[Tom Bishop]

I personally don't believe that there are variations in gravity. Those tidal effects are only being felt in seismometers (gravimeters).

There are certainly no gravitational variations caused by the stars. Far too distant. But variations caused by altitude increase are real enough. Very slight within the range of what you can achieve without resorting to air/spacecraft, but measurable nonetheless.

http://curious.astro.cornell.edu/about-us/42-our-solar-system/the-earth/gravity/93-does-gravity-vary-across-the-surface-of-the-earth-intermediate

I think that link may be basing its argument on theory rather than experiment. I couldn't find any experimental reference. Take a look and see if you can can find what experiment, if any, the author is referencing.

[manicminer]

Check for yourself Tom.  In just a few minutes of web searching I found numerous websites that support the same view. If I can find the information then so can you I'm sure. As I said earlier I would happily travel to Mount Everest (highest point above sea level you can reach directly on the surface) and carry out an experiment myself to confirm the hypothesis but I don't have the means to.  Supply me with the gear and the funds and I will book the flight.

[Tom Bishop]

I did check other sources. The claims are based on theory, not experiment. Here is another source which does talk about the experiments:

https://www.britannica.com/science/gravity-physics/Experimental-study-of-gravitation

Aside from the Gravimeters (sismometers) and the Cavendish Experiment (inconsistent short range experiments), which is addressed on our Wiki, the Encyclopedia Britannica seems to agree that there are no variations in gravity:

Early in the 1970s an experiment by the American physicist Daniel R. Long seemed to show a deviation from the inverse square law at a range of about 0.1 metre. Long compared the maximum attractions of two rings upon a test mass hung from the arm of a torsion balance. The maximum attraction of a ring occurs at a particular point on the axis and is determined by the mass and dimensions of the ring. If the ring is moved until the force on the test mass is greatest, the distance between the test mass and the ring is not needed. Two later experiments over the same range showed no deviation from the inverse square law. In one, conducted by the American physicist Riley Newman and his colleagues, a test mass hung on a torsion balance was moved around in a long hollow cylinder. The cylinder approximates a complete gravitational enclosure and, allowing for a small correction because it is open at the ends, the force on the test mass should not depend on its location within the cylinder. No deviation from the inverse square law was found. In the other experiment, performed in Cambridge, Eng., by Y.T. Chen and associates, the attractions of two solid cylinders of different mass were balanced against a third cylinder so that only the separations of the cylinders had to be known; it was not necessary to know the distances of any from a test mass. Again no deviation of more than one part in 10⁴ from the inverse square law was found. Other, somewhat less-sensitive experiments at ranges up to one metre or so also have failed to establish any greater deviation.

The geophysical tests go back to a method for the determination of the constant of gravitation that had been used in the 19th century, especially by the British astronomer Sir George Airy. Suppose the value of gravity g is measured at the top and bottom of a horizontal slab of rock of thickness t and density d. The values for the top and bottom will be different for two reasons. First, the top of the slab is t farther from the centre of Earth, and so the measured value of gravity will be less by 2(t/R)g, where R is the radius of Earth. Second, the slab itself attracts objects above and below it toward its centre; the difference between the downward and upward attractions of the slab is 4πGtd. Thus, a value of G may be estimated. Frank D. Stacey and his colleagues in Australia made such measurements at the top and bottom of deep mine shafts and claimed that there may be a real difference between their value of G and the best value from laboratory experiments. The difficulties lie in obtaining reliable samples of the density and in taking account of varying densities at greater depths. Similar uncertainties appear to have afflicted measurements in a deep bore hole in the Greenland ice sheet.

New measurements have failed to detect any deviation from the inverse square law. The most thorough investigation was carried out from a high tower in Colorado. Measurements were made with a gravimeter at different heights and coupled with an extensive survey of gravity around the base of the tower. Any variations of gravity over the surface that would give rise to variations up the height of the tower were estimated with great care. Allowance was also made for deflections of the tower and for the accelerations of its motions. The final result was that no deviation from the inverse square law could be found.

...

Thus far, all of the most reliable experiments and observations reveal no deviation from the inverse square law.

