New measure of gravitational constant higher than expected

Sep 09, 2013 by Bob Yirka report

(Phys.org) —A trio of researchers working in France, along with a colleague from the U.K. has re-measured the gravitational constant using the same apparatus they built 12 years ago and have found a small change. In their paper published in Physical Review Letters, the team describes how they reconfigured their original equipment to re-measure the gravitational constant and this time came up with a slightly higher number than before.

The gravitational constant, denoted by G in math equations, has proven to be far more elusive than scientists imagined after it was first measured by Henry Cavendish approximately 200 years ago. The problem is that it's far weaker than other forces such as . Fluctuating stronger forces acting on measurement equipment can cause changes to readings, leading to an inaccurate result. For that reason, scientists have been striving to come up with a way to definitively measure exactly how much force G exerts. In this new effort, the research team went back to the same apparatus they constructed 12 years ago—one that simultaneously measures G in two different ways. This time around, however, they reconfigured their device in ways they believed would make it more accurate—and in so doing found a slightly different result, but now, aren't sure which of their is actually more accurate.

Modern researchers use two main types of methods to try to measure G, the first is a more advanced way to do the same thing Cavendish did two centuries ago, using lasers instead of candle light—it's based on measuring the amount of applied to a thin ribbon set between heavy balls. The other involves applying voltage to a wire using a servo to counteract twisting due to G. In this renewed effort, the researchers ran both types of measurements in their device and averaged the results. In so doing, they discovered measurements revealed a value of 6.67545(18)x10-11 m3 kg-1 s-2, with 27PPM standard uncertainty. This value is 21PPM lower than the last time they ran the experiment (measurements by others have ranged as far as 241 ppm lower). The team is unable to explain why they found a difference, and cannot say with confidence which of their measurements is likely closer to G's actual value.

Research into ways to better measure G will continue of course, with the hope that one day a method will be devised that will not be subject to other more powerful forces, or interpretation.

Explore further: Scientists demonstrate Stokes drift principle

More information: Improved Determination of G Using Two Methods, Phys. Rev. Lett. 111, 101102 (2013) link.aps.org/doi/10.1103/PhysRevLett.111.101102

Abstract
This Letter describes new work on the determination of the Newtonian constant of gravitation, G, carried out at the BIPM since publication of the first results in 2001. The apparatus has been completely rebuilt and extensive tests carried out on the key parameters needed to produce a new value for G. The basic principles of the experiment remain the same, namely a torsion balance suspended from a wide, thin Cu-Be strip with two modes of operation, free deflection (Cavendish) and electrostatic servo control. The result from the new work is: G=6.67545(18)×10-11??m3?kg-1?s-2 with a standard uncertainty of 27 ppm. This is 21 ppm below our 2001 result but 241 ppm above The CODATA 2010 value, which has an assigned uncertainty of 120 ppm. This confirms the discrepancy of our results with the CODATA value and highlights the wide divergence that now exists in recent values of G. The many changes made to the apparatus lead to the formal correlation between our two results being close to zero. Being statistically independent and statistically consistent, the two results taken together provide a unique contribution to determinations of G.

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cantdrive85
1.4 / 5 (29) Sep 09, 2013
Ahhh, the constant which in no way is constant.
I'm curious if they name the papers before the results are in, being that they didn't "improve" anything.
minnickdove
2.1 / 5 (7) Sep 09, 2013
*giggle*

"The team is unable to explain why they found a difference, and cannot say with confidence which of their measurements is likely closer to G's actual value."

brt
3.8 / 5 (23) Sep 09, 2013
in dense aether model...
HannesAlfven
1.3 / 5 (24) Sep 09, 2013
The only peculiar part of the story for some of us is that a consistently non-constant G does not seem to affect the widespread belief that G is a constant. We've got an entire cosmology here built upon an incredibly weak foundation, and a system of education fundamentally designed to make sure that we cannot seriously change course.
Noumenon
3 / 5 (30) Sep 09, 2013
One of the three guys must have gained some weight.
brt
3.3 / 5 (21) Sep 09, 2013
The only peculiar part of the story for some of us is that a consistently non-constant G does not seem to affect the widespread belief that G is a constant. We've got an entire cosmology here built upon an incredibly weak foundation, and a system of education fundamentally designed to make sure that we cannot seriously change course.


