Kenneth Libbrecht interview: A grand unified theory of snowflakes – Canada Boosts

SNOWFALL in Pasadena, California, is so uncommon, it’s virtually exceptional. 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 much more complex and mysterious than you might think. One of many greatest unanswered questions on them is why they seem to return in two distinct varieties.

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

Joshua Howgego: What acquired you interested by snowflakes?

Kenneth Libbrecht: At some point I used to be chewing the fats with one among my college students and we acquired speaking about how crystals develop and tackle shapes. We began desirous about what we might research on this space and I assumed: effectively, water could be low-cost and simple. Then I assumed: truly, that might be the physics of snowflakes, I ponder 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.

What was the large query about snowflakes?

The usual snowflakes you see in vacation decorations – six-pointed, skinny and flat – effectively, that’s not the best way they at all times kind. In addition to skinny, hexagonal plates, they’ll 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 forwards and backwards 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 best way to reply this query was to systematically develop numerous snowflakes in several circumstances and measure their progress. This was 20 years in the past, and for a number of years I stored hitting issues and made no progress. I ultimately found out the entire experiment must be enclosed in a field. You add in water vapour, however the circumstances, like temperature and stress, should be exactly managed. I’ve all these little rods going into the field that I take advantage of to push issues round and switch issues on and off. Then I might develop crystals – principally 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 review simply.

You latterly printed what has been known as a grand unified concept of snowflakes.

Folks had at all times thought that if in case you have a flat floor in a crystal, it at all times grows in the identical manner below given circumstances. What I discovered is that in snowflakes, the scale of the floor issues quite a bit. When 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 grasp this totally, you have to dig down into the main points in regards to the molecular construction of the ice crystal floor and the way it modifications with temperature on completely different surfaces. To this point, my mannequin appears to suit all the information, so it’s encouraging that a minimum of among the thriller has been solved.

Does your work inform us something about what snow could be like on different worlds, akin to Saturn’s icy moon Enceladus?

The diffusion of water molecules via the air impacts snowflakes’ progress in a manner 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 could be variations in snow on different planets. If there’s no environment, you’re going to get blocky crystals, however at excessive stress you’d get extremely skinny ones. After all, the chemistry of the environment might change this, too, in methods which are laborious to foretell.

You could have additionally grown two an identical snowflakes. I assumed that was presupposed 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 exhibiting a perfect-looking crystal. Finally, I labored out how one can develop crystals on a hard and fast assist and movie them. They seemed so a lot better than crystals that fall from the sky. They had been crisper, sharper. Actual snowflakes have had type of a tough life, falling via the environment and banging into different flakes. They’ve additionally begun to evaporate, so the perimeters are at all times somewhat 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 when you develop two snowflakes subsequent to one another within the field and develop them on the identical time, below the identical circumstances, they arrive out very related. Everyone 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 in the case of snowflakes?

My mannequin could be very difficult. Nevertheless it makes numerous predictions and I need to check 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 known as pre-melting, the place a lot 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 specific purpose… there’s simply at all times one thing new to strive.

Once you exit within the snow today, 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 loads 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 after we exit collectively she’s at all times trying on the completely different vegetation – however all of them appear to be weeds to me.