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Star time

Name: Anonymous 2008-02-17 5:22

If I've understood the general theory of relativity, gravity "slows" light, and thus also time. So for a star, is there a significant difference in time difference between the core and the "surface" and does this have anything to say for a star's workings?

How do you measure/count time for a star? Does our system based on 133Caesium half-life work (months/years/millenia)?

Name: Anonymous 2008-02-17 8:30

You measure time in the same way you do it anywhere else. You're looking for problems where there are none.

Name: Anonymous 2008-02-17 10:55

I'll try to be more specific; how long is a minute on earth's surface compared to a minute on Sol's surface. (Is it longer since there's a stronger gravitational forceon Sol?)

Name: Anonymous 2008-02-17 12:55

>>3
From earth time on the sun would seem to pass slower, similarly to the more common example of GPS satellites orbiting the earth.
I don't think it's significant enough to affect the the star process, but it's observable from earth, e.g. by a slight gravitational redshift.

Name: RedCream 2008-02-17 13:53

The question is, if there's a difference in gravity upon local spacetime, and since there's a gravity difference between the core and surface of a star, then:  Does that net difference in time rates cause a measurable difference in how the star's processes function?

Those who take Physics know that the gravity at the center of a start is ZERO.  This rises linearly up to the maximum gravitational pull at the surface of the star.  For the sun, that's about 28G:

http://van.physics.uiuc.edu/qa/listing.php?id=1063

(After that, gravitational pull drops off as a square of the distance.  But you knew that much already.)

So, does a 28G pull at the surface (i.e. photosphere, roughly) of the sun produce measurable effects compared to the core (which is at low-to-zero G), and if so, what are those effects?  Is photonic production lessened?  Etc.

Name: Anonymous 2008-02-17 15:35

Ask Michio Kaku.

Name: Anonymous 2008-02-17 15:43

>>3
Depends on your frame of reference.

Name: Anonymous 2008-02-17 19:03

>>7
Obviously he meant the Earth's surface, as he said "compared to ... the Earth's surface".

So stop being a pedantic dick.  I don't happen to know the answer to that.

Name: Anonymous 2008-02-17 20:06

Someone able to procure a formulae to be used?

I know one for newtonian gravitational field force, but not how acceleration effects time.

g=(γM)/r^2

If a photon were to travel from the core and outwards in a straight line, it would begin at c, then experience a linear decrease in speed (viewed from the earth) until it's out of the main body, it would then start to gain speed in a squared fashion until it reaches c again. Am I rite?

Name: Anonymous 2008-02-17 21:21

>>8
There's nothing obvious about it, douchebag, nor anything pedantic about my answer in >>7. You can compare it to the Earth's surface from space just as easily as you can from anywhere else, and since we're supposedly talking about star internals, the Earth's surface is a pretty irrelevant position to be observing from or comparing to anyway.

Name: Anonymous 2008-02-17 23:22

>>9
Actually, a photon produced in the center of the sun takes some 300 000 years on average to reach its surface, mostly because it keeps hitting electrons and the other shit the star is made of.

And to the second part, no, the speed of a photon in vacuum is always c.

Name: Anonymous 2008-02-18 1:44

>>9
The one thing relativity is based on is that light in a vacuum always moves at the same speed to every observer. How do you fuck this up?

Name: Anonymous 2008-02-18 8:04

>>9
Ignore that dumbfuckery of mine and think of time instead of speed. I feel dumb reading that post again, something I should be...

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