Physics Discussion Thread

[UlanBatori]

And I can answer each of this (A-Guptaji's post - this is like being in an ISIS ambush - VBIEDs coming from too many directions faster than I can aim the ATGMs. Ooo! But TUT is on a roll!
1. Yes, I realize that the mean free path is small because the density is extremely high. And so is the temperature, so most of the particles that the photon meets are electrons, not protons or neutrons. And I will stipulate (since I have no clue but you or someone else posted it) that wavelength of gamma ray ~ wavelength of electron. This usually lends itself in gas dynamic laser lore to what is called "resonant interaction" (very efficient energy transfer).

2. OK, thanks, we agree that the 4000-71000 year Drunken walk is all pakistan. Thanks.

3.

the gamma rays that are produced have no preferred direction of movement; they have no idea of what direction is towards the core and what is towards the surface.

True. But we don't call a photon that is merely spinning around the center of the sun, something that is trying to exit the core. We only consider those whose momentum vector is radial or very very close to that. So, TUT holds: a drunken SUV that drives sideways on the road, will not run headon into a tollbooth set up in the middle of the road. It will be gone off the road in a jiffy and is hence irrelevant.

4. I didn't get the point about the heavy truck vs. the car: the heavy truck obeys TUT far more.

5. How far before momenum is dissipated? Why? Pls read Comment 53 (or one above it in your link): They make it abundantly clear that the interaction involves ***NO*** loss in energy, so the truck does **NOT** slow down. This is what resonant interaction does 4 u. Collisions with a proton may not be so pretty.

6. Last point about equilibrium: The SUN has no intelligent control system, so the argument needs to be inverted. BECAUSE there seems to be no instability, it must be true that things are pretty close to equilibrium. But clearly, over galactic time scales, stars do evolve, just as hydrogen bombs do on a slightly smaller time scale. They are not static. Equilibrium is a short-term view.

[UlanBatori]

Lokeshji: U answered ur own question.

Now the wheel turns and after a random interval disengages. The ball is now let go with a lower velocity at a random direction. The wheel is very heavy so it has barely moved

.

U r describing a bowling machine like Mohammed Amir.

Momentum is conserved by the reactions exerted by the wheel and its supports on the Earth, which made the Earth deflect in its spin and its orbit around the sun. This caused changes to the gravitational pull acting on the Sun, and may have caused Solar Flares. So don't do this experiment.

Otherwise, per the accepted knowledge given in Comment 53, there is no loss of momentum: the ball traveling at a million mph will not be deflected at all, though it may now be in a million pieces, entangled with the dust and gas molecules that your wheel and spring turned into.

[member_22733]

LOL. Hypothetical UB garu Hypothetical. Also, in my mechanics problem all of it is in space and also if there are millions of balls hitting each wheel , it will start oscillating around in its mean position (i.e get hot).

Comment #53 was explaining transmission of light waves through a transparent medium. I think that absorption and re-emission != transmission of light through a transparent medium. Both are quantum mechanical, but they are not the same.

[UlanBatori]

Well.. I'd say that if gamma rays can go through the core, then it is a transparent medium for gamma rays. The interaction described is about the same. For visible light, wavelength is quite large compared to that of a gamma ray, so particles as well as SUV size (not mass or momentum) considered are much bigger. Point is that the process is an absorption followed a VERY short time later by emission along the same momentum vector. Relay race.

[member_22733]

Do the gamma rays go through the core?

[UlanBatori]

Now that TUT has been established, let me set up an IED and depart. For my money (and hopefully it is not), Quantum Entanglement and Teleportation are far better investments for NaMo and GOI. As that develops, ppl will c that it was all discovered 1,71,000 years ago when that photon started in the solar core. Basically, it is the idea that two particles (twins with all quantum numbers identical except one has an opposite sign, say spin quantum number), will react INSTANTLY to changes in each other's quantum numbers, even though separated by an arbitrarily large distance.

