prove" this theory would be suspect and need to be retested in a manner that does not enable the results to be skewed by gravity. While the theory may be valid, the concept of putting an atomic clock up in space to test the theory would be akin to putting a meter stick up in space, finding the stick had warped from the journey, and to then say the warped meter stick was proof things were longer/shorter in space... Thoughts anyone?
javjav
5 / 5 (3) Apr 30, 2012
Than it is as accurate as the kilometer is which is not more accurate than a cesium clock.


The fiber length can be calculated by sending a light pulse to a mirror in the other side then reflected back to the origin. You only need the new clock at the origin for a precise measurement of the pulse travel time, which gives you an equally precise measurement of the fiber length. (first you may also need to measure the fiber propagation speed precisely, but you can also use the new clock for a precise value on a small fiber segment)

m
Noumenon
2.8 / 5 (16) Apr 30, 2012
The theory of relativity with time dialation was tested using atomic clocks, but I don't think those doing the experiments took into account the difference gravity would have on the oscillations of the cesium atom.


Of course they did. That IS time dilation.
Deathclock
1.7 / 5 (12) Apr 30, 2012
The theory of relativity with time dialation was tested using atomic clocks, but I don't think those doing the experiments took into account the difference gravity would have on the oscillations of the cesium atom.


Gravitational time dilation...
Deathclock
2 / 5 (12) Apr 30, 2012
Let me geuss they need the exact length of the optical path which they calculated with kilometers.

Than it is as accurate as the kilometer is which is not more accurate than a cesium clock.

Am i wrong here? What is the formula they used?


You are wrong, as usual. The instruments that I design (Optical Time Domain Reflectometers) can accurately measure a 250km length of fiber to within a fraction of a millimeter, and they can do it about 100 times a second.
kaasinees
0.5 / 5 (31) Apr 30, 2012
You dont understand do you?

Metric system is pretty accurate but not as accurate as a cesium clock. Therefore if you using a metric unit in your equations it becomes just as accurate as the metric system which is less accurate than the cesium clock.
And thus my question as to how they did their measurements.

http://en.wikiped...teristic
Deathclock
2.9 / 5 (15) Apr 30, 2012
No, you don't understand, it's possible to determine distance down to any arbitrary resolution all the way to like picometers. To assume that they are using coarse measurements is foolish. You are a fool.
Dichotomy
1 / 5 (4) Apr 30, 2012
Hmmm. I'm not sure about the gravitation time dialation since it sounds like circular logic. Continuing with the analogy of a meter stick (since meter sticks and clocks are both tools used to measure), if the meter stick comes back and is 1.000001 meters long it isn't necessarily because things are different lengths in space, its because the meter stick was "stretched" while it was in space due to gravity or other outside factors. Likewise when the atomic clock is used how do we know the clock wasn't "stetched" rather than proving this theory of relativity? (no I'm not trying to be difficult, I just don't have friends who would quality fo be on the Big Bang Show.
axemaster
5 / 5 (7) Apr 30, 2012
Metric system is pretty accurate but not as accurate as a cesium clock. Therefore if you using a metric unit in your equations it becomes just as accurate as the metric system which is less accurate than the cesium clock.
And thus my question as to how they did their measurements.

Oh good lord. You don't think anybody actually measures that platinum bar or whatever it is, do you? Hell, if you want an accurate measurement, I have a technique that can resolve wavelength differences on the scale of 10^(-21) meters - that's right at the quantum limit! All the accurate instruments are calibrated using atomic spectra, which are incredibly precise. Don't assume that people are just mucking around here...
kaasinees
0.3 / 5 (29) Apr 30, 2012
Then how come some science projects fail to get correct measuring equipment? Incompetence? And how long do these measuring equipment last before they get contaminated?

Sure they can keep increasing accuracy by using the new clocks as javjav mentions. But it will happen again just on much smaller scale, ie the the old metre stick and the old kilo ball.

The danger of it is that is assumed that such measurement is precise to such degree without taking account for various fluctuation factors which have caused major statistical errors in a few science projects.