Experiments with ordinary pendulums test the principle of equivalence to no better than about one part in 10⁵. Eötvös obtained much better discrimination with a torsion balance. His tests depended on comparing gravitational forces with inertial forces for masses of different composition. Eötvös set up a torsion balance to compare, for each of two masses, the gravitational attraction of Earth with the inertial forces due to the rotation of Earth about its polar axis. His arrangement of the masses was not optimal, and he did not have the sensitive electronic means of control and reading that are now available. Nonetheless, Eötvös found that the weak equivalence principle (see above Gravitational fields and the theory of general relativity) was satisfied to within one part in 10⁹ for a number of very different chemicals, some of which were quite exotic. His results were later confirmed by the Hungarian physicist János Renner. Renner’s work has been analyzed recently in great detail because of the suggestion that it could provide evidence for a new force. It seems that the uncertainties of the experiments hardly allow such analyses.

Eötvös also suggested that the attraction of the Sun upon test masses could be compared with the inertial forces of Earth’s orbital motion about the Sun. He performed some experiments, verifying equivalence with an accuracy similar to that which he had obtained with his terrestrial experiments. The solar scheme has substantial experimental advantages, and the American physicist Robert H. Dicke and his colleagues, in a careful series of observations in the 1960s (employing up-to-date methods of servo control and observation), found that the weak equivalence principle held to about one part in 10¹¹ for the attraction of the Sun on gold and aluminum. A later experiment by the Russian researcher Vladimir Braginski, with very different experimental arrangements, gave a limit of about one part in 10¹² for platinum and aluminum.

Galileo’s supposed experiment of dropping objects from the Leaning Tower of Pisa has been reproduced in the laboratory with apparatuses used to determine the absolute value of gravity by timing a falling body. Two objects, one of uranium, the other of copper, were timed as they fell. No difference was detected.

By the start of the 21st century, all observations and experiments on gravitation had detected that there are no deviations from the deductions of general relativity, that the weak principle of equivalence is valid, and that the inverse square law holds over distances from a few centimetres to thousands of kilometres. Coupled with observations of electromagnetic signals passing close to the Sun and of images formed by gravitational lenses, those observations and experiments make it very clear that general relativity provides the only acceptable description of gravitation at the present time.

[markjo]

If you can find some experiments that do claim to see deviations, I'm happy to put it in the Wiki in support of CG. I don't really care either way. What I found when I went looking for them, provided in the Variations of Gravity page, suggest that there are no deviations.

If you couldn't find any experiments showing variations, it's because you didn't look very hard.  This is an experiment so simple that literally anyone with an accurate enough scale can perform themselves.  The Kern Gnome Experiment is one such experiment that has been presented and discussed several times.

Here is another experiment using a jewelry scale and a tungsten reference mass:
https://www.metabunk.org/codys-lab-how-weight-changes-with-location-and-velocity.t8783/

Now, whether those variations are due to celestial gravitation or other influences is a different matter. 

BTW, according to RET, the gravitational effects of the sun and moon are too small to be measured by anything but the most sensitive gravimeters.

[markjo]

I did check other sources. The claims are based on theory, not experiment. Here is another source which does talk about the experiments:

https://www.britannica.com/science/gravity-physics/Experimental-study-of-gravitation

Aside from the Gravimeters (Sismometers) and the Cavendish Experiment (inconsistent short range experiments), which is addressed on our Wiki, the Encyclopedia Britannica seems to agree that there are no variations in gravity:

Tom, that Britannica article is talking about capital 'G' (universal gravitational constant), not little 'g' (acceleration due to gravity).  The two are very different and should not be confused. 
https://www.nextgurukul.in/nganswers/ask-question/answer/What-is-difference-between-g-and-G/Gravitation/14878.htm

[Tom Bishop]

If you couldn't find any experiments showing variations, it's because you didn't look very hard.  This is an experiment so simple that literally anyone with an accurate enough scale can perform themselves.  The Kern Gnome Experiment is one such experiment that has been presented and discussed several times.

Here is another experiment using a jewelry scale and a tungsten reference mass:
https://www.metabunk.org/codys-lab-how-weight-changes-with-location-and-velocity.t8783/

I believe that we have discussed this in the past. Those aren't professional experiments from mainstream science. In the gnome experiment a scale calibrated for one area and then sent around to members of the public. A similar occurrence is happening in the other link.



https://www.arlynscales.com/scale-knowledge/factors-can-affect-scales-accuracy/

    Factors That Can Affect Your Scale’s Accuracy

    ...

    Differences in air pressure – Scales can provide inaccurate measurements if the air pressure from the calibration environment is different than the operating environment.

In the scale experiments the scales are calibrated for one environment and taken to another. That the equator has a difference in pressure than the poles is well known.

