[greeniemax (OP)]

Earth gravitational anomaly is a physical problem where gravity of the earth is different in different places, some think they have the answer while others think it doesn't answer completely.

[imatfaal]

Greeniemax

Do you have links that you share so that members could read up before answering?   
We know that gravity varies with the density of the rock and height above sea-level and other factors - see this BBC article - is this what you are referring to, or something more complicated?

[Bored chemist]

Why is this set up as a poll?

[CliffordK]

Also the Grace Project.  See notes on Gravity around the world.  Gravity also varies with centrifugal force which varies with the distance from the equator.  And, of course, Earth's bulge.

One of the problems with the space generated diagrams such as the one above is that they don't fully take into account surface elevation.  So, The Andes, Himalayas, and Rocky Mountains show up as prominent red spots due to excess rock, but in fact, the surface gravity may be lower due to higher elevation.

The Grace satellites are also being used to monitor changes in ice, elevation, and ocean depth, which can show up as changes in the local gravity over time as measured from space.

No new theory is necessary.  One just needs to realize that gravity isn't uniform.  Still the 9.8 m/s² is a good estimate of the surface gravity of Earth.  However, one should keep in mind that it is only accurate to 2 significant figures.

[Geezer]

Why is this set up as a poll?

Sorry - no Polish jokes allowed.

[greeniemax (OP)]

Well I set up a poll because I wanted to see how many people actually think its an issue that can't be explained.

I tried reading lots about it but most of write up doesn't actually give a real reason for why gravity world wide is lined up with hot spots and when you compare it to depression in Indian Ocean we could see that there are no hot spots or volcano in that area. Is earth being liquid underneath has anything to do with change in gravity?

In case we just take altitude for the place it doesn't explain everything because we see high gravity near the pacific rim, maybe I have missed something but this is my assumption that for some reason we have higher gravity near hot spots.

[greeniemax (OP)]

It would be lovely if more people could give their feedback in written or in polls.

I would really like to understand this issue so we could get to bottom of this.

[Soul Surfer]

As Clifford says The term "gravitation anomaly" is a misnomer and tends to imply some departure from normal physical laws.  This is not the case. What is being measured as accurately as possible is the accurate gravitational field of the earth by its departure from that of a precise uniform sphere. So the correct term is probably gravitational anomaly.

It is perfectly obvious to everyone that the earth is not uniform, there are oceans of different depths and mountains of different sorts of rocks and different heights.   This means that gravity is stronger near to dense rock and weaker near to light materials it is also lower at great heights and tends to be higher close to the centre of the earth up to a point when it starts to get less deep down in mines. The mapping of precise gravitational fields on the earth's surface has been used for many decades for prospecting for minerals and in particular oil because oil is rather light compared with rock.

This experiment is aimed at measuring the precise fields and field gradients with the aim of learning more about the structure and composition of the earth and absolutely nothing to do with checking the accuracy of any physical laws which are always assumed to be correct.

[greeniemax (OP)]

Agreed Earth isn't uniform that means earth gravitation should be high or low based on altitude of the place, which isn't seen in the map, for instance you said "it is also lower at great heights and tends to be higher close to the center of earth" problem is that Himalayas, Rocky mountain and Chilean coast (which is a height) are locations of high gravity so lower gravity isn't seen in these places, if you take higher gravity is in higher altitude than it doesn't make sense when you have north Atlantic ocean and Eastern pacific rim near Japan.

For other reason if we take that dense rock into consideration, that would be fine if you take Himalayas but doesn't make sense for Iceland, Malaysia or Hawaii because we find molten rocks (Under the earth - High volcanic activity) and these rocks are lower in density than solid rocks.

Only one thing matches with the map world volcano map, its almost 1 to 1, could it be that mass has little to do with the world gravity and gravitational pull is based upon mass and energy?

[Cheese2001]

I would suggest most of the deviations are explained well in the source document of the spinning globe picture above:

http://earthobservatory.nasa.gov/Features/GRACE/page3.php [nofollow]

The local value for acceleration due to gravity changes, but we aren't changing the model of gravity.  We are using the well understood model of gravity to measure:

"These techniques provide critical input to many scientific models used in oceanography, hydrology, geology, and related disciplines, and will be used for a variety of applications including:

    measuring the changing mass of polar ice caps;
    measuring changes in water resources on land
    understanding shallow and deep ocean current transport;
    understanding sea level change resulting from ocean temperature and water mass changes;
    understanding atmosphere-ocean mass exchange;
    understanding the forces that generate Earth’s geomagnetic field; and
    understanding internal Earth forces that move tectonic plates and result in earthquakes and volcanic eruptions."

Hope this helps.

[greeniemax (OP)]

Thanks for the nice write up and link, but if you look at the explanation of map it doesn't even make sense.

