Humans have a passion for reinventing things that have already been invented by nature. Concrete is a stunning example of this behaviour. Any rational being, after completing even a cursory survey of the natural resources of Earth, would conclude that rocks are one of the most plentiful natural resources, just behind dirt, salt water, and insects. Not so humans.

Unhappy with the shape and quality of the existing supply, some enterprising fellow found that if you mix the right amount of sand, small white chalky rocks and water together, it turns into a soupy slurry which eventually hardens into a man-made rock. Major problems ensue if you have neglected to put it in the right place before this occurs.

Improvements in concrete technology have enabled the building of the Hoover Dam, most of Tel Aviv and Brasilia, and thousands of tracts of the most hideous housing blocks ever designed.