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Q&A: General Astronomy and Space Science

Q:
In a book I recently read, the author alleges that cosmic rays are made of high-energy photons which collide with each other to form particles, and so all the particles are "frozen light" because they are formed when photons slows down.
My understanding is that cosmic rays are made of protons and atomic nuclei which collide and form other particles, giving off some photons in the process, and that photon does not slow down to become anything else (the decrease in the frequency of a photon is not the same as the decrease in speed) and its existence as far as is now known is independent of other bosons and leptons. Can you confirm either notion?

A:
Photons travel at the speed of light, this is almost always true (there are interesting experiments taking place at Harvard and other places which have been able to slow light down, but in nature we only see photons traveling at the speed of light). If there were a photon-photon collision in the atmosphere, it would happen at the speed of light. Any particles resulting from the collision would be very short lived, and I believe they are not the cosmic rays that we observe.

Cosmic rays are mostly high-energy protons and helium nuclei, as you mention. Part of the cosmic rays originate from the Sun, generated by solar flare events. We believe the remainder come from interstellar space, likely from supernova and perhaps from even larger explosions, a star collapsing into a black hole for example. We're actually not sure of the origin of much of the cosmic ray flux. There are many different astrophysical processes that could send high-energy particles flying out and we're not sure which ones contribute how much to the cosmic ray flux we observe.

We have a useful article on cosmic noise on the Chandra webpages:
http://chandra.harvard.edu/chronicle/0102/cosmic_effect/index.html

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