Earth's Gravitational Shape In Detail

RobHart writes "The European Space Agency (ESA) has released detailed information about the Earth's gravitational shape, based on data from the ESA's GOCE satellite (Gravity Field and Steady-State Ocean Circulation Explorer). The link includes an interesting animation of the data, using an appropriately distorted Earth."

Comments

Gravitational hole in the Indian Ocean?

[G3ckoG33k]

Cool to see how the gravitation patter largely ignores the contours of the continent.

But, is there a gravitational hole in the Indian Ocean? Could it have been an asteroid? Perhaps leading to the "fast split" of Africa and India?

Just speculating.

Re:Gravitational hole in the Indian Ocean?

[Anonymous Coward]

Or an alien spaceship made of neutronium crash landed there millenia ago!

Re:Gravitational hole in the Indian Ocean?

[Rakshasa Taisab]

Oh please... Don't give the nutjobs any more ideas.

Re:Gravitational hole in the Indian Ocean?

[ThunderBird89]

Neutronium is extremely dense, so it would be a bulge.

Apart from that, I thought the ocean floor was mapped there. Pointers to a crater would have been spotted already, at the very least on the magnetic maps, no?

Re:Gravitational hole in the Indian Ocean?

[BodeNGE]

It's R'lyeh of course, the lat long in the book were of course incorrect to preserve mankinds' sanity.

Re:Gravitational hole in the Indian Ocean?

[Anonymous Coward]

It's just the Earths Navel.

Re:Gravitational hole in the Indian Ocean?

[Anonymous Coward]

But, is there a gravitational hole in the Indian Ocean? Could it have been an asteroid? Perhaps leading to the "fast split" of Africa and India?

That's where the moon was born.

Re:Gravitational hole in the Indian Ocean?

[u17]

But, is there a gravitational hole in the Indian Ocean? Could it have been an asteroid? Perhaps leading to the "fast split" of Africa and India?

It's a huge deposit of unobtanium!

Re:Gravitational hole in the Indian Ocean?

[bejiitas_wrath]

Some nutcases claim that the Earth is hollow and there are holes at the poles leading to the hollow Earth. I hope this does not fuel the fires of conspiracy theories. But this will give us a proper insight into the Earth`s interior.

Re:Gravitational hole in the Indian Ocean?

[qmaqdk]

But, is there a gravitational hole in the Indian Ocean? Could it have been an asteroid? Perhaps leading to the "fast split" of Africa and India?

No, the blue areas are the weakest areas. Indonesia and Iceland are the places to go for gravity.

Re:Gravitational hole in the Indian Ocean?

[Anonymous Coward]

From the article:
"The geoid is the surface of an ideal global ocean in the absence of tides and currents, shaped only by gravity"

So that would suggest the 'hole' in the Indian ocean is a area of greater gravity. I am not sure if you meant hole as in less gravity or more?

To me the picture colors are off. The Red should be the deep holes and the blue should be the peaks.

Re:Gravitational hole in the Indian Ocean?

[Anonymous Coward]

The BBC article is much better.

From that article:

Gravity is strongest in yellow areas; it is weakest in blue ones.

...

Even so, a boat off the coast of Europe (bright yellow) can sit 180m "higher" than a boat in the middle of the Indian Ocean (deep blue) and still be on the same level plane.

Isn't that backwards? Shouldn't you be lower where the gravity is stronger?

Re:Gravitational hole in the Indian Ocean?

[condition-label-red]

Some more animations a la YouTube:

• Higher res copy of animation in article
• View of northern/southern hemispheres

Re:Gravitational hole in the Indian Ocean?

[Alef]

Nope. Higher gravity attracts more water, so the sea level is higher (compared to the surface of a perfect sphere the size of the Earth).

Or you can think about it in this way: The sea level forms a surface of equal gravity (otherwise there would be a "slope" somewhere, and the water would move down it). Where there is higher gravity, the sea level needs to be farther from the Earth's center to be on that surface and experience the same gravity.

Re:Gravitational hole in the Indian Ocean?

