Det.Conan ha scritto:


Ormai la questione e' diventata di natura medico-patologica.
Spero.Non vorrei che ci fosse dell'altro sotto...

Gamma-rays simply pass through most materials and thus cannot be reflected by a mirror like optical or even X-ray photons. The tools of high-energy physics, however, are borrowed to detect and characterize gamma-ray photons and allow scientists to observe the cosmos up to energies of 1 TeV (1,000,000,000,000 eV, where an optical photon has an energy of a few eV) or beyond!

Gamma-rays interacting in the atmosphere create what is called an air shower. This describes the process of the original photon undergoing a pair production interaction high up in the atmosphere, creating an electron and positron. These particles then interact, through bremsstrahlung and Compton scattering, giving up some of their energy to creating energetic photons, which in turn pair produce creating more electrons which then bremsstrahlung..., well, you get the idea. The result is a cascade of electrons and photons which travel down through the atmosphere until the particles run out of energy.
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Depending on the energy of the initial cosmic gamma-ray, there may be thousands of electrons/positrons in the resulting cascade which are capable of emitting Cerenkov radiation. As a result, a large "pool" of Cerenkov light accompanies the particles in the air shower. This pool of light is pancake-like in appearance, about 200 meters in diameter but only a meter or so in thickness. Air Cerenkov detectors, as the name implies, rely on the detection of this pool of light to detect the arrival of a cosmic gamma-ray.

If you could see gamma rays - photons with a million or more times the energy of visible light - the Moon would appear brighter than the Sun!

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So why is the Moon bright? High energy charged particles, known as cosmic rays, constantly bombard the unprotected lunar surface generating gamma-ray photons.

In fact, the gamma rays ... pack over 35 million electron volts (MeV) compared to a mere two electron volts (eV) for a typical visible light photon.

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The gamma rays are produced as the atmosphere interacts with high energy cosmic rays from space, blocking the harmful radiation from reaching the surface