# Electromagnetic spectrum and "cosmic rays" **URL:** \ **Category:** Factual Questions\ **Created:** [May 5, 2007, 5:26am UTC](https://boards.straightdope.com/t/electromagnetic-spectrum-and-cosmic-rays/402858 "2007-05-05T05:26:44Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [May 5, 2007, 5:26am UTC](https://boards.straightdope.com/t/electromagnetic-spectrum-and-cosmic-rays/402858/1 "2007-05-05T05:26:44Z")
Quite frequently diagrams of the electromagnetic spectrum will list x-rays, gamma rays, and “cosmic rays”. Since the latter are particles with rest mass and not photons, isn’t this scientificly illiterate? ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [May 5, 2007, 8:39am UTC](https://boards.straightdope.com/t/electromagnetic-spectrum-and-cosmic-rays/402858/2 "2007-05-05T08:39:45Z")
“Cosmic rays” is a mixed bag. There are photon cosmic rays with the kinetic energy of a pitched baseball, though they are few. I have found extremely high energy cosmic photons an interesting tidbit out there for years. X-rays are defined as coming from an X-ray tube and by recent extension as also coming from accelerators. Gamma rays are defined as coming from the Gamma emission in radioactive decay. Cosmic rays are defined as coming from the heavens. The electromagnetic spectrum charts assign regions to these based on traditions of which wavelength regime each occupies, but the wavelength isn’t definitive. ---
**Author:** ![mks57](https://avatars.discourse-cdn.com/v4/letter/m/b9bd4f/32.png) [@mks57](https://boards.straightdope.com/u/mks57)\ **Post date:** [May 5, 2007, 11:29am UTC](https://boards.straightdope.com/t/electromagnetic-spectrum-and-cosmic-rays/402858/3 "2007-05-05T11:29:56Z")
The definition of “cosmic ray” is fuzzy. Some older sources include high-energy particles **and** photons. More recent sources restrict cosmic rays to high-energy particles, and categorize all high-energy photons as gamma rays. It’s misleading, at best, to list cosmic rays as part of the EM spectrum. ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [May 6, 2007, 12:42am UTC](https://boards.straightdope.com/t/electromagnetic-spectrum-and-cosmic-rays/402858/4 "2007-05-06T00:42:48Z")
Ah, so it’s legit to include them as part of the EM spectrum if you mean “photon cosmic rays” or “high energy gamma rays of cosmic origin”. Thanx all! ---
**Author:** ![Pasta](https://avatars.discourse-cdn.com/v4/letter/p/ecccb3/32.png) [@Pasta](https://boards.straightdope.com/u/Pasta)\ **Post date:** [May 6, 2007, 7:16pm UTC](https://boards.straightdope.com/t/electromagnetic-spectrum-and-cosmic-rays/402858/5 "2007-05-06T19:16:35Z")
**Lumpy** , do you have an example diagram you could link to? I’ve never come across an EM spectrum diagram with “cosmic rays” on it. While the cosmos does have its share of photons of various energies, I’d consider it simply incorrect to include the phrase “cosmic rays” on an EM spectrum. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 6, 2007, 7:25pm UTC](https://boards.straightdope.com/t/electromagnetic-spectrum-and-cosmic-rays/402858/6 "2007-05-06T19:25:13Z")
I’m pretty sure I’ve seen it, too, but the probable source would have been grade-school science textbooks, which I’ve since learned can be completely ignored as to the truth of their contents. ---
**Author:** ![mks57](https://avatars.discourse-cdn.com/v4/letter/m/b9bd4f/32.png) [@mks57](https://boards.straightdope.com/u/mks57)\ **Post date:** [May 6, 2007, 7:34pm UTC](https://boards.straightdope.com/t/electromagnetic-spectrum-and-cosmic-rays/402858/7 "2007-05-06T19:34:03Z")
[http://www.newi.ac.uk/buckleyc/waves.htm](http://www.newi.ac.uk/buckleyc/waves.htm) ---
**Author:** ![Pasta](https://avatars.discourse-cdn.com/v4/letter/p/ecccb3/32.png) [@Pasta](https://boards.straightdope.com/u/Pasta)\ **Post date:** [May 6, 2007, 7:47pm UTC](https://boards.straightdope.com/t/electromagnetic-spectrum-and-cosmic-rays/402858/8 "2007-05-06T19:47:43Z")
Yeah, that’s just wrong. :dubious: I think that the fact that one has to go to some guy’s HTML table hosted at the North East Wales Institute of Higher Education to find an example suggests that its a rare mistake, at least. ---
**Author:** ![mks57](https://avatars.discourse-cdn.com/v4/letter/m/b9bd4f/32.png) [@mks57](https://boards.straightdope.com/u/mks57)\ **Post date:** [May 6, 2007, 7:49pm UTC](https://boards.straightdope.com/t/electromagnetic-spectrum-and-cosmic-rays/402858/9 "2007-05-06T19:49:59Z")
[QUOTE=Pasta] Yeah, that’s just wrong. :dubious: I think that the fact that one has to go to some guy’s HTML table hosted at the North East Wales Institute of Higher Education to find an example suggests that its a rare mistake, at least. [/QUOTE] I’ve seen the same thing in many other places, that was just a convenient example. ---
**Author:** ![mks57](https://avatars.discourse-cdn.com/v4/letter/m/b9bd4f/32.png) [@mks57](https://boards.straightdope.com/u/mks57)\ **Post date:** [May 6, 2007, 7:57pm UTC](https://boards.straightdope.com/t/electromagnetic-spectrum-and-cosmic-rays/402858/10 "2007-05-06T19:57:46Z")
Another example: [http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch6/atom\_emr.html](http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch6/atom_emr.html)