[kvvbassboy]

Cool to see how the gravitation patter largely ignores the contours of the continent.

On the contrary, this is not entirely true. Looking at the complete 2D contour you can see that the contour lines of either high or low gravitational areas are almost always centered in the oceans, whereas the continents and landmasses almost always in the middle of the gravitational scale.

My completely uninformed gut feeling tells me that this data could go a long way in explaining why continents are located (or drifted to) where they are, and could possibly also make predictions about continental drifting in the future.

Re:Gravitational hole in the Indian Ocean?

[Anonymous Coward]

No, the hole in the Indian ocean is an area of less gravity. In this representation of a global ocean, more gravity attracts more water causing the water level to raise from the water flowing from the area of less gravity which is now lower. Yellow and red then are the areas with greater gravity and the blue are less exactly as shown.

Re:Gravitational hole in the Indian Ocean?

[Samantha Wright]

Your theory is hard to not like.

Re:Gravitational hole in the Indian Ocean?

[nschubach]

The US has less gravitational force than Europe... does that mean there are giant cavernous regions below the US?

Maybe it explains why there are more fat people in the US because they don't have to work as hard on a daily basis to keep themselves standing. (/joke)

Re:Gravitational hole in the Indian Ocean?

[Anonymous Coward]

Cool to see how the gravitation patter largely ignores the contours of the continent.

Interestingly, the red areas fit well across the blue separations, as if they would have split long ago-- like plate tectonics on on the gravitational masses. But, the continents would have had to appear either much later or on a different layer to overlap the gravitational masses. Early Earth plate tectonics or on a second layer? Maybe a geologist could shed more light on this...

Re:Gravitational hole in the Indian Ocean?

[Chibi Merrow]

But, is there a gravitational hole in the Indian Ocean? Could it have been an asteroid?

I worked on a system that let a Geologist at my University study the gravity data of the Chicxulub impact structure on the shore of the Yucatan peninsula... Based on that experience, if that gravity hole were caused by an impact I'd expect to see a high gravity area in the center from the mantle "rebounding" back up through the crust following the impact.

On top of that, Chicxulub was a pretty big impact--probably the one that ended the dinosaurs--and you can't even see it at the resolution of that animation. That hole in the Indian Ocean is several orders of magnitude larger. Nearly the size of the continental U.S. Even assuming for the moment the planet wouldn't have just broken up in that impact, I think it's unlikely such a large impact occurred recently enough in geological history to not have been erased by plate tectonics.

Re:Gravitational hole in the Indian Ocean?

[c0lo]

The US has less gravitational force than Europe... does that mean there are giant cavernous regions below the US?

Maybe it explains why there are more fat people in the US because they don't have to work as hard on a daily basis to keep themselves standing. (/joke)

T'is caused by the trade deficit and foreign debt, both come with a "negative weight".

Re:Gravitational hole in the Indian Ocean?

[TheDarkMaster]

Interesting. Since you seem to know the subject, if the void is not an impact crater so what could be the cause of the void? I'm not a geologist, but to me it suggests that is maybe the empty "space" left by the continental shelf of India when she was in the direction of China

Re:Gravitational hole in the Indian Ocean?

[Chibi Merrow]

I'm no geologist as well, but I think the explanation you just offered sounds very plausible. :)

obl xkcd

[Anonymous Coward]

http://xkcd.com/852/

USofAians always cheats...

Re:obl xkcd

[Anonymous Coward]

best xkcd ever!

Low gravity in US

[Anonymous Coward]

Could the low gravity in US explain the general US overweight? Too easy living, so to speak?

Re:Low gravity in US

[Anonymous Coward]

It also explains how they could fake the moon landings.

You know, with all that low gravity they got there. Bouncy bouncy in the desert.

fake math+fake science+holycost=distorted earth

[Anonymous Coward]

so it's us. the planet remains (so far today) cosmosically perfect. butt whose day is today? so does it matter that our fatal holycost real sex religious training kicks in even harder 1X per weak or worse?

