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Old Oct 5th 2014, 11:39 PM   #1
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Cosmic rays: electromagnetic radiation or particles?

Hi: In a physics textbook from 1968, a picture representing the electromagnetic spectrum, is divided into several regions: power transmission, AM radio, ..., X rays, gamma rays, cosmic rays, and the figure says: "The electromagnetic spectrum: ....... The scale ends in the vicinity of the highest-energy secondary cosmic rays that have been observed up to the present time". On the other hand, Wikipedia says:

The term ray is a historical accident, as cosmic rays were at first, and wrongly, thought to be mostly electromagnetic radiation. In common scientific usage[4] high-energy particles with intrinsic mass are known as "cosmic" rays, and photons, which are quanta of electromagnetic radiation (and so have no intrinsic mass) are known by their common names, such as "gamma rays" or "X-rays", depending on their frequencies".
Can it be that the nature of cosmic rays (whether they are waves or particles with non-zero rest mass) was not known as recently as 1968? Or perhaps there is no contradiction between the two statements?
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Old Oct 6th 2014, 12:03 AM   #2
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Originally Posted by ENRIQUESTEFANINI View Post
Hi: In a physics textbook from 1968, a picture representing the electromagnetic spectrum, is divided into several regions: power transmission, AM radio, ..., X rays, gamma rays, cosmic rays, and the figure says: "The electromagnetic spectrum: ....... The scale ends in the vicinity of the highest-energy secondary cosmic rays that have been observed up to the present time". On the other hand, Wikipedia says:



Can it be that the nature of cosmic rays (whether they are waves or particles with non-zero rest mass) was not known as recently as 1968? Or perhaps there is no contradiction between the two statements?
Cosmic rays are composed of an assortment of high energy particles. Muons, photons, neutrinos, and probably more. Their source is mainly unknown. Some suggestions range from supernovas to black holes to gamma ray bursts to name a few.

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Old Oct 6th 2014, 05:51 AM   #3
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Well then they are in part electromagnetic radiation, as long as photons enter their composition. Thanks a lot.
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