Challenges involving packing – how densely objects can fill a space – are among the most ancient and persistent problems in mathematics and science.

Of course, grocers have long known how to pack equal-sized spheres: Witness how they stack oranges. But what about other shapes? The fall Hans Bethe Lecture will explore how we study all manners of packing.

Paul Chaikin, professor of physics at New York University, will give a talk, “How Many M&M’s in That Jar? Particle Packings, Frustration and Why Things Crystallize,” Oct. 2 at 7:30 p.m. in Schwartz Auditorium, Rockefeller Hall.

“Paul Chaikin is one of the preeminent scientists studying packing,” said Itai Cohen, professor of physics and faculty host for the lecture. “He has a unique gift for explaining these phenomena in simple-to-understand ways and to be able to illustrate the problems geometrically.”

Chaikin, who earned his Ph.D. from the University of Pennsylvania in 1971, has made founding contributions to the field of nanolithography. Perhaps his best-known contribution is showing how and why ellipsoids – such as M&M’s – pack more densely than spheres. In 2005 he helped found the Center for Soft Matter Research and joined the faculty at New York University.

A member of the National Academy of Science, Chaikin is also a fellow of the American Academy of Arts and Sciences, the American Physical Society and the Institute of Physics (London). He was an A.P. Sloan Foundation fellow and a John Simon Guggenheim fellow and received the 2018 Oliver E. Buckley Condensed Matter Prize from the American Physical Society. He co-authored the text, “Principles of Condensed Matter Physics.”

As part of the Hans Bethe Lecture series, Chaikin will give a physics colloquium, “Quantifying Hidden Order Out of Equilibrium,” Sept. 30 at 4 p.m. in Schwartz Auditorium; and a theory seminar Oct. 1 at 4 p.m. in 700 Clark Hall.

The Hans Bethe Lecture series, established by the Department of Physics and the College of Arts and Sciences, honors Bethe, Cornell professor of physics from 1936 until his death in 2005. Bethe won the Nobel Prize in physics in 1967 for his description of the nuclear processes that power the sun.

Linda B. Glaser is a staff writer for the College of Arts and Sciences.