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File: RandomPhysicsQuestion Here's a question I've been sent. I have no idea how to go about this because I've never done any General Relativity, and I just don't have the time at the moment to read up on it. So, is there anyone out there for whom this is easy/obvious? Thanks. ---- !! Gravitational Deflection of Light? I'm looking for an expression for the deflection of light in a strong, static gravitational field. Referring to 'deflection of star light past the sun' in Sean Carroll's "Spacetime and Geometry" - equation 7.80 for the "transverse gradient": $\nabla\perp\Phi = \frac{GM}{(b^2 + x^2)^{3/2}}\vec b$ [[[> https://www.solipsys.co.uk/images/DeflectedLight.png ]]] Deflection angle is $\alpha = {2GMb} \int {\frac{dx}{(b^2 + x^2)^{3/2}}} = \frac{4GM}{b}$ This is only valid for weak fields/small deflection. And I'm not looking for a general integral solution - I'd like to plot photon paths in strong fields, so I'm looking for the instantaneous deflection, which I'll plot/integrate numerically, based on mass, radial distance from mass, and angle of photon trajectory. It should not use Schwarzschild coordinates, because I don't want the singularity at r=Rs and it only needs to be in 2 dimensions, because of spherical symmetry. So, is there an expression for the polar coordinates $r_2,$ $\theta_2$ and trajectory $a_2,$ for a photon travelling from $p_1$ to $p_2,$ using $M,$ $r_1,$ $\theta_1,$ $a_1,$ $L$? $L$ can be small (1/c ?)