Ha! Bwaaahahahahaha! Tell me what evidence you have to support the idea that G is not a constant? This should be good...

I already have an idea of what you're going to say and I'm going to laugh my ass off.
Noumenon
2.9 / 5 (31) Sep 09, 2013
Could AWT be used to sooth my back pain?
brt
2.9 / 5 (15) Sep 09, 2013
Tell me what evidence you have to support the idea that G is not a constant? This should be good.
Actually it's just the reason, why the scientists are developing http://phys.org/n...59.html. My theories are never based on single observation and/or experiment - I do require many of them before I will start to deal with them seriously.
Could AWT be used to sooth my back pain?
This is the result of gravitational imbalance of your body (the void in your head) and it cannot be cured so easily.


No, not from you, from the original poster of the comment to which the words they speak make laughy laugh tummy fuzz which with what I say funny clownpenis.
El_Nose
4.9 / 5 (15) Sep 09, 2013
@Teech

If by drift you mean that as we as scientists are able to manufacture more precise instruments and through theory define models that exclude more and more noise then yes the speed of light has drifted lower. But a more accurate way of stating the same thing is ... after 100 years we have more precise measurements of the speed of light than what was possible in 1850.

I believe ... ( my belief not fact ) I believe that advances in the quality of measurements tends to lead to slight changes in the value of things being measured. The numbers produced become -- more accurate.
rug
2.6 / 5 (17) Sep 09, 2013
The deviation is too small to hinder any of the current theories. The normal error deviation is generally much larger this this. Trying to accomplish a precise measurement is completely worthwhile but hardly matters in the current large scheme of things.
Noumenon
2.1 / 5 (25) Sep 09, 2013
Could AWT be used to sooth my back pain?
This is the result of gravitational imbalance of your body (the void in your head) and it cannot be cured so easily.


Before many years already my Doctor says I could relieve the pain at the water surface with the ripples, which is why I was asking.
brt
4.1 / 5 (13) Sep 09, 2013
The deviation is too small to hinder any of the current theories. The normal error deviation is generally much larger this this. Trying to accomplish a precise measurement is completely worthwhile but hardly matters in the current large scheme of things.


nough said.

Measurements of the gravitational constant are more of an average of values since gravity depends on the interaction with matter. To say that you have to worry about noise when trying to measure gravity is like saying that you have to worry about dilution when you drop your drink in the ocean.

Measuring gravity at small enough volumes is the equivalent of trying to measure wave function collapse. And it carries about the same significance on current models.
Q-Star
4.1 / 5 (26) Sep 09, 2013
The pluralistic ignorance of emergent phenomena has actually many psychosocial reasons - we even cannot list them here.


But if we could list them here, I would put schizo-effective disorder at the top of the list. Especially when it manifests with delusions of grandeur.

brt
3.9 / 5 (19) Sep 09, 2013
The pluralistic ignorance of emergent phenomena has actually many psychosocial reasons - we even cannot list them here. For example the fact, the contemporary physics is difficult and it requires high level of expertise and specialization doesn't help the mutual reconciliation of seemingly unrelated experiments and observations too. The contemporary experts usually even don't realize the related observations in another areas of physics, because they're too oriented to their own scope of specialization. You may read about the http://aetherwave...ess.html here, for example.


OR you're a crackpot.
brt
3.5 / 5 (13) Sep 09, 2013
Measurements of the gravitational constant are more of an average of values since gravity depends on the interaction with matter
If its so, why we should measure the gravity "in smallest volume", if such measurement is unreliable? The large scale observations based on Kepler laws are much more relevant. But they depend on meter and time definitions, which unfortunately depend on vacuum density too in their present form (the system of SI units and its laser based prototypes). So what you can actually observe inside of vacuum of increasing density are just changes in eccentricity of gravitational systems, not their expansion or periodicity change as such. We should compare the periodicity of Earth rotation with clock based on distant pulsars for example.


