Explaining Variations of Free-Fall Gravity on Earth?

[StarHunter]

TL;DR Summary

Explaining Earth's changing gravity at sea level or independent of altitude, latitude or lunar influence.

I stumbled upon gravitational variations that do not coincide with altitude, latitude or lunar interference. The only logical explanation I have for this would be the geology or makeup of the earth below those locations. But what is the variation of the Earths makeup below the crust? From my understanding it is fairly homogenous at least at specific depths/locations going to the core. So, if most of the geological variation is on the crust, I don't believe the crust could cause +-0.1m/s variation in the acceleration field. Another theory I had would be thermal vectors in the liquid areas of the Earth obstructing the density layers (lava lamp theory) that would take place without them and in turn would create a more stable and consistent acceleration field. If the Lava Lamp Theory were to be correct, at what speed should we be able to observe these changes?

https://www.britannica.com/science/...ation-around-Earth-the-Moon-and-other-planets
https://www.earthdata.nasa.gov/learn/sensing-our-planet/matter-in-motion-earths-changing-gravity

Thank you

 

[PeterDonis]

I stumbled upon gravitational variations that do not coincide with altitude, latitude or lunar interference.

Do you mean things described in the articles you reference?

 

[StarHunter]

Do you mean things described in the articles you reference?

No, they were used as a reference. Moreso explaining Earth's changing gravity at sea level or independent of altitude, latitude or lunar influence.

 

[PeterDonis]

No, they were used as a reference.

Then where did you "stumble on" these variations you claim?

 

[StarHunter]

Then where did you "stumble on" these variations you claim?

Data is on the Nasa website.

 

[StarHunter]

Then where did you "stumble on" these variations you claim?

https://www2.csr.utexas.edu/grace/

 

[PeterDonis]

Data is on the Nasa website.

Data for what? I see no calculations in your OP.

 

[PeterDonis]

https://www2.csr.utexas.edu/grace/

How does this relate to the claims you make in your OP?

You should be aware that personal theories and personal speculations are off limits here at PF. Your OP looks like personal theories and personal speculations.

 

[StarHunter]

How does this relate to the claims you make in your OP?

You should be aware that personal theories and personal speculations are off limits here at PF. Your OP looks like personal theories and personal speculations.

I did not see that anywhere and I find that hard to believe as that is a key function of a forum. Math and science are ever evolving, and I have seen countless posts and threads where theory is discussed. At the end of the day I was looking for an explanation of an observed phenomenon. I don't think that is off limits...

 

[PeterDonis]

I did not see that anywhere

It's right there in the rules that you signed up to:

Generally, in the forums, we do not allow the following:

• Discussion of theories that appear only on personal websites, self-published books, etc.
• Challenges to mainstream theories (relativity, the Big Bang, etc.) that go beyond current professional discussion
• Attempts to promote or resuscitate theories that have been discredited or superseded (e.g. Lorentz ether theory); this does not exclude discussion of those theories in a purely historical context
• Personal theories or speculations that go beyond or counter to generally accepted science
• Mixing science and religion, e.g. using religious doctrines in support of scientific arguments or vice versa.
• Philosophical discussions are permitted only at the discretion of the mentors and may be deleted or closed without warning or appeal

I find that hard to believe as that is a key function of a forum

Not this one. PF is for helping people to understand mainstream science, not for speculating.

At the end of the day I was looking for an explanation of an observed phenomenon. I don't think that is off limits...

It isn't. But claims like this in your OP are not doing that:

I don't believe the crust could cause +-0.1m/s variation in the acceleration field

Another theory I had would be thermal vectors in the liquid areas of the Earth obstructing the density layers (lava lamp theory) that would take place without them and in turn would create a more stable and consistent acceleration field.

 

[StarHunter]

It's right there in the rules that you signed up to:

Not this one. PF is for helping people to understand mainstream science, not for speculating.It isn't. But claims like this in your OP are not doing that:

I was suggesting potential answers that ARE mainstream that I may be unaware of. As for the theories aspect, I will refrain from that in the future. I was looking for a productive discussion and your hostility is not adding anything constructive.

 

[DaveC426913]

So, if most of the geological variation is on the crust, I don't believe the crust could cause +-0.1m/s variation in the acceleration field.

