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Researchers Develop the Most Detailed Map of Gravitational Variations Ever
schliz writes "An Australian-German team of researchers has developed the most detailed map of gravitational variations ever, using satellite data, gravitational readings and small-scale topographical models. They say the data will help civil engineers and miners, and will be available for free online. Gravitational fields vary because the Earth isn't perfectly spherical. According to the new map, the field is 0.7% greater near the North Pole (9.83ms-2) than at Peru's Nevado Huascaran summit (9.76ms-2). The difference is 40% more than previously expected."
Here is a direct link to the map if you are wondering where you'll be the lightest :)
Some people die at 25 and aren't buried until 75. -Benjamin Franklin
The gravity field spikes hard there.
They say the first thing to go is your penis. Well, it's either that or your brain. I forget which...
the more challenging and involved effort will be the calculus of integrating this detailed graviton map into future "your mother is so fat" jokes.
Good people go to bed earlier.
From the article: That means a 100kg person weighs 700g more near the North Pole, where gravity is 9.83ms-2, than at Peru’s Nevado Huascaran summit, where gravity is 9.76ms-2.
They are implying that mass is a function of gravity. Everybody who has had the most basic fundamentals of physics knows that mass doesn't change, only weight(measured in newtons)
Knowledge is power. Knowledge shared is power lost.
I wouldn't dare use this "map" for any serious purposes. It appears all they did was add the fine details from a topographic map to the rather low resolution results of other surveys. There's no high resolution direct measurement of gravity here.
Why the two images in the post don't match?
it's great and all that they posted a pretty picture but they forgot to add a key or a legend of some kind. a color gradient scale with some kind of metric is the least they could do, even the weather channel knows that!
i'm sure the people who made this are the same damn kids that keep walking on my! </rant>
Anons need not reply. Questions end with a question mark.
Indeed,
The US, the French and probably the Russians have their own classified gravity maps. Essential to improve inertial guidance of ICBMs so the ones launched by submarines match the precision of ground based ones. I had a colleague whose works on acoustics where classified by NATO. It means he was forbidden to publish his work. I Guess this hasn't changed a lot and that a too precise gravity map could not be released even today.
It would be fun to play with this data.
Anyone have a torrent?
"Gravitational fields vary because the Earth isn't perfectly spherical."
Uhm, not just that. Gravitational fields also vary because different places on Earth (or other bodies, for that matter) have materials with different density under them, forming so-called mascons.
Ezekiel 23:20
Are you sure this wasn't to increase the precision of the sub navigation itself, as opposed to more precise calculations of missile trajectories? Despite the fact that the unevenness of the Earth's gravity field has to be taken into consideration to some extent, beyond certain spatial resolution, this becomes meaningless - the small local variations essentially cancel each other out in their perturbative influence on the trajectory as the missile is passing overhead at high velocity, and from a high altitude, observing the influence of these changes on the trajectory is difficult anyway (much like a set of point lights illuminating a distant object almost uniformly, as opposed to a closer one passing along the lights). What the gravity field does for you in a submarine, however, is the option to use high-resolution gravimetric maps and an on-board precise gravimeter as another feed for the navigational system to improve the precision of the navigation and to decrease the time drift of the combined feed, which is much more important for precise launches. Without this, the submerged sub would only have INS. (You won't catch the GPS signal underwater, and you can't rely on it anyway since the enemy could either jam it of somehow disable the network before the attack.)
Ezekiel 23:20
Folks who fly ICBM's need very accurate masscon (mass concentration) maps for guidance. So I'll bet that various governments militaries have more accurate maps. They do, after all, have a bevy of satellites whose orbit perturbations allow the computation of such things to any degree of accuracy desired ;>
Whether they make displays as nice, I don't know.
In absolute it may be innacurate, but it may still be the most detailed ever in the sens of published work available to the public. The publication / availability of information is a critical factor for scienctifc work.
No scientific work is complete before it has been published and peer reviewed.
If by "heavy", you mean mass, then that is certainly the case: by working upwards in the conservative field, your mass increases towards an asymptote as you're removing the negative binding energy.
Ezekiel 23:20
maybe I'm not understanding the situation of the gravity here.
The government which is strong enough to protect you from everything is strong enough to take everything from you.
From Newton, the gravitational potential from a point source is mass*G/distance. With topography, there are two things acting. Because mountains are high, they are further away from the Earth's center of mass (typically, the Earth's gravitational potential map is modeled as a multipole expansion of Legendre polynomials centered at point source at the center of the earth).
However, there is also the gravity of the mountain(s) itself pulling you down. In most mountain ranges, there is lower gravity because of isostasy. The crust is floating on the mantle. Contintental crust is less dense than oceanic crust, and thicker. That is why it is higher than the floor of the ocean. It floats up more like a piece of styrofoam on water. Mountain ranges like the himalaya usually have thicker crust which displaces more of the upper mantle around it than thinner crust in places like Missouri. The crust in the Himalaya/Tibet is around 70 km thick, whereas normal continental crust is more like 30. Assuming close to isostatic equilibrium, from buoyancy the 70 km thick crust (averaging 5 km in elevation so 65 km below sea level) has roughly the same weight as 30 kilometer thick non-montane crust + 35 km of mantle.
However, in the mountains, you are further away from the center of the earth, so there is less gravity.
Seamounts are a different story. They are small, so instead of being in isostatic equilibrium the crust supports them like an elastic beam. They are also made out of heavy oceanic crust. That means they have high gravity because their mass isn't compensated. However, they do sink eventually. That is why if you look at the Hawaii/Emporer seamount chain, the Big Island is the newest and highest, while they get lower and eventually are no longer above sea level as you get older.
If you don't understand any of my sayings, come to me in private and I shall take you in my German mouth.
Also, looking at the world map, it is a map of Bougeur anomalies (or using some other correction), which are gravitational anomalies corrected for the elevation they are taken at and the mass of the topography. That is why a good portion of mountainous areas are shown in red.
The map of Australia is just straight-up gravity (and is different from Australia in the global anomaly map).
If you don't understand any of my sayings, come to me in private and I shall take you in my German mouth.