Getting flamed for being skeptical and curous about the equation is obviously not science.
axemaster
1 / 5 (1) Apr 30, 2012
The theory of relativity with time dialation was tested using atomic clocks, but I don't think those doing the experiments took into account the difference gravity would have on the oscillations of the cesium atom.


Of course they did. That IS time dilation.

I think you guys are talking past each other. There are two time dilations involved here - time dilation due to the clock's height above the earth, and time dilation due to the cesium atom bouncing up and down inside the clock. I'd hazard a guess that since gravity is something like 10^(20) times weaker than electromagnetic forces, it's very unlikely that it was factored into the calculation for the potential well for the clock. On the other hand, relativistic effects of moving the clock up a few hundred or thousand miles above the Earth would tend to be much more noticeable.
axemaster
not rated yet Apr 30, 2012
Then how come some science projects fail to get correct measuring equipment? Incompetence? And how long do these measuring equipment last before they get contaminated?

Be more specific. What projects are we talking about here?
CHollman82
2.5 / 5 (11) Apr 30, 2012
The theory of relativity with time dialation was tested using atomic clocks, but I don't think those doing the experiments took into account the difference gravity would have on the oscillations of the cesium atom.


Of course they did. That IS time dilation.

I think you guys are talking past each other. There are two time dilations involved here - time dilation due to the clock's height above the earth, and time dilation due to the cesium atom bouncing up and down inside the clock. I'd hazard a guess that since gravity is something like 10^(20) times weaker than electromagnetic forces, it's very unlikely that it was factored into the calculation for the potential well for the clock. On the other hand, relativistic effects of moving the clock up a few hundred or thousand miles above the Earth would tend to be much more noticeable.


There are two types/causes of time dilation, one is gravitational and one is relative velocity.
axemaster
5 / 5 (1) Apr 30, 2012
Yeah my bad. I said time dilation inside the clock, which was wrong. I simply meant the slight change in the potential well due to the gravitational force, which might affect the frequency.
Deathclock
2.1 / 5 (11) Apr 30, 2012
But your point is valid, we experimentally confirmed the predictions of Einstein by comparing two synchronized atomic clocks run in different inertial reference frames and found that they lost synchronization as the math predicted, but did we actually measure a change in the passage of "time" or merely an affect on that which we use to measure it?
Graeme
not rated yet May 01, 2012
Even more important than gravitational time dilation, which chould certainly be apparant at these precisions, would be the changes in disperson of the optic fibre due to aging, temperature and pressure variations. You could expect the apparent length to change over the day in a cycle. This will cause the propogated clock to seem to speed up and slow down.
vacuum-mechanics
1 / 5 (9) May 01, 2012
Talking about the conventional time dilation, unfortunately modern physicists still cannot explain how it works, or what its physical mechanism is! Is it just because of time itself dilates or because of the mechanism of the clock? May be the paper below could give some hint.

http://www.vacuum...mid=6=en
AmritSorli
1.4 / 5 (9) May 01, 2012
Good to know: signal moves in space only and time is a numerical order of signal motion:
http://phys.org/n...ace.html
Origin
1 / 5 (5) May 01, 2012
Good to know: signal moves in space only and time is a numerical order of signal motion:
Nope, it doesn't and the time is the forth dimension of space-time. The only difference from relativity is, that the space-time has more than four dimensions.
AmritSorli
2 / 5 (8) May 01, 2012
Good to know: signal moves in space only and time is a numerical order of signal motion:
Nope, it doesn't and the time is the forth dimension of space-time. The only difference from relativity is, that the space-time has more than four dimensions.


GPS works in a 3D. Where is your 4th dimension, did you measure it ever ?
Noumenon
2.4 / 5 (14) May 01, 2012
But your point is valid, we experimentally confirmed the predictions of Einstein by comparing two synchronized atomic clocks run in different inertial reference frames and found that they lost synchronization as the math predicted, but did we actually measure a change in the passage of "time" or merely an affect on that which we use to measure it?


From the point of view of a physicist who should only base theories on measurable entities,... that IS time, i.e. the comparison of the number of cycles of one entity to that of another. That's it.

