A visitor to a lighthouse wishes to determine the height of the tower. The visitor ties a spool of thread to a small rock to make a simple pendulum, then hangs the pendulum down a spiral staircase in the center of the tower. The period of oscillation is 9.01 s. What is the height of the tower? The accel- eration due to gravity is 9.81 m/s2 . Answer in units of m.