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DEAL: For $25 - Add A Second Phone Number To Your Smartphone for life! Use promo code SLASHDOT25. Also, Slashdot's Facebook page has a chat bot now. Message it for stories and more. Check out the new SourceForge HTML5 Internet speed test! × ## Danish Research Center To Explore Mysteries of Earth's Interior56 An anonymous reader writes "The DanSeis Centre at the University of Copenhagen has just received a grant of more than €3 million from the Danish Ministry of Science, Innovation and Higher Education to investigate and tackle one of geoscience's great mysteries: do mantle plumes, hypothetically buoyant regions of heated mantle material rising towards the earth's surface, actually exist?" This discussion has been archived. No new comments can be posted. #### Danish Research Center To Explore Mysteries of Earth's Interior More Login ## Danish Research Center To Explore Mysteries of Earth's Interior Comments Filter: • #### Foregone conclusion.... (Score:2) ...it's a plume filled danish. • #### Re:Foregone conclusion.... (Score:4, Funny) on Friday March 16, 2012 @04:49AM (#39374971) If the planet is consuming too many plum filled danishes, I can certainly understand hot bubbles of materials rising up. Oh, sorry, you said "plume," not "plum." Never mind. Also, for anyone who thought of hot grits and/or Natalie Portman while reading the above, you've got issues bro. • #### Great News (Score:5, Funny) on Friday March 16, 2012 @04:14AM (#39374821) Journal I will be watching this closely, as I have often wondered what on Earth is at the center of a Danish [wikipedia.org]. • #### Re: (Score:1) Normally that would be "remonce" which is a mix of butter, sugar and often marcipan (or finely chopped almonds) • #### Re: (Score:2) That's 'marzipan'. • #### It's the Bagrols you have to worry about. (Score:2) Plumes, who cares about feathers deep underground? • #### What about the discontinuity of gravity? (Score:5, Informative) on Friday March 16, 2012 @05:01AM (#39375029) Why is the force of gravity at the core zero? http://en.wikipedia.org/wiki/File:Earth-G-force.png [wikipedia.org] http://en.wikipedia.org/wiki/File:Slice_earth.svg [wikipedia.org] And why the hell is there a Gutenberg discontinuity where gravity increases the closer you get, then drops down to zero? i.e. The Gutenberg Discontinuity, is the boundary, as detected by changes in seismic waves, between the Earth's lower mantle and the outer core about 1800 miles below the surface. It is also called the core-mantle boundary. http://en.wikipedia.org/wiki/Mohorovi%C4%8Di%C4%87_discontinuity [wikipedia.org] • #### Re:What about the discontinuity of gravity? (Score:5, Informative) on Friday March 16, 2012 @05:22AM (#39375095) "Why is the force of gravity at the core zero?" Because the integral of the forces acting on some mass at the center of the Earth is zero. Or to put it differently: You are being pulled by (approximately) equal forces in all directions. • #### Re: (Score:2) IIRC no integral is needed; the vector sum of forces will do. • #### Re: (Score:2) "...the vector sum of forces will do." Yes, assuming point masses. But that means that you are summing atoms. For practical purposes I would make an integral over the volume of the Earth. • #### Re: (Score:2) It depends on the definition of centre. If by centre you mean centre of mass, that is the same as saying: "we define the centre to be the place where gravity is zero". • #### Re:What about the discontinuity of gravity? (Score:4, Informative) <rgb@nOspAM.phy.duke.edu> on Friday March 16, 2012 @09:55AM (#39376627) Homepage Gravity does not increase once you are inside the Earth's surface unless perhaps you are moving down towards a large, cow-shaped lode of pure Uranium. Newtonian gravitation satisfies a Gauss Law (like electrostatic fields) and aside from minor perturbation due to the Earth being rotationally deformed and the tides, the field starts at zero at the origin/center and smoothly increases as one moves toward the surface in any direction, then smoothly decreases (like$latex 1/r^2\$) once one is outside of it. Rotation (e.g. coriolis forces) alter the perceived local acceleration by a hair as a function of latitude. The slight equatorial bulge and compressibility of the core material keep the field from increasing ideally/linearly (as it would for a perfect sphere of uniform density). Finally, the Sun and the Moon create further local acceleration perturbations that are not strictly speaking variations in the Earth's field, but that result from the non-uniformity of the Sun and Moon's fields and the fact that the center of mass of the Earth has a different acceleration than points on its surface as it interacts with them both (the tides).

