The problem, three ways
Curious
The Navier–Stokes equations describe how water and air move, and engineers use them every day. Yet nobody had proved that their solutions stay well behaved forever: could a smooth flow suddenly develop an infinitely sharp spike? In September 2026 OpenAI claimed that, pushed from outside in a carefully chosen smooth way, it can.
Undergraduate
The equations are ∂ₜu + (u·∇)u = νΔu − ∇p + f with ∇·u = 0, on ℝ³ or on the torus. The Clay description asks for one of four alternatives: smooth solutions for all time without forcing on ℝ³ (A) or the torus (B), or breakdown in finite time with smooth forcing on ℝ³ (C) or the torus (D). Leray proved in 1934 that weak solutions exist for all time; whether they stay smooth is the question.
Specialist
Partial regularity (Caffarelli, Kohn and Nirenberg) confines any singular set, and Tao's averaged equations showed that energy methods alone cannot rule out blowup. The Córdoba–Martínez-Zoroa programme constructs forced singularities; the 2026 claims push the forcing to C^∞ within Clay's decay and energy conditions, first for Euler, porous media and Boussinesq (Buckmaster and Alpöge), then for Navier–Stokes (OpenAI).