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}}</ref> Cosmic rays are composed primarily of high-energy [[proton]]s and [[atomic nuclei]]. They are of mysterious origin. They were given the name "rays" in the mistaken belief that they were a form of electromagnetic radiation. However, cosmic rays are particles rather than just photons. Due to relativistic effects, cosmic rays have a very high mass and reach energies of up to 10<sup>14</sup> eV.
}}</ref> Cosmic rays are composed primarily of high-energy [[proton]]s and [[atomic nuclei]]. They are of mysterious origin. They were given the name "rays" in the mistaken belief that they were a form of electromagnetic radiation. However, cosmic rays are particles rather than just photons. Due to relativistic effects, cosmic rays have a very high mass and reach energies of up to 10<sup>14</sup> eV.
=== Discovery ===
In 1909 [[Theodor Wulf]] developed an [[electrometer]], a device to measure the rate of ion production inside a hermetically sealed container. Wulf used it to find higher levels of radiation at the top of the [[Eiffel Tower]] than at its base. However, his paper was not widely accepted. In 1911, [[Domenico Pacini]] wanted to determine if ionizing radiation came from the Earth or from other sources. He measured simultaneous variations of the rate of ionization over a lake, over the sea, and at a depth of 3 meters from the surface. His measurements suggested that there was a source other than just the Earth.<ref>
{{cite journal
|author=D. Pacini
|date=1912
|title=La radiazione penetrante alla superficie ed in seno alle acque
|journal=[[Il Nuovo Cimento]], Series VI
|volume=3 |pages=93–100
|doi=10.1007/BF02957440
}}
:Translated and commented in {{Cite arxiv
|author=A. de Angelis
|date=2010
|title=Penetrating Radiation at the Surface of and in Water
|arxiv=1002.1810
|class=physics.hist-ph
}}</ref> [[File:Pacini measurement.jpg|thumb|left|Pacini makes a measurement in 1910.|160px]]
In 1912, Victor Hess carried three enhanced-accuracy Wulf electrometers<ref name=HessNobelPresSp>{{cite web|url=http://nobelprize.org/nobel_prizes/physics/laureates/1936/press.html |title=Nobel Prize in Physics 1936 – Presentation Speech |publisher=Nobelprize.org |date=1936-12-10 |accessdate=2013-02-27}}</ref> to an altitude of 5300 meters in a [[hot air balloon|free balloon]] flight. He found the ionization rate increased approximately fourfold over the rate at ground level.<ref name=HessNobelPresSp/> Hess eliminated the Sun as the radiation's source by making a balloon ascent during a near-total eclipse. With the moon blocking much of the Sun's visible radiation, Hess still measured rising radiation at rising altitudes.<ref name=HessNobelPresSp/> He concluded "The results of my observation are best explained by the assumption that a radiation of very great penetrating power enters our atmosphere from above." In 1913–1914, [[Werner Kolhörster]] confirmed Victor Hess' earlier results by measuring the increased ionization rate at an altitude of 9 km. Hess received the [[Nobel Prize in Physics]] in 1936 for his discovery.<ref>
{{cite web
|author=V.F. Hess
|date=1936
|title=The Nobel Prize in Physics 1936
|url=http://nobelprize.org/nobel_prizes/physics/laureates/1936/index.html
|publisher=[[The Nobel Foundation]]
|accessdate=Sept4, 20
}}</ref>
==Effects==
Cosmic rays react with Nitrogen and Oxygen in the Earth's atmosphere that among other things results in Ozone depletion. Cosmic rays also react with Carbon to form Carbon-14. Until the time of nuclear testing, the amount of <sup>14</sup>C has been relatively constant, which is the basis for carbon-dating of materials.
Cosmic rays can interfere with electronic devices and make space travel more dangerous.
==References==
==References==
<references/>
<references/>
[[Category:Physics]]
[[Category:Physics]]