This is pretty cool, but don’t worry – the Eiffel Tower isn’t going to be toppling over anytime soon (unless that lame scene in the terrible G.I. Joe movie actually happens in real life!). Anyway, because heat causes metal to expand, the Tower also does so on sunny days. However, because the Sun only shines on one side of the structure at a time (except at noon), this expansion only takes place on the part of the Tower that is soaking up rays! This causes the ENTIRE structure to lean away from the sunlight when the temperature is high. Fortunately, this bend is nothing dangerous, but let’s be honest – an 18 cm incline is still over half a foot, and an enormous tower leaning over that far still sounds pretty scary!