We’ve always understood there to be four fundamental forces of nature; gravity, weak and strong nuclear forces and electromagnetic, but a new breakthrough in particle physics means we may be on the path to discovering a fifth “force of nature”.

So what is this fifth force? The fifth force is based upon “long-range spin-spin interactions” of atoms, which have only ever been theorized but never proven. If this force is indeed proven to exist, it would make a connection between the interaction of atoms of the deep mantle and those at Earth’s surface. Essentially, it suggests that the particles can “sense” each others presence, and are affected by this interaction. The information we could gather from this would open new doors into understanding the make up of Earth’s mantle, which has generally been too inaccessible for us to fully understand.

To appreciate the idea of what “long-range spin-spin interactions” are, we need to consider the interaction between the spinning of electrons, neutrons and protons in the lab and the spinning of the electrons within the Earth. The spinning and polarization of these electrons is influenced by the Earth’s geomagnetic field. To observe this, researchers, led by Larry Hunter, professor of physics at Amherst College, created the first comprehensive map of electron polarization within Earth that details the magnitude and electron spins throughout Earth.

But what is spin? Well, every atomic particle has the property of “spin”; a vector, or an arrow, pointing it in a particular direction. That includes all of the protons, neutrons and electrons that make up all of our Earth; the mantle, the crust and the core. The mantle in particular, lying between the crust and core, has a dense make up of iron-bearing minerals. These atoms are influenced slightly by Earth’s magnetic field, which causes some of the particles to become “spin-polarized”. Instead of random spin points, there is now some net orientation of the spinning particles.

The pictured artist’s impression depicts 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).

Now here is the weird part; when experiments remove the influence of the magnetic fields, there is still some factor influencing the spin-polarization of these particles! It is this mystery factor that scientists have been attempting to isolate and theorize to be “long-range spin-spin interactions”. The idea behind this is that there is a long-range interaction, aligned by the geomagnetic field, between the spins in the experimental device and the electron spins within the Earth; that it is not merely electromagnetism influencing the particles, but that the particles can “sense” each other.

Whilst no experiments have provided conclusive findings to confirm this “fifth force”, this new research has been a breakthrough in supporting the theory. The findings of this research have helped to infer that any interactions, if they exist, are incredibly weak and, thus, more sensitive equipment must be used to search for this elusive fifth force. The possibility of future experiments discovering this fifth force has exciting potential for both particle physics and geoscience.



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2 Comments Add yours

  1. diannegray says:

    This is amazing. It’s astounding how little we know about where we live and what forces are a work! 😀

    1. Spider42 says:

      True, true… but the good part then is that if we keep an open mind we can learn something new everyday! 🙂

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