The Eiffel Tower is made of puddled iron, an old form of wrought iron. When it heats up, the metal expands. That is normal physics, not damage.
The atoms take in energy, vibrate more intensely, and move apart. Volume grows. Height grows with it.
How much does it rise?
From cold winter days to the hottest summer days, the tower stands 5 to 6 inches (12 to 15 centimeters) taller. The difference is small, and it can be measured.
The sun adds a lean.
It does not heat the sides equally. The warmer side stretches a little more, and the summit tips a fraction of a degree away from the sun.
As the sun moves through the day, the top traces an almost circular arc about 6 inches (15 centimeters) in diameter. After dark, the temperatures even out and the tower returns to its original position.
The frame was designed to accommodate both the extra height and the tilt.
In practice, the structure is a giant thermometer. Its height and daily lean follow the heating and cooling of Paris.
The iron does not sit still.
The eye simply cannot see it.
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