Talk:Sun/Archive 3

See Archive 1 for discussions older than April 2006.

Red Giant

On this page it says the sun will be a red giant in 5 billion years, but on the red giant page, it says 6 billion. Does anyone know so we can have consistand info? Jaderaid 12:36, 20 March 2006 (UTC)

Well, you should just get used to these kinds of deviations in astronomy. One of my astronomy-professors once said that to astronomers pi is approximately 1, and he was only half-joking I think. The point is that the numbers used for these types of calculations have so big uncertainties that that different scientists get very different answers. 1 billion years isn't necessary that big a difference in astronomy. :p -- Siljebj, 03.02, 16 June 2006 (UT)

Fate of the Sun

I don't see anywhere in the article about how long the sun will last and its eventual fate. From some sources, I heard it's 5 billions years. Please include this information. Thank you. --141.213.196.250 03:42, 3 April 2006 (UTC)

See the 4th paragraph of "General information" in the article. Dragons flight 03:44, 3 April 2006 (UTC)

hotter than hell

this is amazing how hot can be one star.still over years looks impossible. —The preceding unsigned comment was added by Pentagonshark666 (talk • contribs) 19:18, April 6, 2006 (UTC) how hot is the sun in degrees?

The Sun's surface is about 9,900°F and its core is about 10 to 22.5 million°F. Football (sport) 10:02, 19 May 2006 (UTC)

Age of the sun

Our article states that it is 4.6 billion years old. Other sources such as [1] and this [2]. What is the basis of our claim? Capitalistroadster 07:06, 7 April 2006 (UTC)

Amelin et al. ("Lead Isotopic Ages of Chondrules and Calcium-Aluminum-Rich Inclusions", Science 297, Sept. 6, 2002.) requires that the time of solar ignition be near but not younger than 4.56717 +/- 0.0007 Gyr ago. Dragons flight 03:43, 9 April 2006 (UTC)

brightest?

Is it true that our Sun is the brightest star to be seen from one light year away? In other words, it's much much much brighter than all other stars in the greater neighbourhood? --Sonjaaa 06:05, 20 April 2006 (UTC)

Depends on which direction. One light year in the direction of Sirius, I *think* the Sun would still be brightest, but there aren't any other stars within one light year of the Sun, so it's not much of a neighborhood. If you define "neighborhood" with a radius more like 10 light years, then no, the Sun is definitely not the brightest. You know all about apparent magnitude and absolute magnitude, right? --arkuat (talk) 06:09, 20 April 2006 (UTC)

age

Since the Sun is about 4 billion years old and the Earth is 4.6 billion years old how has the Earth been around?

according to our articles on each one, the Sun is 4.6 billion years old, and the Earth is 4.57 billion years old. hope that helps.--Alhutch 03:34, 9 May 2006 (UTC)

Support of life

I'm not sure if this was already mentioned but the sun indirectly supports all known life on the planet yet the introductory paragraph states almost. Can this be changed?

Actually some life, such as that found around black smokers on ocean floors, does not rely on the Sun, so 'almost' is correct. Worldtraveller 00:32, 10 May 2006 (UTC)

Aurora(e)

"... causing aurorae, known as aurorae borealis in the northern hemisphere and aurorae australis in the southern hemisphere."

It's probably not a matter of great importance, but the plural of "aurora borealis" should be "aurorae boreales". Likewise for the southern variant ("australes"). However, it may seem pedantic to make the change, since the plural form is probably much less familiar than the singular. Also, I am not completely certain whether the adjective does not refer to another word instead of "aurora" (for instance "pole" or "hemisphere"), so I may be wrong anyway. --Iblardi 16:28, 4 June 2006 (UTC)

Opening paragraph

There's a woefully ungrammatical sentence in the very first paragraph. I don't know enough about the topic to infer what was actually meant, but could someone more informed fix it up? Soo 17:23, 12 July 2006 (UTC)

Tell us which sentence? Worldtraveller 17:39, 12 July 2006 (UTC)

Sorry, I hacked it this morning to fix it. The photosynthesis sentence.zowie 19:19, 12 July 2006 (UTC)

Much better, thanks :) Soo 10:56, 13 July 2006 (UTC)

Gas and plasma

The section on the Sun's magnetic field mentions that "All matter in the Sun is in the form of gas and plasma due to its high temperatures." I though that the material in the Sun was 100% ionized, so the amount of gas is trivial? --Iantresman 19:50, 12 July 2006 (UTC)

In the inner layers, yes, but in the photosphere there's gas and even water vapour. Worldtraveller 20:09, 12 July 2006 (UTC)

But as a whole, the Sun is perhaps, what, 99.999% plasma? To suggest that gases and water vapour are a component would be like suggesting the seas are made of water, gold and drift wood? --Iantresman 21:50, 12 July 2006 (UTC)

Not really. The water vapour has significant effects on solar properties such as the temperature of sunspots and the like. Worldtraveller 21:59, 12 July 2006 (UTC)

So the perecentage of plasma making up the Sun is about what? --Iantresman 22:23, 12 July 2006 (UTC)

Slightly less than 100%. From what I've seen of your edits you're extremely keen on emphasising how much plasma there is everywhere, and you seem to be trying to deny there's anything other than plasma in the Sun. Why is that? Worldtraveller 23:03, 12 July 2006 (UTC)

The Sun is composed essentially entirely of plasma, in the sense that the DeBye radius is short compared to the mean free path throughout the Sun. There are some neutrals, especially near the temperature minimum region, but there are enough ionized atoms everywhere that the material qualifies as plasma. Within the solar physics community it is common to refer to "gas" when one is emphasizing the kinetic aspects of the material and to "plasma" when one is referring to interactions between the material and the magnetic field, as in "Active region loops are formed by the force-free magnetic field, but only some of the field lines happen to be full of gas" (loosely quoted from a conversation at the AAS/SPD meeting two weeks ago in Durham, New Hampshire). Another similar quote: "In the corona, beta is low and the magnetic field shapes everything, but in the photosphere, beta is high and the gas runs the show".

