In today's Rare Earth on concrete, I somehow omitted my favourite thing about it:
To make concrete you need cement, which needs limestone. And the calcium in limestone was all collected by tiny sea creatures, building their shells atom by atom from the water around them. So the calcium in every single bit of concrete has passed through a sea creature. We only have skyscrapers because of marine life.
[The ace pic is from a WSJ column I wrote on this]