You don't understand what the gravitational constant is.
Q-Star
4 / 5 (21) Sep 09, 2013
We should compare the periodicity of Earth rotation with clock based on distant pulsars for example.


After ya finish up with your comparisons, let me know how ya deal with all the stuff between the pulsars and us. Or do the watery ripples null out any errors due to extraneous gravitational fluctuations in the dense aethers for many years?
beleg
3 / 5 (8) Sep 09, 2013
What is so bias about accuracy? I'm with Nose on this.
And...
If accuracy uncovers what was previously not within measurement tolerance, so what?
Label this emergence for all I care.
dtxx
2.5 / 5 (18) Sep 09, 2013
Could AWT be used to sooth my back pain?
This is the result of gravitational imbalance of your body (the void in your head) and it cannot be cured so easily.


Before many years already my Doctor says I could relieve the pain at the water surface with the ripples, which is why I was asking.


Make sure you stay out of the electic sun when doing so. You don't want to get shocked when the neutrons repel each other.
RealScience
5 / 5 (13) Sep 09, 2013
If its so, why we should measure the gravity "in smallest volume", if such measurement is unreliable? The large scale observations based on Kepler laws are much more relevant.


@Teech2:
Because using large scale observations such as planetary orbits would require knowing the masses of the planets to great precision.

Since we currently determine the masses using gravitational effects and G, using those G-determined masses to then determine G would be circular reasoning.

Other ways of determining the masses of the planets (even of the earth itself) have much bigger uncertainties than even the 241 ppm difference between the older and newer 'Cavendish-style' small-scale experiments.
Torbjorn_Larsson_OM
2.7 / 5 (7) Sep 09, 2013
Sigh. Yirka. Completely fuzzy article, not reflecting what the researchers found.

They argue that:

1) Their values are mutually consistent within their precision and are inconsistent with the CODATA consensus (with lower precision).

2) Since they rebuilt the experiment, they made two independent measurements. "The many changes made to the apparatus lead to the formal correlation between our two results being close to zero. Being statistically independent and statistically consistent, the two results taken together provide a unique contribution to determinations of G."

And that's it.
Torbjorn_Larsson_OM
3.4 / 5 (11) Sep 09, 2013
First rule of trolls, "no feeding".

This time it is also unnecessary, since they simply reject the described finding of a constant G that everyone else can read off of the abstract. They aren't even wrong.
cantdrive85
1 / 5 (19) Sep 09, 2013
I guess the word "constant" is arbitrary. Here I thought that was what lawyers were for, but now we see it's necessary for apologists as well. One of these days they may figure out which "constant" they'll use.
rug
1.3 / 5 (12) Sep 09, 2013
That was my thought. I was wondering if they had taken that into consideration and I haven't seen anything that says one way or the other.
no fate
2 / 5 (4) Sep 10, 2013
BTW http://arxiv.org/...2058.pdf that the gravitational constant varies with orientation (tidal effect of Moon or Sun?). Maybe they just should try to rotate their gravitational balance.


Good link. I hadn't read this one before.
Paraphrasing - G is still a constant in relation to mass, the fact that other bodies alter the gravitational influence of the primary doesn't mean the constant changes, just the field in relation to the measurement based on the presence of other masses.
GSwift7
3.6 / 5 (16) Sep 10, 2013
Good lord, the level of STUPID in this thread has been re-evaluated with higher precision than ever before and has been found to be higher than ever thought possible.

Yo! Dumbasses, listen up.

The value of G must be constant, whether we are able to measure it or not. The consequences of G not being constant would mean that physics in one part of the Universe are not the same as physics in another part. That, my STUPID friends, is called science fiction.

Without a constant G, you wouldn't conserve momentum as you move through space. This would break Maxwell's equations, along with just about everything else. EVERYTHING says that G must be constant. If it isn't, the Uiverse as we know it just wouldn't work.

This is basic stuff.

Whether we can accurately measure the value of G is another story, but irrelevant to the fact that it's a constant.

