techwonder said:
Is there a formula that readily says how much space is bent?
You want a simple formula that gives some idea of how much a given mass will bend space.
A partial answer is to assume there is a spherical mass M and a lightray that passes within a distance R (of the center) of the object. then there is an extremely simple formula that tells the ANGLE the ray is bent by the thing's gravity. Perhaps you already know that formula and want something fancier. but if not it certainly gives some idea of the size of the geometrical effect of a concentration of matter
the angle in radians is
\frac{4GM}{c^2R}
for the sun the quantity
\frac{4GM}{c^2}
is 6 kilometers, so if a ray of light passes 6,000,000 km from sun center
then it will be bent by an angle of 6/6,000,000 radians
or 1/1,000,000 of a radian.
you can plug in different masses for M, like mass of a galaxy or mass of the Earth, and see what angles light is bent
it gives a way of appreciating how very very slight the effect on the geometry of spacetime is, from even real hefty concentrations of matter
if you keep asking, chroot will probably tell you more of the story, but this is at least a start
[edit: thanks Labguy! I have edited this to conform with Labguy's pointer, originally I had R an order of magnitude smaller]