LEGO, as much as I admire it, is Big Pissiks run Wild. GOI loves it because, like all GOI Initiatives, the work (and coincidentally, baksheesh) is in Land Allotment, Construction Contracts. Pissicists love it because of all the gamma rays shining on them by association with EmmEyeTee, Call-tek etc. But at the core, it is as significant as building a big high-voltage transmission tower on ur nullah.

This is SuperConducting SuperCollider redux, except NOW we hear that you don't really NEED SCSC. Phew! What a saving!

NaMo/GOI should invest big-time in Quantum entanglement and Teleportation. Imagine! NaMO can appear anywhere in the duniya without having to put up with havai-babus of Air India Ek. Also, vindication for a LOT of things now considered "mythical". JMIED.

[UlanBatori]

Do the gamma rays go through the core?

Now now, as AmberG might say, question answered hajaar posts ago. The whole funfest about the Drunken Random Walk was about Gamma Rays trying to get from core to outside. Apparently the fusion is at the core, then there is fission, then just hot gases and chemical reactions outside that. I ain't bin there!

So the gist is that if gamma rays are observed outside, then it is because they came from the fusion core. So yes.
(or from lightning bolts near the telescope...)

[member_22733]

Ismaaal correction on your IED:

They dont "react" instantly , they dont react at all. You cannot transmit information using a wave-function collapse (which you would have to do to measure the quantum number).

All it says is once the wave function collapses you know the quantum numbers of the now far away electron/photon etc. You cannot transmit information (aka energy) using that means

[Bade]

Only QED is UB==JohneeG !!

[member_22733]

Do the gamma rays go through the core?

Now now, as AmberG might say, question answered hajaar posts ago. The whole funfest about the Drunken Random Walk was about Gamma Rays trying to get from core to outside. Apparently the fusion is at the core, then there is fission, then just hot gases and chemical reactions outside that. I ain't bin there!

So the gist is that if gamma rays are observed outside, then it is because they came from the fusion core. So yes.
(or from lightning bolts near the telescope...)

Aiyooo saaaar. Gamma rays is naat what is getting from inside to outside. Its energy. Also the Sun has a black-body spectrum meaning that there will be some energy in the tail end (gamma rays), they could either have been retransmitted at super high energy or never hit anything in the plasma so came straight down from the core.

But I dont recall anyone ever saying that the core is completely transparent to gamma rays.

[UlanBatori]

That may be as it may be, but ppl have shown experimentally that they CAN transmit information instantly over a distance (last read on Wikipedia) of over 1.6 km. These labs are relatively small, and packed with high-tech equipment. Huge applications, starting with cryptology. See this as a starting point, it went through Beer Review apparently (though for the NEW NIAC, that's not saying much)

[UlanBatori]

Ah, Lokeshji,

Gamma rays is naat what is getting from inside to outside.

Naat so. Get outside the atmosphere, and you get zapped with X-rays and Gamma rays. Sit inside an aluminum box and the X-rays hitting aluminum send out "spalling" (alpha particles?) which kills u.
Let's not shift the goalposts just because TUT has completely destroyed the superstitions, hain?

AFAIK, gamma rays are clear indication of fusion reactions - or lightning which may contain a bit of fusion. You can search for a map of Gamma Ray Bursts observed from Space, looking towards Earth.

[sudarshan]

Let us also assume that instead of cars we have heavily loaded trucks, and in their collisions with toll booths they get deflected upto +/- 0.1° with respect to their original direction, because they carry most of the momentum. Consider that these trucks are meeting 10^5 toll booths per meter, and figure out on the average how far a truck might go before it is completely turned around.

So what part of this, exactly, negates the random walk premise? Each collision might only deflect a photon by an infinitesimal amount, but with so many collisions going on, a photon can get deflected substantially, right?

If the photon is instead absorbed and re-emitted, why does it have to preserve its original direction? Something to do with the "quantum superposition, which can't be explained to high-schoolers like you," like in that comment in the link pasted earlier?

