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Science

Earth's Gravitational Field Is Getting Flatter 270

Posted by Hemos from the getting-flatter-all-the-time dept.
RJG2 writes "MSNBC has an article stating that Earth's gravitational field has changed, becoming stronger towards the equator, thus becoming flatter. The cause has yet to be determined, but it is assumed changes in ocean levels are responsible."
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Earth's Gravitational Field Is Getting Flatter More

Earth's Gravitational Field Is Getting Flatter

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  • Maybe they'll settle for a flat gravitational field?
  • Shouldn't the opposite be happening? Global Warming is being blamed for the melting of the polar caps, if that's the case then shouldn't the gravitational field be even more round?
    • No.

      Where does the melted ice go? -> equator.
      What makes gravity? -> mass.

      More mass at the equator means more gravitational force.
    • Since the earth is spinning, the water tends to be forced to the equator by centrifugal force (although I think more correctly it's centripedal force, but whatever). So no matter where the water comes from, it will tend to flow to the equator.

      Actually one likely side-effect of long term global warming is, ironically, an ice age. The water moves to the equator, and this causes the earth to spin slightly slower. The side-effect being that this cools the earth. I forget exactly why this is because I learned it in high school physics which was just over a decade ago.

      • Re:Nope, it flows to the equator (Score:4, Informative)

        by God! Awful ( 181117 ) on Friday August 02, 2002 @05:52PM (#4001874) Journal

        Since the earth is spinning, the water tends to be forced to the equator by centrifugal force (although I think more correctly it's centripedal force, but whatever).
        IMHO, high school physics teachers really dropped the ball in explaining this one. A whole generation of high school graduates is confused about centrifugal vs. centripedal.

        A body that is spinning around an axis or orbiting around point must be under continual force. Otherwise, they would simply fly off in a straight line at a tangent to the curve. This is the centripedal force. The centrifugal force is a "pseudo force", which means that it only exists in a non-intertial frame of reference.

        Basically, what happens is that when you accelerate (whether in a straight line or in a circle), your inertia feels like a force in your frame of reference. When you sit in a moving car, from your point of view you feel like you are sitting still and the car is moving. We know that when an object is at rest, the forces on it are balanced. Therefore, in your frame of reference you feel a pseudo force which balances out the force that is being applied on the car. The pseudo force is really just the effect of your inertia.

        So how does this apply to the water? Well, everything on Earth has inertia, and this inertia wants to keep it going in a straight line, even though the Earth is rotating. Solid objects, such as humans are obviously kept in place by simple static friction and wind resistance. Water and air are more mobile and they are less subject to friction (although they are still very subject to air/water pressure). That is the main reason why wind and ocean currents are very obvious whereas continental drift takes centuries.

        So in reality, it is the inertia of the water that makes it more buoyant at the equator. The water at the equator is spinning faster than the water at the poles, so it is slightly less subject to gravity. Therefore it bulges out, "making room" for some extra water from the poles to move towards the equator.

        -a

  • Yo mamma (Score:3, Funny)

    by wilburdg ( 178573 ) on Friday August 02, 2002 @04:28PM (#4001300)


    Yo mamma so big that... n/m

  • This reminds me. (Score:2, Interesting)

    by Kenja ( 541830 )
    Aren't we past due for the poles to flip?

  • Shorter and Fatter (Score:5, Funny)

    by Tall Rob Mc ( 579885 ) on Friday August 02, 2002 @04:28PM (#4001302)
    Judging by the diagram, this means that the Earth is getting shorter and fatter. Is this news? Thats what happens when you get older...

    • Mid life crisis? (Score:4, Funny)

      by CrazyDwarf ( 529428 ) <michael.rodman@gmail.com> on Friday August 02, 2002 @04:47PM (#4001480) Homepage
      It could be worse, we could be combing Ozone over from areas around the north pole.

