Pisa: Who Dropped the Ball?
1174 AD
1174 1174
10.24E43.43N
ARC

PISA, ITALY
	Almost from the moment it was started in 1172, the bell tower for the Pisa Cathedral began to lean. A weak foundation only seven feet deep, coupled with sandy soil and seeping water from the nearby Arno River all contribute to the Leaning Tower of Pisa's tilting tendency.
	Though already leaning, Giovanni di Simone coordinated the completion of the tower between 1275 and 1303. In this early period of architecture, leaning towers were not uncommon. No doubt, part of the reason the tower still stands after 800 years is that di Simone used methods and materials known to him (but lost to us) to compensate for the tilt.
	It is said that while a professor at the University of Pisa, in Italy, Galileo demonstrated from this tower that bodies of the same material, but different weights, fall with equal speed. If he did perform this experiment, it was probably done less in the interests of science than to discredit his opponents, professors who followed Aristotle's view of physics.
	Whether Galileo dropped anything over the edge of the tower, it is well documented that in 1612, a competing professor dropped balls of unequal weight from the tower. Surprisingly, the balls did NOT hit the ground at the same time. Indeed, the smaller ball hit the ground while the larger ball still had a few inches to go. This caused Galileo considerable embarrassment, though we now understand that air resistance was greater for the larger object, making it fall more slowly.
	On average, the Leaning Tower of Pisa tilts an additional millimeter per year, though in 1989 it only moved .2 millimeters. At one millimeter per year, the tower has another 100 to 150 years before it falls.
	Every few years, Italian authorities propose renovations to prevent the tower's collapse. These proposals inevitably produce an outcry from architects and politicians who are afraid repairs might cause more damage, and from local businessmen who worry that they will lose money if the tower is closed for an extended period.
	If the tower had never leaned, do you think it would attract over 1,500 visitors a day? Maybe it's not so bad to be a little off center.