[member_22733]

UBji,

Quantum teleportations works differently. Let me explain.

You need an sample and a "quantum state measurement device". The device goes through EACH molecule of the sample and creates a list of quantum states that each molecule is in.

Then you need to send that information using classical communication (limited by speed of light), and then use some techniques with quantum entaglement to recreate the sample at the remote side. I knew how this was done looong ago, but too lazy to pull it up.

In any quantum teleportation, you always need classical communication to complete it. IMVVVVVHO.

[A_Gupta]

UBji,
What is TUT?

[Bade]

Not to mention the scattering centers are not sitting still inside stars. Don't they have momentum too. So how is initial photon able to keep direction intact while conserving net momentum of the system ?

[member_22733]

Ah, Lokeshji,

Gamma rays is naat what is getting from inside to outside.

Naat so. Get outside the atmosphere, and you get zapped with X-rays and Gamma rays. Sit inside an aluminum box and the X-rays hitting aluminum send out "spalling" (alpha particles?) which kills u.
Let's not shift the goalposts just because TUT has completely destroyed the superstitions, hain?

AFAIK, gamma rays are clear indication of fusion reactions - or lightning which may contain a bit of fusion. You can search for a map of Gamma Ray Bursts observed from Space, looking towards Earth.

Very nice But, pray tell me, how much of the energy is gamma and how much is light, how much is xrays ????

[A_Gupta]

4. I didn't get the point about the heavy truck vs. the car: the heavy truck obeys TUT far more.

5. How far before momenum is dissipated? Why? Pls read Comment 53 (or one above it in your link): They make it abundantly clear that the interaction involves ***NO*** loss in energy, so the truck does **NOT** slow down. This is what resonant interaction does 4 u. Collisions with a proton may not be so pretty.

There is no loss in energy, but there a change in direction of momentum.

[Neshant]

Not that I'm into conspiracy theories, but here's an interesting interview from the late 90s.
Its about a physicist named Bob Lazar who claimed to have worked on a top secret US govt project for faster than light travel.
Apparently he got booted from his job and went public with the information.

It gets more bizarre however. He claims this technology is being back-engineered form alien craft.

Now normally I'd dismiss this kind of stuff as garbage.
But surprisingly my BS detector does not go off when he describes what he knows - other than its a little light on details.
I believe he is telling the truth, or at least he believes he's telling the truth.

[UlanBatori]

Last VBIED first: No, the Comment 53 says no change in MOMENTUM. Momentum is a vector. Two vectors cannot be the same unless both magnitude and direction are same.

Next VBIED: "how much of the energy is gamma and how much is light, how much is xrays ?" No clue. Discussion was about Gamma photons. I dont even know frequency of X-ray compared to gamma ray.

Next: "scattering centers are not sitting still inside stars. Don't they have momentum too. So how is initial photon able to keep direction intact while conserving net momentum of the system ?"

Vector math - Think COMPONENTS. The toll booth may be shifted a bit into the left lane because it was already moving that way, but the SUV comes out along the momentum of the original SUV. Maybe it's changed lanes. Note that particles are probably not moving at very significant speed compared to c - not that it matters much.

Next "What is TUT"? Now I don't want to say "Saara Ramayan patha, phir poocha" etc, but TUT is the Tollbooth Unified Theory, if u c above, the 1 & Only theory to explain everything in relative-stick physics.
Next:

Quantum teleportations works differently. Let me explain.

Kindly don't bring facts and confuse this fine discussion. Pls do a search: Ppl have shown instantaneous information exchange over 1.6 km (I guess their hands were not longer than that). That's far enough apart to measure time and confirm that it is **NOT*** limited by speed of light. I am saying that with the type of investment being demanded in LEGO, QT could be advanced with MUCH more benefit to desh.