Apparently it's enough that you'll weigh less here in the Great White North than among our neighbors to the south. (About a tenth of a ounce less, but still...)

https://www.cntraveler.com/stories/2014-04-14/the-laurentide-ice-sheet-maphead

 

[PeterDonis]

At the end of the day I was looking for an explanation of an observed phenomenon

That observed phenomenon, I presume, being the variation of acceleration due to gravity? The articles you referenced already do a good job of explaining where that comes from. Is there something in them that you are having trouble understanding?

gravitational variations that do not coincide with altitude, latitude or lunar interference.

Those are very small, about one part in a million according to the articles you reference. That's much smaller than the $0.1$ m/s^2 amount that you appear to find questionable (and it's not clear where you are getting that number from); one part in a million is about $0.00001$ m/s^2.

 

[PeterDonis]

I was suggesting potential answers that ARE mainstream that I may be unaware of.

If they are mainstream, you should be able to give mainstream references for them. I am not aware of any mainstream reference for "Lava Lamp Theory" in this domain, but if you are, please give it.

I see no other suggested answer in your post, just doubt about a number, $0.1$ m/s^2, that I can't find in any of your references so I don't know where you got it from. And, as I've noted, it's several orders of magnitude larger than the number given in your references.

 

[PeterDonis]

I was looking for a productive discussion

The best way to start one is to correctly describe what the references you are relying on actually say.

your hostility is not adding anything constructive.

Enforcement of the rules is not hostility. It's my job as a moderator.

 

[StarHunter]

That observed phenomenon, I presume, being the variation of acceleration due to gravity? The articles you referenced already do a good job of explaining where that comes from. Is there something in them that you are having trouble understanding?Those are very small, about one part in a million according to the articles you reference. That's much smaller than the $0.1$ m/s^2 amount that you appear to find questionable (and it's not clear where you are getting that number from); one part in a million is about $0.00001$ m/s^2.

You are correct, in consequence any measured variation in general only deviates +-0.0698m/s^2. At least as measured with GRACE (https://www2.csr.utexas.edu/grace/publications/).

Even looking visually.

As far as my initial reference, ""Because the distribution of materials deep inside the Earth varies, its gravity field has hills and valleys. The ocean tries to lay along that hilly surface," said Michael Watkins, GRACE project scientist" and "The Earth's gravity field changes from one month to the next mostly due to the mass of water moving around on the surface,". Again that would come back to my initial question. At what level would the geology changes occur and why are they occurring. I would infer that it would be thermal vectors?

 

[PeterDonis]

You are correct, in consequence any measured variation in general only deviates +-0.0698m/s^2

Where does this number come from? (A link to a page that just lists a bunch of publications is not a valid reference for a specific claim.) It's quite a bit larger than one part per million.

At what level would the geology changes occur and why are they occurring.

All of the references you give mention the Earth's crust.

I would infer that it would be thermal vectors?

This is where you get into speculation again, unless you can give a reference for what "thermal vectors" are and why they might be relevant.

 

[StarHunter]

Apparently it's enough that you'll weigh less here in the Great White North than among our neighbors to the south. (About a tenth of a ounce less, but still...)

https://www.cntraveler.com/stories/2014-04-14/the-laurentide-ice-sheet-maphead

Thats interesting but I don't understand the explanation as with the ground "springing back" the density would decrease but the mass would stay the same or even increase with more water in the ground. I may be very wrong.

 

[StarHunter]

Where does this number come from? (A link to a page that just lists a bunch of publications is not a valid reference for a specific claim.) It's quite a bit larger than one part per million.All of the references you give mention the Earth's crust.This is where you get into speculation again, unless you can give a reference for what "thermal vectors" are and why they might be relevant.

"The acceleration g varies by about 1/2 of 1 percent with position on Earth’s surface, from about 9.78 meters per second per second at the Equator to approximately 9.83 meters per second per second at the poles." In OP Britannica reference.

and
"Gravity on the Earth's surface varies by around 0.7%, from 9.7639 m/s2 on the Nevado Huascarán mountain in Peru to 9.8337 m/s2 at the surface of the Arctic Ocean.[6] In large cities, it ranges from 9.7806[7] in Kuala Lumpur, Mexico City, and Singapore to 9.825 in Oslo and Helsinki." https://en.wikipedia.org/wiki/Gravity_of_Earth

Convection/thermals:
https://www.climate-policy-watcher.org/plate-tectonics/convection-and-the-earths-mantle-the.htmlAlso "Because the distribution of materials deep inside the Earth varies, its gravity field has hills and valleys"
OP NASA reference.

