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Energy transport in the Sun
1982, Robert Noyes, The Sun Our Star says
The energy released in (the core) as a gamma ray ... is destined to spend the next 10 million years struggling to the surface. BUT 2002, Freedman and Kauffmann, Universe, says As a result, it takes approximately 170,000 years for energy created at the sun's centre to travel 696,000 km to the solar surface and finally escape as sunlight. Any thoughts on why this has idea changed so radically in 20 years? (Or if either or neither is right?)  Martin Frey http://www.hadastro.org.uk N 51 02 E 0 47 
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#2




*Martin Frey* wrote:
1982, Robert Noyes, The Sun Our Star says The energy released in (the core) as a gamma ray ... is destined to spend the next 10 million years struggling to the surface. BUT 2002, Freedman and Kauffmann, Universe, says As a result, it takes approximately 170,000 years for energy created at the sun's centre to travel 696,000 km to the solar surface and finally escape as sunlight. Any thoughts on why this has idea changed so radically in 20 years? (Or if either or neither is right?) In lectures a few years ago I believe I was told it was of the order of 1 million years. Alas I don't recall much else of those particular lectures now. However, speculating wildly and trying to remember how photon random walks drift[1], the only thing I can think of is if the first figure is a calculation based solely on the small net outward motion in a photon's 'random' walk, and the second figure is this random walk drift plus effects due to deep convection and that it's this convective effect that has been modelled and added in the last 20 years. [1] I'm trying to remember if random walk drift is due to the pressure gradient, therefore the density gradient, and the effect this has on the 'mean time before collision'. So a photon is able to travel ever so slightly further in the direction away from the core before it collides with a particle because there's ever so slightly less material in that direction than in the coreward direction.  Andrew Urquhart  Contact me: http://andrewu.co.uk/contact/  Apologies for the wrong timestamp on my post  blame my ISP  'Staccato signals of constant information A loose affiliation of millionaires and billionaires'  Paul Simon 
#3




"Andrew Urquhart" wrote:
In lectures a few years ago I believe I was told it was of the order of 1 million years. Alas I don't recall much else of those particular lectures now. However, speculating wildly and trying to remember how photon random walks drift[1], the only thing I can think of is if the first figure is a calculation based solely on the small net outward motion in a photon's 'random' walk, and the second figure is this random walk drift plus effects due to deep convection and that it's this convective effect that has been modelled and added in the last 20 years. [1] I'm trying to remember if random walk drift is due to the pressure gradient, therefore the density gradient, and the effect this has on the 'mean time before collision'. So a photon is able to travel ever so slightly further in the direction away from the core before it collides with a particle because there's ever so slightly less material in that direction than in the coreward direction. Thanks, Andrew That's my understanding  from the books  of how the net outward flow is achieved. I know there's been some refinement of the depth of the convection zone thanks to solar seismology but not enough to cope with a 60 fold reduction from 10 million years or even a 6 fold reduction from your remembrance of 1 million. Maybe my 1982 book just got it wrong (shame because its a very readable acount that I had rated highly).  Martin Frey http://www.hadastro.org.uk N 51 02 E 0 47 
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