Cosmic Rays

High-energy subatomic particles mainly originating outside the Solar SystemThe Sun and set of objects orbiting around it including planets and their moons and rings, asteroids, comets, and meteoroids. that continuously bombard the Earth from all directions. They represent one of the few direct samples of matter from outside our solar systemDefinable part of the universe that can be open, closed, or isolated. An open system exchanges both matter and energy with its surroundings. A closed system can only exchange energy with its surroundings; it has walls through which heat can pass. An isolated system cannot exchange energy or matter with and travel through space at nearly the speed of lightSpeed at which electromagnetic radiation propagates in a vacuum. Although referred to as the speed of light, this should be more properly called the 'speed of a massless particle’ as it is the speed at which all particles of zero mass (not only photons, but gravitons and massless neutrinos if. These charged particles – positively charged protons or nuclei, or negatively charged electrons – are composed mainly of (~85%) protons – nuclei of hydrogenLightest and most common element in the universe (~92% by atoms; ~75% by mass). Hydrogen's isotopes are: • ¹H (99.9885 %)
• ²H (0.0115 %), also called deuterium.
• ³H, also called Tritium, is a radioactive (t½ = 12.32 y) by-product of atmospheric thermonuclear tests in Earth's hydrosphere and atmosphere.
, the lightest and most common elementSubstance composed of atoms, each of which has the same atomic number (Z) and chemical properties. The chemical properties of an element are determined by the arrangement of the electrons in the various shells (specified by their quantum number) that surround the nucleus. In a neutral atom, the number of in the universeThat which contains and subsumes all the laws of nature, and everything subject to those laws; the sum of all that exists physically, including matter, energy, physical laws, space, and time. Also, a cosmological model of the universe. – but they also include nuclei heliumHelium (He) Second lightest and second most abundant element (after Hydrogen) in the universe. The most abundant isotope is 4He (99.9998%), 3He is very rare. Helium comprises ~8% of the atoms (25% of the mass) of all directly observed matter in the universe. Helium is produced by hydrogen burning inside alpha particlesTerm used to describe a helium nucleus (⁴He nucleus). Alpha particles were discovered by Ernest Rutherford (1871-1937) in 1898. (~14%) and heavier nuclei (~1%), all the way up to lead or, according to some scientists, even uranium.

When they collide with atoms and molecules in the upper atmosphere, they generate cosmic ray “showers.” The initial collision produces pions (π), which quickly decay into muons (m) and γ-rays. Muons decay further into electrons (e-), positrons (e+), and neutrinos (n). Deceleration of the electrons and positrons in the atmosphere produces a flash of light that can be observed from the ground with special telescopes; however, most of the secondary cosmic ray particles that reach sea-level are undecayed muons.

The Earth’s atmosphere and magnetic field shield the biosphereVolume including the lower part of the troposphere (as high as living organisms can fly or be lofted) and the surface of the earth (including the oceans and uppermost crust), encompassing all the living matter of the earth. from some of the most damaging high-energy cosmic ray particles.

Cosmic rays are used to determine the amount of time a meteoriteWork in progress. A solid natural object reaching a planet’s surface from interplanetary space. Solid portion of a meteoroid that survives its fall to Earth, or some other body. Meteorites are classified as stony meteorites, iron meteorites, and stony-iron meteorites. These groups are further divided according to their mineralogy and or return mission samples have spent in space – the cosmic ray exposure age.