    • Actually its pretty scary... (Score:5, Interesting)

      by Evil Pete ( 73279 ) on Friday August 02, 2002 @08:47PM (#4002687) Homepage

      There appears to be a movement of a huge mass from the poles to the equator over the last 4 years. The article describes how they excluded the obvious culprits: melting ice, earth movements, atmosphere etc. And finally concluded that it is related to ocean circulation. Now that gives me the creeps!

      Why the creeps? Because ocean circulation changes can happen relatively quickly and are implicated in the starting / stopping of ice ages. They are crucial indicators for climate change. And when the ocean circulation changes there is nothing humans can do about it.

      Hopefully it either isn't the oceans or if it is it wont have a serious effect (dont believe my own words here ... but it sounds comforting). Whatever, this requires some serious investigation, just hope they got it wrong.

      • Or maybe it's an early indicator of a gravitational field reversal, or additional buffeting of the Earth's magnetic field by increased solar winds from the peak solar cycle?
      • It would be folly for us to expect our planet's climate to stay the way it is forever. For as long as we can look back the climate has been wildly fluctuating. However, if you are alive now, I can guarantee you that your ancestors survived the last ice age, and they managed to do it without any notable industry, technology, or global society.

        Don't panic yet. Life is resilient and humans are resilient.

        Given enough time, we'll eventually develop the technology to fix our climate where we like it. (Which will probably spark heated debates about where to set the global thermostat.) And in the interim, there's no good reason to panic.

      • The article describes how they excluded the obvious culprits: melting ice, earth movements, atmosphere etc. And finally concluded that it is related to ocean circulation. Now that gives me the creeps! Why the creeps? Because ocean circulation changes can happen relatively quickly and are implicated in the starting / stopping of ice ages. They are crucial indicators for climate change. And when the ocean circulation changes there is nothing humans can do about it.

        Why are you more worried about ocean circulation than melting ice, atmoshperic changes, etc.? We can't do shite about any of them...

      • And when the ocean circulation changes there is nothing humans can do about it.

        I have to disagree here. There has to be something we can do about it- it may be expensive, it may require a hell of a lot of research and maybe some geo-engineering with 100 megaton bombs or other "long levers", but imho it seems silly to think that we can be currently unconsciously changing the world's climate on one hand (greenhouse effect) and yet be completely unable to consciously change it back.
  • Ain't that what they call menopause?
    • So that explains all of the heat streaks (aka hot flashes), wildfires (heartburn), flooding (sweating), and earthquakes (mood swings) that have been going on lately.

  • Awesome! (Score:3, Funny)

    by sdo1 ( 213835 ) on Friday August 02, 2002 @04:29PM (#4001308) Journal
    Cool! I can loose weight not by dieting, but by just moving further north!

    -S
    • I don't think so?

      There are two competing factors, the force away from the center of the earth caused by the Earth's rotation, and that of gravity. The Earth is about 15km different in diameter from poles to equator, with the equator being further away than the poles. While it might be true that the Earth's gravity field (the gravitational equipotential field, or the "geoid" I believe) has been getting flatter, it still isn't round. While I haven't checked the equations lately, I think gravity still wins out over the rotational part, and you'd be _heavier_ when you moved to the poles, due to being in closer proximity to the center of the earth.
    • Perfect! A billion fat people moving north should balance the ocean right out and we'll be back to normal in no time!
  • Planet Earth has simply slimmed down from 18 down to 17 trillion tons, all by using the Ab Roller...and it can work for YOU! Call now, operators are standing by...

  • Does this mean eventually we'll have a "sweet spot", like what was shown on Enterprise? Will we be able to go the say, the Artic Circle, and push off a mountain and experience some zero-G fun? And like, how will the climates and enviroments of places further from the equaitor alter? This sounds interesting, yet scary at the same time.
    • Yes, the Earth has a zero-G "sweet spot". It's even caused by the same phenomenon as on the Enterprise, cancelling gravitational fields, except this one is real. No, absolutely nothing mentioned in the article will change the zero-G sweet spot Earth has.

      Discovery of the location of the "sweet spot" is left as an exercise for the reader, or a student of freshman college physics.
  • Has anyone tried correlating the geographical distribution of high-density PC populations with the more intense regions of gravitational pull?

