Once the tallest structure in the world, Eiffel Tower has been the iconic symbol for Paris and to the France. It was built in 1889 as a puddle iron lattice tower standing magnificently above all. The tower is the tallest building in Paris and the most-visited paid monument in the world; millions of people ascend it every year. Named after its designer, engineer Gustave Eiffel, the tower was built as the entrance arch to the 1889 World's Fair. The tower stands 324 metres (1,063 ft) tall, about the same height as an 81-storey building. The tower has three levels for visitors. Tickets can be purchased to ascend, by stairs or lift, to the first and second levels. The walk from ground level to the first level is over 300 steps, as is the walk from the first to the second level. The third and highest level is accessible only by elevator. Both the first and second levels feature restaurants.
Three hundred workers joined together 18,038 pieces of puddle iron (a very pure form of structural iron), using two and a half million rivets, in a structural design by Maurice Koechlin. Eiffel was assisted in the design by engineers Émile Nouguier and Maurice Koechlin and architect Stephen Sauvestre. The risk of accident was great as, unlike modern skyscrapers, the tower is an open frame without any intermediate floors except the two platforms. However, because Eiffel took safety precautions, including the use of movable stagings, guard-rails and screens, only one man died. The tower was inaugurated on 31 March 1889, and opened on 6 May. Eiffel had a permit for the tower to stand for 20 years; it was to be dismantled in 1909, when its ownership would revert to the City of Paris. The City had planned to tear it down (part of the original contest rules for designing a tower was that it could be easily demolished) but as the tower proved valuable for communication purposes, it was allowed to remain after the expiry of the permit. The military used it to dispatch Parisian taxis to the front line during the First Battle of the Marne.
The pig iron structure of the Eiffel Tower weighs 7,300 tonnes while the entire structure, including non-metal components, is approximately 10,000 tonnes. As a demonstration of the economy of design, if the 7,300 tonnes of the metal structure were melted down it would fill the 125 metre square base to a depth of only 6 cm (2.36 in), assuming the density of the metal to be 7.8 tonnes per cubic metre. Depending on the ambient temperature, the top of the tower may shift away from the sun by up to 18 cm (7.1 in) because of thermal expansion of the metal on the side facing the sun. Researchers have found that Eiffel used empirical and graphical methods accounting for the effects of wind rather than a specific mathematical formula. Careful examination of the tower shows a basically exponential shape; actually two different exponentials, the lower section overdesigned to ensure resistance to wind forces. Several mathematical explanations have been proposed over the years for the success of the design; the most recent is described as a nonlinear integral equation based on counterbalancing the wind pressure on any point on the tower with the tension between the construction elements at that point. As a demonstration of the tower's effectiveness in wind resistance, it sways only 6–7 cm (2–3 in) in the wind.
Since the beginning of the 20th century, the tower has been used for radio transmission. Until the 1950s, an occasionally modified set of antenna wires ran from the summit to anchors on the Avenue de Suffren and Champ de Mars. They were connected to long-wave transmitters in small bunkers; in 1909, a permanent underground radio centre was built near the south pillar and still exists today. On 20 November 1913, the Paris Observatory, using the Eiffel Tower as an antenna, exchanged sustained wireless signals with the United States Naval Observatory which used an antenna in Arlington, Virginia. The object of the transmissions was to measure the difference in longitude between Paris and Washington, D.C. Today, both radio and television stations broadcast their signals from the top of the Eiffel.
On 10 September 1889 Thomas Edison visited the tower. In 1910 Father Theodor Wulf measured radiant energy at the top and bottom of the tower, discovering at the top more than was expected, and thereby detecting what are today known as cosmic rays. On 4 February 1912 Austrian tailor Franz Reichelt died after jumping 60 metres from the first deck of Eiffel tower with his home-made parachute. In 1914 a radio transmitter located in the tower jammed German radio communications during the lead-up to the First Battle of the Marne. In 1925 the con artist Victor Lustig "sold" the tower for scrap metal on two separate, but related occasions. In 1930 the tower lost the title of the world's tallest structure when the Chrysler Building was completed in New York City.
From 1925 to 1934 illuminated signs for Citroën adorned three of the tower's four sides, making it the tallest advertising space in the world at the time. From 1940–1944 upon the German occupation of Paris in 1940, the lift cables were cut by the French so that Adolf Hitler would have to climb the steps to the summit. The parts to repair them were allegedly impossible to obtain because of the war. In 1940 German soldiers had to climb to the top to hoist the swastika, but the flag was so large it blew away just a few hours later, and was replaced by a smaller one. When visiting Paris, Hitler chose to stay on the ground. It was said that Hitler conquered France, but did not conquer the Eiffel Tower. A Frenchman scaled the tower during the German occupation to hang the French flag. In August 1944, when the Allies were nearing Paris, Hitler ordered General Dietrich von Choltitz, the military governor of Paris, to demolish the tower along with the rest of the city. Von Choltitz disobeyed the order. Some say Hitler was later persuaded to keep the tower intact so it could later be used for communications. The lifts of the Tower were working normally within hours of the Liberation of Paris.
In 1980s a restaurant and its supporting iron scaffolding midway up the tower was dismantled; it was purchased and reconstructed on St. Charles Avenue and Joesphine Street in the Garden District of New Orleans, Louisiana, by entrepreneurs John Onorio and Daniel Bonnot, originally as the Tour Eiffel Restaurant, later as the Red Room and now as the Cricket Club (owned by the New Orleans Culinary Institute). The restaurant was re-assembled from 11,000 pieces that crossed the Atlantic in a 40-foot (12 m) cargo container. On New Year's Eve 1999 the Eiffel Tower played host to Paris' Millennium Celebration. On this occasion, flashing lights and four high-power searchlights were installed on the tower, and fireworks were set off all over it. An exhibition above a cafeteria on the first floor commemorates this event. Since then, the light show has become a nightly event. The searchlights on top of the tower make it a beacon in Paris' night sky, and the 20,000 flash bulbs give the tower a sparkly appearance every hour on the hour.
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