Why does the Tower of Pisa lean???
The Tower of Pisa was supposed to stand up straight like any tower. It wasn't meant to lean. Construction started in 1173 and went for about 180 years. It first became clear that the tower was leaning when the third story was completed. Then they tried to do something to correct the tilt and to prevent the tower from falling over. It leans, engineers think, because its foundation is built on sand. It stands at 184 feet (56 meters) high. At present the Tower of Pisais roughly 17 feet (5.1 meters) out of alignment. It means that if you were to drop a stone from the top it wouldhit the grund 17 feet from the base of the tower. If the leaning isn't brought to a halt the tower will fall one day. Engineers hope they can prevent that. Only the bell tower at that top doesn't lean because it was added later. Galileo Galilei was a scientist who was born in Pisa in 1564. Legend says that he dropped two cannonballs, one 100 times as heavy as the other, together from the top of the tower to show that both would hit the ground at the same time. Whenever he did this or not, Galileo's careful experiment did show that objects of different weights fall at the same speed if the effects of air resistance are discounted. It is also said that he discovered the principle of a pendulum's swing by watching swaying chandeliers in the tower. The science of dynamics had made very little, if any progress from Aristotle's time until Galileo's. It was thought that if two objects, one 10 times as heavy as the other, were dropped together the lighter would take 10 times as long to hit the ground. It wasn't known that objects wih lighter density get lift from the resistance of the air below them, while heavier objects do not. The cedit for proving the went to Galileo, although similar experiments had been conducted in Holland during Galileo's time by a Dutch Physicist named Simon Stevin.