You made it! Each month we write a funny question and leave it at water fountains around New York City as a way for people to engage with math.
You don’t need to know any math to participate! We are seeking silly answers only. Fill out the form below for a chance to win a prize!
October 18th is World Okapi Day! To celebrate, we’re asking a fountain question about okapis in a different dimension.
As always, you don’t need to know a lick of math for a chance to submit an answer and win a prize. Just skip straight to the form below!
What’s the weird dimension?
One of math’s Millennium Prize Problems is related to the Poincaré conjecture. The Prize Problems have been swirling in the media ever since OpenAI solved the one about Navier-Stokes in September 2026. Back to Poincaré:
[Henri] Poincaré, almost a hundred years ago, knew that a two dimensional sphere is essentially characterized by this property of simple connectivity, and asked the corresponding question for the three dimensional sphere. This question turned out to be extraordinarily difficult.
(Clay Mathematics Institute 2026)
In 2002, Grigori Perelman solved the Poincaré conjecture for dimension 3. He won a million dollar prize. And turned it down! The topological version of this conjecture has more or less been solved in all dimensions — including 4. (Freeman 1982)
The unsolved part concerns the smooth Poincaré conjecture for dimension 4. We do not know, to this day, if there are exotic 4-spheres. What’s up with that dimension?
And can we find okapis there?
“This is the weird dimension. Nobody has managed to formulate a useful and viable conjecture for the classication of smooth, compact four-dimensional manifolds. ”
NOTE: These will always be placed on fountains with an easily removable adhesive.
Psst…we’re runners. So we made sure to pick working fountains!
Previous fountains
September 2026
The Grassmannian is a fascinating geometric object (well, family of geometric objects) I discovered recently.
Please read or listen to Steven Strogratz’s interview with MacArthur winner Lauren Williams to learn more! Of course we don’t care if you know about the Grassmannian or not. We just want to know if you’d eat it.
PS: I reached out to Steven Strogratz and he actually commented on this fountain question! It’s probably why I kept it up for so long.
June 2026
May 2026
