- #1

demonelite123

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So if a beam of light travels from radius r

_{0}to smaller radius r

_{1}, hits a mirror, and travels back to r

_{0}, I am trying to find how much proper time has passed for an observer fixed at r

_{0}. So far, i have that this path can be parametrized by r = r

_{0}and t = x, where x is just my parameter. Therefore, r' = 0 and t' = 1. Using the formula for arc length, i have that the proper time is given by [itex] \int \sqrt{1 - \frac{2M}{r_0}} dx [/itex].

this is where i am stuck as i am having trouble determining the limits of my integral. can someone give me a hint or two in the right direction? thanks