Saying G isn't constant is exactly the same as suggesting that Pi isn't constant.
brt
4 / 5 (8) Sep 10, 2013
Guys, if you would judge just the particular article (which is necessarily only incremental, like any other study), you cannot get the insight into recent trends. http://adsabs.har...8..813V, that the gravitational constant can be time/gravity field dependent, but because you are just a bored IT trolls, who never read/remember anything more, than just the actual article, then indeed every indicia appears insignificant and ad-hoced for you. For short-sighted minds even the highly curved world appears flat and linear. Just try to think about it.


see Gswift7's comment.
brt
3.7 / 5 (9) Sep 10, 2013
If its so, why we should measure the gravity "in smallest volume", if such measurement is unreliable? The large scale observations based on Kepler laws are much more relevant.


@Teech2:
Because using large scale observations such as planetary orbits would require knowing the masses of the planets to great precision.

Since we currently determine the masses using gravitational effects and G, using those G-determined masses to then determine G would be circular reasoning.

Other ways of determining the masses of the planets (even of the earth itself) have much bigger uncertainties than even the 241 ppm difference between the older and newer 'Cavendish-style' small-scale experiments.


yeah, but where's the x-factor? It can't be right if it doesn't have a certain feel to it; a certain groovy quality that can't be explained. Like water...on the surface of ripples or some shit like that.
rug
2 / 5 (12) Sep 10, 2013
I crown thee King of the smart asses. That was rather funny.
Reg Mundy
1 / 5 (15) Sep 10, 2013
Ain't no gravity. Cavendish experiment measures force necessary to accelerate the metal balls away from each other to maintain separation as they expand.
no fate
3 / 5 (8) Sep 10, 2013
Ain't no gravity. Cavendish experiment measures force necessary to accelerate the metal balls away from each other to maintain separation as they expand.


I'm sure that I am experiencing gravity right now....
Porgie
1 / 5 (11) Sep 10, 2013
Well the earth is picking up hundreds of tons of dust and debris every year. I would think that would change things.
barakn
4.2 / 5 (5) Sep 10, 2013
The solar system is penetrated with dense cloud of interstellar gas, which is rich of dark matter and makes the vacuum relatively heavier. The massive objects which are floating in it become relatively lighter, which is what the change of gravity constant is about. -Teech2
Maybe if you are Archimedes and dark matter is the water in your tub. But no, by it's very nature dark matter does not interact with ordinary matter and can pass through it unimpeded. Ordinary matter thus does not displace dark matter and could not be made lighter by "floating" in it. Nor would there be a measurable force of gravity on an object from a large homogeneous cloud of dark matter because of the usual argument of symmetry. The greatest gravitational force would be exerted by the closest particles, but the force applied by the particles on one side of an object would be canceled by an equal and opposite force by particles on the other side of the object.
barakn
3.9 / 5 (7) Sep 10, 2013
IMO the source of dark matter could be the galactic plane in which solar system is currently residing (a giant version of fly-by anomaly) and/or shadow of Great dark rift (a giant version of Allais effect) and/or ejection of dark matter from center of galaxy (a giant version of solar protuberance), the passing of dense cloud of interstellar gas through solar system and/or the approach some large but invisible planet (Nibiru/Planet X) or combination of these above. -Teech2
Which ignores a very basic feature of the experiment. The measurements are of relative displacement as the test masses are moved closer and further away. And because the force of gravity from a slow-moving, distant source such as the Sun or Niburu or from a large homogenous mass like an interstellar cloud will be the same between one measurement and the next, these outside forces cancel out of the equation.
barakn
4.2 / 5 (5) Sep 10, 2013
In fact, the only way something like dark matter could interfere with this experiment is if the dark matter's density varied greatly on a scale similar to that of the experiment, i.e on the scale of meters, kilograms, and seconds. And because there's no reason to expect the dark matter to move preferentially in the frame of reference of Earth, this suggests the dark matter is capable of sensing the Earth and changing course to move with it. And thus I propose that Dark Matter Rocket Cats (DaMaRCs for short) have been preferentially targeting the BIPM experiment, using their rockets to hover near and slowly move around the test masses as the experiment progresses. I would have proposed witches on broomsticks, but they are just a bit too big. And if the DaMaRCs seem too far fetched for you, Zephir, consider that they make far more sense than what you have proposed. It's things like this that reveal how little you know despite the immense word salads you serve up on a daily basis.
Reg Mundy
1 / 5 (15) Sep 11, 2013
Ain't no gravity. Cavendish experiment measures force necessary to accelerate the metal balls away from each other to maintain separation as they expand.


