--- title: "The Eiffel Tower Grows Taller in Summer. By Enough to Actually Matter." id: "86898" type: "post" slug: "eiffel-tower-grows-taller-summer" published_at: "2026-09-29T13:12:21+00:00" modified_at: "2026-09-29T13:12:23+00:00" url: "https://econopass.com/eiffel-tower-grows-taller-summer/" markdown_url: "https://econopass.com/eiffel-tower-grows-taller-summer.md" excerpt: "On a hot July afternoon in Paris, the Eiffel Tower is approximately 15 centimetres taller than it was in January. It is also leaning. Both are measurable, both are documented, and neither is a metaphor. Marco Bellinari explains the physics..." taxonomy_category: - "Stranger Than Fiction" taxonomy_post_tag: - "Bizarreworld" - "EiffelTower" - "ScienceFacts" - "StrangerThanFiction" - "unbelievablefacts" --- # The Eiffel Tower Grows Taller in Summer. By Enough to Actually Matter. - [Marco Bellinari](https://econopass.com/author/marco-bellinari/) - September 29, 2026September 29, 2026 ![Eiffel Tower Grows Taller](https://econopass.com/wp-content/uploads/2026/09/Eiffel-Tower-Grows-Taller.jpg "Eiffel Tower Grows Taller") On a hot July afternoon in Paris, the Eiffel Tower is not where it was in January. It is taller. And it is leaning. Both of these things are true, both are measurable, and neither of them is a metaphor. The tower that Gustave Eiffel’s engineers assembled for the 1889 World’s Fair was built from 7,300 tonnes of wrought iron. Iron, like virtually every solid material, expands when it heats up. The atoms inside it vibrate faster, they push outward against each other, and the material grows. On a human scale, the effect is negligible. On the scale of a 300-metre iron structure exposed to direct summer sun, it is not. > The number that governs how much iron grows with temperature is called the **coefficient of linear thermal expansion**. For wrought iron, that figure is approximately 12 millionths of a metre per metre per degree Celsius. Multiply by 300 metres of tower height. Multiply by the temperature difference between a Paris January and a Paris July afternoon, accounting for the fact that direct sunlight pushes the metal surface well above the air temperature. The arithmetic produces a figure of roughly **15 centimetres**. On the hottest summer days, the Eiffel Tower stands approximately 15 centimetres taller than it does in midwinter. Fifteen centimetres is not enormous. But it is not nothing. It is the height of a coffee cup. It is enough to be measured precisely, consistently, and repeatedly by engineers who monitor the structure. The Eiffel Tower’s operating company acknowledges a figure of around 15 centimetres in summer expansion on its official record, though some calculations using only ambient temperature differences produce a more conservative estimate of around 5 centimetres. The higher figure accounts for direct solar radiation heating the metal surface beyond air temperature, which is the more physically accurate scenario on a clear July afternoon. The lean is the part most people do not know about, and it is in some ways more striking than the growth. > When the sun shines directly on one face of the tower, that face heats faster than the shaded faces. The heated side expands more quickly. The result is that the tower bends: the summit shifts several centimetres away from the sun, tilting like a slow compass needle pointing away from its heat source. Engineers have described it as behaving like a very large, very slow sundial. The lean is small enough to be invisible to the naked eye from the ground, but it is measurable, and it reverses as the sun moves across the sky. Gustave Eiffel knew about thermal expansion. It was not an oversight. The original engineering drawings for the tower included expansion joints precisely to accommodate the predictable movement of iron under temperature change. The same principle governs the gaps you see in railway tracks, the expansion joints in motorway bridges, and the reason that the Golden Gate Bridge in San Francisco changes length by over a metre between its coldest and warmest states. Thermal expansion is not a flaw in structural engineering. It is a phenomenon that structural engineering is built around. What makes the Eiffel Tower’s case interesting is the scale. A railway track expansion joint handles millimetres. A motorway bridge joint handles centimetres. The Eiffel Tower handles centimetres too, but across a structure that 7 million people visit every year and that most of them believe is a fixed, permanent, unchanging feature of the Paris skyline. > It is not fixed. It breathes with the seasons. It leans with the sun. The structure Eiffel’s critics called a useless iron monstrosity, a blot on the Parisian skyline that leading French intellectuals signed a petition to have demolished before it was even finished, has been quietly demonstrating basic physics to anyone paying close enough attention for 135 years. The tower was scheduled for demolition after 20 years. It survived because its height made it an invaluable radio transmission antenna. The structure they wanted to tear down became the reason Paris could communicate with the world. There is one final detail worth knowing. The Eiffel Tower is repainted every seven years, using approximately 60 tonnes of paint each time, applied by hand by a team of painters working in sections from top to bottom. The paint is one of the things that slows the iron’s reaction to temperature, acting as a partial insulator against the most extreme solar heating. Without the paint, it would grow a little taller still. *The world is stranger than anyone told you. I am just keeping count.* **Marco Bellinari** Think that was strange? These books will finish the job. [The Eiffel TowerGustave EiffelView on Amazon](https://www.amazon.com/dp/3836509032?tag=econopass01-20&linkCode=ogi&th=1&psc=1) [Eiffel’s TowerJill JonnesView on Amazon](https://www.amazon.com/dp/0143117297?tag=econopass01-20&linkCode=ogi&th=1&psc=1) [The Invention of ParisEric HazanView on Amazon](https://www.amazon.com/dp/1844677052?tag=econopass01-20&linkCode=ogi&th=1&psc=1) ## Sources - [Artful Parent. The Eiffel Tower can grow up to 15 centimetres taller during a Paris summer. Thermal expansion and the lean explained.](https://artfulparent.com/j-the-eiffel-tower-can-grow-up-to-around-15-centimetres-taller-during-a-paris-summer-because-its-7300-tonnes-of-iron-expand-in-the-heat-and-the-structure-also-leans-slightly-away-from-the-sun-as-the/) - [Fact Myth. The Eiffel Tower Gets Taller in the Summertime. Coefficient of thermal expansion calculations.](https://factmyth.com/factoids/the-eiffel-tower-gets-taller-in-the-summertime) - [The Daily Fact. The Eiffel Tower Grows Taller in the Summertime. Engineering context and paint maintenance.](https://thedailyfact.beehiiv.com/p/the-daily-fact-18) #### A Note from Marco Bellinari Thank you for reading. Every fact in this article is documented and sourced. You will find the references at the bottom if you want to dig further. I hope it surprised you at least once. That is always the intention. I would love to hear your thoughts. Follow Econopass on social media and share your reaction hereafter as a social comment. And if you do not want to miss the next story, hit follow. There is always another forgotten truth waiting to be told. [📖 Read More](https://econopass.com/author/marco-bellinari/) Nobody Will Believe This. Share It. [Set as Preferred Source](https://www.google.com/preferences/source?q=econopass.com) Disclosure: This article may contain affiliate links. This means we may earn a commission if you click on a link and make a purchase at no extra cost to you. This applies to featured Amazon products or any other Econopass's partners. 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