$1 Million Millennium Problem #4
The Navier-Stokes Equations
~ A formula please ~
The Navier-Stokes equations would appear to be similar to the partial differential equations routinely solved by science and engineering undergraduate students. But to date, no one has a clue as to how to find a formula that solves this particular class of equations.
See Keith Devlin's "The Millennium Problems: The Seven Greatest Unsolved Puzzles of Our Time, Basic Books, 2002.