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Mar3-12, 11:14 PM
Sci Advisor
PF Gold
bcrowell's Avatar
P: 5,597
Your integrand doesn't have any variable in it. The [itex]r_0[/itex] shouldn't be inside the integral; it should relate to a limit of integration.

You could try setting [itex]ds^2=0[/itex] and then separating variables and integrating to get a relation between r and t for the light beam.