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A grand unified
theory of snowf lakes
Snowflakes can form in two different ways to produce myriad shapes,
but no one understood exactly why – until Kenneth Libbrecht
investigated. He tells Joshua Howgego about his frosty discoveries
S
NOWFALL 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.What was the big question about snowflakes?
The standard snowflakes you see in holiday
decorations – six-pointed, thin and flat – well,
that’s not the way they always form. As well as
thin, hexagonal plates, they can grow into tall,
hexagonal columns, like the shape of a pencilMost snowflakes
are made of
columns (near
left) or plates (far
left), but some are
hybrids (below left)58 | New Scientist | 18/25 December 2021