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GNOME Idle Science

Garden Gnome Tests Earth's Gravity 144

Posted by samzenpus
from the he's-not-heavy dept.
sciencehabit writes "Researchers have long hypothesized that objects weigh less at Earth's equator because the planet's spin and shape lessen gravity's pull there versus at the poles. Satellite accelerometers have confirmed this, but a digital scale manufacturer decided to test things the old-fashioned way. Enter the Kern garden gnome. When placed on a scale at the South Pole, the intrepid ornament weighed 309.82 grams versus 307.86 grams at the equator, a difference of 0.6%."
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Garden Gnome Tests Earth's Gravity

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  • This is why (Score:3, Funny)

    by Anonymous Coward on Wednesday March 21, 2012 @05:38PM (#39434241)
    I buy my drugs at the North pole.
  • by Anonymous Coward on Wednesday March 21, 2012 @05:38PM (#39434243)

    So it has come to this.

  • by Iamthecheese (1264298) on Wednesday March 21, 2012 @05:41PM (#39434271)
    That should be more than enough for heavy metal arbitrage.
  • Nice to see some practical science that illustrates a point.

    myke

  • by buchner.johannes (1139593) on Wednesday March 21, 2012 @05:42PM (#39434289) Homepage Journal

    Next to the standard kilogram, there will be a standard garden gnome.

    0.6% is not a small number. I'm looking forward to discussing the next international health survey and asking "Did you normalize your weights for gravitational variance?"

    • by gardyloo (512791)

      0.6% is NOT a small number. Unfortunately, it's also not NEARLY the right percentage, calculated from those given masses (technically: g-reduced weights, since mass is assumed invariant).

    • My problem with the use of a "gram" to make this measurement, is that a "gram" is a measurement of Mass, rather than a measurement of weight. By presenting the weight in grams, they have illustrated the inaccuracy of their scale, rather than the variance of local gravity. As there doesn't appear to be a unit of weight in the Metric system, they perhaps should have expressed the value in Pounds.

      • Or centi-Newtons.
  • Makes sense (Score:5, Funny)

    by 93 Escort Wagon (326346) on Wednesday March 21, 2012 @05:42PM (#39434297)

    I know that, whenever I see a garden gnome, I feel a powerful urge to use it to test gravity. Especially if there's a large asphalt or cement driveway nearby.

  • by stevegee58 (1179505) on Wednesday March 21, 2012 @05:43PM (#39434299) Journal
    Occupy the South Pole!
  • Wrong units... (Score:5, Informative)

    by MrKevvy (85565) on Wednesday March 21, 2012 @05:43PM (#39434309)

    "When placed on a scale at the South Pole, the intrepid ornament weighed 309.82 grams versus 307.86 grams at the equator..."

    The grams is a unit of mass, which is invariant depending on gravity. The metric unit of weight is the kilopond [wikipedia.org].

    • by PRMan (959735) on Wednesday March 21, 2012 @05:50PM (#39434375)
      That's why we in the US still use pounds. That way, it's always accurate.
      • Re: (Score:2, Informative)

        by Anonymous Coward

        The Imperial (US) unit of mass if the Slug (really - look it up). So we here in the US have the same dichotomy.

        • by artor3 (1344997)

          Not quite. The slug is a unit of mass, but so is the pound ...sometimes. We have the pound-mass and the pound-force, with the latter being described as the weight of an object with a mass of one pound-mass under standard Earth gravity. The slug is then defined based on the pound-force as an amount of mass that accelerates at 1 ft/s^2 when exposed to one pound-force of force.

          If you're thinking that having two nearly identically named units to describe two closely linked parameters is just asking for someo

    • Re:Wrong units... (Score:5, Informative)

      by tepples (727027) <tepples@[ ]il.com ['gma' in gap]> on Wednesday March 21, 2012 @05:51PM (#39434381) Homepage Journal

      True. But in fact, these scales appear to measure things in kgf and cut off the f, giving 0.30982 kgf vs. 0.30786 kgf.

      Random related anecdote: I used to work for an e-tailer, and trade-legal scales used for calculating postage for goods to be shipped to a customer have to have buttons to calibrate for the gravity at any given latitude. In dimensional terms, this acts as a conversion factor from kgf to kg.

