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Earth Space Science

Earth's Gravitational Shape In Detail 78

Posted by timothy from the explains-my-scale's-malfunction dept.
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."
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Earth's Gravitational Shape In Detail More

Earth's Gravitational Shape In Detail

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  • Gravitational hole in the Indian Ocean? (Score:5, Interesting)

    by G3ckoG33k ( 647276 ) on Sunday April 03, 2011 @05:38AM (#35698288)

    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.

    • Oh please... Don't give the nutjobs any more ideas.
    • It's R'lyeh of course, the lat long in the book were of course incorrect to preserve mankinds' sanity.

    • Re: (Score:2)

      by u17 ( 1730558 )

      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: (Score:2)

      by qmaqdk ( 522323 )

      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.

      • 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: (Score:3)

          by c0lo ( 1497653 )

          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".

    • Some more animations a la YouTube:

    • 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 [esa.int] 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

    • 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

      • 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

  • Didn't it use to be highly classified data? (Score:4, Interesting)

    by tibit ( 1762298 ) on Sunday April 03, 2011 @06:37AM (#35698430)

    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?

    • 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? (Score:4, Informative)

        by tibit ( 1762298 ) on Sunday April 03, 2011 @05:08PM (#35702292)

        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.

    • Re: (Score:2)

      by headhot ( 137860 )

      Not just missiles, but sub navigation too.

    • Re: (Score:2)

      by Zoxed ( 676559 )

      > 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/ [esa.int] suggests some data is free, other requires ESA approval.
      Or use this Java app: http://earth.esa.int/EOLi/EOLi.html [esa.int] ?

    • 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".

  • its own inhabitants..." ;-)
    SCNR, with a nod to Douglas Adams.
  • They used elevation and colors to indicate gravity strength. Are the radii supposed to be linearly comparable? The differences look too big.

    • Re: (Score:3)

      by pgn674 ( 995941 )

      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 [bbc.co.uk]. The article also gives further explanation of what the model represents.

  • Interactive Globe on BBC article (Score:1)

    by Anonymous Coward

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

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

    • 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.

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

    • Re: (Score:2)

      by dotbot ( 2030980 )
      (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: (Score:2)

      by Pembers ( 250842 )
      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".

      • 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 [wikipedia.org].

        The design allowed for an offset of over two meters.

    • 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.

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

  • 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?

    • 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 wou

  • 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 t

    • Re: (Score:1)

      by osu-neko ( 2604 )
      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...
  • ... 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!

  • Time to ride the gravitational waves?

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

    • Re: (Score:1)

      by earls ( 1367951 )

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

  • 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...

  • 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?

  • 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...

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