Science raises weighty question with travelling gnome

Mar 20, 2012
A collection of gnomes in Sydney, Australia. Physicists looking at anomalies in Earth's gravity have turned to a garden gnome named Kern, which has been shipped around the globe to have himself weighed at locations ranging from Lima, Mumbai and Mexico to Sydney, New Caledonia and the South Pole.

Physicists looking at anomalies in Earth's gravity have turned to a garden gnome named Kern, which has been shipped around the globe to have himself weighed at locations ranging from Lima, Mumbai and Mexico to Sydney, New Caledonia and the South Pole.

The experiment is a twist on the "travelling gnome" prank, in which a garden ornament is mysteriously stolen, photographed at various locations -- with the pictures posted on the Internet -- and then returned home.

The project promotes the wares of a German maker of hi-tech scales, but also has a serious application, by measuring differences in Earth's gravity that also affect weight.

"Most people don't realise Earth's actually varies slightly," experiment coordinator Tommy Fimpel said in a press release.

"One of the main causes is variations in the shape of the planet. Believe it or not, the Earth is actually potato-shaped, so you'll weigh up to 0.5 percent more or less, depending on where you go. We thought our Gnome Experiment would be a fun way to measure the phenomenon."

Scientists who take part in the project receive a flight case that comprises Kern, of which only one has been made, plus a set of precision scales.

So far he has weighed most -- 309.82 grammes (10.9285 ounces) -- at the Amundsen-Scott Research Station in Antarctica, where the inertial pull produced by Earth's rotation is strong.

His next stops are Snolab, a Canadian facility two kilometres (1.2 miles) below the surface of the Earth that is the deepest laboratory in the Earth, and the underground Large Hadron Collider, the famous particle smasher at in Switzerland.

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User comments : 20

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ormondotvos
1 / 5 (2) Mar 20, 2012
What the hell is "inertial pull"?

"the inertial pull produced by Earth's rotation"
Vendicar_Decarian
3.7 / 5 (3) Mar 20, 2012
The Gnome's weight is given in grams.

Sad and pathetic, even on the gnome home planet of Gnearth.

Estevan57
2 / 5 (21) Mar 21, 2012
"...The gnome home planet of Gnearth." Good one.

There's Gno place like Gnome. Gno business like Gno business...

I would be interested in the least that that it had weighed, for contrast. Location too, will it be weighed directly above the magnetic poles?
Graeme
not rated yet Mar 21, 2012
Is anything being learned from this or is purely an advertisement for the scales? Are the scales really accurate to 5 significant figures? Not only are there grams there are ounces too for the metricly disabled people.

Perhaps it will need to be weighed in a nuclear reactor core to see if the scales are radiation resistant. Or perhaps it could be placed inside the LHC superconducting magnets, that should test how impervious to magnetic fields the scales are, or maybe the gnome will be levitated.
Eikka
2.3 / 5 (3) Mar 21, 2012
The Gnome's weight is given in grams.

Sad and pathetic, even on the gnome home planet of Gnearth.


While it's true that mass and weight are not the same, they could be using the kilogram-force, or in this case the gram-force which is defined as 9.80665 mN, for which the unit is g_f (g subscript f)

It's common to use the kilogram-force, or the gram-force interchangeably with kilogram and gram, because the closest whole number unit of weight in SI, 1 DN and 1 dN are further off from the actual weight of a kilogram or a gram, so that it's more practical to simply think of mass and weight as the same.

Which of course leads to some confusion. The SI isn't without its internal inconsistencies either, which leads to the use of these non-noffical so called "convenience units", which include the liter because a cubic meter is too large, the hour because the second is too small, the gram-force because deciNewtons are too inaccurate, and the bar because the Pascal is so tiny.

