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Because the Earth is too large to fit in an X-ray or MRI scanner, a group of physicists in Spain have discovered an attractive new way to use atomic particles that are constantly flowing through the Earth.
The researchers used neutrinos to probe the interior of the earth and use it to perform completely new measurements of the Earth's mass.
Neutrino is a strange little thing. They are one of the most abundant particles in space, but they are hard to find. They are similar to electrons, but have no charge and are almost zero in mass, so they rarely interact with normal materials when passing through space at near-light speeds.
Billions of neutrinos zip through your body now. You can see why they are called ghost particles.
Historically, our detection efforts have been poor, while in Antarctica IceCube neutrino detectors have opened a new world of neutrino science.
Using one year of IceCube data, physicists from the Physics Institute (IFIC) in Valencia, Spain, were able to study the Earth's interior.
It worked almost exactly like X-rays. When you take an X-ray, the ray passes through your body. They pass mainly through soft tissues such as muscles and organs. However, dense materials such as bones absorb light at a higher rate, resulting in a skeleton image that does not reach the other detector.
But instead of using X-rays, we used atmospheric neutrinos and experimentally used showers generated when active particles from space collided with Earth's atmosphere. These zoom into the Earth – but they can be absorbed into the atomic nucleus of the passing substance.
The higher the density, the higher the absorption rate. This allowed the research team to work together on the density of the earth.
"The use of atmospheric neutrinos allows us to obtain neutrinos in all directions with a wide range of energies and sufficient fluidity," explains IFIC physicist Sergio Palomares-Ruiz.
"Since the absorption of atmospheric neutrino flux depends not only on the energy of the neutrino but also on the amount of material that crosses it, by studying the changes in the absorption of neutrinos in different directions to different energies,
(Donini et al., Nature Physics)
The other angle is a big factor. Some neutrinos traveled all the way through the nucleus of the earth. While the other neutrinos traveled at an oblique angle that completely skipped the nucleus.
By analyzing both concentrations and angles, the team provided a tool to calculate planetary densities at various depths.
Traditionally, the density of the earth is estimated from the way earthquakes generated by earthquakes propagate. However, seismic waves can not penetrate the inner core.
Andreas Donini, IFIC physicist, says, "Neutrino is everything, providing valuable information about the unknown nucleus of the Earth's magnetism.
The team learned something new about our planet. Earth's density maps, masses of planets and moments of inertia were all calculated using neutrino data, and the previous measurements are consistent with the other measurements and are less detailed.
But the point of the study was not to learn something new about Earth, but to learn something new about what we can learn from neutrinos. And the result on that score is really amazing.
"Our findings demonstrate the feasibility of this approach to study the internal structure of the Earth that complements traditional methods of geophysics.
Nevertheless, neutrinos data are still relatively inadequate. Researchers hope their research will encourage the release of more recent IceCube data as well as more neutrinos science in the future.
This paper Natural Physics.
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