Time is not a discoverable entity in itself,.. it is an a-priori intuition of the mind. The mistake continues to be that people think it is a substantial entity of reality in itself. It is a mechanism (intuition) evolved for the mind to order experience for consciousness. It is a relation between things. SR (simultaneity) even shows it is not absolute, and qm cannot be consistently rationalized using such intuitions dependent on mind.
Deathclock
2.7 / 5 (12) May 01, 2012
I agree with you Noumenon
A_Paradox
not rated yet May 01, 2012
Extremely precise time keepingand the ability to communicate the world time standard across long distancesis vital to myriad applications, including in navigation, international commerce, seismology, and fundamental quantum physics. Unfortunately, the satellite-based links currently used to communicate that standard are not up to the task of transmitting such a stable signal

I am ignorant for sure, and no doubt suffering from various 'gifts of maturity' but I can't help feeling that there is a bit of hype around this subject of time keeping. Apart from GPS and related technology, neutrino detection and measurement, and the coordination of widely separated radio telescopes, who really needs this kind of time keeping?
Deathclock
2.2 / 5 (10) May 01, 2012
I am ignorant for sure, and no doubt suffering from various 'gifts of maturity' but I can't help feeling that there is a bit of hype around this subject of time keeping. Apart from GPS and related technology, neutrino detection and measurement, and the coordination of widely separated radio telescopes, who really needs this kind of time keeping?


Optical networks are designed and maintained with the use of instruments such as optical time domain reflectometers. The precision of the instrument determines the tolerances of the network and the clock rate of the instrument determines it's precision. Extremely accurate time keeping to the sub-nanosecond level is REQUIRED to design high speed fiber optic communication systems.

To answer your question, you need this type of time keeping, to post the message that you posted to ask the question.
Tachyon8491
1.4 / 5 (9) May 01, 2012
Time is not a discoverable entity in itself,.. it is an a-priori intuition of the mind.


I quite agree that the perception of time, its attributional appointment as being a 4th dimension orthogonal to a cartesian dimensional matrix, is a function of consciousness. However, cause cannot be simultaneous with effect in causal evolutions. Cause precedes effect on a temporal basis. In the macrodomain this allows deterministic prediction and retrodiction along an "imaginary" temporal axis. In the quantal microdomain cause-effect relations are regarded as subject to indeterminism which effectively implies "acausality" - the absence of cause. Einstein intensily disagreed with that, rejecting predictive determinisn but defending causal determinism in "God does not play dice with the universe." Other aspects are tachyon/tardyon relation, and Feynman diagrams in which temporal particle tracks are exactly reversible in their antiparticle equivalents. There's still plenty to "time" about...
Noumenon
1.7 / 5 (11) May 02, 2012
However, cause cannot be simultaneous with effect in causal evolutions. Cause precedes effect on a temporal basis. In the macrodomain this allows deterministic prediction and retrodiction along an "imaginary" temporal axis.


It is because such concepts are presumed before hand, so cause will precede effect by definition. In other words causality is not a thing, it is a relation.

There is no discoverable analytic link between cause and effect, there is instead only a constant conjunction of observed events, synthesized through association by mind. As with time and space, causality is an applied concept in ordering experience.

It is not a surprise that such intuitions break down outside the realm where the mind has evolved them for use at the macro domain.

From a positivists point of view, it is important to regard our conceptual framework as mind dependent, so as not to artificially force reality to conform to these a-priori intuitions, as Einstein wished to do.
axemaster
not rated yet May 02, 2012
However, cause cannot be simultaneous with effect in causal evolutions.