Eikka
2.3 / 5 (3) Mar 21, 2012
Practically speaking, if you're living in a metric country that uses the System Internationale as its offical system of measurement, the only unit that you'll use every day that is actually metric is the meter. (and perhaps the second, if you're keen on timing things)

Liters, hours, kilograms as weight, bars as pressure, Celsius as the temperature outdoors, kilowatt-hours as energy; It's all actually not metric as far as the modern definition of metric is concerned, which is ironic.

But fortunately these units align with the SI so well that it doesn't pose a problem in conversion. All you have to remember is a couple conversion factors between the units.

Like, how many kWh of energy does it take to heat up a bucket of water to a boil if the specific heat capacity of water is 4.19 kJ/kg/K

Which is also ironic.
DarkHorse66
1 / 5 (2) Mar 21, 2012
I did post some comments about the litre before, see: http://www.physor...nt-.html
but 1 litre is exactly equal to 10cm cubed, if we have 1 litre of water, we have 1 kilogram of water. Water has a density of 1. This is where the real usefulness of the litre comes in. Makes a handy conversion tool. You might also like these:
http://www.engine...290.html
http://www.unit-c...on.info/
That last, the mind boggles at some of the conversion units available. It even does drams, gills, barns, furlongs and 'ton of TNT'!..I didn't know that there were such units as the zepto and yocto (smaller than the atto, see 'metric')...
Have fun! Cheers, DH66
DarkHorse66
1 / 5 (2) Mar 21, 2012
What the hell is "inertial pull"?

"the inertial pull produced by Earth's rotation"

You're right. No such animal. Inertia is the property of resistance to movement for an object. It doesn't 'pull' anything. For those who want to understand a bit more about the real nature of inertia:
http://zonalanded...tia.html

Regards, DH66
antialias_physorg
5 / 5 (1) Mar 21, 2012
http://www.esa.in...x_0.html
has the pictures of the gravity geoid derived from the GOCE mission.

so you'll weigh up to 0.5 percent more or less

I actualy was blindsided by that one on a physics test once. After coming back from a prolonged stay in the US (including school attendance) I had memorized the gravitational acceleration for Florida (which was given in textbooks as 9.79 at the time IIRC), which was different from the one printed in german textbooks (9.81).

Led to some confusion and then to some interesting 'eureka' moments among students and staff.

Eikka
1.7 / 5 (3) Mar 21, 2012
Water has a density of 1. This is where the real usefulness of the litre comes in. Makes a handy conversion tool.


Not exactly, and this is where the French ran into trouble when they tried to define the gram as a cubic centimeter of water. You see, water changes in density for up to 42 grams between freezing and boiling, at sea level I might add, and it's closest to a kilogram when it's 4 degrees C which is why lakes don't freeze from the bottom up.

So in calculating the weight of things, some cunning entrepreneur could sneeze you out of a good percentage of your goods simply by fiddling with the weights. But more importantly, the chemists were in trouble because they no longer knew how much stuff exactly is a gram.

Which is why they made a standard kilogram out of metal.
Eikka
2.3 / 5 (3) Mar 21, 2012
Inertia is the property of resistance to movement for an object. It doesn't 'pull' anything.


In a moving system of coordinates, inertia appears as a pulling or pushing force. It's just a matter of perspective.

Attach a concrete block to your waist with a rope and start running. The yank you'll eventually feel is your inertia pulling on the rope.
Estevan57
1.9 / 5 (26) Mar 21, 2012
I prefer cubits per fortnight for all measurements.
antialias_physorg
5 / 5 (1) Mar 21, 2012
I prefer the "barn" as in "can't hit the broad side of a ..." (which is a real unit and in active use in nuclear and high energy physics).
http://en.wikiped...8unit%29

Derived units are the "outhouse" and the "shed".

Physicists have a sense of humor, too.
DarkHorse66
1 / 5 (2) Mar 22, 2012
In a moving system of coordinates, inertia appears as a pulling or pushing force. It's just a matter of perspective.
Attach a concrete block to your waist with a rope and start running. The yank you'll eventually feel is your inertia pulling on the rope.