      • Re:Wrong units... (Score:4, Interesting)

        by snookums (48954) on Wednesday March 21, 2012 @06:44PM (#39435023)

        I once saw an ad for a digital bathroom scale that claimed it "never needs calibrating" and was "accurate to 0.1%". I immediately called bullshit* on this in my head and am glad to know that I was justified in doing so.

        * Note that this was in Australia where we actually measure our mass in kg, rather than our weight in lb. It may well have been that accurate as a weighing machine, but not as a "massing" machine.

        • How does an Australian actually measure their weight? I thought you were all held on with magnets?

        • Bathroom scales don't need to be as precise. In the United States, for example, they're marked "not legal for trade". But perhaps it's calibrated for the center of the populated portion of the state or territory where it is sold, and its internal kgf to kg conversion is indeed accurate to 0.1% within that area. For example, scales shipped to the Northern Territory would be calibrated differently from scales destined for New South Wales or Victoria.
        • by Muad'Dave (255648)

          My scale cheats! If I get on it, I get reading 'A'. If I get on it again, I get reading 'A'. If I press on it with just one leg and coax it to reading something much less than A, the next time I get on it it reads only somewhat near 'A'. It caches the last read value and if the new value is 'close' it returns the previous weight to make you think it's accurate and precise.

    • by Anonymous Coward

      Or as an alternative, you could use the more know unit of weight Newton.

    • by Anonymous Coward

      You're measuring force here. The SI measure of force is a Newton (N) = 1 kg * m * s^2

      • by Anonymous Coward

        It's N = kg * m / s^2. (or N = kg*m*s^-2)

    • Newtons would also have been fine.
    • Dude, the link you provided is entitled Kilogram-force. When you're talking about pounds you don't specific if you're talking about pound-mass or pound-force, as it's obvious from the context which it's supposed to be. We use the same conventions in SI-land, it's obvious from the context of the article that it's talking about kilogram force, and not kilogram-mass.

      Also, unless things have changed in the 5-years I've been out of uni, the SI unit of weight is the Newton.

      • by mcgrew (92797) *

        Also, unless things have changed in the 5-years I've been out of uni, the SI unit of weight is the Newton.

        So, how many grams does a Newton [wikipedia.org] weigh?

    • by pnewhook (788591)

      The grams is a unit of mass, which is invariant depending on gravity. The metric unit of weight is the kilopond [wikipedia.org].

      Sort of. The metric system is no longer used and has been replaced with SI. The kilopond or kgf is not part of the recognized SI system, and instead it used the Newton (N). When people now mention metric they actually are saying SI, but regardless, kilopond is not in that system of measures.

    • by Kymermosst (33885)

      Kilopond is incorrect as well, since the unit is defined for fixed gravitational accelleration. Since gravitational acceleration does vary slightly depending on where you are on earth, and the idea was to detect this and other "weight-reducing" effects at various points on the the earth, making it a fixed value makes no sense here. The correct unit to use is just newtons.

  • Hmm... (Score:5, Funny)

    by xstonedogx (814876) <xstonedogx@gmail.com> on Wednesday March 21, 2012 @05:50PM (#39434365)

    Does it also test the Earth's travelocity?

    (I'm so, so sorry. I'm a sick man. I need help.)

    • Re: (Score:1, Offtopic)

      by SQLGuru (980662)

      I had mod points yesterday......alas I don't have them today. I would have spent them on this comment.

    • Does it also test the Earth's travelocity?

      Imagine a travel agency called "Traspeed". It'd be like Hotwire or Priceline, filling unused seats on a flight and unused rooms in a hotel. Except you wouldn't even get to pick where your vacation will be, just "a ski resort" or "a beach resort" or "an amusement park" or the like. So you never know where you're going, but you know how fast you'll get there.

      • by Ambvai (1106941)

        That'd actually be quite fun, if it was cheap enough. I'd be kind of concerned about safety though.

      • So you never know where you're going, but you know how fast you'll get there.

        Instead of "Traspeed", may I suggest "Heisencation"?