Tom, that Britannica article is talking about capital 'G' (universal gravitational constant), not little 'g' (acceleration due to gravity).  The two are very different and should not be confused. 
https://www.nextgurukul.in/nganswers/ask-question/answer/What-is-difference-between-g-and-G/Gravitation/14878.htm

I disagree. The article makes no designation. The Universality of Free Fall and the Equivalence Principle says that gravity operates exactly as if the earth were accelerating upwards at constant acceleration. If there was a difference in the speed of gravity as an object fell, it would be a violation of the Weak Equivalence Principle. The WEP is constantly tested, and violations at any range or sensitivity have been searched for over the last several hundred years.

[Tom Bishop]

BTW, according to RET, the gravitational effects of the sun and moon are too small to be measured by anything but the most sensitive gravimeters.

Look into what mainstream says about it. They acknowledge that those experiments should detect the gravity of the sun and say that it shows that there are "preferred curves" in spacetime that the bodies follow.

https://wiki.tfes.org/Variations_in_Gravity#Official_Explanation:_Selective_Gravity

[markjo]

Tom, that Britannica article is talking about capital 'G' (universal gravitational constant), not little 'g' (acceleration due to gravity).  The two are very different and should not be confused. 
https://www.nextgurukul.in/nganswers/ask-question/answer/What-is-difference-between-g-and-G/Gravitation/14878.htm

I disagree. The article makes no designation.

Of course it does.  It's quite obvious that they're talking about the constant of gravitation (capital 'G').

There also has been a continuing interest in the determination of the constant of gravitation, although it must be pointed out that G occupies a rather anomalous position among the other constants of physics. In the first place, the mass M of any celestial object cannot be determined independently of the gravitational attraction that it exerts. Thus, the combination GM, not the separate value of M, is the only meaningful property of a star, planet, or galaxy. Second, according to general relativity and the principle of equivalence, G does not depend on material properties but is in a sense a geometric factor.

The Universality of Free Fall and the Equivalence Principle says that gravity operates exactly as if the earth were accelerating upwards at constant acceleration. If there was a difference in the speed of gravity anywhere, it would be a violation of the Weak Equivalence Principle. The WEP is constantly tested, and violations at any range or sensitivity have been searched for over the last several hundred years.

We've been over this one too.  The EP only applies locally in a homogeneous gravitational field.  Tidal forces from outside influences invalidate any test of the EP.

[QED]

I dont have to reference any experiment.

Then it appears that you have no argument.

Please reference an experiment for your idea that gravity varies by altitude. A lot of that is based on theory.

A tremendous plethora of data exists such that the variations across the the entire earths surface have been mapped several times.

https://www.nasa.gov/audience/foreducators/k-4/features/F_Measuring_Gravity_With_Grace.html

Gravimeters are seismeters and operate under the theory of "gravity waves" and "infragravity waves". It's not a direct measurement of gravity: https://wiki.tfes.org/Gravimetry

Also, that's not an experiment for gravity by altitude.

Measuring gravity waves is a direct measurement of gravity. The theory of gravity includes gravity waves, so your objection is nonsensical.

Well of course it measures gravity by altitude. Did you read it? It also measures gravity fluctuations by local density variants. It is a very sophisticated measurement, and done very well I might add!

[QED]

If you couldn't find any experiments showing variations, it's because you didn't look very hard.  This is an experiment so simple that literally anyone with an accurate enough scale can perform themselves.  The Kern Gnome Experiment is one such experiment that has been presented and discussed several times.

Here is another experiment using a jewelry scale and a tungsten reference mass:
https://www.metabunk.org/codys-lab-how-weight-changes-with-location-and-velocity.t8783/

I believe that we have discussed this in the past. Those aren't professional experiments from mainstream science. In the gnome experiment a scale calibrated for one area and then sent around to members of the public. A similar occurrence is happening in the other link.



https://www.arlynscales.com/scale-knowledge/factors-can-affect-scales-accuracy/

    Factors That Can Affect Your Scale’s Accuracy

    ...

    Differences in air pressure – Scales can provide inaccurate measurements if the air pressure from the calibration environment is different than the operating environment.

In the scale experiments the scales are calibrated for one environment and taken to another. That the equator has a difference in pressure than the poles is well known.