  • earth getting fatter (Score:2, Interesting)

    by Anonymous Coward
    That's weird because I just saw a news story yesterday that the Earth is getting FATTER at the equator, due to movement of some magma mass or something. You'd figure gravity would be slightly less as a result. It already bulges out at the equator anyhow.
  • Could observing change in the gravitational field help in determining what exactly is gravity?

    I mean, sometimes it's easier to observe something which have variable input-output then observing something which is constant. At least when you have some control over the input/outpout part.

    But if they can manage to determine exactly what input on earth has changed which could impact gravity, could it help them find what is gravity? Any physicist out there more knowledegable then me? (There sure is, I'm not even a physicist...)
  • Time to break out that push up bra

  • Whew! (Score:4, Funny)

    by r_j_prahad ( 309298 ) <r_j_prahad AT hotmail DOT com> on Friday August 02, 2002 @04:33PM (#4001359)
    I've been blaming my weight gain on candy bars and junk food. What a relief to find out it's actually just more gravity!

    And maybe the shrinking waistband in all my pants is due somehow to the warping effect the extra gravity is having on space?

  • Change In Time? (Score:5, Interesting)

    by ackthpt ( 218170 ) on Friday August 02, 2002 @04:34PM (#4001372) Homepage Journal
    I've been hearing about this on the BBC for the past couple of days. The thought that occurred to me was this: if mass is moving from the poles to the equator, will the rotation of the earth slow, even a tiny amount, but enough that we have to adjust time in a few years?

    I expect so.

    • The earth's rotation is slowing anyway. This is the reason that they insert those "leap seconds" every few years to compensate for the lost time. To my knowledge like 16 leap seconds have been added since the government started tracking time with atomic clocks. I'm to lazy to find a link now though, as its just about time to drive home ;)

      • A reference on leap seconds (Score:5, Informative)

        by Adam J. Richter ( 17693 ) on Friday August 02, 2002 @05:09PM (#4001620)
        The earth's rotation is slowing anyway. This is the reason that they insert those "leap seconds" every few years to compensate for the lost time.

        At first, I did not believe that such a small change could account for the leap seconds, but you're right [navy.mil]:

        Through the use of ancient observations of eclipses, it is possible to determine the average deceleration of the Earth to be roughly 1.4 milliseconds per day per century.

        [...] Over the course of one year, the difference accumulates to almost one second, which is compensated by the insertion of a leap second into the scale of UTC with a current regularity of a little less than once per year. Other factors also affect the Earth, some in unpredictable ways, so that it is necessary to monitor the Earth's rotation continuously.

        In order to keep the cumulative difference in UT1-UTC less than 0.9 seconds, a leap second is added to the atomic time to decrease the difference between the two. This leap second can be either positive or negative depending on the Earth's rotation. Since the first leap second in 1972, all leap seconds have been positive and there were 22 leap seconds in the 27 years to January, 1999. This pattern reflects the general slowing trend of the Earth due to tidal braking.

        • Based on this information, if the earth loses about 1 second every year, and given: 60 secs/min *60 min/hr *24 hrs/day, there are 86,400 seconds in a day. It follows then that in 86,400 years, the earth stops and starts turning backwards. Obviously this has to be the explanation for geomagnetic reversals. The earth as a washing machine.

          • Actually the Earth is very slowly settling into being tidally locked with the Sun, much like the moon is tidally locked with earth.

            Eventually, one side of the Earth will end up facing the Sun constantly. However, it'll take a very long time.

      • True, but like everything, the earths rotation is more complex. Every once in a while a storm get enough wind to speed things up. (And presumably the reverse happens too) Thats why the leap seconds don't happen with any pattern.

      • The earth's rotation is slowing anyway. This is the reason that they insert those "leap seconds" every few years to compensate for the lost time

        No. Thats a misunderstanding. The earths is slowing down. But this is measured in milliseconds pr century and is completely negligible in this context.