Now let me dig deep again. Back around 1998-99, the then NIAC (which was a real institution, compared the present NASA manager-scam) funded Quantum Teleportation. After Phase 1, they were just bombarded with too much yadayadayada and hence asked the researchers to focus on cyber security aspects of the technology, and forget about the instantaneous part. Did through there & u will c the original stuff. VERY Nowadays these guys are clearly under orders not to talk about the true potential. How's that 4 a CT?

[member_22733]

Next VBIED: "how much of the energy is gamma and how much is light, how much is xrays ?" No clue. Discussion was about Gamma photons. I dont even know frequency of X-ray compared to gamma ray.

He he he. Its already measured as black body radiation. Here is a pic:


You can see non zero energies in the smaller wavelengths? Which means most energy will be in visible region but some energy will definitely be xrays and gamma rays. So you can get an idea of the ratio. If it follows this distribution (which it does), then it has thermalized.

[Bade]

Engineers are too dangerous a breed for humanity (sanity). Need to ban them and sent to Siberian gulags...not Physicists like Sakharov....

Now I see momentum conservation being redefined to vector conservation by decree of Modi-Sarkaar to save teleportation. Damn the Planck's radiation law (observed BB spectrum even for early universe, sun, earth or any other object) and other established observations.

[member_22733]

Hey now! I am a Modi Bhakt and an Engineer. Please dont turn Stalin on us.

[A_Gupta]

Last VBIED first: No, the Comment 53 says no change in MOMENTUM. Momentum is a vector. Two vectors cannot be the same unless both magnitude and direction are same.

Not sure which comment you're talking about, unless it is the one about light propagating through, say glass. The phenomenon there is very different from light (gamma rays) propagating in the core of the sun.

For light traveling through glass this following is certainly not an analogy, take it as a metaphor. Read the first little bit here about the speed of signal propagation in an ideal transmission line.
http://www.physics.utoronto.ca/~phy225h ... pulses.pdf
Then think of the glass - the material medium with its atoms and electrons bound in place with binding energies much higher than the energy of the photon, and only able to oscillate in place - as providing an impedance to the propagation of light, different from that of the vacuum.

For the photon in the core of the sun, think of say bowling balls and billiard balls undergoing elastic collisions. Even the big heavy bowling ball will eventually change direction and even U-turn after sufficient collisions.

[member_22733]

Last VBIED first: No, the Comment 53 says no change in MOMENTUM. Momentum is a vector. Two vectors cannot be the same unless both magnitude and direction are same.

Not sure which comment you're talking about, unless it is the one about light propagating through, say glass. The phenomenon there is very different from light (gamma rays) propagating in the core of the sun.

I have been saying that they are different for a while, but the message seems to have lost in the chaos.

Transmission != Reflection != Absorption != Re-Emission

Different processes, different timescales.

[UlanBatori]

Pissikists confuse every issue with either "Planck-Heisenberg/ Schrodinger/Random Walk/LIGO/LEGO/" and toss out these big words that poor yak-herders have to go carefully type on Googal search every time. Momentum conservation says that unless a net force is exerted, incoming momentum = outgoing momentum. Which means magnitude and direction. Works for light interacting with solar sails, plank or no plank. Lokesh, I suspect that X- and Gamma- are somewhat way beyond UV, aren't they? But as I said, this is a complete diversion. No one has been arguing about visible or infrared escaping from core of the Sun. U can just step outside on a sunny day and agree that this stuff comes from the Sun, E-Z. But I hope u don't catch any Gamma and X. Incidentally, why is that? I assume that it is because the gamma and X encounter enough BIG bodies (molecules, nuclear particles >> wavelength of X or Gamma) and get absorbed. Inshallah v have enough nitrogen and O2 and O3 to do this.

[member_22733]

UB garu,

lets switch off the momentum conservation for a while, and lets say there is no momentum imparted by this scattering process. Sun would collapse gravitationally. { EDIT: that was straigth from djinn pijjicks school, for the sun, it would mean it will become more and more compact and burn out rather quickly getting bluer and bluer in the process).

