Kenneth Libbrecht interview: A grand unified theory of snowflakes

Snowflakes can form in either a plate or column shape, but no one understood why – until physicist Kenneth Libbrecht investigated. His theory is the result of two decades making snow in the lab


15 December 2021

Six pointed snowflake

Courtesy of Kenneth Libbrecht

SNOWFALL in Pasadena, California, is so rare, it’s almost unheard of. Except, that is, at the California Institute of Technology, where Kenneth Libbrecht can conjure it up using the world’s most sophisticated snowflake-making equipment.

As a physicist, Libbrecht has tackled some fairly epic questions, like the nature of gravitational waves and the internal workings of the sun. But he also has a delightful sideline in the science of snowflakes, which are far more complex and mysterious than you might think. One of the biggest unanswered questions about them is why they appear to come in two distinct types.

Libbrecht went on a 20-year odyssey to solve this mystery. Recently, he published the fruits of that journey in the form of a monograph that runs to more than 500 pages. It contains a kind of grand unified theory of snowflakes, explaining for the first time how and why they grow into the delicate shapes they do.

Joshua Howgego: What got you interested in snowflakes?

Kenneth Libbrecht: One day I was chewing the fat with one of my students and we got talking about how crystals grow and take on shapes. We started thinking about what we could study in this area and I thought: well, water would be cheap and easy. Then I thought: actually, that would be the physics of snowflakes, I wonder how that works? Apropos of nothing – I was just curious – I started reading up on research on snowflakes and I found it really fascinating.

“I can turn knobs to control the conditions exactly, so I can get these designer snowflakes”

What was the big question …