On modified theories of gravity

[xiaomaclever]

I am confused about the modified theories of gravity. We all know there is the Schwarzschild solution for GR. The solution can give right prediction for the solar-system experiments, such as Light deflection, perihelion shift of the Mercury and gravitational time delay. Whether all kinds of modified theories of gravity should have the same Schwarzschild solution, otherwise they will be ruled out by the solar-system experiments. I know some modified theories of gravity don't have the Schwarzschild-like solution for spherically symmetric vacuum spacetime.

 

[mfb]

They all have to give Newtonian gravity and at least the same first order deviation as GR in weak fields (gravitation in the solar system is weak). They might give different results on a galactic scale (very weak fields) and in strong fields.

 

[bcrowell]

A good book on this topic is "Was Einstein Right?"