Talk:Sun

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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)

(Also, while you're at it, you may want to improve the wording of the caption as well, maybe along the lines of

Motion of the barycenter of the Solar System relative to the Sun

--213.168.116.136 (talk) 21:08, 19 June 2011 (UTC))

Period removed, the caption already contains the 2nd. Vsmith (talk) 22:00, 19 June 2011 (UTC)

Thanks so far. On my second point (which is more of a personal suggestion), I think that omitting the "the"s as the current caption does is a bit awkward. Consider the current wording:

Motion of barycenter of Solar System relative to the Sun

versus my suggestion:

Motion of the barycenter of the Solar System relative to the Sun

If you think the former is better, feel free to leave it as is. (Just wanted to note the difference since you appear to have overlooked my suggested addition of two "the"s.) --84.44.228.41 (talk) 15:09, 20 June 2011 (UTC)

Heh - seems I'm blind sometimes. Vsmith (talk) 17:10, 20 June 2011 (UTC)

np. thanks a bunch! --84.44.228.41 (talk) 17:31, 20 June 2011 (UTC)

Speed of SUN

User:Materialscientist you wrote "the value is way off and is of unclear relation to the lead of this article" [1]. Light particles part of SUN are traveling at 186,413.22 miles per second while sun is expanding. You can compare it to a balloon traveling while its blown. The edit made by me was well referenced "The velocity of sun by Sayan a thirteen century (died 1387) commentator of Rigveda cited to be 186,413.22 miles per second "tatha ca smaryate yojananam. sahasre dve dve sate dve ca yojane ekena nimishardhena kramaman" and its translation is "[O Sun,] bow to you, you who traverse 2,202 yojanas in half a nimes.". As per Prof Kak the velocity comes to "186,413.22 miles per second" http://www.ece.lsu.edu/kak/sayana.pdf, (accessed 15 Feb 2011), the referenced information is accessed from Indian Journal of History of Science, vol. 33, 1998, pp. 31-3". Please explain why you reverted the same?Ganesh J. Acharya (talk) 04:51, 7 July 2011 (UTC)

(edit conflict) Apparently you are confusing velocity of the sun and speed of light, which is what Kak is writing about, and which is not relevant to the lead of this article. Materialscientist (talk) 04:54, 7 July 2011 (UTC)

I am referring to what Sayan has cited, isn't it about the speed of SUN? Ganesh J. Acharya (talk) 04:58, 7 July 2011 (UTC)

Please read again his article, and this article (the infobox gives a summary of velocities of the Sun). Materialscientist (talk) 05:00, 7 July 2011 (UTC)

But, it does not inform about velocity of Sun while it is expanding. Sayan is citing about the Sun's expanding velocity. Ganesh J. Acharya (talk) 05:11, 7 July 2011 (UTC)

The cited source doesn't say anything of the sort. It examines what Sayana might have meant - if he meant the speed of light, then according to one interpretation of the measurements used he was very close (perhaps by coincidence), but if he meant the speed of the Sun he was hopelessly wrong. There's no mention of any "expanding" in there -- Boing! said Zebedee (talk) 05:28, 7 July 2011 (UTC)

"but if he meant the speed of the Sun he was hopelessly wrong", Does physics say velocity of expansion of Sun is not velocity of Sun? If a balloon is blown the outer diameter does that not travel? "Velocity" is the measurement of the rate and direction of change in the position of an object. So, does part (LIGHT) of SUN not change positions while they expand? So, when light (Particles of SUN) travels does not mean Sun travels (while expanding)? Ganesh J. Acharya (talk) 05:47, 7 July 2011 (UTC)

Please quote the part of the cited source that talks about "expansion" - I've read it twice and I can't find any mention of it -- Boing! said Zebedee (talk) 05:51, 7 July 2011 (UTC)

(PS: As an aside, the Sun has never expanded at anything remotely close to 186,000 miles per second - in fact, I don't know whether it has ever expanded at all, has it? -- Boing! said Zebedee (talk) 05:54, 7 July 2011 (UTC))

Assuming balloon travels at X speed while it expands, can one reply the following when one is asked "Q. At what speed is the balloon traveling?"... "A. The balloon is traveling at X speed" Ganesh J. Acharya (talk) 06:08, 7 July 2011 (UTC)

I repeat, again and for the last time, there is NOTHING about expansion in the cited source! -- Boing! said Zebedee (talk) 06:19, 7 July 2011 (UTC)

Is it written that the following is cited by Sayan "[O Sun,] bow to you, you who traverse 2,202 yojanas in half a nimes." and this velocity comes to "186,413.22 miles per second" Ganesh J. Acharya (talk) 06:25, 7 July 2011 (UTC)

And where in that sentence can you see the word "expand" or "expansion"? -- Boing! said Zebedee (talk) 06:28, 7 July 2011 (UTC)

