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Could somebody please explain to me how you can calculate the effects of gravity in general relativity in a practical way? (Or point me to a site where these things are explained in an understandable way)

I keep trying to read articles and courses about it, but whenever it gets interesting, all the words disappear from the page and are replaced by curly d's and upside down triangles with subscripts and superscripts all around them. I could swear they are even moving about on the page ;-)

OK, I'm exaggerating a bit, I do have a fairly good background in mathematics, I even managed to get a master's degree somehow, but GR just seems to be too much about symbols and too little about genuine understanding (unlike SR, which I've got a pretty good grasp of). So my mind basically goes tilt whenever it sees a page full of GR incantations.

- How would you calculate, for example, the curvature of a ray of light when it passes the sun in Einstein's famous solar eclipse experiment?

- Or how do you explain the precession of Mercury's perihelion?

- Or for something simpler, how do you calculate the gravitational effects between two moving objects (with distances, masses, etc... depending on the reference frame)?

What exactly makes the relativistic result differ from Newtonian calculations? For example, for the curvature of light, Is it the fact that light slows down near a heavy mass (as observed from far away) and therefore curves a bit more when it passes the sun? Or is there more going on?

Can you just use Newtonian attraction and throw in some corrections for slower clocks, shorter rods, slower light and a finite speed of gravity? Or do you have to abandon Newtonian attraction completely and make a full switch to tensor calculus to get any accurate results?

I imagine adjusting Newton's laws isn't easy, since different observers don't agree on distances, speeds, how long it took gravity to go from source to destination, or the mass of the objects involved. But maybe they would still apply in the frame of an observer using his measurements and a few corrections?

If not, how exactly do you calculate the acceleration of an object or the curvature of a ray of light in a field of gravity? Any tricks or shortcuts to make the math bearable and actually understand what you're doing?

Thanks!

Michel

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# Practical calculations for gravity

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