Cosmic Radiation : Why Atomic Rays Are Electrically Neutral

Cosmic radiation is the flow of atomic nuclei and high energy particles (that is to say

, relativistic) that circulate in the interstellar void. It also means today "cosmic rays" in the name of astro. Some of these particles, solar sources, galactic and extragalactic we can go through, interfere with DNA through the rock and the buildings and deeply penetrate the soil and subsoil planets.The study of cosmic radiation began in the early twentieth century with the work of Victor Hess.Part of the low energy cosmic rays (relative to the rest of cosmic rays on the order of MeV), trapped by Earth's magnetic field, participates in the formation of the Van Allen belts.

It begins in 1900 when Charles Thomson Rees Wilson discovers that latmospher is continuously ionized. He thinks that it 'due to natural radiation from the Earth. His research on atmospheric electricity, ionization and condensation lead him to design the first cloud chamber.

But soon, scientists are intrigued by cleaning excess the century compared to the amount normally due to natural radiation from the ground. In 1912, Austrian physicist Victor Franz Hess measures the rate according to Dionisi laltitude with a golden leaf electrometer embedded in a balloon. Lionisation decreases up to 700 m, then increases beyond. There is little difference between day and night. Hess concludes that the cosmic origin (that is to say outside the solar system) of this radiation. These results are confirmed by Robert Millikan who works with balloons.

Hess also believes that these rays are electrically neutral. This is contrary to 1928 where it is shown that most of the radiation reaching the Earth's surface is made up of charged particles. Millikan assumed, so that they result from the interaction between the neutral space rays (gamma radiation) and the molecules of the atmosphere. Arthur Compton shows that radiation is actually varies with the latitude where it is measured (lowest at the equator than the poles) because of the influence of Earths magnetic field, demonstrating the very thing it is charged particles.

In 1938, the French astronomer Pierre Auger discovered that these particles form the air showers. These particles are called "secondary" particles as opposed to "primary" constituting the stream before interaction with the atmosphere.

It is primarily responsible for its part of protons (between 85 and 90) and helium nuclei (from 9-14), the remainder consisting of electrons of different nucleons (nuclei of atoms) and that miniscule amounts of antimatter light (antiprotons and positrons). The neutral party in turn is composed of gamma rays and neutrinos. This is not always counted in the cosmic radiation.

Primary particles (entering the atmosphere) have an energy that can reach 1020 eV. Outside of neutrinos, particles detected in soil are mostly secondary particles from air showers, much less energy.

The most abundant particles at sea level is the muon, because it interacts with matter little: there are an average per square centimeter per minute. Despite his lifetime of 2.2, corresponding to a maximum distance of 660 m at the speed of light, the muon traverses much larger distances due to the effect of time dilation predicted by special relativity.

by:Barbara Herbert

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