The physics and physicists behind snowflakes
By Amelia Taylor-Hochberg, Photographs courtesy of Ken Libbrecht
There is absolutely nothing special about a single snowflake.
Whether or not their inalienable uniqueness can be scientifically proven is just as fruitless as comparing toenails or sunflower seeds – so I won’t be going any further there, and neither will Kenneth Libbrecht. As a Caltech physicist who has become the “preeminent” authority on the science of snowflakes, Libbrecht gets asked the “are any two snowflakes exactly alike” question a lot. So much so that his (exhaustive) answer is on his website, which you can see for yourself here.
To dispel any doubt, he goes into the subtleties of the question – it depends on how you qualify “alike”, and on what you count as a “snowflake”, and of course the sheer size of the sample group. Of course this is more scientific rigor than philosophical conjecture, but it’s impossible to steer completely clear of the big, humanistic questions snowflakes pose – what is the philosophical nature of “likeness”? What qualifies as the semantic referent of a snowflake? Regardless of whether they could exist, what is the cosmological chance of seeing two identical snowflakes?
Sorry, I didn’t mean to go any further into that point. How Libbrecht came to study snowflakes has little to do with their colloquial American role as the key symbol for uniqueness. Simply, he was intrigued by their mystery. When I spoke with Libbrecht about the initial inspiration behind his research, there wasn’t much of a grand origin story. It was simply a head-scratcher, something that came up in casual conversation with a colleague in the late 1990s, and piqued his interest. It soon became clear to him that not much was known about why snowflake structures grow and look as they do, and that few people were looking into it scientifically. And so, an opportunity arose that was too clear to ignore.
At that time, Libbrecht was doing research at Caltech under LIGO, the Laser Interferometer Gravitational-Wave Observatory. Devoted to studying gravitational waves of cosmic origins, LIGO is effectively the tool to detect the proof in the Theory of Relativity’s pudding. In its initial form running observations in the early aughts, LIGO was the most expensive initiative ever funded by the National Science Foundation, costing $365 million (approximately 5 percent of the NSF’s annual funding budget) and spearheaded by researchers at Caltech and MIT. The worldwide effort included researchers from 40 institutions and approximately 550 scientists – a big honking deal with lots of invested parties.
By the time he became involved with LIGO, Libbrecht was already quite comfortable at Caltech, having first studied there as an undergraduate in the late 1970s, then returning to teach physics in 1984, after completing a PhD at Princeton. Teaching, serving as the Executive Officer for the Physics Department, and researching under LIGO served up a full plate, but one that nonetheless failed to be satisfying. As a project of such magnitude, LIGO was by nature impersonal – so many people chasing the same problem, progressing very slowly, if at all, towards a momentous goal.
And then, snowflakes, these discrete objects of symmetrical wonder – beautiful, but common, and still highly mysterious. While nothing in Libbrecht’s prior work made the path to snowflakes obvious, it was (and is) a joy to him: “it was my anti-LIGO, it was just small, just me.” In the midst of LIGO, he began tinkering with ice crystals, studying the underlying physics that explain how and why they grow as they do.
While Libbrecht is most certainly a big fish in the tiny research pond of snowflake science, he isn’t the only one.
There are a variety of approaches to studying snowflake crystal growth not overly concerned with the physics: climatologists may focus on how crystal growth correlates with weather and atmospheric phenomena, while material scientists might occupy themselves with the chemical make-up of ice crystals. Libbrecht’s approach is unique to these, because he isn’t concerned with applying his observations anywhere. His carrot at the end of the stick is less glamorous, but in a way, more scientifically romantic – pursuit of knowledge for the sake of knowing, to shine light on what was previously in shadow.
Then again, light can also be the problem. Everyone is quick to point out the irony of a southern-Californian physicist being the preeminent authority on a wintry icon, but this isn’t field research. While Libbrecht does occasionally harvest “wild” snowflakes, taking trips to the near altitudes of the Sierras or collecting snowflakes in Moscow or Hokkaido, this isn’t to bring them back to a lab, or to take formal measurements. Instead, in a relatively quick and dirty procedure, he catches the snowflakes on a black piece of posterboard, gently picks them up on the end of a paintbrush, and deposits them onto a microscope slide. He then snaps a digital photo, and the snowflake inevitably melts (although you can watch him teach Martha Stewart how to preserve snowflakes here).
But to understand how they grow, he has to be able to actually observe the formation of a snowflake, and its growth into (with some luck) the intricately symmetrical forms we recognize as snowflakes. What distinguishes snowflakes from sleet or hail is that they're not frozen water, they're frozen water vapor. Snowflakes naturally form when water vapor in clouds freezes, after which they make their way out of the cloud layer and down to earth.
This tends to be a pretty violent procedure – by the time the snowflakes reach humans, they’ve been severely buffeted against one another by their atmospheric habitat’s natural dynamics, such that they tend to get pretty beat up. It’s rare to find a perfectly symmetrical, intact, undamaged snowflake in nature — not because they rarely occur, but because they rarely last. Their lives in the wild are nasty, brutish and short.
