24 May 2000 · Collège de France, Paris
A million-dollar question
Does every smooth flow stay smooth for ever, or can the equations break?
In May 2000 the Clay Mathematics Institute announced seven Millennium Prize Problems, with a million dollars for each solution. One is about the Navier–Stokes equations.
Start with a smooth, gentle flow in three-dimensional space, with finite energy. Will the solution stay smooth for ever? Or can the speed somewhere become infinite in a finite time, a blow-up?
In two dimensions it was proved in the 1960s that the answer is: smooth for ever. In three dimensions, nobody knew.
The reason is a purely three-dimensional effect: vortex stretching.
Chapter VI · Step 10 · 2000
The Millennium Prize problem
The seven Millennium Prize Problems were announced in Paris on 24 May 2000. The Navier–Stokes problem, in the official statement by Charles Fefferman, can be solved by proving any one of four statements: (A) smooth solutions always exist in ordinary 3D space, (B) the same in a periodic box, (C) there is a smooth starting flow and a smooth outside force for which the solution breaks down, or (D) the same breakdown in a periodic box.
- Two dimensions
- Solved
smooth solutions exist for ever (proved in the 1960s)
- Three dimensions
- Open since 2000
for the prize problem
- Leray (1934)
- Small flows stay smooth
and “weak” solutions always exist
- Tao (2016)
- An averaged version blows up
hinting at a possible route for the real equations
Only one Millennium problem, the Poincaré conjecture, has been officially declared solved. Grigori Perelman declined the prize in 2010.
Sources:
Clay Mathematics Institute: Navier–Stokes Equation;
Wikipedia: Navier–Stokes existence and smoothness;
Wikipedia: Millennium Prize ProblemsWhy three dimensions are hard
A spinning tube that is pulled
Stretch a vortex and it spins faster, like a figure skater pulling in their arms.
A vortex is a tube of spinning fluid. In three dimensions the flow can pull its two ends apart.
Because the fluid cannot be compressed, the tube must get thinner as it gets longer. And as it narrows, it spins faster, just as a skater spins faster by pulling in their arms.
Faster spin can stretch the tube further, which makes it spin faster still. Could this feed on itself until the speed becomes infinite? That is the blow-up question.
In two dimensions there is no direction to stretch in, so this cannot happen. That is why the 2D problem was solved long ago.
Chapter VI · Step 11 · An intuition for blow-up
Vortex stretching
Vortex stretching is the lengthening of vortices in three-dimensional flow, which increases the spin along the stretching direction because angular momentum is conserved. In incompressible flow a stretched tube must also get thinner. It drives the turbulent energy cascade toward small scales, and it is absent in two-dimensional flow.
Viscosity fights back by smoothing out sharp spins. The open question was which wins in the end: can stretching outrun viscosity and make the velocity infinite in finite time?
Illustrative only. This animation shows the idea of stretching, not the specific solution claimed in 2026. Use the slider on the scene to stretch the tube yourself and watch its spin rate in the readout.
Source:
Wikipedia: Vortex stretching8 September 2026 · An unverified claim
A blow-up, announced
An AI company says it has found a flow that breaks the equations. Mathematicians are still checking.
On the eighth of September 2026, OpenAI announced that an internal AI system, running about ten thousand agents for eighty-eight hours, had found a solution that blows up.
It describes a vortex that spirals inward and gets more and more elongated, like spaghetti, until its speed becomes infinite in a finite time, while the energy stays finite. The construction uses a smooth outside force.
The proof was checked by the Lean proof assistant. Lean confirms the logic, but experts must still check that the formal statement matches the Clay problem. It has not been peer reviewed, and OpenAI says it will not claim the prize.
Credit is disputed. Tristan Buckmaster and Levent Alpöge had announced closely related results a day earlier, building on methods by Diego Córdoba and Luis Martínez-Zoroa. OpenAI says its work was independent.
Some mathematicians also say the version without an outside force, the one many consider the heart of the problem, remains open.
Chapter VI · Step 12 · September 2026
The 2026 claim, and what is still open
Status as of 12 October 2026: an unverified claim. Not yet peer reviewed. The Clay Mathematics Institute still lists the problem as “Active” and has not awarded a prize; its rules require publication in a qualifying outlet, at least two years, and general acceptance by mathematicians before it considers a solution.
What was claimed
On 8 September 2026 OpenAI said an internal model, run as about 10,000 coordinated agents for 88 hours, produced a proof that a smooth, initially resting fluid with a smooth outside force can develop a singularity in finite time with finite energy: statement (C) of the Clay problem. It describes “a vortex… that spirals inward and gets increasingly elongated, like spaghetti.” A Lean formalization was released. OpenAI says it does not intend to claim the prize.
How it is being received
- Clay On 11 Sep the institute said it shares the excitement “as we contemplate the announcement that the Navier–Stokes problem has apparently been settled”, and that its process is “deliberately unhurried”.
- Checking Lean checks that each step follows; whether the formal statement captures the Clay problem is human work still under way.
- Scope A 17 Sep preprint by Constantin, Ignatova and Vicol argues the method cannot work without an outside force. Some experts say the force-free problem, which many regard as the central one, remains open.
The dispute over credit
Tristan Buckmaster (NYU) and Levent Alpöge (who works at Anthropic) posted related blow-up results, including for the forced 3D Euler equations, the day before. Both teams built on an approach developed by Diego Córdoba and Luis Martínez-Zoroa. Buckmaster, who used AI models including OpenAI’s Codex, raised questions about whether OpenAI’s system had any access to their work and about how a joint release was discussed; he said he was not accusing anyone. OpenAI acknowledged their priority on forced Euler, said its proofs differ, and after an investigation said his Codex prompts could not have influenced its system. These accounts have not been independently resolved.
The animation is illustrative: a swirl tightening toward a point, not a plot of the claimed solution.
Sources:
OpenAI: On the Navier–Stokes Millennium Prize Problem (8 Sep 2026, updated 10 Sep);
Clay Mathematics Institute: Navier–Stokes Announcement (11 Sep 2026);
Clay Mathematics Institute: Navier–Stokes Equation;
Clay Mathematics Institute: Rules for the Millennium Prize Problems;
Smithsonian Magazine (10 Sep 2026);
NYU Shanghai RITS (9 Sep 2026);
Quanta Magazine (8 Sep 2026);
Science News (9 Sep 2026);
Scientific American: “Did OpenAI solve the wrong Navier–Stokes problem?” (21 Sep 2026);
Constantin, Ignatova & Vicol, arXiv:2609.20803 (17 Sep 2026)