New way to probe Earth's deep interior using particle physics proposed

Feb 21, 2013
The picture depicts the long-range spin-spin interaction (blue wavy lines) in which the spin-sensitive detector on Earth’s surface interacts with geoelectrons (red dots) deep in Earth’s mantle. The arrows on the geoelectrons indicate their spin orientations, opposite that of Earth’s magnetic field lines (white arcs). Credit: Marc Airhart (University of Texas at Austin) and Steve Jacobsen (Northwestern University).

Researchers from Amherst College and The University of Texas at Austin have described a new technique that might one day reveal in higher detail than ever before the composition and characteristics of the deep Earth.

There's just one catch: The technique relies on a fifth force of nature (in addition to gravity, the weak and strong and ) that has not yet been detected, but which some think might exist. Physicists call this type of force a long-range spin-spin interaction. If it does exist, this exotic new force would connect matter at Earth's surface with matter hundreds or even thousands of kilometers below, deep in Earth's mantle. In other words, the building blocks of atoms—electrons, protons, and neutrons—separated over vast distances would "feel" each other's presence. The way these particles interact could provide new information about the composition and characteristics of the mantle, which is poorly understood because of its inaccessibility.

"The most rewarding and surprising thing about this project was realizing that could actually be used to study the deep Earth," says Jung-Fu "Afu" Lin, associate professor at The University of Texas at Austin's Jackson School of Geosciences and co-author of the study appearing this week in the journal Science.

This new force could help settle a scientific quandary. When earth scientists have tried to model how factors such as iron concentration and physical and chemical properties of matter vary with depth—for example, using the way earthquake rumbles travel through the Earth or through laboratory experiments designed to mimic the intense temperatures and pressures of the deep Earth—they get different answers. The fifth force, assuming it exists, might help reconcile these conflicting lines of evidence.

Earth's mantle is a thick geological layer sandwiched between the thin and central core, made up mostly of iron-bearing minerals. The atoms in these minerals and the subatomic particles making up the atoms have a property called spin. Spin can be thought of as an arrow that points in a particular direction. It is thought that Earth's magnetic field causes some of the electrons in these mantle minerals to become slightly spin-polarized, meaning the directions in which they spin are no longer completely random, but have some preferred orientation. These electrons have been dubbed geoelectrons.

The goal with this project was to see whether the scientists could use the proposed long-range spin-spin interaction to detect the presence of these distant geoelectrons.

The polarized electron-spin density on a plane that contains Earth's rotation axis and Amherst, Mass., generated by a computer simulation. The black arrows indicate only the direction of the electron spins, while the color shading of the plot indicates the magnitude of the polarized electron spin density. The density of the arrows on the plot is not meaningful. The component of the field into or out of the page is not shown. The electron spin density within the core (white central circle) is assumed to be zero. The violet arrow corresponds to the north orientation and location of the Amherst apparatus. The vertical axis is along Earth's rotation axis, and the axis labels have units of kilometers. Credit: Daniel Ang and Larry Hunter (Amherst College)

The researchers, led by Larry Hunter, professor of physics at Amherst College, first created a computer model of Earth's interior to map the expected densities and spin directions of geoelectrons. The model was based in part on insights gained from Lin's that measure electron spins in minerals at the high temperatures and pressures of Earth's interior. This map gave the researchers clues about the strength and orientations of interactions they might expect to detect in their specific laboratory location in Amherst, Mass.

Second, the researchers used a specially designed apparatus to search for interactions between geoelectrons deep in the mantle and subatomic particles at Earth's surface. The team's experiments essentially explored whether the spins of electrons, neutrons or protons in various laboratories might have a different energy, depending on the direction with respect to the Earth that they were pointing.

"We know, for example, that a magnet has a lower energy when it is oriented parallel to the geomagnetic field and it lines up with this particular direction—that is how a compass works," explains Hunter. "Our experiments removed this magnetic interaction and looked to see if there might be some other interaction with our experimental spins. One interpretation of this 'other' interaction is that it could be a long-range interaction between the spins in our apparatus and the electron spins within the Earth, that have been aligned by the geomagnetic field. This is the long-range spin-spin interaction we were looking for."

Although the apparatus was not able to detect any such interactions, the researchers could at least infer that such interactions, if they exist, must be incredibly weak—no more than a millionth of the strength of the gravitational attraction between the particles. That's useful information as scientists now look for ways to build ever more sensitive instruments to search for the elusive fifth force.

"No one had previously thought about the possible interactions that might occur between the Earth's spin-polarized electrons and precision laboratory spin-measurements," says Hunter.

"If the long-range spin-spin interactions are discovered in future experiments, geoscientists can eventually use such information to reliably understand the geochemistry and geophysics of the planet's interior," says Lin.