Re:fake math+fake science+holycost=distorted earth

[jhoegl]

Now even holy costs?

campaign slowguns re-emerging again

[Anonymous Coward]

royals & holycosters; 'for a lesser non--distorted world population by eugenetics'. 'it looks however you want you to believe it looks' . 'stop pretending your butt hurts', or we'll give you something to vote on, again.

sounds like another series of those highly expensive, deceptive, & televised stand-up talknician pageants getting ready to go down on us?.

Didn't it use to be highly classified data?

[tibit]

Wait a minute, didn't accurate geoid use to be highly classified information? As in "used for missle inertial navigation" kind of classified? I wouldn't be surprised if the German data could be imported into the U.S., but couldn't be re-exported, for example... Does anyone know more about this?

Re:Didn't it use to be highly classified data?

[Anonymous Coward]

There's someone about to knock on your door. They DON'T have pizza.

Re:Didn't it use to be highly classified data?

[Wizard Drongo]

My (completely uninformed) guess, is that in these days of GPS and other sat-based navigation, the geode isn't quite as special as once it was. And I don't think they're releasing full-res data....that wee potato pic is cute, but wouldn't be of much help to you for planning a flight trajectory...

Re:Didn't it use to be highly classified data?

[headhot]

Not just missiles, but sub navigation too.

Re:Didn't it use to be highly classified data?

[cavedweller96]

The policy is that they will release all data. Whether or not they follow through is the question....

Re:Didn't it use to be highly classified data?

[Zoxed]

> I wouldn't be surprised if the German data

Peter Pedant points out that GOCE is an ESA mission, so I assume the data is owned by ESA, not Germany.
http://earth.esa.int/dataproducts/accessingeodata/ suggests some data is free, other requires ESA approval.
Or use this Java app: http://earth.esa.int/EOLi/EOLi.html ?

Re:Didn't it use to be highly classified data?

[DerekLyons]

Wait a minute, didn't accurate geoid use to be highly classified information? As in "used for missle inertial navigation" kind of classified?

Does anyone know more about this?

I think this falls under the heading of "those who know can't talk, those who don't won't shut up".

Re:Didn't it use to be highly classified data?

[tibit]

I think that a lot of U.S. nuke missile arsenal predateds GPS -- maybe they upgraded avionics to take advantage of it, I don't know. If there was to be any sort of a nuclear showdown, then the GPS would either go down or the clear data would be turned off, only encrypted one remaining. I think that if you're after long range weapons, you really need INS, and for that accurate geoid is a must. I would presume that any sort of a ballistic or cruise missle guidance system would have targeting accuracy specified without GPS augmentation (inertial only), with augmentation providing a "free" improvement if available.

Apart from GPS and GLONASS, there is no "other" sat-based navigation available yet. Getting any sort of a satnav receiver through its paces of military QA, you can't really add support for other systems on a whim. I think that all satnav receivers installed in U.S. weapons support GPS, and won't support anything else in the next decade or two.

You don't use the geoid to plan any sort of a trajectory. You use it for inertial navigation -- for converting outputs of your inertial reference sensors (gyros and accelerometers) into a position fix. To do this accurately, you need accurate, low-drift and low-noise sensors. Once your sensors get good enough, improving their accuracy doesn't improve the accuracy of your fix! To get any further improvement, you need to improve the accuracy and resolution of your geoid data. By my back-of-the-envelope calculations, GOCE's geoid is supposedly (based on published details) good enough to match the best inertial reference sensors out there, and would allow you to obtain the best inertial fix that's possible with current technology.

"A potato so round it was thought a planet even by

[D4C5CE]

its own inhabitants..." ;-)
SCNR, with a nod to Douglas Adams.

The economy... Re: Low gravity in US

[D4C5CE]

No, it's just the evaporating "weight" of the dollar (and cardboard walls of mortgaged real estate) I'm afraid. ;-)

Re:The economy... Re: Low gravity in US

[Anonymous Coward]

so why is the rent still 2 damn high?

What's the scale?

[srussia]

They used elevation and colors to indicate gravity strength. Are the radii supposed to be linearly comparable? The differences look too big.

Re:What's the scale?

