Blog Posts

$$ \def\G{{\vec{\Gamma}}} \def\bm#1{{\vec{#1}}} $$ Why do waves never build a sandcastle? We often see the waves dissolve a carefully constructed sandcastle, but we never see the sea gather disparate grains of sand from the seabed and deposit them in the same shape on the beach. Both of these processes are in some sense allowed by the microscopic laws of physics, and yet we only ever observe one of them in real life.