Explore further: Better forecasts for sea ice under climate change

More information: "Using the Earth as a Polarized Electron Source to Search for Long-Range Spin-Spin Interactions," by L. Hunter et al, Science, 2013.

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User comments : 14

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Maggnus
4.5 / 5 (8) Feb 21, 2013
A lot of "ifs" and "maybes" in this article!
nigel_beardwood
1 / 5 (1) Feb 21, 2013
Particles connected by spin at a distance? Does this not sound like quantum entanglement?
packrat
1 / 5 (3) Feb 21, 2013
Yea but I would call it quantum entanglement gibberish in this particular case. How are they supposed to entangle electrons 1000's of miles apart to begin with?
Anda
4.2 / 5 (5) Feb 21, 2013
"There's just one catch: The technique relies on a fifth force of nature (in addition to gravity, the weak and strong nuclear forces and electromagnetism) that has not yet been detected"

Just a little catch :)
ValeriaT
not rated yet Feb 21, 2013
Not only they're looking for another force, they're looking for new "unparticle" with it (not including the spin-polarized electrons).
axemaster
5 / 5 (2) Feb 21, 2013
A lot of "ifs" and "maybes" in this article!

Yeah, science is like that. After all, if they already knew the answers, there wouldn't be any point looking, now would there?
cantdrive85
1 / 5 (3) Feb 21, 2013
The long range spin interaction or quantum entanglement as some may call it, is the physical confirmation of the longitudinal electric force. Their "fifth force" is most likely said force, and no such fifth force need be invented, just a better understanding of the existing forces. EM in particular, transverse (speed of light) and longitudinal (longitudinal forces act in real time over cosmic distances). If they can figure out how to change the spin axis of particles, might they find anti-gravity?
LarryD
3 / 5 (2) Feb 21, 2013
Quote from NSF
National Science Foundation- (NSF) funded researchers at Amherst College in Massachusetts and the University of Texas at Austin have described a new technique based in particle physics that might one day reveal, in more detail than ever before, the composition and characteristics of the deep Earth.

There's just one catch: the technique relies on a fifth force of nature that has not yet been detected, but some particle physicists think it might exist. ..."

I have been unable to open the nsf.gov link though. Perhaps someone else might have better luck. Sounds like the 'old fashioned' 3rd magnetic pole...Never heard anymore about that either
alq131
1 / 5 (1) Feb 22, 2013
So why does the article or the researchers hide their search for a spin-spin particle in the probing of the earth? Why not just say they have devised an experiment to find this new particle and/or force. Seems like probing the earth is completely unrelated.

Like saying, I have this great way to overcome our energy problems-a perpetual motion machine--imagine that we could now power houses, drive cars all without traditional energy use. This would save trillions a year on drilling, production etc of oil and would greatly increase human productivity...oh wait, there is that small detail of having a perpetual motion machine...
Tinkerdoctor
1 / 5 (1) Feb 23, 2013
Do you remember the Newman machine based on his new electromagnetic thory. This is very similar. (The patent office refuse to patent it they regard it as perfetual motion machine)
ValeriaT
3.7 / 5 (3) Feb 23, 2013
I don't understand, how they got into this colored map of polarized electron density. It just reflects the geomagnetic field including its south-atlantic magnetic anomaly. Of course the electrons in magnetic minerals are getting oriented with geomagnetic field and no fifth interaction or unparticles are required for it.
electron spins within the Earth, that have been aligned by the geomagnetic field. This is the long-range spin-spin interaction we were looking for.
But these electrons are already aligned with geomagnetic field due magnetic field lines - how they want to distinguish "fifth force" from it? And we know, many minerals are even remembering the shifts of magnetic poles - we are deducing geomagnetic history of Earth from it. How they do want to recognize some fifth force in such a mess? For me it's an example of mainstream officially supported crackpotism.
rah
1 / 5 (1) Feb 23, 2013
I would like to propose a particle detector using an amplified version of this spin spin field, but using an invisible nano force, feedback circuit. It would essentially act as an MRI for the Earth, but could be moved counter clockwise to produce HD/3D profiles. The obvious side benefit would be anti-gravity waves generated and stored in water.
LarryD
1 / 5 (1) Feb 23, 2013
This is a genuine question chaps, perhaps one of you (ValeriaT perhaps) can put me rhight. The article is obviosly aimed at people like me who don't know any better but...why is it assumed that electron spin at the core is zero? If electron spin becomes zero would this not have an effect on zero point energy? Are there special conditions where electron spin becomes zero? If electron spin is zero then then how can the Pauli exclusion principle (in atomic orbitals)be applied? (are there no atomic processes in this case?) Going to get my Chem books out now.....
Graeme
not rated yet Mar 17, 2013
The reason it is supposed to be zero in the core is that electric currents should be confined to near the surface of a conductor.

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