Neutrinos interact so little that among 100,000 billion solar neutrinos passing through the Earth, one or less than one less than one interacts or be stopped!
#COSMIC RAYS SKIN#
In addition, 65 billion neutrinos pass through every square centimeter of our skin every second as if we were transparent. Many pass through our bodies every second. The flux of these cosmic particles is approximately 240 per metre squared per second at ground level. Nevertheless, they are the source of exposure to radiation when they reach the surface of the Earth. Secondary cosmic particles are not the product of radioactive decays. The numbers being discussed are tiny, but the doses absorbed by frequent flyers and in-flight crew should be carefully monitored. Plane flights at an altitude of 8,000 metres expose their passengers to a dose rate a hundred times greater than that felt at sea level, but only during a few hours : A passenger travelling from London to New York would only receive a dose of 0.032 mSv - the equivalent of a dental X-ray. IN2P3The highest doses are therefore absorbed by astronauts in space flights, who may be exposed to an excess of 1 mSv per day. For purposes of comparison, the average dose of natural radioactivity absorbed in one year is 2400 microsieverts. The rate of exposure to cosmic rays, represented here in microsieverts (millionths of a sievert) per hour, increases with altitude. The further away you are from the Earth surface, the less effective the Earth's magnetic shield. In this way hundreds of these particles pass through our bodies every second, although the number increases with altitude. Secondary particles may reach the ground. Among the charged particles are muons, unstable parents of the electron, able to long runs in the atmosphere. When primary cosmic rays collide with the nuclei in the atmosphere, they give rise to a shower of secondary particles charged and neutrals. The majority of the cosmic rays we get on Earth come from the Sun, the explosion of stars (supernovae), pulsars and others remote galactic sources. These cosmic rays have very different energies and can be created in a vast number of ways. The Earth is constantly being bombarded by very energetic particles coming from the furthest reaches of our galaxy and even beyond. These chain reactions produce also several types of neutrinos. Some of these, such as the mesons, are extremely short lived whereas others, such as muons, live long enough to reach the ground. If they have enough energy, their initial collision can spark off a chain reaction, resulting in the formation of a shower of particles. They are stable particles, such as protons, light nuclei, gamma rays or even electrons. Primary cosmic particles travel enormous distances before they collide with the Earth.
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