Math Encounters

Now offering FREE, online sessions!

Math Encounters is MoMath’s popular free public presentation series celebrating the spectacular world of mathematics, produced with support from the Simons Foundation.  For further information, call the National Museum of Mathematics at 212-542-0566 or e-mail

Next up

“Number Theory Problems: From Easy to Undecidable”

with Bjorn Poonen

August 5 at 4:00 pm and 7:00 pm EDT (New York)

Rational numbers are fractions such as -2/7.  It turns out that the circle x2+y2=3 has no points whose coordinates are rational numbers, while the circle x2+y2=5 has infinitely many.  Why do these equations behave so differently?  What about more complicated equations: is there a method to decide whether there are any solutions in rational numbers?  Join Bjorn Poonen, Distinguished Professor in Science at MIT, as a search for answers leads to questions about prime numbers, geometry, and problems that a computer will never be able to solve.

Special introduction by C. Kenneth Fan, President of Girls’ Angle.

This is a live-streamed event.  Occasional video recordings are made available for a fee at

Register for the 4:00 pm session
Register for the 7:00 pm session

Upcoming Math Encounters presentations

Photography notice

By registering for a Math Encounters presentation, you agree that you may be photographed or videotaped by Museum staff and associates.

Books by the speakers

We are happy to offer books edited or authored by Math Encounters speakers through our online shop.

Math Encounters available on YouTube and DVD

Math Encounters presentations are generally posted to our YouTube page within 1-2 months of filming. Due to copyright issues, some presentations may not be reproduced on the Internet. Presentations posted online are also available for purchase via our online shop. Click here to purchase yours today!

Previous Math Encounters presentations

Presented by the Simons Foundation and the National Museum of Mathematics

Please note that all children under the age of 16 must be accompanied by an adult.