The outward momentum imparted (in the radial direction) keeps the sun where it is.

[Bade]

UBji, the photon (gammas) scattering off particles (electrons, protons, etc) needs to seen as at least a two-body system in which momentum is conserved not individually...and those particles are not at rest inside stars which is a plasma of charged particles, nuclei etc. Hydrogen fusing to Helium etc...details not important for this discussion on conservation of momentum. So no way the initial direction of the said photon remains the same. As I said gamma rays are not visible photons (eV range in energy) as these as energetic enough to create electron positron pairs near scattering centers. So the whole analogy of elastic collisions go out of the window. Those toll booths in your model can create more cars and anti-cars with glancing collisions. TUT is dead in the water and so is the creator...only solace is in seeking sharanam in physics as interpreted by the despised wise men of physics.

[UlanBatori]

TUT is dead in the water

{Sigh!}

Galileo's championing of heliocentrism and Copernicanism was controversial within his lifetime, when most subscribed to either geocentrism or the Tychonic system.[8] He met with opposition from astronomers, who doubted heliocentrism due to the absence of an observed stellar parallax.[8] The matter was investigated by the Roman Inquisition in 1615, and they concluded that it could only be supported as a possibility, not as an established fact.[8][9] Galileo later defended his views in Dialogue Concerning the Two Chief World Systems, which appeared to attack Pope Urban VIII and thus alienated him and the Jesuits, who had both supported Galileo up until this point.[8] He was tried by the Inquisition, found "vehemently suspect of heresy", forced to recant, and spent the rest of his life under house arrest.[10][11] It was while Galileo was under house arrest that he wrote one of his finest works, Two New Sciences. Here he summarized the work he had done some forty years earlier, on the two sciences now called kinematics and strength of materials.[12][13]

Whatever pissikists lacked, it was never Power. What the pakistan is a Stellar Parallax? Remember - this was bunch of dudes (dudettes were banned) so brilliant that they were convinced that the Earth was flat! Reminds you of some of the big words being tossed around here? LIGOtism 1600?

[TSJones]

......so why does heat build up in car when windows are rolled up? I should think glass is a poor insulator.....

......is it because when the atoms of glass are struck by photons so that when they start vibrating at the same frequency of infrared so that infrared can no longer escape from inside the car?

as explained by writer from astronomy magazine.....

[Viv S]

Greenhouse effect. Radiation from the hot sun is short-wave dominant. Much more penetrative than the long wave radiation emitted by the hot car interior.

(Unless you were being sarcastic .. I can't tell on this loony thread anymore.)

[UlanBatori]

Hmm. Thx Viv. One learns something new every day. So if the short-wave dominant gamma rays hit molecules inside the core, they eventually get absorbed and emit long wave, and that's what makes the Sun so hot!

[UlanBatori]

UBji, the photon (gammas) scattering off particles (electrons, protons, etc) needs to seen as at least a two-body system in which momentum is conserved not individually...and those particles are not at rest inside stars which is a plasma of charged particles, nuclei etc. Hydrogen fusing to Helium etc...details not important for this discussion on conservation of momentum. So no way the initial direction of the said photon remains the same. As I said gamma rays are not visible photons (eV range in energy) as these as energetic enough to create electron positron pairs near scattering centers. So the whole analogy of elastic collisions go out of the window. Those toll booths in your model can create more cars and anti-cars with glancing collisions. TUT is dead in the water and so is the creator...only solace is in seeking sharanam in physics as interpreted by the despised wise men of physics.

OK, this is VBVBIED class attack. Not so EZ to deflect because of so many diversionary attacks. But.. let's see.