Tom, that Britannica article is talking about capital 'G' (universal gravitational constant), not little 'g' (acceleration due to gravity).  The two are very different and should not be confused. 
https://www.nextgurukul.in/nganswers/ask-question/answer/What-is-difference-between-g-and-G/Gravitation/14878.htm

I disagree. The article makes no designation. The Universality of Free Fall and the Equivalence Principle says that gravity operates exactly as if the earth were accelerating upwards at constant acceleration. If there was a difference in the speed of gravity as an object fell, it would be a violation of the Weak Equivalence Principle. The WEP is constantly tested, and violations at any range or sensitivity have been searched for over the last several hundred years.

There is no such thing as the speed of gravity, that sentence is unphysical.

We have discussed the equivalence principle before in the context of reconciling the lack of downward wind from a UA. You had incorrectly applied this principle to that situation as well, and I did you the courtesy of explaining your mistake, which you acknowledged by bowing out of the conversation.

I’m afraid in this context you are also incorrectly applying the principle, and in the exact same fashion.

It would be my pleasure to help you understand it better, so that future discussions are more fruitful for you.

To clarify, deviations in local gravity is not a violation of the equivalence principle. Your mistake is that you are implicitly transforming from one non-inertial reference frame to another non-inertial reference frame, without using the Lorentz transformation equations, so it makes sense that you would find a result that does not seem correct.

[Tom Bishop]

Of course it does.  It's quite obvious that they're talking about the constant of gravitation (capital 'G').

There also has been a continuing interest in the determination of the constant of gravitation, although it must be pointed out that G occupies a rather anomalous position among the other constants of physics. In the first place, the mass M of any celestial object cannot be determined independently of the gravitational attraction that it exerts. Thus, the combination GM, not the separate value of M, is the only meaningful property of a star, planet, or galaxy. Second, according to general relativity and the principle of equivalence, G does not depend on material properties but is in a sense a geometric factor.

The article does not state that it is talking about a "big G" versus a "little g". The experiments are testing the acceleration of bodies in free fall or the attraction from external gravity.

We have discussed the equivalence principle before in the context of reconciling the lack of downward wind from a UA. You had incorrectly applied this principle to that situation as well, and I did you the courtesy of explaining your mistake, which you acknowledged by bowing out of the conversation

As I recall in that conversation you were backed into a corner, essentially claiming that if the earth was not rotating that the weight of the air would constantly increase on the surface of the earth. I don't see the need to engage with that.

If you believe that there would be a difference in a container of air accelerating upwards and "gravity", then I would suggest that you read up on the equivalence principle. It's the same. Your response was "but the earth is rotating!" The rotation of the earth does not keep the air pressure or weight on the surface of the earth from constantly increasing. Refrain from rediculous discussions.

I had assumed that you saw your error, but I guess not. Do please tell us all about how, if the earth were not rotating, that air pressure or weight would constantly increase on the surface of the earth.

[QED]

Of course it does.  It's quite obvious that they're talking about the constant of gravitation (capital 'G').

There also has been a continuing interest in the determination of the constant of gravitation, although it must be pointed out that G occupies a rather anomalous position among the other constants of physics. In the first place, the mass M of any celestial object cannot be determined independently of the gravitational attraction that it exerts. Thus, the combination GM, not the separate value of M, is the only meaningful property of a star, planet, or galaxy. Second, according to general relativity and the principle of equivalence, G does not depend on material properties but is in a sense a geometric factor.

The article does not state that it is talking about a "big G" versus a "little g". The experiments are testing the acceleration of bodies in free fall or the attraction from external gravity.

We have discussed the equivalence principle before in the context of reconciling the lack of downward wind from a UA. You had incorrectly applied this principle to that situation as well, and I did you the courtesy of explaining your mistake, which you acknowledged by bowing out of the conversation

As I recall front that conversation you were backed into a corner, essentially claiming that if the earth was not rotating that the weight of the air would constantly increase on the surface of the earth. I don't see the need to engage with that.

If you believe that there would be a difference in a container of air accelerating upwards and "gravity", then I would suggest that you read up on the equivalence principle. It's the same. Your response was "but the earth is rotating!" The rotation of the earth does not keep the air pressure or weight on the surface of the earth from constantly increasing. Refrain from rediculous discussions.

I had assumed that you saw your error, but I guess not. Do please tell us all about how, if the earth were not rotating, that air pressure or weight would constantly increase on the surface of the earth.

A nice try. After your marble analogy failed, you floundered, and almost hysterically asked me how the two scenarios could possibly be different. I explained how a rotating earth is different than the inside of a rocket ship!

Which was quite easy to do, Tom.