  • by decora (1710862) on Wednesday March 21, 2012 @05:50PM (#39434369) Journal

    the mass of the earth is the same whether it's spinning or not. the spin causes centripetal acceleration, which is in the opposite direction of the acceleration due to gravity. i.e. the 'centrifugal force' cancels out a little bit of the 'gravitational force', but the gravity force itself is only slightly different because of shape, not because of the spin itself.

    or am i missing something?

    • Earth != sphere (Score:4, Informative)

      by tepples (727027) <tepples@[ ]il.com ['gma' in gap]> on Wednesday March 21, 2012 @06:09PM (#39434635) Homepage Journal
      The earth's shape is a geoid [wikipedia.org], which is flattened compared to a sphere [wikipedia.org]. Because the distance from center of mass to the surface is smaller at the poles than at the equator, gravity is stronger at the poles, and the weight of an equal mass is greater.
      • by rHBa (976986)
        So if you wanted to feel the greatest possible gravitational force for a given mass you should squash it into a flat disk and stand in the middle?
      • changes gravity.

        i.e. they are specifically claiming that 'gravity is different due to the spin'. but the spin is only relevant in that the earth's "geoid" shape is thought to be due to the spin. the spin itself doesnt change how gravity works. at least not that i am aware of. if the earth stopped spinning all of a sudden, but remained a geoid... then the gravity at the poles wouldn't change, nor would the gravity at the equator. the only thing gone would be the centripetal acceleration due to spin. things w

        • and if the earth sped up by a huge amount, things would 'weigh' a lot less. in fact, some things would go flying off into space... if earths outer edge somehow managed to reach escape velocity (in some unimaginable cataclysm). gravity itself wouldn't have changed though.

        • by kiwimate (458274)

          an interesting question about your point is this - if you take stuff to the top of a mountain, does it weigh 'more' or 'less' than at sea level?

          More. High school physics teaches us that F=(GM1M2)/R squared

          • by enrgeeman (867240)

            You mean less, I hope. It weighs less at the top of a mountain than it would at sea level because the distance(R) is bigger.

            • by kiwimate (458274)

              Ack, sorry, yes. My bad. Apparently my university maths did dreadful things to my high school physics.

        • by cwebster (100824)

          changes gravity.

          i.e. they are specifically claiming that 'gravity is different due to the spin'. but the spin is only relevant in that the earth's "geoid" shape is thought to be due to the spin. the spin itself doesnt change how gravity works. at least not that i am aware of. if the earth stopped spinning all of a sudden, but remained a geoid... then the gravity at the poles wouldn't change, nor would the gravity at the equator. the only thing gone would be the centripetal acceleration due to spin. things would 'weigh less' because they lacked centripetal acceleration not because gravity suddenly changed.

          an interesting question about your point is this - if you take stuff to the top of a mountain, does it weigh 'more' or 'less' than at sea level?

          The spin does cause the Earth to be shaped like an oblate spheroid as you mention but it does alter the gravity you experience as well. The local balance of forces if you are at rest relative to the Earth involves gravitational force and an apparent force (centrifugal) caused by centripetal acceleration. This alters your effective gravity that you experience ever so slightly (ie g_eff = g_newtonian + f_cent, where f is a specific force [units ms-2 or N/kg]) .

    • It's warmer at the equator than at the poles, and everybody knows things weigh less when they heat up. That's why they expand.

    • by mcgrew (92797) *

      Spin doesn't decrease gravity's pull, but it counteracts it, giving it the same effect -- lower measured weight at the equator, no effect on mass of either object.

  • Wrong units (Score:5, Insightful)

    by mmontour (2208) <mail@mmontour.net> on Wednesday March 21, 2012 @05:51PM (#39434391)

    It's sometimes an acceptable shorthand to express a weight in grams, but not when that's the whole point of the story. The _mass_ in grams is (hopefully) not changing. The _weight_ in newtons (or any other dimensionally-correct unit you prefer) is what's changing.

    If you're using a device that measures weight and reports it in grams, then you need to re-calibrate it against a known reference mass at each new location.

    p.s. don't forget about buoyancy. Accurate measurements need to be done in a vacuum chamber.

    • by 32771 (906153)

      I'm sure we could measure the mass of the garden gnome through inertial measurements.

