The Eiffel Tower, an emblem of France, undergoes subtle yet significant alterations in its height annually. During the summer months, the structure extends slightly beyond its officially stated 300 meters, only to contract again when winter arrives. According to the publication Conversation, experts attribute this phenomenon to principles of physics and the inherent characteristics of the metal used in its construction.
The primary driver behind the tower’s “breathing” is the thermal expansion of the metal. The Eiffel Tower was erected using wrought iron, which, much like most solid substances, expands when subjected to heat and contracts when cooled. An increase in temperature prompts the metal’s atoms to move more vigorously, thereby increasing the space separating them.
In Paris, winter temperatures can occasionally dip below –20°C, while summer highs can reach +40°C. Furthermore, direct sunlight can cause the metal surfaces to heat up to as much as +70°C. Collectively, this creates a temperature swing of 100 degrees, causing the tower to lengthen or shorten by several centimeters.
Engineers have calculated that the variance between the Eiffel Tower’s tallest and shortest seasonal dimensions measures approximately 12 to 15 centimeters. Additionally, uneven heating caused by direct sunlight often warms one side of the structure more intensely, resulting in a slight bowing towards the heat source.
These fluctuating movements are amplified by the tower’s surprisingly low weight—roughly 7300 tons, contrasted with the approximately 6300 tons of air contained within its framework. Gustave Eiffel specifically selected wrought iron for its blend of durability and minimal mass, which contributes to this light, open latticework structure’s remarkable wind resistance.
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