I'm sure that I am experiencing gravity right now....

No, you are experiencing acceleration as the Earth expands forcing you upwards. As you and everything else is also expanding, you do not perceive this. If Newton had grasped this simple fact when the apple struck him on his nut instead of inventing this weird new force, "gravity", the whole of mainstream science would not have been subverted this last few centuries.
barakn
3.7 / 5 (6) Sep 11, 2013
The dark matter model of gravity constants changes doesn't really on some gravity force from distant objects.
I already pointed out that the closest dark matter particles exert the greatest force. But no, there's no "dark matter model of gravity constants changes."
So you should keep the judging what is possible and what isn't to more qualified people.

So in other words you don't have a successful defense against my arguments and had to resort to an Argumentum ad hominem. Nice.
no fate
2.7 / 5 (7) Sep 12, 2013
Ain't no gravity. Cavendish experiment measures force necessary to accelerate the metal balls away from each other to maintain separation as they expand.


I'm sure that I am experiencing gravity right now....

No, you are experiencing acceleration as the Earth expands forcing you upwards. As you and everything else is also expanding, you do not perceive this. If Newton had grasped this simple fact when the apple struck him on his nut instead of inventing this weird new force, "gravity", the whole of mainstream science would not have been subverted this last few centuries.


If all was expanding equally, I wouldn't be sure that I was perceiving gravity as there would be no force differential to act upon me to keep me here. There is still gravity.
no fate
2.7 / 5 (7) Sep 12, 2013
Simply stated Reg, if something effects everything equally, in exactly the same way, it is assigned the variable "0" in an equation as said effect is indiscernable to the other variables in the equation. Therefore you cannot use your theory of universal expansion to isolate any specific observation in your reference frame.
Shootist
1.4 / 5 (11) Sep 12, 2013
Paging Dr. Manuel? Will Doctor Oliver Manuel please pick up the house phone? Older Iridium prototype discrepancies have been isolated.
Reg Mundy
1 / 5 (15) Sep 12, 2013
@no fate
If a rigid body expands, anything on its surface is being forced away from the centre and experiences acceleration. Otherwise, it would be absorbed into the body. So, no gravity, and therefore no need for gravitons, gravitinos, gravity waves, Dark Matter, Dark Energy, etc. etc.
If you really want to exercise your mind, try applying expansion theory to the n-body problem, which is unsolvable using gravity.
Shootist
2.8 / 5 (16) Sep 12, 2013
Could AWT be used to sooth my back pain?


No but it makes a passable enema.
no fate
3.3 / 5 (7) Sep 13, 2013
Reg, the only expansion theory involving the earth I have heard of is diastrophism. Not applicable as a gravity substitute so let me ask you this: When I jump, and the earth rapidly expands so that it is under my feet again, why am I the only one who can sense this rapid expansion and how did I cause it by jumping?
mrego
1 / 5 (6) Sep 13, 2013
Q might have just been playing with the gravitational constant (big G, not little g).
See: Deja Q episode.
Reg Mundy
1 / 5 (17) Sep 13, 2013
@no fate
As far as I know, diastrophism concerns distortions in Earth's crust, and is irrelevant to this thread. As for your testing gravitational v. expansion theory by jumping, you are obviously jumping from the wrong sort of places. You need bridges, high buildings, cliffs, etc. to get a proper effect, and you should try to turn a half somersault so that you can more closely observe the ensuing impact. Afterwards, it should all be clear to you, and you will not need any further explanation of expansion theory.
Gmr
4.1 / 5 (9) Sep 14, 2013
Wow, Reg. Touchy much about your pet theory? Usually inducements to suicide require a lot more animosity, but it appears you've succumbed after only one hole was poked in your careful canvas. Face it - your theory has been considered and rejected by many people many times over many years - as much as it might seem a brilliant insight, it's right up there with many others that people experience while on recreational drugs.
Reg Mundy
1.5 / 5 (16) Sep 15, 2013
@Gmr
Don't you have a sense of humour? Nobody takes these exchanges seriously - I certainly don't, and judging by some of the content of this thread if most of the other contributors are not joking, they must be deeply deranged.
Gmr
2 / 5 (4) Sep 15, 2013
All I can surmise from interpreting it as "humor" is accepting your theory as fact equates with brain death.
Q-Star
3.9 / 5 (11) Sep 15, 2013
All right ya guys. Ya heard the Zeph, knock it off. He has some serious science to share and ya are distracting him.
Kiwini
1.5 / 5 (15) Sep 15, 2013
All right ya guys. Ya heard the Zeph, knock it off. He has some serious science to share and ya are distracting him.