        The reason for the frequent insertions of leap seconds is that the definitions of the time-span of a second and our definition of the length of a year (in seconds) don't match up. If we adjusted our definition of a second just a little bit we could tune the length of a second to make it fit our definition of the length of a year, and then we only needed to make a correction once a century.
    • The Earth's rotational rate is changing due to energy lost during ocean and earth tides (the solid part of the earth goes up and down in response to the gravitational tugging of the moon as well), as well as a differential rotation between the Earth's inner and outer core, etc. I don't think a small change in sea level will do too much compared to what is already occuring. The Earth has a radius of about 6371 Km, pretty much all of it having a denisty _significantly_ larger than water (a good chunk of the earth consists of nickel-iron after all!). I don't think a couple more meters of water will do much.
      • I don't think a couple more meters of water will do much.

        And how much will our future space elevators slow the Earth over time? These equatorial spokes won't be very massive but they'll extend thousands of kilometers like giant arms, and additionally, Earth'll lose momentum for every unit of mass that never returns to the surface.

        I'm sure it'd still be a miniscule but measurable effect.

        But hey! We could always attach giant solar sails to the ends of these spokes such the sun's solar energy would "spin" the Earth back up to equilibrium. :-)

        --

        • Hmm... funny! :-)

          BUT, to get an idea of the size of the earth, if you were to draw a big circle on a piece of paper, the crust of the earth, the part we spend all our time on and haven't ever drilled through even half of it, would be over represented by the thickness of the line. (Crustal thickness on average is say 40 Km, the earth is 6371 Km in diameter, that's about .63%. By percent weight its even smaller (by alot)). A good 6000 km diameter of the earth is made of nickel-iron (DENSE!), and the mantle of the earth aint too light either.

          And even if we don't ever get the weight back from space elevators, I bet the time integrated weight of all the space dust and meteors we sweep out of space over millions of years would offset it.

          Anyway, I just don't think most Slashdotters understand the magnitude of the volumes and forces they are talking about. The tidal forces of the moon are much more significant, and even that's barely measurable integrated over very long time periods.

          But what the hell. I'm a geophysics grad student, and am probably a little over anal about these things. :-)

    • Re:Change In Time? (Score:3, Interesting)

      by Fenris2001 ( 210117 )
      In short - yes. But it won't have any major effect. The number of seconds in a year already fluctuates as large weather systems (El Nino) change the amount of water vapor in the atmosphere. Like a spinning ballet dancer extending her arms, excess water in the atmosphere near the Equator causes the Earth's rotation to slow. However, the total change is miniscule - something like half a nanosecond per year. Particle physicists and others who need extremely accurate measures of time make adjustments for these effects. The rest of us don't notice.
    • will the rotation of the earth slow, even a tiny amount, but enough that we have to adjust time in a few years?

      I could certainly use sleeping in a 36 hour day... Too bad daylight will last longer too ;) and latenite coding will be overwhelmingly long.
      But by then, so many years will have passed that computers will be the ones coding and passing out to keep us alive, à la Matrix

  • Back to the Future quote (Score:5, Funny)

    by uncoveror ( 570620 ) on Friday August 02, 2002 @04:35PM (#4001382) Homepage
    "There's that word again, heavy. Is there a problem with the Earth's gravitational pull?"

  • Ocean levels? (Score:3, Interesting)

    by Arandir ( 19206 ) on Friday August 02, 2002 @04:37PM (#4001406) Homepage Journal
    What changes in ocean levels? Did this just happen yesterday or something?

    Considering that I live at an altitude of 20 feet and one mile from the ocean, I would think I would be one of the first people to know if the ocean level was changing. From what I can tell, the level of the Pacific Ocean is still the same as it was when I was a kid.
    • This doesn't necessarily mean anything... if you read the article it also says that due to the ice-age rebound some areas go up 1/4 of an inch a year.

      If you were in an area that goes up only, say, 1/10th of an inch a year, your 'the level of the sea hasn't changed' observation would mean that the sea level has, in fact, gone up 2 inches (let's assume you were a kid 20 years ago)

    • From what I can tell, the level of the Pacific Ocean is still the same as it was when I was a kid.

