The simplest example of acceleration is constant acceleration, which Hartle does (in part)in his Examples 5.3–5.5. Let's do more with that example. (a) The world line of an inertial observer

sitting atx = 5/(4a) crosses the curved world line of the accelerated observer at two points ↑ =figure. For the inertial observer, what proper time elapses between these crossings? (b) For the accelerated observer, what proper time elapses between these crossings? (c) The inertial observer can (eventually) see anything in this spacetime. But there are points the accelerating observer can never see! Where are they?