Kenneth Libbrecht interview: A grand unified idea of snowflakes

By Joshua Howgego

You’ll be able to learn this premium archive article without spending a dime as a part of New Scientist’s 2022 creation calendar. To take pleasure in this and different festive gems, sign-up to grow to be a registered reader without spending a dime.

SNOWFALL in Pasadena, California, is so uncommon, it’s nearly unparalleled. Besides, that’s, on the California Institute of Expertise, the place Kenneth Libbrecht can conjure it up utilizing the world’s most subtle snowflake-making tools.

As a physicist, Libbrecht has tackled some pretty epic questions, like the character of gravitational waves and the inner workings of the solar. However he additionally has a pleasant sideline within the science of snowflakes, that are way more complicated and mysterious than you may suppose. One of many largest unanswered questions on them is why they seem to come back in two distinct varieties.

Libbrecht went on a 20-year odyssey to unravel this thriller. Lately, he revealed the fruits of that journey within the type of a monograph that runs to greater than 500 pages. It accommodates a type of grand unified idea of snowflakes, explaining for the primary time how and why they develop into the fragile shapes they do.

Joshua Howgego: What obtained you curious about snowflakes?

Kenneth Libbrecht: Someday I used to be chewing the fats with one in all my college students and we obtained speaking about how crystals develop and tackle shapes. We began fascinated by what we might research on this space and I assumed: effectively, water can be low-cost and simple. Then I assumed: truly, that may be the physics of snowflakes, I’m wondering how that works? Apropos of nothing – I used to be simply curious – I began studying up on analysis on snowflakes and I discovered it actually fascinating.

“I can flip knobs to manage the circumstances precisely, so I can get these designer snowflakes”

What was the massive query about snowflakes?

The usual snowflakes you see in vacation decorations – six-pointed, skinny and flat – effectively, that’s not the way in which they at all times kind. In addition to skinny, hexagonal plates, they will develop into tall, hexagonal columns, like the form of a pencil in miniature. It was found in Japan within the Nineteen Thirties that these two types of snowflake will kind at completely different temperatures. Plates will kind at round -2°C, columns at about -5°C after which plates once more at about -15°C. It’s such a loopy sample that it flops backwards and forwards like that. I actually needed to know why it occurs, nevertheless it turned on the market was no reply – it was a whole thriller.

How did you examine this conundrum?

I made a decision the way in which to reply this query was to systematically develop numerous snowflakes in numerous circumstances and measure their progress. This was 20 years in the past, and for a number of years I saved hitting issues and made no progress. I ultimately found out the entire experiment needs to be enclosed in a field. You add in water vapour, however the circumstances, like temperature and strain, must be exactly managed. I’ve all these little rods going into the field that I exploit to push issues round and switch issues on and off. Then I might develop crystals – largely I grew ones which are smaller than the width of a human hair after which studied them below a microscope. In the event that they get too massive, they’re too difficult in form to check simply.

You lately revealed what has been referred to as a grand unified idea of snowflakes.

Folks had at all times thought that when you have a flat floor in a crystal, it at all times grows in the identical approach below given circumstances. What I discovered is that in snowflakes, the dimensions of the floor issues rather a lot. In the event you think about a hexagonal, plate-like snowflake, it has two broad surfaces after which six a lot thinner surfaces across the edge. It seems that these thinner surfaces develop a lot quicker than the broader surfaces, and this creates a runaway impact the place you get thinner and thinner plates. The enjoyable factor is that this pattern reverses – at sure temperatures, it’s the broader surfaces that develop quicker, and so that you get column-like crystals.

To know this totally, it’s essential to dig down into the small print in regards to the molecular construction of the ice crystal floor and the way it modifications with temperature on completely different surfaces. Thus far, my mannequin appears to suit all the info, so it’s encouraging that a minimum of a few of the thriller has been solved.

Does your work inform us something about what snow can be like on different worlds, reminiscent of Saturn’s icy moon Enceladus?

The diffusion of water molecules by way of the air impacts snowflakes’ progress in a approach that reinforces the molecular results to create the skinny edges seen in plate-like and hollow-column crystals. After I develop crystals in a vacuum, none of this occurs. So, yeah, there can be variations in snow on different planets. If there’s no environment, you’re going to get blocky crystals, however at excessive strain you’d get extremely skinny ones. After all, the chemistry of the environment might change this, too, in methods which are onerous to foretell.

You’ve gotten additionally grown two an identical snowflakes. I assumed that was alleged to be not possible.

This began when, early on in my snowflake work, I realised there have been no good movies of snowflakes rising. I needed to make one displaying a perfect-looking crystal. Ultimately, I labored out the best way to develop crystals on a set assist and movie them. They seemed so a lot better than crystals that fall from the sky. They have been crisper, sharper. Actual snowflakes have had type of a tough life, falling by way of the environment and banging into different flakes. They’ve additionally begun to evaporate, so the sides are at all times a bit of rounded.

Within the lab, although, I can flip knobs to manage the circumstances precisely – I may even change issues barely to make the rising crystals department – and so I can get these designer snowflakes. Then I realised that should you develop two snowflakes subsequent to one another within the field and develop them on the similar time, below the identical circumstances, they arrive out very related. All people appears to have heard this outdated adage that no two snowflakes are alike, however then this loopy individual is making snowflakes which are alike.

What sorts of questions are nonetheless unanswered with regards to snowflakes?

My mannequin may be very difficult. But it surely makes numerous predictions and I wish to take a look at these out, see what occurs and hopefully refine the mannequin. One of many predictions is that attention-grabbing issues may occur to snowflakes near their melting level. You may see what’s referred to as pre-melting, the place many of the snowflake is a inflexible crystal, however on the floor the molecules get disordered. I’ve been attempting to discover that. I’m additionally attempting to make bigger crystals; I’d wish to make the world’s largest snowflake. For no explicit purpose… there’s simply at all times one thing new to strive.

Whenever you exit within the snow lately, do you see it in a brand new gentle?

I grew up in North Dakota, the place it will get very chilly and now we have numerous snow. I used to see six-pointed star flakes, massive ones, however I didn’t know any of these things. Now I do know lots higher what to search for. I’ll exit and have a magnifier and be on the lookout for completely different sorts of flakes – like capped columns, as an illustration, that are like a particular hybrid of the plate and column varieties. I name it snowflake watching. The humorous factor is, my spouse is a botanist, and once we exit collectively she’s at all times trying on the completely different crops – however all of them appear like weeds to me.