Gamma Photon interaction with electron is the only thing I can consider here, based on the old wars in this thread. Apparently the wavelengths are on the same order, so this is like a resonant interaction. When a photon is absorbed, the momentum of the electron has a momentum increase by that amount. Along what direction? The direction of the incident photon, or course. So during the interaction time, the electron zips along that direction like a Southern Railways good car after it has been bumped by a shunting engine. Then a photon zips out with the original momentum of the incident photon - the reaction will push the electron backwards. There is no need to complicate matters further, this IS 2-body interaction. All the other issues are there, but irrelevant, this is the beauty of the laws of pissicks.

energetic enough to create electron positron pairs near scattering centers

Bully for them. And when they meet they're gone in a flash, the poor things. But irrelevant here. We are only interested in the question of how long it takes for info in the gamma regime gets out from the core to the surface.

[Bade]

But you cannot calculate time to surface, ignoring all known physics mechanisms in that energy regime. Of course you can as a toy model, but will give erroneous answers.

I will buy your toy model, when you can collect enough data to support your model. Solar physics and innards are quite well understood imo ( i believe AmberG refered to it earlier with regards to work of Bachall et al), except for the details of macro phenomena and its prediction, like space weather as in sunspot cycles and flares etc...

Even here there is ongoing work, check RayChaudhuri from IISc...a recent book of his deals with what we know so far. Cambridge press I believe.

[UlanBatori]

But you cannot calculate time to surface, ignoring (common sense)

NOW v r in agreement. I never did. This whole thing was started with a rather sneering declaration along the lines of

DID U KNOW IT TAKES 4000 YEARS FOR A GAMMA PHOTO TO REACH THE SUN'S SURFACE FROM THE CORE? THEN IT TAKE ONLY 8 MINUTES TO REACH EARTH!

(OR 71,000 YEARS..)

I merely thought about the assumptions behind that declaration. First pooch was whether the shock waves from a major event (nuclear detonation-class) inside the sun wouldn't reach the surface far faster, traveling at Mach 5 or so for the local temperatures. Against all common sense and Momentum Conservation, the Establishment is stuck in the Drunken Random Walk, and claiming 4000 to 71,000 years (a nice tight understanding of solar innards there., showing the physics have really been nailed down.) Just saying that someone has published a book means little - most books by akadummies as u know, reflect the notes that they used in classes, handed down from their teachers, from their teachers... some can be traced further upstream than Galileo, surely.
Time for The Forces of Common Sense to declare victory, having brought the Forces of Insolent Might to their knees. Wise time to exit, I think. I fully expect the to resume here lamenting the contamination of complacent superstition with traces of doubt due to commonsense..

[Bade]

Well some of the streams of argument in the name of free expression and counter arguments have their own signature in dogmas. So fair and square and the twain shall not meet. In the end though measurements always win hands down against dogma.

[Amber G.]

Well some of the streams of argument in the name of free expression and counter arguments have their own signature in dogmas. So fair and square and the twain shall not meet. In the end though measurements always win hands down against dogma.

Excellent point.

[Amber G.]

But you cannot calculate time to surface, ignoring (common sense)

NOW v r in agreement. I never did. This whole thing was started with a rather sneering declaration along the lines of

DID U KNOW IT TAKES 4000 YEARS FOR A GAMMA PHOTO TO REACH THE SUN'S SURFACE FROM THE CORE? THEN IT TAKE ONLY 8 MINUTES TO REACH EARTH!

(OR 71,000 YEARS..)

I merely thought about the assumptions behind that declaration. First pooch was whether the shock waves from a major event (nuclear detonation-class) inside the sun wouldn't reach the surface far faster, traveling at Mach 5 or so for the local temperatures. Against all common sense and Momentum Conservation, the Establishment is stuck in the Drunken Random Walk, and claiming 4000 to 71,000 years (a nice tight understanding of solar innards there., showing the physics have really been nailed down.) Just saying that someone has published a book means little - most books by akadummies as u know, reflect the notes that they used in classes, handed down from their teachers, from their teachers... some can be traced further upstream than Galileo, surely.
Time for The Forces of Common Sense to declare victory, having brought the Forces of Insolent Might to their knees. Wise time to exit, I think. I fully expect the to resume here lamenting the contamination of complacent superstition with traces of doubt due to commonsense..

