Solve General Relativity Equation: Steps & Tips

[The black vegetable]

Maybe I'm just being stupid, missing something simple ? How do you get from the top two equations to the second equation? Many thanks

 

[Ibix]

It's a weak field approximation. What could "weak field" mean here?

 

[PeroK]

You could use the binomial expansion.

$(1+ \frac{\phi_a}{c^2})^{-1} \approx (1 - \frac{\phi_a}{c^2})$

The quoted result is to first order in $1/c^2$.

 

[The black vegetable]

ah that's great thank you, I will look into binomial expansion, never met it before :)

 

[haushofer]

You're doing general relativity, but have never seen the binomial expansion before? Be cautious about other mathematical knowledge lacking then, I'd say. Good luck anyway ;)