Pretty sure this is false in the reference frame occupied by a photon. Since they are moving at the speed of light, all events visible to them would be simultaneous.
Tachyon8491
1 / 5 (5) May 02, 2012
In other words causality is not a thing, it is a relation.
Of course it is a relation. I did not allege its being a "thing." Except of course that a relation is a conceptual term including a sense of potential realised as explicate potency in the application of directed energy - and as such "a thing." Not my primary concern there as much as it seems yours.
Pretty sure this is false in the reference frame occupied by a photon.
This appears a skewed attempt at falsifying the relation between cause and effect - even taking into account that De Broglie wavelength of a photon which is large, the infall of a photon from the solar corona hitting a mineral crystal on Earth and triggering an electron jump to higher orbit beyond Fermi level takes "human appointed units" of around 8 minutes at lightspeed. If we conceptually dismiss the concepts of cause and effect altogether (implying their non-existence) we impoverish not only physical empiricism but psychodynamics as well.
Tachyon8491
1 / 5 (5) May 02, 2012
The idea that there is no detectable analytical link between cause and effect is to me a non-sequitur. In music each rhythmically quantised moment, the vertical, harmonic aspect, is a "frozen snapshot" of a society in temporal quantization, where these harmonic moments themselves are composed of melodic entities in coordinative simultaneity, chord upon chord progressing in causal, contrapuntal evolution. Ontologically, the evolutional change in a physical, attributional constellation, occurs in exactly the same analogised manner when taking ontological complexity as hierarchically composed (e.g. Wolfram-Langton Class IV entities.) We can do away with causality entirely, and even questions of determinacy versus quantum indeterminacy, do away with ontological quantization, including questions of emergentism, and stare at everything in a Zen-like objectivity - back to animatism perhaps... I prefer using entries in the common reference frame - not reticent in evolving those either.
Tachyon8491
1 / 5 (5) May 02, 2012
The question of "objective reality" still appears to be unresolved... There is however only ONE reality, despite as many subjective realities extant as there are individual minds in its subjective interpretation. All philosophy, metphysics, theoretical physics and pragmatic empiricism continually derive more approximate subsets of an "ultimate model" where that is a teleological idealism in its projection. We will not cease pursuing that despite all the pitfalls well understood in Neurolinguistic programming: generalisation, substitution, conflation, distortion and elimination of fractal and composite percept. Bergsonian / Popperian approximation, experimental proof and falsification remain instrumental. The fact that psychodynamics are fundamental in processing perceptual constellations does not make the universe an anthropocentric hallucination. We encode intentionality and the handling and application of directed, informed energies in lexemised, syntagmatic conceptual linguistics -
Tachyon8491
1 / 5 (4) May 02, 2012
It's the human way - there are obviously as many languages as there are species - but this also goes deeper: there's photonic, electronic, and nucleonic - etc. etc. all inter-translatable and acting in exogenous stimulus for self-reorganising reactivity (which is what you do, when you do ANYTHING) "Speaking, for example, is sensomotor reorganisation of physiology coupling acoustic vibration to the "non-self" preceded by neuronal-cerebral reorganisation in synaptic connectivity, coherent neuronal field-action and differential concentration flows of neurotransmitters. There, psychodynamics is primary to its explicate effects - another cause-effect relation. Of course, there are those like Francis Crick, who, pragmatic (and nail-biting fundamentalist) believe that consciousness is epiphenomenal. He should study van Lommel's cases on NDEs... At least Penrose and Hameroff's ORch-OR theory is a little more advanced.
Noumenon
1 / 5 (6) May 02, 2012
The fact that psychodynamics are fundamental in processing perceptual constellations does not make the universe an anthropocentric hallucination. We encode intentionality and the handling and application of directed, informed energies in lexemised, syntagmatic conceptual linguistics


Yes, I do not agree with idealism, nor reject an objective reality existing apart from mind (hence my screen name). I point out only that such a-priori intellectual faculties, evolved to operate on macro-scale, can lead one astray at the qm scale.

Intuitional concepts like "time" are artifacts resulting from mind evolving and operating on sense experience. Einstein expected reality to conform to these inner intuitions. This was an arbitrary subjection of reality, and impeded science.

The idea that there is no detectable analytical link between cause and effect is to me a non-sequitur.


Science is inductive, fundamentally, on account of this fact.
Fleetfoot
5 / 5 (2) May 03, 2012
Then how come some science projects fail to get correct measuring equipment? Incompetence? And how long do these measuring equipment last before they get contaminated?


