Gravitational Time Dilation Inside the Sun

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Mikael17
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TL;DR
time dilatation inside the sun
How can time dilation, lets say 500000 km inside the sun be calculated ?
 
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Using the appropriate spacetime metric, which i must admit I don't know. Try searching the Internet for it.
 
Dale said:
One of the assumptions is constant density, so that probably isn’t the best assumption, but it should be a reasonable approximation given the resulting simplification
To do much better you'd need a density and pressure profile, and I would suspect you'd have to do it numerically. Especially if you stopped pretending it was a non-rotating sphere.
 
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Ibix said:
To do much better you'd need a density and pressure profile, and I would suspect you'd have to do it numerically. Especially if you stopped pretending it was a non-rotating sphere.
Yes. I agree that anything more exact than this would probably have to be numerical.
 
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Here is a "recipe" from MTW's Gravitation:

Textbook page, section 23.7 'How to Construct a Stellar Model', listing line element, mass equation, OV hydrostatic equilibrium equation, equations of state and source equation for phi, with a paragraph on integrating outward from the centre.

Printed textbook page, section 23.7 'How to construct a stellar model', discussing a one-parameter sequence of stellar models set by central pressure, with the star's surface where pressure reaches zero.
 
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Ibix said:
Is ##n## (23.28c and d) defined somewhere? Number density of particles?
Here:
Textbook page section 23.4, Description of the matter inside a star, stating that matter inside a star is idealized as a perfect fluid with density rho, pressure p, baryon number density n, 4-velocity u^mu, and stress-energy tensor T^{mu nu} = (rho + p)u^mu u^nu + p g^{mu nu}, equations 23.11 and 23.12.
 
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Ibix said:
To do much better you'd need a density and pressure profile, and I would suspect you'd have to do it numerically. Especially if you stopped pretending it was a non-rotating sphere.
Dale said:
This would be the interior Schwarzschild metric:
https://en.m.wikipedia.org/wiki/Interior_Schwarzschild_metric

One of the assumptions is constant density, so that probably isn’t the best assumption, but it should be a reasonable approximation given the resulting simplification
Dale said:
Yes. I agree that anything more exact than this would probably have to be numerical.
The weak field approximation is going to be way more accurate than the interior Schwarzschild metric in this case. Input a solar model for the density and voila.

(I actually did this computation not too long ago for a cosmology course I took for undisclosed reasons. The teacher was somehow surprised when I used the standard solar model for the density profile 😉)
 
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Orodruin said:
The weak field approximation is going to be way more accurate than the interior Schwarzschild metric in this case. Input a solar model for the density and voila.
I have to admit that it didn’t even occur to me!