Hunt Begins for Particle Behind Fifth Force of Nature on Earth

Forget the Higgs boson particle. There's a new one that particle physicists are after, and it's tied to a new fundamental force of nature. Researchers from Amherst College and the University of Texas, including lead author Larry Hunter and colleagues, have described a new technique that may one day reveal the composition and characteristics of deep Earth. The only catch? The technique relies on a fifth force of nature that has not yet been detected--the particle that physicists are now seeking could be behind it.

The type of force is called a long-range spin-spin interaction. If it does indeed exist, this force would connect matter at Earth's surface with matter hundreds or thousands of miles below in the Earth's mantle. To explain it better, the building blocks of atoms (electrons, protons and neutrons) separated over vast distances would still be able to "feel" each other's presences. This interaction could then provide scientists with new information about the deep mantle of our Earth.

So where does or would this force actually come from? There are currently three possibilities. The first is a particle called the unparticle, which behaves like light particles (photons) in some ways, and like particles of matter in others. The second possibility is called the Z', similar to the Z-boson that carries a weak nuclear force. The third is that there is no new particle at all, and that the theory of relativity may have some component that is affecting spin.

Currently, scientists have not found a new particle tied to the force. However, they did find that the long-range spin-spin interaction had to be smaller by a factor of one million than earlier experiments demonstrated. In fact, if the force exists, it's so small that the gravitation force between two particles such as an electron and a neutron is a million times stronger, according to Livescience.com.

The new study of this force, published in the journal Science, deals with the theoretical. Yet if it exists, this new force could help settle questions that have long lingered in this field. When earth scientists have tried to model how factors such as iron concentration and physical and chemical properties of matter vary with depth, they get different answers. A fifth force could help explain these differences in the models.

"The most rewarding and surprising thing about this project was realizing that particle physics could actually be used to study the deep Earth," said Jung-Fu Lin, co-author of the study, in a press release.

The scientists plan to continue searching for this force and the reason behind if. If they succeed, it could mean a whole new way for researchers to examine our Earth.