Talk:Sun

Template:WP1.0

Age of the Sun & its eventual death

Nothing is mentioned on the age of the Sun or when it is going to die —Preceding unsigned comment added by 124.184.255.157 (talk) 02:03, 11 May 2011 (UTC)

It is in there. Re read the article's section "life cycle", http://en.wikipedia.org/wiki/Sun#Life_cycle. 98.112.76.201 (talk) 14:36, 8 June 2011 (UTC)

Age of sun is left is only 4,24,969 years. as per cycle done . — Preceding unsigned comment added by 210.89.69.179 (talk) 01:36, 17 June 2011 (UTC)

Today's knowledge

Can we add in that this knowledge about the sun is only today's knowledge of astronomy and space and is not confirmed? There is no reason to get children scared about living in the current world and they shouldn't feel they are living on a ticking time bomb. The current knowledge of stellar evolution will more likely change over their lifetime. Sunshinekind (talk) 03:24, 5 March 2011 (UTC)

Wikipedia is not going to qualify every statement of scientific understanding with "according to current consensus, which might change." (That is implicit.) Nor is Wikipedia written to avoid scaring kids - but if it was, we might first want to address, say, the article on Jeffrey Dahmer. A threat that's about 5.5 billion years in the future is just about the last thing that would need to be "softened." Jeh (talk) 04:09, 5 March 2011 (UTC)

I understand that Wikipedia doesn't need to explain every scientific theory. But from what I know about science (I grew up in a family of scientists) you still need to mention it as a theory (eg Big Bang Theory) as it cannot been scientifically proven as fact. I'm not against all the work astrophysicists have done to try and solve the mystery, I just think the stellar evolution of the sun should be seen as current theory. Just remember once upon a time we used to 'know' the earth was flat - but we were clearly wrong. Sunshinekind (talk) 09:34, 5 March 2011 (UTC)

Please can you give a credible source for your claim that scientists published the fact that earth is flat. --Stone (talk) 11:31, 5 March 2011 (UTC)

But we still don't need to explain science on every science-based article, and say stuff like "It's only a theory". If people want to learn about science in general - about how science works, what "theory" means in scientific terms (it doesn't mean "just an idea, not a fact" - gravity is still a "theory", but we're not all going to start floating away any time soon), etc, we have a bunch of more general articles covering all of that - Portal:Science is a good start. -- Boing! said Zebedee (talk) 11:05, 5 March 2011 (UTC)

To Sunshinekind: Um, science never claims to have "scientifically proven as fact" anything. (Mathematics, yes. Not science.) Theories can be proven false, but not proven true; the best science ever does in that direction is to find more and more evidence that supports a theory and while finding none to reject it. Jeh (talk) 17:07, 5 March 2011 (UTC)

Thanks for the input. I see where you are coming from - I guess I just struggle with the idea of the world not being here one day. Quite sad really, its very beautiful Sunshinekind (talk) 01:40, 6 March 2011 (UTC)

Only at one time will anything in the universe be open to the title of 'fact' This is when or if a unified field theory paired with several thousand years of research yet to come, Reveal the infinite chain of cause and effect on the smallest and largest magnitudes of any perceived force, object or indeed concept. That is to say 'we know it inside and out' And fortunately I for one don't believe this is possible given our fallible, restricted perceptions bore down by our beautifully flawed biology. I'd rather wonder about the cosmos in all it's possibilities than tediously recite its details. peace. (TheGarden1988 07:57 30/5/2011) — Preceding unsigned comment added by TheGarden1988 (talk • contribs) 06:56, 30 May 2011 (UTC)

Yes, only God knows the "true facts", but there is no reason why Wikipedia cannot state the best current theories for those of us who not only stand back in wonder and awe but also wish to understand some of the subtleties and complexities. Dbfirs 07:06, 30 May 2011 (UTC)

photon travel times in solar radiative zone are wrong

the numbers on the diffusion time of photons within the solar radiative zone are wrong.

they were derived from a wrong assumption.

yes that even happens in physics.

have a look to the references and to

http://www.springerlink.com/content/l256u14247171u67/

someone with the authority, please change it.

thanks

morten

132.230.90.122 (talk) 18:04, 31 March 2011 (UTC)

Thanks for pointing out this interesting article (doi:10.1023/A:1022952621810). However, the article does not say that the usual numbers for the diffusion time scale of photons are wrong, but that they do not reflect the time scale of energy transfer in the Sun, which is governed by the longer Kelvin-Helmholtz time scale. Spacepotato (talk) 23:39, 4 April 2011 (UTC)

thats correct let me rephrase my statement:

even though the photon diffusion time within the solar radiation zone is of the order of 10^5 years this can not be considered as the time a photon needs to travel through the solar radiation zone (SRZ). in the SRZ photons are in thermodynamic equilibrium with the plasma. hence they diffuse (travel) on a thermal (Kelvin – Helmholtz) time scale to the bottom of the convection zone.

in the wikipedia article it is stated:

"Therefore it takes a long time for radiation to reach the Sun's surface. Estimates of the photon travel time range between 10,000 and 170,000 years.[44]"

in my opinion this is at least missleading. see doi:10.1023/A:1022952621810:

"According to the virial theorem, the total internal energy of a star in hydrostatic equilibrium is of the order of the absolute magnitude of the gravitational energy. As a consequence, the time scales obtained by dividing these two energies by the luminosity are approximately equal – the Kelvin–Helmholtz time. For the Sun the Kelvin–Helmholtz time scale is t_KH ≈ 3×10^7 years. This is the time needed by the star to settle to equilibrium after a thermal perturbation. Since in the solar interior energy is transported by radiation, the time scale associated with radiative transport should be of the same order."

