1) At the base of the Eiffel Tower, four curved pillars tilt inward at an angle of 54 degrees. As the pillars rise, and eventually join, the angle of each gradually decreases. At the top of the Tower, the merged pillars are almost vertical (zero degrees). French engineer Gustave Eiffel calculated that 54° angle as one that would minimize wind resistance. In interviews at the time, Eiffel said that his Tower’s shape was “molded by the forces of the wind,” notes Patrick Weidman. He’s an engineer now retired from the University of Colorado Boulder.

Weidman and a colleague analyzed the shape of the Tower. They also examined Eiffel’s original notes and blueprints. The two experts determined that a single elegant mathematical expression known as an exponential best describes the Tower’s curves. The researchers described their conclusions in the July 2004 issue of the French journal Comtes Rendus Mecanique.

Educators and Parents, Sign Up for The Cheat Sheet Weekly updates to help you use Science News for Students in the learning environment Client key* E-mail* Go

2) The Tower took 2 years, 2 months and 5 days to build. For 41 years after it opened in 1889, the Eiffel Tower remained the tallest building in the world. The Chrysler Building in New York City eventually surpassed the Tower’s height in 1930. But Eiffel’s building remained the tallest in France until 1973.

3) The Tower weighs 10,100 metric tons and has 1,665 steps. It was assembled from 18,000 parts, held together by 2.5 million rivets. To keep it from rusting, the Tower is repainted with 60 metric tons of paint every 7 years. It takes about 18 months for 25 painters using 1,500 brushes to repaint the entire Tower.

4) Because heat causes the metal Tower to expand and cold causes it to shrink, the height of the Tower can vary with the outside temperature by 15 centimeters (5.9 inches). Winds can cause the top of the Tower to sway, side-to-side, by up to 7 centimeters (2.8 inches).

5) Roughly 250 million people have visited the tower since it opened. Take a virtual tour in French or English here.

6) A month after its opening, the Tower had working elevators. This was a huge feat, considering the curves of the Tower and the weight those elevators had to carry. The Tower still has two of its original elevators. Each year, the Tower’s elevators travel a combined distance equal to 2.5 trips around the world, or more than 103,000 kilometers (64,000 miles).