I then proceeded to explain how that difference not only supported the equivalence principle, but also resulted in weather on our planet (you got that for free).

Then I finished by underlining step-by-step how, in fact, it was your scenario that violated the equivalence principle.

You then disappeared.

Welcome back though! I look forward to picking up where we left off! Have you found some new possible workarounds?

[Tom Bishop]

Your argument was that with UA that the weight of the atmosphere would constantly increase. This is wrong. There is no difference between a container filled with air accelerating upwards and a container being pulled down by gravity. See the Equivalence Principle. Your rebuttal of "but the earth is rotating!!" is quite odd, and incorrect. The rotation of the earth in RE does not prevent the weight of the atmosphere from constantly increasing.

Please justify your assertion.

[QED]

Your argument was that with UA that the weight of the atmosphere would constantly increase. This is wrong. There is no difference between a container filled with air accelerating upwards and a container being pulled down by gravity. See the Equivalence Principle. Your rebuttal of "but the earth is rotating!!" is quite odd, and incorrect. The rotation of the earth in RE does not prevent the weight of the atmosphere from constantly increasing.

Please justify your assertion.

This is moving backwards. We left the conversation having attended to this point already. Please review the conversation previously, and return here with an updated question.

The conversation was a week ago, so I suppose it’s possible you have just forgotten. Honestly, given your previous myriad diversionary discussion tactics, it is difficult for me to trust this is due to a poor memory rather than self-imposed selective amnesia intended to frustrate progress in the debate.

You seem to have no difficulty remembering old points that you believe support your position.

I’ll be here when you get back. I’m not going anyway.

[Tom Bishop]

That is exactly what you said. It is right here:

You are describing a violation of the equivalence principle. A container filled with gas will behave the same under gravity or under upwards acceleration. Gradually increase the size of that container and it behaves the same. There isn't a point where it suddenly violates the equivalence principle.

I agree. But a RE is not a container like a spaceship. It is also rotating, and so one must account for the effects of rotational drag, which is precisely why we have weather!

What I am saying is that on a FE, we would not have this rotation, and so the equivalence principle would indeed be violated - because we do not feel increasing pressure like we would on a space ship.

Now again, please justify your absurdity. You are suggesting that if the earth were not rotating the weight of the atmosphere would continually increase.

[QED]

That is exactly what you said. It is right here:

You are describing a violation of the equivalence principle. A container filled with gas will behave the same under gravity or under upwards acceleration. Gradually increase the size of that container and it behaves the same. There isn't a point where it suddenly violates the equivalence principle.

I agree. But a RE is not a container like a spaceship. It is also rotating, and so one must account for the effects of rotational drag, which is precisely why we have weather!

What I am saying is that on a FE, we would not have this rotation, and so the equivalence principle would indeed be violated - because we do not feel increasing pressure like we would on a space ship.

Now again, please justify your absurdity. You are suggesting that if the earth were not rotating the weight of the atmosphere would continually increase.

Yes indeed. Go ahead and copypasta me previous replies as well. It isn’t all in there. We had an entire conversation, and you are referencing my last reply and saying it does not contain the information of the entire conversation.

Absurdly, and anecdotally, this is what AG Barr did during the congressional hearing: piecemealing the totality until any one section was not convincing on its own. Don’t do that!

[Tom Bishop]

The comments prior to that are just of you claiming that the weight of the atmosphere would continuously increase with UA.

Since you wanted to continue that conversation by bringing it up, please enlighten us on why the rotation of the earth prevents the weight of the air at sea level from continuously increasing. I am sure that many others in our community would like to know.

[manicminer]

Since air is not a solid but a combination of different gases I am not sure you can say that air has a weight as such. Rather it has a number density (number of particles per unit volume). That will be greater near the surface and less the higher you reach in altitude. That is what people mean when they describe the air as being more 'rarified' at higher altitude. There are less oxygen atoms per unit volume as you get higher which is why people start to suffer with altitude sickness at 8000ft or higher.

It is more correct to describe the pressure of the air, and needless to say air pressure is greater at the surface because of a summative effect from gravity coming from below and the pressure of air particles higher up pushing down on the particles nearer the surface.  I would also expect air pressure at the surface to be on average slightly higher at the poles compared to the equator due to the lesser effect of the Earths rotation.

[WellRoundedIndividual]

Whether or not you believe in CG and UA, the wiki is better now. Thank you, Tom for updating it. You may proceed to argue over whether you understand a gravimeter or not.