Modern Physics

cosmic rays

Cosmic rays are high-energy radiations coming from different regions of space that reach the Earth every day. Some cosmic rays have energies between 100 and 1000 TeV (teraelectron-volts). Most cosmic rays are made up of particles such as protons, electrons and atomic nuclei.

What are cosmic rays?

Cosmic rays were discovered in 1912 by Victor Hess during experiments involving atmospheric balloons. These are highly energetic particles that move with speeds very close to the speed of light and that hit the Earth all the time.

Thanks to their enormous kinetic energy , these particles can easily pass through even a few centimeters of lead. When they interact with the Earth’s atmosphere, they give rise to a large number of particles , usually pions and muons, which are short-lived particles and which, for this reason, are usually observed mostly in the higher regions of the atmosphere.

Cosmic rays have the ability to affect the genetic code of living beings, inducing them to mutate. In this sense, the Earth’s thick atmosphere protects most living beings. It is also worth mentioning that a large number of scientists believe that cosmic rays may have contributed strongly to the evolution of life on Earth.

In addition to our atmosphere, the Earth’s magnetic field also plays an important role in protecting us from much of cosmic radiation – that which is electrically charged. About 90% of all particles that come from space and hit Earth are protons, 9% are alpha particles (nuclei of the helium atom), 1% are electrons, and about 0.25% are heavier elements such as atoms. lithium, beryllium and boron.

The percentage of heavy elements that reach Earth is much higher than the presence of these elements in the Universe. For this reason, physicists believe that the heaviest elements arise from collisions between cosmic rays and intermediate-weight atoms, such as carbon and oxygen, produced in the cores of stars .

What can cosmic rays cause?

When cosmic rays collide with atoms in the atmosphere, they produce what we call a shower of particles , which is the result of a large number of subsequent collisions between atoms and cosmic rays, giving rise to a large number of mesons, such as pions, kaons and muons.

Despite spanning hundreds of kilometers, detecting a shower of particles is not so simple. Currently, light detectors are used, capable of amplifying many times the brightness emitted by a shower of particles. This glow, in turn, originates from what we call Cherenkov radiation — a process of light emission that happens when a particle moves in a transparent medium at a speed greater than the speed at which light would propagate in that same medium.

Here on Earth, a small part of the particles produced by cosmic showers reach the surface, so this phenomenon does not harm the health of living beings, thanks to the attenuation of energy promoted by the atmosphere itself. However, in space, the effect of cosmic rays can be devastating – telecommunications satellites, telescopes, atmospheric balloons and other electronic devices that are launched into Earth orbit are subject to a huge incidence of cosmic rays and therefore need to be built to withstand the effects these particles have on your electronic circuits.

Where do cosmic rays come from?

Cosmic rays can either originate in the Sun or in the vicinity of the Solar System or even in other distant galaxies Astronomical observations collected in 2013 by the FGTS telescope ( acronym for Fermy Gamma-Ray Space Telescope ) indicate that much of the cosmic rays that reach Earth originate in large stellar explosions – supernovas. Furthermore, the cores of galaxies also appear to produce a lot of cosmic rays.

The figure shows the flux of cosmic rays passing through the Earth with respect to their respective energy level. The yellow, low-energy level refers to particles emitted by the Sun. The blue level refers to cosmic rays originating in our galaxy, and the pink level refers to extragalactic cosmic rays.

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