Even in industry, all test equipment is regularly calibrated via a documented chain from the prime sources. If projects are using equipment which is out of cal. then, yes, they are incompetent.

Getting flamed for being skeptical and curous about the equation is obviously not science.


The length of a fibre is the same in each direction so if you send a signal both ways, the end-to-end delay is half the round-trip delay, that is the equation you need and it doesn't matter what units you use.
Fleetfoot
5 / 5 (2) May 03, 2012
I think you guys are talking past each other. There are two time dilations involved here - time dilation due to the clock's height above the earth, and time dilation due to the cesium atom bouncing up and down inside the clock. I'd hazard a guess that since gravity is something like 10^(20) times weaker than electromagnetic forces, it's very unlikely that it was factored into the calculation for the potential well for the clock.


Hazarding a guess is not a good idea unless you have a feel for the numbers. If you are discussing Hafele-Keating where they flew a clock round the world, the gravitational part is larger than the speed part (they aren't two different effects, both are covered by GR) and of course they integrated the entire altitude and speed histories. They weren't incompetent fools as you are (perhaps unwittingly) implying.
Fleetfoot
5 / 5 (2) May 03, 2012
Even more important than gravitational time dilation, which chould certainly be apparant at these precisions, would be the changes in disperson of the optic fibre due to aging, temperature and pressure variations. You could expect the apparent length to change over the day in a cycle. This will cause the propogated clock to seem to speed up and slow down.


All these effects will cause the round-trip time to change. Subtract half and you correct the error. At the end of the day, they have to measure the degree to which their system works to find out if there are other, perhaps unknown effects with which their solution fails to cope. That's what validation testing is all about.
Fleetfoot
5 / 5 (2) May 03, 2012
Amrit Sorli wrote:

GPS works in a 3D. Where is your 4th dimension, did you measure it ever ?


GPS works using the signals from four satellites and solves four simultaneous equations to find four unknowns, x, y, z and t. If you only have three satellites available, it must make an assumption, such as being at mean sea level, to remove one unknown. Here is a paper on it:

http://www.nbmg.u...0GPS.pdf

axemaster
5 / 5 (5) May 03, 2012
the infall of a photon from the solar corona hitting a mineral crystal on Earth and triggering an electron jump to higher orbit beyond Fermi level takes "human appointed units" of around 8 minutes at lightspeed.

No it doesn't... In the reference frame of the photon only two events exist - emission and absorption - and they take place simultaneously. This is a result of Lorentz contraction - to a photon, our universe is a two dimensional plane perpendicular to its direction of motion. Furthermore, since no signals arrive along the plane, the effective field of view shrinks to a 0 dimensional point in space-time. There is no room for causality in this picture, since time itself doesn't exist.
Tachyon8491
1 / 5 (5) May 03, 2012
No it doesn't... In the reference frame of the photon only two events exist - emission and absorption - and they take place simultaneously.
Right, sure - Let a new protostar reach fusion temperature in the Andromeda galaxy - of course a photon emitted at that moment then reaches your retina instantly hmm?, except that in my case it takes another two million years to *see* it. You entirely missed the implied syntagmatic structure of my conceptual phrasing -
the infall of a photon from the solar corona hitting a mineral crystal on Earth and triggering an electron jump to higher orbit beyond Fermi level takes "human appointed units" of around 8 minutes at lightspeed
Please, tell me the electron orbital jump occurs at the moment of emission of the photon from the solar corona - see that? You are confusing reference frames and dismissing transformations between them. It is exactly these which are so very interesting. Study Orch OR and PNI on which I have written academically.
antialias_physorg
5 / 5 (1) May 06, 2012
In the reference frame of the photon only two events exist - emission and absorption - and they take place simultaneously. This is a result of Lorentz contraction - to a photon, our universe is a two dimensional plane perpendicular to its direction of motion. Furthermore, since no signals arrive along the plane, the effective field of view shrinks to a 0 dimensional point in space-time. There is no room for causality in this picture, since time itself doesn't exist.

Thank you. Couldn't have said it better.