"On the other hand, a photon-diffusion time scale has been estimated as t_d ≈ 1.7 × 10^5 years (Mitalas and Sills, 1992). This is the time photons would need to diffuse in a random walk through the Sun; it is short in comparison to the Kelvin–Helmholtz time. This short time scale could be mistaken for the time scale of energy transport in the Sun; indeed it has been discussed occasionally in the context of how the energy generated in the solar core gets out to the surface (e.g., Lang, 2001). It is the purpose of this note to point out that, due to the large heat capacity of the solar interior, energy transport in the solar interior is in fact governed by the Kelvin–Helmholtz time scale."

i still belive the numbers given in the article are not derived from the correct assumptions. as a compromise i propose something like the following:

Therefore it takes a long time for radiation to reach the Sun's surface. Estimates of the photon travel time range between 10,000 and 30,000,000 years depending on whether a random walk process or thermal diffusion is considered as the driving mechanism of energy transport.[44] & doi:10.1023/A:1022952621810

thanks

morten

132.230.90.122 (talk) 13:36, 14 April 2011 (UTC)

I think that the difference between the two different numbers is as follows. The photon diffusion time assumes that a single photon starts near the center of the Sun and scatters, without being absorbed or emitted, until it reaches the outer edge of the Sun, or, better, the convective zone (see Mitalas & Sills, Bibcode:1992ApJ...401..759M.) In reality though energy transport does not conserve photon number, as one starts with gamma rays with energies on the order of MeV and ends up with much lower-energy photons. So, I don't disagree with the paper doi:10.1023/A:1022952621810, but I think that the longer timescale is relevant to the collective process of energy transport, involving a large number of photons (and matter), and not to an individual photon. Therefore, I would suggest adding something like the following after the sentence in the article "Estimates of the photon travel time range between 10,000 and 170,000 years":

Since energy transport in the Sun is a process which involves photons in thermodynamic equilibrium with matter, the time scale of energy transport in the Sun is longer, on the order of 30,000,000 years. This is the time it would take the Sun to return to a stable state if the rate of energy generation in its core were suddenly to be changed. (reference: doi:10.1023/A:1022952621810)

Spacepotato (talk) 22:40, 14 April 2011 (UTC)

It doesn't help that some people DEFINE "photon diffusion time" in the sun as total thermal energy in the sun, divided by luminosity (total energy output). A ratio that does give something like the Kelvin-Helmholtz time of 30 million years (and is something like how THEY derived it), but I do not think it automatically the mean time for diffusion of an average photon from core to photosphere. At best it gives the THERMAL ENERGY diffusion time, but that is given by the physical size of the Sun and something like the diffusivity-- a function of both thermal diffusion (whether by radiation or not) and heat capacity. The later is the limiting factor, as there's something like 1000 times more total "heat" (thermal energy) than light in the core of the sun (my back of the envelope calculations show something like 10^16 J/m^3 thermal energy at the core but only 10^13 J/m^3 from pure photon gas at 15 million K). So most of the Sun's energy is stored as kinetic energy of plasma particles, not photons. That vast heat capacity buffers any changes in energy output on a 30 million year time scale, so in a sense it doesn't matter how fast photons get out (even if they were the same photons, which as has been pointed out, they are not). SBHarris 05:57, 16 April 2011 (UTC)

Oxygen is a metal?

"The most abundant metal is oxygen (1%)..." I thought the oxygen was not a metal. Witchunter (talk) 17:17, 19 April 2011 (UTC)

To astrophysicists, all elements other than hydrogen and helium are metals. See Metallicity. Spacepotato (talk) 01:33, 20 April 2011 (UTC)

Recommend remove this sentence: When expanding the spectrum of light from the Sun, a large number of missing colors can be found.

The sentence is meaningless as it stands, and has bad grammar to boot. It may be intended to state that there are a large number of absorption lines. If so, the sentence should read something like, "There are on the order of X absorption lines in the visible part of the Solar spectrum." —Preceding unsigned comment added by Cosmicjay (talk • contribs) 00:25, 24 May 2011 (UTC)

I've removed the sentence and linked to the article on Fraunhofer lines. Feezo (send a signal | watch the sky) 20:28, 4 June 2011 (UTC)

Replaced the false color image of sun in the lede

Refer to Template_talk:Solar_System_Infobox/Sun#Replaced_the_false_color_image_of_sun. talk section of info box . Dave3457 (talk) 00:45, 16 June 2011 (UTC)

This is a false color image of the sun and is not what the sun looks like. The wavelength of light used is a single extreme ultraviolet wavelength.

This is what the sun actually looks..

There is, what I feel to be a very important debate going on about what the lede image of the sun should be in this article. The present image is very misleading. Please go to the above link and give your input. Dave3457 (talk) 04:08, 17 June 2011 (UTC)

Debate? I don't see a debate. You answered yourself. Not much of a debate. In fact, neither image is true. Both are taken through filters, because you can't look at the Sun in true light. Serendi^podous 06:32, 17 June 2011 (UTC)

Refer to above link for response. Dave3457 (talk) 04:05, 18 June 2011 (UTC)

editsemiprotected

Please remove the erroneous final period from the image caption

Motion of barycenter of Solar System relative to the Sun.

in section Motion and location within the galaxy, in accordance with WP:CAPTIONS. Thank you! --213.168.116.136 (talk) 21:05, 19 June 2011 (UTC)