When you mention about Velocity of an object is that necessary to mention in what mode (weather expanding or not) is it traveling?Ganesh J. Acharya (talk) 06:33, 7 July 2011 (UTC)

It says "traverse"! It does not say "expand"! Please, just tell us where you got this "expansion" business from? -- Boing! said Zebedee (talk) 06:39, 7 July 2011 (UTC)

Do an object "traverse" while that expands? Ganesh J. Acharya (talk) 06:41, 7 July 2011 (UTC)

No, traversal has got nothing to do with expansion, and there is no mention of expansion in the Kak paper -- Boing! said Zebedee (talk) 06:50, 7 July 2011 (UTC)

"traversal has got nothing to do with expansion" it's scientifically an incorrect statement. Ganesh J. Acharya (talk) 06:57, 7 July 2011 (UTC)

Sorry dude, but I'm not going to waste any more time arguing with you - there is no mention of expansion in the paper, traversal is not expansion, the idea that the Sun has ever expanded at 186,000 miles per second is simply nonsense - and that's all there is to it. I'll leave you to see if you can get a consensus to support your interpretation -- Boing! said Zebedee (talk) 07:02, 7 July 2011 (UTC)

Arguments are for good aren't they? they help arriving at an appropriate "consensus" don't they? Ganesh J. Acharya (talk) 07:30, 7 July 2011 (UTC)

I repeat what I wrote before and leave it for everyones consensus. Assuming balloon travels at X speed while it expands along the radius, can one reply the following when one is asked "Q. At what speed is the balloon traveling?"... "A. The balloon is traveling at X speed". In the same manner SUN is a mass of incandescent gas which is expanding while its rays are traversing indefinitely in the Universe. As with the expanding balloon for the question on velocity "Q. At what speed is the balloon traveling?" the answer can very much be "A. The balloon is traveling at X speed", even in case of Sun, the answer very much is "The Sun traverse 186,413.22 miles per second". Because sunlight (the other-most layer of SUN) is very much part of Sun as the outer most visible layer of the balloon is to the balloon.Ganesh J. Acharya (talk) 09:22, 7 July 2011 (UTC)

And I'll repeat once more that there is no mention whatsoever of anything expanding in the cited source and that Sayana doesn't mention sunlight, so what you are saying is utterly irrelevant. I've looked back at your Talk page history, including your previous username, and it seems you've long had a problem with personal interpretation and analysis of primary sources. You really should have learned by now that the only thing that goes into Wikipedia articles is material that can be directly referenced to reliable sources, and not personal analysis or speculation - and certainly not your personal attempts to square Vedic sources with science. You are perfectly welcome to believe that Sayana was talking about the "expansion of light" from the sun if you want, but unless he specifically said that or there are reliable sources that make that argument, it simply does not belong on Wikipedia. -- Boing! said Zebedee (talk) 09:36, 7 July 2011 (UTC)

What is Expansion Scientifically?

How would you explain "A Matter Expands" scientifically? Ganesh J. Acharya (talk) 06:15, 7 July 2011 (UTC)

Look, here's what the abstract says...

"In his commentary on the Rigveda, the fourteenth century scholar Sa ̄yan.a mentions a specific speed for the sun which can be used to de- termine the distance to the sun. Vartak has interpreted this statement to stand for the speed of light but we cannot place that in any reason- able historical context. The distance to the sun implied by Sa ̄yan.a’s statement suggests that there was another astronomical tradition in India which is now lost."

And the quote from Sayana is...

"Thus it is remembered: [O Sun,] bow to you, you who traverse 2,202 yojanas in half a nimesa.'"

It's clearly talking about a *traversal* speed - ie the speed with which the Sun moves across the sky - and says nothing whatsoever about expansion. And if the actual traversal speed is known, the distance can be calculated. Unfortunately, Sayana produces a hopelessly incorrect value for the Sun's traversal speed and therefore for its distance too. Sayana's speed is close to the actual speed of light, and others have suggested that is what he meant, but Dr Kak's paper suggests that that is coincidence and Sayana simply got it wrong, basing his figures on some now-lost tradition. -- Boing! said Zebedee (talk) 06:38, 7 July 2011 (UTC)

Yes, I think Sayana's claim belongs in an article about the history of India, not this article. Whether is is an amazingly accurate estimate of the "expansion" of light from the sun, or just a strange coincidence can be discussed there. Dbfirs 07:44, 7 July 2011 (UTC)

The concept of "expansion" is not even hinted at anywhere in the paper, so it really isn't anything to do with "expansion of light from the sun" at all -- Boing! said Zebedee (talk) 08:43, 7 July 2011 (UTC)

Shape

It says the sun is 'almost perfectly spherical' is there a technical word to describe the suns shape for example the earth is geoid.