"Gravity anomaly maps (see globe below) show how much the Earth’s actual gravity field differs from the gravity field of a uniform, featureless Earth surface. The anomalies highlight variations in the strength of the gravitational force over the surface of the Earth. Gravity anomalies are often due to unusual concentrations of mass in a region. For example, the presence of mountain ranges will usually cause the gravitational force to be more than it would be on a featureless planet — positive gravity anomaly. Conversely, the presence of ocean trenches or even the depression of the landmass that was caused by the presence of glaciers millennia ago can cause negative gravity anomalies."

We know that mountains are due to plate tectonic and volcanic activities, even though there are mountains near pacific ring of fire but they are much smaller than earth surface, that means radius (r) will be less in these places compared to a place which is 100m above sea level, this would automatically make the gravity less because there is difference of 4-5km between two surfaces, now it doesn't matter but mountains can't have huge concentrations of compressed rocks of 4-5km.

But if you look at it from point of view of simple amount of heat present in the earth it gives almost perfect answer.

http://www.zonu.com/detail-en/2009-11-19-11208/Gravity-anomalies-in-the-world.html

http://geospatialdesktop.com/2009/01/gmt_overlay_map/

Please check and compare the links below, that simply imply that gravity isn't attraction between masses but attraction between energy and mass, which is crazy but this is what it implies. I'll post another question that would be a good so called pointer in same direction, I'm not going to post it here because not everyone would see it and will be able to post something on it.

I'm sure they would think I'm talking coo-coo but if you check the maps above its almost accurate.

[Cheese2001]

I read your posts, but I don't come to the same conclusion you did.  Newton's gravity is correct for round, featureless object.  At long distances, planetary distances for example, the roughness of the planetary surface doesn't matter, it's just too small to matter.

GRACE is attempting to map the differences between a round featureless globe to the one we live on.  The higher density of the mountainous regions are a bigger influence on the local value for acceleration due to gravity than the increased height above the geoid.  The rocks are of higher density than water (obvious, since rocks sink in water), so the gravity is slightly higher on a mountain than sitting on a boat.  Mountains are moved higher due to tectonics and volcanic activity, but the gravity delta is due to the mass distribution on the planet, not the heat. 

Because gravity is so well understood, we can use a satellite at a known distance above the earth to measure the mass distribution of the earth.

[imatfaal]

Nice answers 2001 a Cheese Odyssey - and welcome to the Forum

[greeniemax (OP)]

Dear Cheese maybe I'm unable to understand you or you're unable to understand me. Let me give it one more shot and try to explain what I'm saying, I'll post my next question related to exactly this but asked in a different way.

The higher density of the mountainous regions are a bigger influence on the local value for acceleration due to gravity than the increased height above the geoid.

When mountain is created using plate tectonic like Himalayas it would have higher density, but that density is also limited, but if mountain is created using volcanic action the density of that mountain is low, under sea mountain ranges near Philippines, Malaysia and Indonesia would have less density compared to a normal sedimentary rock from a normal earth region. Due to liquid rock underneath the mountain surface and because of trapped water and air particles when lava bubbles out.

Secondly most of these mountains are underwater, that means distance from center of the earth for this mountain peak would be less than surface of the earth. Let me say it once more in a different way, underwater mountain (x) would have less distance to center of the earth (r) compared to surface of the earth (y). Thus (x->r) < (y->r), because above the mountain inside the sea its water, which is less dense. i.e. Pacific rim, underwater sea near Fiji Islands, Hawaii (underwater), North Atlantic cannot have higher gravitational pull compared to Central USA or Brazil. Because more mass more gravity, this is exactly what we don't see in these maps.

In case we are getting this errors (anomaly) it means that there is something wrong, things don't work out as they should this is why its called "anomaly".

http://www.ngu.no/geodynamics/gplates/gravi-450dpi.jpg

If you look in the above very accurate map of gravity you'll see that below sea level trenches have high gravitation, they are very clear in the above map, point is why? My theory is that gravitational pull isn't between two masses but

g=(M1+E1)+M2-E2

g is Gravitational Effect
M1 = Mass of First Object
E1 = Free Energy of First Object
M2 = Mass of Second Object
E2 = Free Energy of Second Object

[Cheese2001]

Sorry, mate, I can't help you.  Newtonian gravity doesn't account for energy impacting local gravitational values.

Newtonian physics can explain the local value of gravity in terms of variable density about a body, a rotational reference frame, and the distance from the point of interest to the point mass center of the system.

You start with F_gravity = m * a = G * M_earth * m / r²

Good news: the lower case "m" terms cancel. 

