Feynman described turbulence as &quot;the most important unsolved problem of classical physics.&quot;<p>Another quote, attributed both to Heisenberg and to Horace Lamb:
&quot;When I meet God, I am going to ask him two questions: Why relativity? And why turbulence? I really believe he will have an answer for the first.&quot;<p>And the very related problem of the existence and smoothness of solutions to the Navier-Stokes equations is one of the famous millennium problems.