What is the mass of the Earth? Scientists used neutrinos to measure

While scanning the interior of Earth using neutrinos, a team of scientists from Spain also used these subatomic particles to measure the mass of the Earth. Their result is in agreement with the current best estimate, which was measured using the value of the gravitational constant (G).

What is the mass of the Earth?
What is the mass of the Earth? Physicists from CSIC-Universitat de València and Universitat de Barcelona has used data from the IceCube detector in Antarctica to measure
neutrinos passing through the Earth. This helped them to calculate our planet’s mass and density.

Three physicists from CSIC-Universitat de València and Universitat de Barcelona has used data from the IceCube Neutrino Observatory Notes 1 in Antarctica and measured neutrinos passing through the body of Earth. This also helped them to calculate our planet’s mass and density. They published their findings in a study titled “Neutrino tomography of Earth” on Nature Physics.

Measuring the density and the mass of Earth using Neutrinos

A neutrino is a subatomic particle that is very similar to an electron but has no electrical charge and a very small mass, which might even be zero. They interact very rarely with matter, but when they do react with the molecules of water in the ice, they can create charged leptons (electrons, muons, or taus). These charged leptons can, if they are energetic enough, emit Cherenkov radiation, an electromagnetic radiation emitted when a charged particle (such as an electron) passes through a dielectric medium at a speed greater than the phase velocity of light in that medium (in this case, water ice).

Then, this light can be detected by photomultiplier tubes within the digital optical modules making up the IceCube.

Normally, the neutrinos zip clean through the entire Earth without interacting the matter making up the planet, but, sometimes, they smash into the nucleus of an atom and are absorbed instead. How often this process happens can reveal the density of the stuff the neutrinos traveling through.

The angle of a neutrino reaching the IceCube is also important – it reveals the particle’s path: a neutrino coming from the opposite side of the Earth, at the North Pole, would pass through all the layers – crust, mantle, and core before reaching the IceCube at Antarctica. But one that comes in at an angle might pass through only the crust, for example.

So, to calculate the density of Earth’s layers, the researchers counted how many neutrinos were able to get through the planet at different angles to IceCube.

IceCube Explained: IceCube Neutrino Observatory at the University of Wisconsin-Madison. The IceCube Neutrino Observatory is the first detector of its kind, designed to observe the cosmos from deep within the South Pole ice. Encompassing a cubic kilometer of ice, IceCube searches for nearly massless subatomic particles called neutrinos. These high-energy astronomical messengers provide information to probe the most violent astrophysical sources: events like exploding stars, gamma-ray bursts, and cataclysmic phenomena involving black holes and neutron stars. APS-TV talked to scientists at the IceCube Neutrino Observatory at the University of Wisconsin–Madison to understand just how this massive detector came to be.

The Mass of Earth

Using this method, the researchers calculated the mass of the Earth (M) between 5.7×1024 kg and 7.6×1024 kg.

According to the most precise gravitational measurement, the Earth’s mass is M=(5.9722±0.0006)x1024 kg.

Researchers say “clearly, albeit within large uncertainties, both results are in very good agreement.”

The researchers also estimate the mass of the Earth’s core. The result for this quantity is between 1.83×1024 kg and 3.69×1024 kg, which is slightly larger than the result from geophysical density models that estimate the mass of the core to be ~33% of the total mass of the Earth.

Since this novel technique doesn’t yet reveal anything new about the Earth, researchers note that as the IceCube collects more data through the years, measurements of the planet using neutrinos will become more precise.

In the future, this technique also could help physicists to determine whether the Earth contains dark matter within and if so, how much.

Notes

  1. The IceCube Neutrino Observatory is a neutrino observatory constructed at the Amundsen-Scott South Pole Station in Antarctica. Its thousands of sensors are located under the Antarctic ice, distributed over a cubic kilometer.

Sources

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