[pgn674]

They used elevation and colors to indicate gravity strength. Are the radii supposed to be linearly comparable? The differences look too big.

I was wondering that too, and I found an answer: "The differences have been magnified nearly 10,000 times to show up as they do in the new model.": BBC News - Gravity satellite yields 'Potato Earth' view. The article also gives further explanation of what the model represents.

Interactive Globe on BBC article

[Anonymous Coward]

The BBC posted this article on Thursday which includes a large interactive globe.

http://www.bbc.co.uk/news/science-environment-12911806

Re:Interactive Globe on BBC article

[N Monkey]

The BBC posted this article on Thursday which includes a large interactive globe.

http://www.bbc.co.uk/news/science-environment-12911806

I saw the headline on another news website - on 1st April - which said (something like) "Earth is potato shaped". Due to the unfortunate timing, I didn't take it seriously.

Use of data?

[skywatcher2501]

Might be an rtfa question, but what are such measurements useful for? What could one do with such data?

Re:Use of data?

[dotbot]

(Based on my highly limited knowledge of the subject) it enables observations about the earth to be compensated for non-uniform gravitational pull, so you can get a better idea of what is really happening and stand a better chance of explaining why. For example, now we know where water is effectively flowing uphill and downhill, we can better estimate the actual ocean current forces from the observed currents, so start to guess at what is causing them.

Re:Use of data?

[Pembers]

One use of the data would be to create a uniform worldwide definition of "sea level". Countries have their own standards for it. We know they're not the same, but we don't always know by how much they differ. When the Channel Tunnel (between Britain and France) was being dug, and the diggers from each end met in the middle, they found they were about 50cm out - each side had been measuring their depth relative to their own definition of "sea level".

Re:Use of data?

[the_other_chewey]

When the Channel Tunnel (between Britain and France) was being dug, and the diggers from each end met in the middle, they found they were about 50cm out - each side had been measuring their depth relative to their own definition of "sea level".

[citation needed] - Yes, they were off by about 35-50cm (depending on the source - also, there are three
tunnels, so those numbers might be for different ones). However, this was hailed as an enormous success
for surveying at the time, thanks to advanced laser measurnig technology and special high-precision gyrotheodolites.

The design allowed for an offset of over two meters.

Re:Use of data?

[wagnerrp]

It allows satellite orbits to be more accurately predicted. Things like geostationary satellites must carry large amounts of fuel because these differences in gravity cause them to drift outside their desired station.

Re:Yep very strange hole...

[skyride]

That link is not safe for life.

Bermuda Triangle?

[Anonymous Coward]

Could this help explain and avoid lost planes and boats at sea?

Re:Bermuda Triangle?

[oztiks]

Funny you say that, there is a blue patch right near the Triangle!!! Having said that there is an even bigger one in the Indian Ocean so I'd say no.

However .... The Indian Ocean is the purported to be location of the lost city of Atlantis so you never know :)

Re:Bermuda Triangle?

[dogsbreath]

Funny you say that, there is a blue patch right near the Triangle!!! Having said that there is an even bigger one in the Indian Ocean so I'd say no.

However .... The Indian Ocean is the purported to be location of the lost city of Atlantis so you never know :)

WAS the purported location of the FORMERLY lost city of Atlantis, which of course was in Spain all along, FWIW ;->

heh

[MobileTatsu-NJG]

Yo mama's so fat, we can se here she lives on this map!

Measurable effect?

[LS]

So If I weighed something in a bright yellow zone, then in a dark blue zone, would I be able to see a difference on an ordinary scale?

Re:Measurable effect?

[Anonymous Coward]

Nope.

Otherwise Weight Watchers and Jenny Craig would hold their meetings in India...

Re:Measurable effect?

[Anonymous Coward]

At least if you use kilogram, the kilogram is defined by the atomic composition of the prototype kilogram and does not include gravitation. For example a kg water measured in a high gravity area is less than a kilogram water measured in a low gravity area, but both weight one kg.

Re:Measurable effect?