 

[PeterDonis]

"The acceleration g varies by about 1/2 of 1 percent with position on Earth’s surface, from about 9.78 meters per second per second at the Equator to approximately 9.83 meters per second per second at the poles." In OP Britannica reference.

Yes, that's a variation due to the change in altitude (the poles are about 13 miles closer to the Earth's center than the equator). You said you were talking about variations not due to change in altitude. (Strictly speaking, the equatorial value should also include the effects of the Earth's rotation; I'm not sure if the Britannica number does that.)

"Gravity on the Earth's surface varies by around 0.7%, from 9.7639 m/s2 on the Nevado Huascarán mountain in Peru to 9.8337 m/s2 at the surface of the Arctic Ocean.[6] In large cities, it ranges from 9.7806[7] in Kuala Lumpur, Mexico City, and Singapore to 9.825 in Oslo and Helsinki." https://en.wikipedia.org/wiki/Gravity_of_Earth

Again, these are variations due to changes in altitude and latitude (because the distance from the surface to the core varies with latitude), which you said is not what you were talking about.

Convection/thermals:
https://www.climate-policy-watcher.org/plate-tectonics/convection-and-the-earths-mantle-the.html

Thanks, that makes it much clearer what you are referring to. I'm not sure if variation due to this is included in the variations the GRACE experiment measures.

Also "Because the distribution of materials deep inside the Earth varies, its gravity field has hills and valleys"
OP NASA reference.

Yes, the article does use the phrase "deep inside the Earth", but the rest of the article makes clear that by "deep" they mean "deep down in the crust" (for example, one person quoted says the GRACE data "can give us an idea of how much water is available deep in the Earth for irrigation and agriculture"--such water "deep in the Earth" still has to be somewhere in the crust, we can't extract water from the mantle or core), which, while "deep" on a human scale, is not very far inside the entire Earth.

 

[StarHunter]

Yes, that's a variation due to the change in altitude (the poles are about 13 miles closer to the Earth's center than the equator). You said you were talking about variations not due to change in altitude. (Strictly speaking, the equatorial value should also include the effects of the Earth's rotation; I'm not sure if the Britannica number does that.)

Yes, and when I was making my correction I was referring to the total measured deviation meaning that your value of 0.00001 m/s^2 is more likely to be accurate.

Again, these are variations due to changes in altitude and latitude (because the distance from the surface to the core varies with latitude), which you said is not what you were talking about.

Correct

Thanks, that makes it much clearer what you are referring to. I'm not sure if variation due to this is included in the variations the GRACE experiment measures.

I would think if it was a factor, then it would inevitably be measured but may have been nulled after running some math on the subject. Potentially figuring that it was a negligible variable.

Yes, the article does use the phrase "deep inside the Earth", but the rest of the article makes clear that by "deep" they mean "deep down in the crust" (for example, one person quoted says the GRACE data "can give us an idea of how much water is available deep in the Earth for irrigation and agriculture"--such water "deep in the Earth" still has to be somewhere in the crust, we can't extract water from the mantle or core), which, while "deep" on a human scale, is not very far inside the entire Earth.

Good catch.

If it turns out 0.00001 m/s^2 is a more accurate measurement, then this makes a lot more sense to me.

 

[PeterDonis]

I would think if it was a factor, then it would inevitably be measured

From what I can gather, GRACE doesn't measure specific things that are causing the variations in $g$; those have to be inferred. Such inferences would have to be based on other observations--for example, observing the hydrologic cycle directly in order to correlate variations in $g$ that GRACE measures with changes in water distribution, as the article describes. We don't have any way of directly observing the mantle so it might not be possible to correlate such variations with GRACE measurements.

 

[StarHunter]

From what I can gather, GRACE doesn't measure specific things that are causing the variations in $g$; those have to be inferred. Such inferences would have to be based on other observations--for example, observing the hydrologic cycle directly in order to correlate variations in $g$ that GRACE measures with changes in water distribution, as the article describes. We don't have any way of directly observing the mantle so it might not be possible to correlate such variations with GRACE measurements.

Yes, I agree. Well said. And if thermal vectors were such a big factor, I would think we would see different deviation patterns and more generalized patterns. Although there are some larger area patterns they appear with altitude, mountain ranges, except for east USA where the Appalachian Mountains are. And I would expect an increase at volcanic sites or ranges. Maybe the material in the vectors is more homogeneous than I initially thought and are not pulling up more dense minerals/elements from closer to the core.