Navier-Stokes equation*

20181007_0843351

wrinkled river
hiding
writhing leviathans

 

 

 

*The Navier-Stokes equation describes fluid flow, from supersonic flight to the emptying bathtub, and is conceptually quite straightforward. However it has not been solved in general and is listed as one of the seven most important problems in mathematics, with a $1M prize.