I don't know if this was me or TSJ's post which started this, (the point was simply to point to a case where EM waves (or photon) may have time lag) but did not realize that it would be taken as an attack on someone's H&D ...don't explode Relax sirji, I did not do any blasphemy and no one was accusing photon to do a haram thing by making it drink. No need of doing madam jalebi on us.

And yes I feel sorry that goo came out but none of us was responsible that the valve came

off in [your] hand and the green goo poured all over the desk.

Stop pouring that goo all over again. .. and PLEASE stop "ulta_chor_kotwal_ko_dante" type refrain that people are .

Besides, I believe I did say.. (
I was sincere and it was not an attack on anyone's H&D.

UB,

If you REALLY wanted to understand or discuss what is the significance of " 4000 years delays due to photon", you could have asked it in a way that I think you are interested in learning, and I would have been happy to discuss it.. after all who knows, we may share the same alma mater, you having advantage of being 10 years or so younger... it might just be conceivable that you may be sitting in one of my ( or somebody like me) physics lectures for Engineers...

As far as I can think, There is NO excuse for shear nonsense (IMO of course) ... using math which horrify a high-schooler... (No 1000000000000000 and 0.0000000000000001 are not equally large numbers, as you have implied while calculating the effect of GW and still have not corrected it even after I explained)

***
As some one has pointed out, photons are little different than cars and so one has to be little careful applying models which may seem good but do not agree with experimental results. The critical difference is - if a photon(= light) passes through a medium, it slows down, but as soon as it out, it resumes its speed of c. (This is unlike a bullet, which if passes through/scattered_by a sand bag, keeps slow speed even after it emerges through the media). Another big difference is the speed of photon does NOT depend on what produced it (unlike make and muzzle velocity of a gun in the case of bullet)

Since, it seems it may be helpful, I will put some effort and I will post my perspective on the above in the next post. This is to keep the next post clean and on topic. I have not seen all the posts and did not go through every arguments of UB or JohneeG, and I have no intention of debating everything; but those who are interested may still find my next post useful. Of course same could be found in any good text book or in good physics lecture on the subject.

[A_Gupta]

Well, the Sun's interior is yet to be fully understood:
https://share.sandia.gov/news/resources ... /iron_sun/

Because that role is much greater than formerly surmised, the new, experimentally derived amount of iron’s opacity — essentially, its capacity for hindering the transport of radiative energy originating in nuclear fusion reactions deep in the sun’s interior — helps close a theoretical gap in the Standard Solar Model, widely used by astrophysicists as a foundation to model the behavior of stars.

Our data, when inserted into the theoretical model, bring its predictions more closely into alignment with physical observations,” said Sandia lead investigator Jim Bailey. His team’s work appeared Jan. 1 in the journal Nature.

The gap between the model and observations appeared in 2000 when analysis of spectra emerging from the sun forced scientists to lower their estimates of energy-absorbing elements such as oxygen, nitrogen and carbon by 30 to 50 percent.

The decreased abundances meant that the model then predicted that energy would arrive at the sun’s radiative edge more readily than before. This created a discrepancy between the star’s theoretical structure and its measured structure, which is based on variations in temperatures and densities at different locations.

To make the model once again agree with observations, scientists needed a way to balance the decreased resistance to radiation transport caused by the lowered amounts of the elements.

Look at figure 2 from this page to see calculated versus measured.
http://www.nature.com/nature/journal/v5 ... E-20141225

Anyway, the process by which energy is transported in the sun's core is called radiative diffusion or photon diffusion. The microscopic basis of diffusion is random walks.

I just learned this: the Kelvin-Helmholtz timescale is the time for the sun to radiate away all its energy if we can imagine its fusion reaction shuts down. This is of the order of 10^7 years, precisely because of radiative diffusion. Some good slides are here:
http://www.astro.caltech.edu/~george/ay ... -Lec7x.pdf

[Neshant]