None of these things are even slightly mysterious. None of them are really particularly difficult to calculate, or at least estimate. "Interesting" discoveries from the systematic study of near-Earth and inner-Earth gravity are entirely possible, but one would ordinarily consider the discover of a fifth force, or a short range modulation of the gravitational force, to be "interesting" in this context. In order to make such a discovery, however, one has to know the mass distribution and compute the net relative acceleration one should be observing to very high precision, as one is basically looking for an anomaly, and small deviations from a not-too-well-known or even well-defined base quantity are the most difficult to detect, see the entire (somewhat humorous) debate about global warming for an example).

rgb

P.S. -- Off-topic general query: Wordpress lets one embed latex in comments, and it isn't even particularly focussed on technical subject matters. Is there an equally simple way to embed latex in /. comments? I'd put the ideal form of gravitation inside a sphere inline into this reply, except that nobody wants to read things like \vec{g} = -\frac{GMr}{R^3} \hat{r} or the derivation of same in latex unless they know latex well enough to read it as rendered...
• #### It isn't zero (Score:2)

It is just a lot in any direction. Same reason you are not a stain on the ground from the massive pressure off all the air on top of you. Air pressure is all around and the same all around.

A funny thing is that in theory, if you could drill a hole through the planet and you could jump down it and there was no air resistance you would pop out at the other end at the same speed as you entered. first you accelerate and then you decelerate. Of course, it would never work in real life but it is a fun idea.

For a

• #### Re: (Score:2)

It isn't zero. It is just a lot in any direction.

My physics is rusty, but I'm pretty sure if there's zero acceleration, there's zero force.

• #### Danish... (Score:2)

Crispy on the outside, soft and chewy in the middle?

• #### Dinosaurs, giant diamonds and atomic bombs (Score:2)

It all sounds so cool! Sign me up!

• #### Arne Saknussemm (Score:1)

I wonder if they have Arne Saknussemm working for them? Wasn't he a Dane that led a trail to the Center of the Earth http://en.wikipedia.org/wiki/Journey_to_the_Center_of_the_Earth/ [wikipedia.org]
• #### Re: (Score:1)

by Anonymous Coward

He was Icelandic as I recall. Of course, at the time of Jules Verne, Iceland was technically part of Denmark..

• #### Didn't one of the old versions of... (Score:2)

Didn't one of the earlier versions of "Journey to the Center of the Earth" involve a Dane with a duck?

• #### Re: (Score:2)

Nope. I was thinking that there were Danes involved in that too, but a walk through Wikipedia reveals apparently not. The explorer in Verne's original novel was German. Arne Saknussemm, the (fictional) medieval alchemist whose lead they were following, was an Icelander. Other incarnations have varied things; in the movie (and later animated series) with the duck, the explorer was Scottish. There was one version with a Swede involved. But apparently no Danes.

• #### There is nothing down there but dirt! (Score:1)

Seriously! Yet another gold digging expedition in the name of "Science"

• #### Re: (Score:1)

Scientist playing Minecraft in IRL
• #### Danish (Score:3, Funny)

on Friday March 16, 2012 @07:08AM (#39375437)
The horrible abominations you call Danish pastry over in the US, I wouldn't even feed to the pigs. I wouldn't mind my nationality being associated with a custard-filled fatty pastry, if only it was a delicious custard-filled fatty pastry. For heaven's sake, turn them into bio fuel or something, because they certainly aren't suitable for human consumption.

Same goes for your coffee, by the way. :-)
• #### Re: (Score:2)

You have a point, but not ALL of our stuff sucks. Same thing with beer; if you look at the small producers, we have some pretty good stuff.
• #### Re: (Score:2)

Of course, this is just in jest. At least I know now to politely turn it down, if the company secretary wants to book you into a Holiday Inn, stateside.

Waitress: "D'ya want some more coffee, Hon?"
Me: "NO, NO, I mean, eehhh, no thank you,"

Your large selection of weird brew-beers was a positive surprise, though.
• #### Re: (Score:2)

... Danish pastry over in the US, I wouldn't even feed to the pigs...

Well, DUH. Neither would I. Why would you give something so awesomely yummy to a pig?

• #### Re: (Score:2)

American chocolate has to be the worst in the world.
• #### Just another remake (Score:1)

Reminds me of something: now what was that... There's a Danish researcher and a goose, an older scientist and his young apprentice and a rich lady in pink stretch pants. Are we sure this wasn't an announcement from Disney studios?
• #### Pellucidar (Score:2)

The hollow-earthers were right! The GOP hopefuls should probably campaign on gaining ownership of the natural resources of Pellucidar; it'd fit right in with their anti-anthropomorphic climate change, sustainable fossil fuels, and creationism beliefs. :-D

• #### Old News (Score:2)

I thought that these questions had been conclusively settled, as chronicled in that fine documentary The Core

• #### Inferno? Jon Pertwee? Bueler? Bueler? (Score:2)

Am I the only person who watched Doctor Who reruns on PBS in the 80s? http://en.wikipedia.org/wiki/Inferno_(Doctor_Who) [wikipedia.org]
• #### Re: (Score:2)

Actually, after reading the headline my first thought was of Arne Saknussemm!

• #### Investigatory team (Score:1)

They are sending one scientist, one mountain guide, one unqualified but attractive lab assistant and the guide's pet duck into an extinct volcano to investigate.

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