In the lab, everything is quiet and contained. Libbrecht has hobbled together his own apparatus for growing and photographing snowflakes, using not much more than a styrofoam box, a microscope and an electric needle (at least in the early days). Using a technique first developed in the early 1960s by meteorologist Basil Mason and his team, Libbrecht can grow a remarkable variety of “designer” artificial snowflakes in a vapor diffusion chamber, which creates the analogous cloud atmosphere for the snowflakes to form. By keeping the chamber very cold on the bottom (negative 40 degrees Celsius) and very hot on the top (40 degrees Celsius), water that is piped in at the top trickles down and forms a column of supersaturated air – where more water evaporates into the air than condenses back out of it. Somewhere in the Goldilocks middle, the supersaturated air is just cold enough for snowflakes to form. When a wire needle is inserted into the chamber with its end in the Goldlilocks zone, ice crystals begin to form on the wire’s tip, and when it’s charged with 2,000 Volts, “ice needles” start growing from that end. Libbrecht has created thousands of so-called “designer snowflakes” using this technique, tweaking temperatures and voltages to form different shapes and patterns.
The delicate interaction between temperature and composition of the water vapor is ultimately what determines a snowflake’s shape. And in the vapor diffusion chamber’s styrofoam box, these factors can be controlled and measured: creating the variety of prisms, plates, dendrites, bullet rosettes, capped columns, rimed crystals… any of the seven, 41 or 80 different types of snowflakes, depending on your preferred classification system. Form depends on atmospheric conditions, so certain locales prone to certain weather patterns may consistently produce more of one kind of snowflake than another.
During the early days of Libbrecht’s snowflake research, LIGO and teaching were still his prime responsibilities—snowflakes were wholly a side-endeavor. He wasn’t (and still isn’t) getting any funding from Caltech and, at most, had an undergraduate working with him to grow and photograph the flakes. What he endearingly refers to as his $10,000 a year hobby is sustained entirely through revenue from publishing his photographs, in children’s books, on stationery, and postage stamps. Chances are, if you had a book on snowflakes as a kid during the '90s, it was Ken Libbrecht’s.
So far, Libbrecht has finished eight books on snowflakes (the last is still awaiting publication), richly populated with photographs mostly of “wild” specimens from around the world. Up until relatively recently, his ability to grow “designer” snowflakes in the lab, ones photogenic enough to be published anyway, wasn’t up to snuff, but that changed in the aughts, with practice and drastic advances in digital photography.
Pre-Libbrecht, the accepted authority on snowflake photography was Wilson Bentley, who photographed his first snowflake in 1885 on his family’s farm in Vermont using a black velvet backing, a compound microscope, and a bellows camera – a pretty remarkable collection of technology for his place, purpose and time. That better photos weren’t achieved until over a hundred years after Bentley’s, is a testament to both Bentley’s skill and the relatively vacant research landscape.
Bentley took photographs for no scientifically documented reason. He just wanted to capture what he thought of as “tiny miracles of beauty.” But now the snowflake photography field has flourished dramatically on the Internet, largely thanks to Libbrecht.
When Libbrecht first considered researching snowflakes and saw Bentley’s precedent, he thought, “we could do better than this... and we did”. “We” isn't just Libbrecht's lab anymore. There is now a loyal online community of other burgeoning snowflake photographers. Libbrecht began sharing his photos on Flickr in 2008, and soon other amateur snowflake-photographers arose, taking and sharing impressive and incredibly composed photos of their locally-found flakes, using home-grown techniques. Libbrecht is collaborating now with Flickr-users from Ontario, Moscow and elsewhere for his latest book of snowflake photographs – clearly, demand hasn’t waned.
In the late 1990s, when word of Libbrecht’s research was picking up, he began appearing on local and national television channels, on daytime talk shows like Martha Stewart and popular science features, and graciously slogging through the same repetitive jokes about southern-Californian snowflakes and questions about snowflake uniqueness. In perhaps the only known gig as a snowflake consultant, Libbrecht worked with executives at Disney as an expert on snowflake structures, to ensure that the animated snowflakes of Frozen (2013) were accurate (six-fold symmetry is key). His name appears in the end credits.
Over nearly two decades of research, Libbrecht’s snowflake photography has proved self-sustaining, and he shows no signs of stopping. What began as a scientific inquiry, driven by curiosity, has unfolded into a kind of artist’s dream scenario: the aesthetic pursuit of crafting and photographing snowflakes creates the very objects that fuel the ongoing scientific investigation. Commercial support of the art perpetuates the science – commerce, driving art, driving science. Happy holidays.
Species: Homo sapiens
Habitat: Los Angeles, California
Diet: Omnivorous – Sandwiches, open-faced mostly.
Occupation: Journalist / editor