[Anonymous Coward]

The map shows a surface of equal weight, and corresponds to sea-level when you look at seas. The weight of something depends on how high above that surface it is. What you're looking for is http://en.wikipedia.org/wiki/GTOPO30 .

Re:Measurable effect?

[Mt._Honkey]

Depends on how you weigh it. If you truly measure weight, then yes. If you are really measuring mass, then no. For example: a spring scale will show a difference because the gravitational force is different. If you use a pan balance you will not see a difference, because both the subject and reference masses change their weights by the same fraction. Same goes for any true measurement of mass, such as penning traps or RFQ's.

You would need a good scale, but not extraordinarily good. A 1 kg weight would weigh ~100 mg weight different between the max and min.

Voyage to the center of the earth

[gmuslera]

Used to think that below the comparatively thin earth crust, what goes below is somewhat homogeneous in each layer. But that gravity pull on north america is similar to the one in the tibet and the one in the bottom of the atlantic ocean (in average), while north of europe and north of australia, even undersea, are higher than in the top of the andes, and if well could mean heavy metal deposits up in the crust, maybe it means that there are zones with different composition in the mantle or below..

And if that zone is dynamic, could be interesting to see if/how changes that density map in a few years.

Re:Voyage to the center of the earth

[Anonymous Coward]

And if that zone is dynamic, could be interesting to see if/how changes that density map in a few years.

I guess it depends on your definition of few

Re:Voyage to the center of the earth

[osu-neko]

Why would it be homogeneous? Remember, the only part of the Earth's interior that is liquid is the outer core. The mantle is solid, albeit a fairly plastic solid at its temperature. Things "flow" at rates that make Play-Doh look extremely runny. It's just not going to mix out evenly very easily...

cool...

[Anonymous Coward]

...but can someone explain to me the scale and the unit of measure they use?

the whole heart-gravity map is here

At Last ...

[Mostly a lurker]

... an explanation that I am willing to accept for why I appear to be overweight. Obviously, I am just living in an area where the gravitational pull is unusually strong. The same reason explains my low level of activity. More effort is needed to move, so I am justified in moving less.

I love science!

Cool, now what?

[earls]

Time to ride the gravitational waves?

re-map Japan ?

[Zoxed]

I was wondering if, post earthquake, they will now have to re-map Japan ?

Re:re-map Japan ?

[earls]

Absolutely, without a doubt. The country's terrain changed vividly when a large number of coastal slopes slid into the ocean.

Re:re-map Japan ?

[Anonymous Coward]

I was wondering if, post earthquake, they will now have to re-map Japan ?

Apparently some spots moved up to 4m, so GPS/map alignment will need to be updated eg for Google Maps.
The resolution of the gravity map is a lot lower than that though, so any changes would likely be very minor.

The real inspiration for GOCE

[dotbot]

Marty: Whoa, this is heavy.
Doc: There's that word again, heavy. Why are things so heavy in the future? Is there a problem with the Earth's gravitational pull?

Better to be prepared...

ambiguous colors

[pifko]

At first I thought the color scale meant the gravity pull at the ground level. But then it may also mean the distance of a point on the gravitational geoid shape from the center. The two explanations are not equivalent. So which is it?

Re:ambiguous colors

[Anonymous Coward]

From http://www.esa.int/esaCP/SEM1AK6UPLG_index_1.html#subhead2

The colours in the image represent deviations in height (–100 m to +100 m) from an ideal geoid. The blue colours represent low values and the reds/yellows represent high values.

Earth's gravitational shape

[Sehrish]

(CBS News) That potato-shaped lump in the picture you're looking at is science's most accurate picture to date of how gravity varies across the Earth. It turns out that our world is closer to being a sphereoid than a perfect sphere. Read More about Earth's gravitational shape Essay Writing help

At last

[Anonymous Coward]

Proof that that putt did break uphill

old story...

[hesaigo999ca]

there was an old post on /. from way back about the equator getting thicker in the middle because the polar ice caps were melting and all the water was accumulating towards the middle, (like a skipping rope, when you tighten the ends, more centrifugal force applies towards the middle)....i guess this is the beginning of the next ice age...