      You know accelerate the thing real hard and then measure the dent it leaves in the wall of the wall of the vacuum chamber.

      Maybe we can get the weight through ballistic measurements in the vacuum chamber? Where it lands is determined by gravity.

    • But I don't wish to be weighed in a vacuum chamber, it hurts too much.

  • by Xandrax (2451618)

    Garden Gnomes just showed themselves to be more important to science than Creationalists and global-warming deniers.

    • by ackthpt (218170)

      Garden Gnomes just showed themselves to be more important to science than Creationalists and global-warming deniers.

      Hold your horses - Wait for them to run them through the particle accelerator and we'll just see about that.

  • how much was lost during transport?
    • by ackthpt (218170)

      how much was lost during transport?

      Pretty certain it had the same number of Gnomons (Gn) at both locations, but we'll have to wait for the reports to come in from GIT (Gnomic Institute of Technocracy)

    • We smoked some of the gnome on the way over. Sorry.

  • You are allowed one more chocolate chip cookie at the Equator than on the South Pole.

    • If "one more cookie" equals 0.6% of your total cookie consumption, then you're eating over 1600 cookies. Somehow this does not seem like a typical "dieter".
  • We learned in school that the standard gravity is 9.83 m/s^2 at the poles and 9.78 m/s^2 at the equator. That was more than 15 years ago, so I would say it is a known fact and not a hypothesis?
  • . . . and the equator Gnome had sweated off those extra grams . . .

  • 1) The object's mass
    2) The object's theoretical weight difference at the different locations
    3) The error bounds on the measurement.

    Without any of this, I have no idea if this is shocking news, or merely expected. And I'm on slash dot, while it might be contained within the article, I don't come here to RTFA.
  • Will Kern blend?
  • Afterwards, did they blast it into space?

  • All I have to say is: no shit, Sherlock! This is news how, again?

  • and sets in the west, if you were in a spaceship directly above the north pole looking down on earth which direction is the earth rotating? (counter-clockwise) what if you put a garden gnome at the north pole with one of those geeky propeller hats so the rotation of the earth gave it a slight lift and another gnome at the south pole with a geeky propeller hat so it has a slight lift too, (not sure where i am going with this but just thought i would throw it in the pot 0' gold)
  • Dang, those gnomes get around.
  • by Arancaytar (966377) <arancaytar.ilyaran@gmail.com> on Wednesday March 21, 2012 @07:14PM (#39435367) Homepage

    the intrepid ornament weighed 309.82 grams versus 307.86 grams at the equator, a difference of 0.6%

    This sentence is completely without sense. Barring relativistic effects, the object's mass in grams remains constant. One of those masses is correct (possibly), the other is a measuring error introduced by a scale not calibrated correctly for local gravity. The actual discrepancy is in the weight of the object in Newtons. This is, like, middle-school physics stuff.

    That's like using an iron yardstick to determine that one meter in summer is equal to about 1.005 meters in winter, and conclude that space itself expands and contracts.

  • What is the difference between a Dwarf and a Gnome?

    ... Dwarves ... are real.
    -Gnome Saying
    http://www.youtube.com/watch?v=VEOBDSA3rqQ [youtube.com]
  • Relevant, if on a tangent

    http://youtu.be/ECBYyL_DgSk [youtu.be]

  • I once heard that the reason everything falls downwards is that everything that falls UPWARDS (or sideways) have long since disappeared into space, and have therefore not been able to breed. So everything that's still here on Earth has the "fall downwards"-gene still present.

    Source: http://www.youtube.com/watch?v=8SNZuOHnFDk [youtube.com] (In Swedish, but you get the idea.)

  • by ilsaloving (1534307) on Thursday March 22, 2012 @08:58AM (#39439967)

    Has an equivalent test been done with KDE?

  • Earth's spin affecting weight measurement is hundred year old, settled science. In fact, even the direction of travel has a measurable effect:

    http://en.wikipedia.org/wiki/E%C3%B6tv%C3%B6s_effect [wikipedia.org]

    But, hey, science is all about reproducible results right? Nice to see they reproduce so well.
  • The gnome was of little use ; they could have used an elf instead !

"The way of the world is to praise dead saints and prosecute live ones." -- Nathaniel Howe

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