Bad news:  You have to use the vector form of the equation and the acceleration term has to be that of a non-inertial rotating reference frame.  Change the M_earth term into the volume integral of density as a function of distance from the point of interest.  The radius term in the denominator will remain the distance from the point of interest to the equivalent point mass of the system, but needs to be a vector.  This is beyond my mathematical abilities to even write correctly.

If you'd like to see energy effects on gravity, you need to use the General Theory of Relativity.  That is well beyond my area of expertise. 

I know this is unsatisfying.  My apologies.

[CPT ArkAngel]

It is more a problem of knowing the density of the ground under your feet (from the ground to the earth's center of mass)...

[Atomic-S]

http://www.ngu.no/geodynamics/gplates/gravi-450dpi.jpg

The color code of the referenced map is, to my eye, somewhat unclear. I observe along the western South American coast: on shore areas in red and off-shore areas in pink. Does that mean that the gravitation in these areas is nearly equal, or highly dissimilar? Examining elswhere on the map I see evidence for both interpretations.

[Atomic-S]

My theory is that gravitational pull isn't between two masses but

g=(M1+E1)+M2-E2

g is Gravitational Effect
M1 = Mass of First Object
E1 = Free Energy of First Object
M2 = Mass of Second Object
E2 = Free Energy of Second Object

Actually, your theory is supported by Einstein's relativity, if by M1 and M2 we mean the masses at a base condition, and by E1 and E2 we mean the equivalent relativistic mass added by an energizing condition such as a different temperature that of the base condition. However, the correct expression is (M1 + E1/c²)*(M2 + E2/c²). Note that for common temperature differences, the E terms add only a very tiny correction, probably not detectable.  Rather than this line of inquiry, I am more likely to inquire into the way chemical composition and temperature (including wheter in liquid or solid state) affect densities of rocks, together with an analysis of the distance of the said rocks from the observer. By the way, do we know whether the anomaly maps that we have been viewing are for g at the surface (which varies in altitude), or is it for g at some fixed altitude?  That distinction matters.

[CliffordK]

Another way to look at it.  From Newton's universal law of gravitation



Now, if the Earth is about 5.98×10²⁴ kg. 

But, rather than thinking of the mass of the Earth as a homogeneous body, I could treat every kilogram independently, and thus my mass would define the sum of  5.98×10²⁴ independent direction vectors of the pull of my body towards each separate kg that makes up the Earth.  Better yet, I could break my body up into a little less than 100 kilos, and thus defining   5.98×10²⁶ vectors for each kilo in my body.  Sum, all the vectors, and one gets the actual pull due to gravity. 

Looking at it as the sum of vectors, it is easy to predict that the gravity will be zero in the middle of the earth (ignoring the sun and moon).

If I stood East of of a mountain chain, and then again to the West of the mountain chain, I might actually see the direction of the pull of gravity deviate slightly due to the vector created by the mountain chain towering above me. 

[greeniemax (OP)]

Thank you so much all for feed back its so nice to talk to people who speak your language.

See what I'm talking about has a bit of twist to it, I'm saying matter and matter would have no effect on each other now biggest problem is E=MC² where Matter is made up of energy. But mass we see has energy because its atomic energy similar to energy released in fusion or fission.

The an atom has energy in it and because it forms part of matter it has attraction, this isn't just pure matter, for sure the biggest problem is we have to separate mass as matter and energy, which in current theories are same "matter = energy".

The E I'm talking about is free energy, though the effect of even difference of energy could be seen in H (Hydrogen) and He (Helium), I'll post my second idea here but than I'll put on main for others to see and answer on Sunday.

You see hot anything rises, but mostly we can see this in Liquid and Gasses because they move easily. Okay for sure that is fine because hot elements are less dense and that means they have more empty spaces between them, but makes them lighter.

But being less dense and lighter is our understanding of thing but what makes less dense lighter? Why is less dense thing lighter?

Lets put same idea that I had before to work

g=M1+E1+M2-E2 (This is very simple because I'm not a mathematician)

It simply says if you heat something it would have less attraction due to increase in Energy levels, now same concept of Gravity anomaly applies to objects being lighter when they have higher amount of free energy. Thus two object have attraction toward each other based on amount of free energy and mass.

Free Energy (Energy that could be exchanged by equilibrium or chemical process with other atoms of different types)

Now if you look at the method how GRACE is doing its survey.

Earth is M1 and E1 that changes all the time
GRACE is M2 and E2 that is static and doesn't change.

If you increase either M1 or E1 on Earth it would simply increase the value of g, because value of M2 and E2 is consistent and doesn't change. Thus every time GRACE goes over an area with higher E1 (more energy like a volcano or underwater open volcanic trench) it would show higher gravity levels and but it would also increase if mass increases like mountains or hills.

I hope you guys try to understand what I'm talking about because I'm really bad in explaining things.