Thank you for your moral support, Q-Star. You just helped the progress of the whole human civilization (If not Milky Way as a whole) - and I'm sure, you'll be undoubtedly recognized for it in brief future.

That was sarcasm, not "moral support".
DarkHorse66
1 / 5 (2) Sep 16, 2013
@Franklins
Looks like you have gotten yourself a brand new fan. Wow. You have managed to garner yourself a most interesting and impressive new average rank. That's gotta be a new record...
DH66
Reg Mundy
1.3 / 5 (15) Sep 16, 2013
Oh my God, I've just had a traumatic experience! I actually agree with one of Q-Star's comments! I now realise that there are true believers in this site, who think that some of the contributors are really scientists stating their logically-consistent viewpoints derived from carefully considered facts, rather than wild ponderings originating from either heavy meals prior to sleep periods or misuse of chemical substances.
Accordingly, I humbly submit my profound apologies to all readers, especially Gmr and no_fate, who may have taken umbrage at my frivolity, and promise not to do it any more. From now on, I will stick to real logical theories and sensible comments, for example, There ain't any gravity, its all due to expansion, and no Dark matter, Dark Energy, gravitons, gravitinos, gravity waves, etc., will ever be found.
DarkHorse66
1.8 / 5 (5) Sep 16, 2013
It's just an old voting troll open, who realized, he can send the negative numbers through JSON API of Physorg - not just number one.

Looks like you were right for once, it's all just been corrected. Would be nice though, if they actually started taking proper care of the rest of the ranking trolls....

Regards, DH66
no fate
3 / 5 (6) Sep 16, 2013
@Gmr
Don't you have a sense of humour? Nobody takes these exchanges seriously - I certainly don't, and judging by some of the content of this thread if most of the other contributors are not joking, they must be deeply deranged.


I took it seriously. I went and jumped off the malibu bluffs because I believed you...you were right! If I hadn't figured out that I could use the moons expansion to reverse the earth's expansion (by turning upside down in mid air) it would have been curtains for me, lucky.

Reg Mundy
1.3 / 5 (15) Sep 16, 2013
@Gmr
Don't you have a sense of humour? etc.....


I took it seriously. I went and jumped off the malibu bluffs because I believed you...you were right! If I hadn't figured out that I could use the moons expansion to reverse the earth's expansion (by turning upside down in mid air) it would have been curtains for me, lucky.


Ah, you have misunderstood what actually happened! You see, Time itself is directly related to the state of expansion of matter. Each stage of expansion relates to a different moment in Time, so that the transition from one stage to another generates one quantum of Time. So, when you cunningly reversed your spatial orientation as I advised, you temporarily discombombulated the progression of instants causing your own personal Time to expand unilaterally thus producing a slo-mo Time dilation allowing you to survive the experience and become a new prophet of the only true TOE, thereby throwing into disarray the myrmidons of gravitic theology.
TheGhostofOtto1923
1 / 5 (4) Sep 24, 2013
Could AWT be used to sooth my back pain?
Havent you ever heard of water beds??