Comment by jmount | Hacker News Reader

Comment by jmount | Hacker News Reader

One flaw that bugs me in the article: "the dangerous cosmic radiation spewing from the sun in the form of solar winds." From the Wikipedia: "Cosmic rays are immensely high-energy radiation, mainly originating outside the Solar System." It might not be strictly wrong (as language leaves open that some cosmic rays may come from our sun; and the Wikipedia solar wind article has "The solar wind affects the other incoming cosmic rays interacting with the atmosphere of planets."). But cosmic radiation is most famous for being very high energy (cosmic scale) and of exotic origin. A small pedantic point, but lack of distinction makes me think of this http://explosm.net/comics/3557/ .

Edit: I know cosmic rays are not typically em-radiation. The name rays (which usually denotes em-radition) is a historic accident. Hence "cosmic rays" and "cosmic radiation" are fairly close terms. And yes our sun produces tons of rays and radiation- but not typically at the "cosmic" energy scales.

I don't mind getting down-voted for being overly pedantic (and perhaps worse yet trying to be pedantic, while being possibly wrong- this isn't my field). But some of the follow-ups really look like they are missing the same type of distinction in the exact manner I was originally complaining about (which is why there is some small value in trying point this out).

I don't think it's pedantic at all. In fact there's another mistake in that same sentence: the "dangerous" solar protons aren't from the solar wind, but irregular events like CMEs and solar flares. The solar wind protons are too low in energy (1-10 keV) to have any penetrating ability, either in the atmosphere or in crewed spaceships.

https://en.wikipedia.org/wiki/Solar_wind

https://en.wikipedia.org/wiki/Solar_proton_event

Here's a comparison of proton sources in one chart:

http://ocw.mit.edu/courses/nuclear-engineering/22-01-introdu...

(disclaimer: not my field)

"Cosmic rays" are not the same as "cosmic radiation". Cosmic rays are charged (massive) particles which are moving at relativistic speeds, and are not electromagnetic radiation. In contrast, cosmic radiation consists of photons.

I see the wikipedia article for cosmic rays [0] does state they are radiation, which is misleading and should probably be changed.

[0] https://en.wikipedia.org/wiki/Cosmic_rays

"Radiation" doesn't necessarily mean electromagnetic radiation. After all, alpha- and beta-rays are also called radiation all the time.

Rays usually means em-radiation. But cosmic rays are misnamed from (as they tend to be radiation, but not rays).

Cosmic rays are particle radiation [0], so its not misleading to state that they are radiation.

[0] http://en.wikipedia.org/wiki/Particle_radiation

It can be correct but still misleading. I think, depending on the reader, there's a good chance it's misleading.

Yes, you're correct. My bad. Though, in my experience, "radiation" without a modifier almost always refers to the electromagnetic variety. But I guess that could vary depending on what circles one hangs out in.

This. In medicine, for instance, "radiation" without a modified almost always refers to "ionizing radiation" --ie with enough energy to induce DNA damage by creating free radicals or inducing covalent linkages.

IME in physics, the term "radiation" usually refers to particles whose total energy is much greater than their rest mass. Not all free electrons constitute beta radiation; only those whose velocity is some considerable fraction of the speed of light. Massless particles such as photons, on the other hand, are always radiation according to that definition.

I'm getting lost in terminology: at least one source uses "cosmic radiation" in the exact opposite sense, as a synonym for cosmic rays:

http://pdg.lbl.gov/2008/reviews/rpp2008-rev-cosmic-rays.pdf

I guess it depends on the field one is in. Confusing, though.

AFAIK the term "cosmic radiation" is not really specific. Cosmic rays are cosmic radiation, but the term does not exclusively refer to them.

Cosmic Rays are often started from one singular particle, but by the time they hit the atmosphere, they cause air showers large and small. This is because there's not a whole lot to interact with in space, but there's tons of matter once you start hitting the atmosphere. At ultra high energies, cosmic rays cause extensive air showers leading to radiation in the form of gamma rays, muons, and electrons/positrons through pair production. The electrons are actually called the "electronic shower" There is a distance where the average energy of the photons in the shower is less than 1MeV, causing pair production to cease. This distance into the atmosphere is called Xmax, but it's dependent upon the amount of mass in the atmosphere, not the magnetic field. For lower energy cosmic rays, Xmax is pretty small. For higher energies, Xmax can easily hit us.

Why is this a flaw? Solar flares are a form of cosmic radiation; they're not the only source for it of course, but, as far as I know, one of the (if not the) strongest ones.

I thought solar flares interacted in ways that suppressed cosmic rays (such as http://science.nasa.gov/science-news/science-at-nasa/2005/07... ), not produced them. But it isn't my field, I could easily be the one who is wrong.

The sun definitely produces radiation.

Like light.

But not typically at the so-called "cosmic" energy scale.

"Cosmic" is not an energy scale — it's a word meaning "from space." It's not like cosmic dust is very energetic dust or, more relevantly, like the cosmic microwave background radiation is hugely energetic.

Sun Burn = Radiation Burn

Cosmic rays also don't get deflected by the magnetic field (either photons or very high energy particles). The atmosphere's density shields us from radiation much more than the magnetic field. Also a full half of the sky's radiation is shielded by the ground.

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