      Yeah, but the Atlantic is way higher.

    • The heading and the article are misleading. The change is postulated to be caused by a bulge of Pacific Ocean water SHIFTING towards the equator.

      Derek
  • New Scientist also has an article on this, see
    http://www.newscientist.com/news/news.jsp?id= ns999 92628

    The MSNBC report is misleading - the measurement (by satellites)is of gravity, but the conclusion is about the shape of the planet. The prime suspect, currently, is ocean currents.

  • Ask my ex workmate, it's the NT7 :) (Score:4, Funny)

    by jukal ( 523582 ) on Friday August 02, 2002 @04:41PM (#4001432) Journal
    My ex-workmate is rather convinced (don't ask me why :))) that changes like this are caused by the NT7 asteroid [bbc.co.uk] which, he believes, will shift earth's magnetism that everything will basicly destroy. Yup, he belives it does not hit the earth, it just passes by so that everything gets wicked. He might be almost blind, but he is a hellable coder. So prepare to get extincted!

  • Does this mean (Score:2, Funny)

    by N8F8 ( 4562 )
    I'll be able to float to work in the morning? Or take big moonsteps? Cool!

  • State borders? (Score:3, Funny)

    by OutsideBoston ( 442754 ) on Friday August 02, 2002 @04:52PM (#4001512)
    In related news, officials from North Stonington, CT and Hopkinton, RI have cited their recent border confusion on the "fattening" of the Earth.

    ~N
    • shoutout to Turner G, kickin' from North Stonington!

      At least they didn't shell each other over the border dispute, that could get real messy, what with all the BMWs and cellphones around.
  • So if this change is due to rising ocean, or earth is getting fatter at the equator, won't this affect a whole shitload of other things?:

    earth's rotation -> length of day -> amount of axial wobble change -> seasonal azimuth -> earth climate?

    And if gravity is higher at the equator - won't this affect time, since time slows down in a higher gravity field?
    I'm sure that these changes are all rather insignificant taken separately, but taken together, doesn't this have an impact on accuracy of scientific measurements? Will everything need to be recalibrated?
    • Geez. The Earth's rotation is already slowing due to other things (and has been for a very long time), and the moment of inertia for the Earth is gigantic. A couple meters of water isn't going to change much, and the planetary climate changes are much more sensitive to other things than loosing a tiny bit of rotation every hundred millin years or so.
      • A "couple of meters" change in ocean levels would destroy cities and, in some cases, whole nations. Much of my home state, Florida, would simply disappear. If we were to get more than one or two centimeters increase in just one year, you would do well to consider moving to higher ground within the next decade or so.

        But that's just us. The planet as a whole has indeed been through far worse and emerged unscathed.

        • True, a couple meters would certainly be over stating the matter. I was over exaggerating to be sure.

          However, you are very wrong about the normal variablity of sea level. The level of the Earth's oceans are _not_ the same level all over the world. Due to gravitational anomalies, wind, rotation of the earth, etc., you could raise the level of the ocean in some places quite a bit and never see it in other areas. The greatest variablity comes from temperature differences. Average sea level change has been measured to be as much as 40 cm in some places, and we haven't been measuring for that long. It is very possible to get higher anomalies. The area around Florida gets annual changes of at least a couple cm.

          So, I will retract my rather hasty "meters" in my quick response, but you will forgive me if I don't worry about change of a couple cm, as I would have to head for the hills on a very regular basis.

          Perhaps you meant integrated over the whole globe perhaps?? That would be disturbing. However that was certainly not the type of anomaly the article was referring to.

          • Perhaps you meant integrated over the whole globe perhaps?? That would be disturbing.

            Yeah. If the ocean goes up in one place and down in another, big whoop. But up everywhere...