These usages highlight the duality of useful approximations in the plasma picture: when one is considering gross morphology, beta is generally either quite high or quite low. In the former case, one can treat the electromagnetic effects as a small perturbation on gas theory; in the latter case, one can treat bulk material as a small perturbation on nearly-massless, nearly-ideal MHD. Only relatively rarely is beta near 1. In those cases, all Hell breaks loose and one cannot use either convenient approximation. That happens in the solar transition region, which is one of the reasons it is not well studied. (Another reason is that the transition region is invisible from the surface of Earth, because it can be seen mainly in extreme ultraviolet).

This is sort of a non-issue of terminology: Alfvén, Chapman, and Parker won -- nobody seriously disputes the importance of plasma physics anymore, or has for four decades or so (although the Electric Universe concept and plasma cosmology crowds go too far in the opposite direction).

Another reason to use the sloppier language is that plasma is a word that is not familiar to the layperson (medical personnel tend to think you're talking about blood products in the sky), so speaking of plasma as a magnetized or electrically conductive gas is a convenient way to get one's point across without confusing the audience. Although something like 99.9% of the material in the Universe is in the plasma state, much less than 0.1% of the material within 50 miles of a human being is in the plasma state, so most humans are not as familiar with it as with the other three states of matter.

zowie 23:52, 12 July 2006 (UTC)

• Certainly people tend to use "ionized gas" as a convenient synonym for plasma, and it is trivial to write, for example, "the Sun consists of plasma (an ionized gas)".
• While there is a duality in the properties of a plasma, I would argue that its plasma properties far outweight those of its gaseous properties, even though the latter may be in common usage. For example:

Property	Plasma	Gas
State	99.99%	Trace
Fusion	Yes	No
EM emmission	Yes	No
Magnetic field	Yes	No
Magnetic reconnection	Yes	No
MHD	Yes	No
X-rays	Yes	No
Electric currents	Yes	No
Convection	Yes	Yes

• It does seems that there are so many properties due to plasma, that are not applicable to a gaseous approximation, that it does seem we are not giving the reader as accurate a picture as we could. --Iantresman 00:18, 13 July 2006 (UTC)

Some corrections:

• Nuclear fusion is not a consequence of the plasma state.
• Gases can both emit and absorb electromagnetic radiation.
• The magnetic field can permeate gases (though the gas dynamics are decoupled from the field).
• The magnetic field can reconnect quite well in gases.
• Gases can produce X-rays (e.g. from bombardment by high-energy particles).

As seems to happen frequently between us, Ian, I'm not quite sure what you're driving at. If you want the wording "...plasma (an ionized gas)" rather than "...gas and plasma", I don't see that as a problem. zowie 15:13, 13 July 2006 (UTC)

Thanks for the corrections. I thought that the stellar fusion reactions involved protons and helium nuclei, rather than hydrogen or helium molecules, which would suggest hydrogen and helium plasma?

I'd like to see plasma mentioned in the introductory section, on the grounds that it provides such an influential insight. --Iantresman 19:11, 13 July 2006 (UTC)

Sun in culture and religion

Please let me know if this has already been addressed, but the sun is central to a great deal of human culture, religion, etc. This article seems exclusively science-based and fails to address the importance that people attribute to the sun for cultural or other reasons. Is this addressed anywhere on Wikipedia? FunnyYetTasty 14:44, 13 July 2006 (UTC)

Many moons ago there was such a section to the article (sometime last year -- more than 500 edits ago and I can't be troubled to hunt for it) but it never really grew much -- just spawned arguments over whether David Brin's Sundiver book counted as culture. I'd like to see such a thing, if someone felt like writing about Sun-worshiping cultures, megaliths, origins of astrology in the seasonal variation of sun location, etc. Ideally it would start as a section here and then, if it grew too much, spawn off as did the structure and history sections... zowie 15:21, 13 July 2006 (UTC)

It's a potentially huge subject, with numerous cultures and ages worshipping the Sun, with numerous names for the Sun-god, etc --Iantresman 19:13, 13 July 2006 (UTC)

See also earlier Talk:Sun/Archive 01#Missing culture. For the religious aspects there already is the solar deity article (which could use some more prominent linking here however). For the fiction and other culture I think a separate sun in art and literature should be started. Femto 20:28, 13 July 2006 (UTC)

"our" Solar System

Why the second person? Who is "our"? So much for neutrality! savidan^{(talk) (e@)} 17:22, 17 July 2006 (UTC)

I can't really see what's not neutral about that. Perhaps arrogant, deigning to speak on behalf of all humanity, and maybe not great encyclopaedic style either, but I'm sure it doesn't contravene WP:NPOV! I wouldn't object if it was changed. Worldtraveller 23:44, 18 July 2006 (UTC)

Slash and burn

Why are people cutting vast chunks out of this article [3]? What good does it do to remove that information from this article? I'm sure you could reproduce it elsewhere without removing it from a featured article. 62.249.214.195 14:25, 27 July 2006 (UTC)

More on Human Understanding

Could anyone put more on history of human scientific understanding of the sun? Like history of attempts at measuring its distance from the earth.

Mass of the Sun

The accuracy with which we know the mass of the sun is limited by the accuracy with which we know the gravitational constant - we know GM_sun to about eight decimal places from observing the planets. Perhaps this is worth mentioning, and giving this number? (Or the mass of the sun in geometrized units) --Andrew 20:31, 30 July 2006 (UTC)