A laser beam with a 1 mm diameter is aligned to a detector with a 1 mm diameter so that the beam's center coincides with the detector's center. The laser gradually drifts out of alignment, and the detector loses contact with the laser when the beam center makes an angle of 0.5° with its correctly aligned position. What's the distance between the detector and the laser? Assume the earth is flat; state other assumptions made. Show your work.