            • The article was referring to a gravitational anomaly caused by the ocean raising near the equator, not everywhere. The whole point was that it was "going up in one place and down in another". That's the way gravitational anomalies are formed. If the water is the same elevation all over, the gravity field would certainly change, but change by a scalar amount everywhere, hence no anomaly (neglecting the very long wavelength effect of the missing ice in the ice caps, which is where the water would have to come from). They thought it was from changing long period ocean flow patterns, causing the water surface to "go up in one place and down in another". NOT raising the whole level of the oceans.
  • Seriously. This is cool in a totally irrelevant way, but what the hell am I supposed to do with this information? Bring it up at cocktail parties so that people's blank stares get even blanker? Should I worry about this? Is there some sort of website I can visit for day to day fluctuations? Is there something I can do to stop it, or speed it up (and which one am I supposed to want)?

    I'm serious here! WHAT THE HELL AM I SUPPOSED TO DO WITH THIS INFORMATION?!? I feel like this should be huge or something but I just don't have any kind of context for this. I'm just going to act like I didn't read this article, and maybe get back to work.

    I think I need a drink, I'm leaving early today.
    • Don't worry about it, seriously. There are much stranger things about the Earth than this.

      For instance, the Earth's gravitational field takes a big dip right over India. Why? Hell if anybody knows besides "there's a density anomaly in the mantle under India". The magnetic poles of the earth flip every tens of millions of years or so.

      I can drone on for a while if you want, but I think you get the picture.

      The whole thing is interesting to geophysicists, but it doesn't do anything to effect everyday life.

      Feel safe. Go back to coding or whatever. Have a beer.

      • I didn't so much feel threatened as just unable to file it anywhere. I had this convenient mental file system that I spent years tweaking, and never realized I didn't have a subdirectory in there somewhere for "Totally Random Facts About Changes In Planetary Gravity that are Not Connected To Anything".

        Is binge drinking sort of a hard re-boot for the brain? Does excessive beer equal ctrl-alt-delete in a neural sense? I'll tell you tomorrow.
  • In a related story, [slashdot.org] the earth is getting fatter. Growing at the equator. Hmmm, sounds familiar.
  • all this talk about gravity brings me down. and don't bring up friction either, that's a drag.
  • Funny. If this continues indefinitely, all those people who claimed the world was flat were true visionaries way ahead of their time. Who'da thought that?!

  • round or flat? (Score:3, Funny)

    by Lxy ( 80823 ) on Friday August 02, 2002 @05:33PM (#4001772) Journal
    It took centuries for explorers to convince the world that the earth was round. Now it's flat again. What are we supposed to teach our children?
  • Let's recap:
    • Last week, the sky was falling [cnn.com]
    • Then we found out the scientists were just yanking our chain [cnn.com]
    • In fact it turns out that the gravitational pull of the earth is changing such that when California is finally shaken loose by the San Andreas fault it will simply float off into the sky. The exact opposite of the sky falling. Also, it turns out that Columbus was wrong (the Earth is getting flatter, which implies it must have been significantly flat already) but happened to be in the right century at the right time.
    • In other news, the End of the World (TM) has been rescheduled [bbc.co.uk] for 2880 (no indication yet of whether it will still occur in February of that year).
    I'm getting a little tired of these scientist pranks, but I'm waiting for Greenpeace to sue McDonald's over the Earth's newfound obesity.
  • Mother Earth has hit menopause. Yikes!

  • DiscWorld (Score:2, Funny)

    by rveno1 ( 470619 )
    is this going to be the transforation of the earth into DiscWorld?
  • The PR team responsible for the upcoming adaptation of Solaris awoke to find hundreds of nubile young men and women throwing money and drugs at them, found out that they'd won the Nobel Prize For Just Being You, and bankrupted Vegas in a 24-hour solid winning streak.
    .
  • "Whatever it is, it's big."

    Huh. I thought that was a line that was only used in Hollywood. Not only that, but it is so unbelievable that a real scientist would ever say such a phrase that I have to assume that this isn't real. Either this is an elaborate hoax, or this is all a Hollywood movie that has been kept secret from us for all these years, a la The Truman Show. Whichever, my advice is to "Hold on to your butts."

    For those who were wondering, it's a joke.

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