Erm, it's not my body providing the resistance to the movement/change in velocity of the rock (in this case rock=zero velocity)... In such an instance, I'm trying to use the force of my movements to overcome the inertia of the ROCK by pulling, with the rope allowing for that pulling.I can see where you are going with the 'push/full' analogy. Unfortunately here, your example deals with 2 physically connected masses. We are using that connection to influence the movement of the other object. Where your analogy breaks down is the fact inertia does NOT require physical contact with another mass, in order to want to resist change of velocity....cont
DarkHorse66
1 / 5 (2) Mar 22, 2012
cont...Inertia is a PROPERTY of the mass of the object, NOT a force. And it is force that causes the 'push/pull' effect, regardless of whether it is gravity or EM (or something else). It's a fine distinction I know, but an important one. :) I should say, that this distinction holds even in a moving system. For a single body, the energy for that push/pull still had to come from a primary source, not the inertia itself.
Best Regards, DH66
DarkHorse66
1 / 5 (2) Mar 22, 2012
Water has a density of 1. This is where the real usefulness of the litre comes in. Makes a handy conversion tool.


Not exactly, and this is where the French ran into trouble when they tried to define the gram as a cubic centimeter of water. You see, water changes in density for up to 42 grams between freezing and boiling, at sea level I might add, and it's closest to a kilogram when it's 4 degrees C which is why lakes don't freeze from the bottom up.

It's a bit more complex than that. Here are some links that are more precise as to under which conditions litres and kilograms match up the closest:
http://en.wikiped...ki/Litre
http://en.wikiped...pressure
http://en.wikiped...pressure

Happy Reading, DH66
Eikka
1 / 5 (1) Mar 22, 2012
Erm, it's not my body providing the resistance to the movement/change in velocity of the rock (in this case rock=zero velocity)... In such an instance, I'm trying to use the force of my movements to overcome the inertia of the ROCK by pulling


I was referring to the situation where the rope is slack before you start running. In other words, inertia is pulling on the rope as you stop running, then you are, after you've got your wind back.

But if you're still not convinced, attach two cannonballs with a rope and spin them in space. The rope will have tension in it, which means a force is acting on it, which means something is pulling it. It's not an imaginary force - it is actually there, and you can measure the pull.

For the rope, whenever there is tension, there must be a pulling force. Same way with the inertial pull on earth. Whatever tries to lift you upwards, tries to lift you upwards.
Eikka
1 / 5 (1) Mar 22, 2012
For a single body, the energy for that push/pull still had to come from a primary source, not the inertia itself.
Best Regards, DH66


But for the force to exist, inertia must be present. Which is why it can be said that inertia causes forces. If you touch an object with no inertia, no force is present between your finger and it - it will move without any effort whatsoever.

Force is not energy, however. Energy is the result of a force acting over some distance. That is an important distinction as well. No energy is spent in merely changing the velocity of a moving object, because its speed can remain the same - yet a force appears when the direction of the speed changes.
DarkHorse66
1 / 5 (2) Mar 23, 2012
"But for the force to exist, inertia must be present."

Please correct me if I have misunderstood something, but as far a I am aware, Inertia is a property of mass.(ie arises out of the existence of said mass. Therefore mass must be present for this property to exist and is the real generator of a force. Or: mass is the origin of both, separately. Food for thought: From a particle point of view (for example), a photon has no mass, therefore has no inertia. From a wave point of view, it is EM radiation, therefore is a force. From either point of view, when these things are 'flying' through free and empty space (assume any massive bodies are too far away to impact/pull on trajectory), they are neither generating inertia, nor are they subject to inertia. Also 'c' is not a variable quantity within a single medium, so 'resistance to change in move. not appl. Therefore photon particles/waves cannot exist according to the quoted statement. What are your thoughts on this?
Best regards, DH66
RazorsEdge
3 / 5 (2) Mar 25, 2012
Whatever "inertia pull" is I'd expect it to be weakest in Antarctica.

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