Kenneth Libbrecht interview: A grand unified idea of snowflakes

By Joshua Howgego

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SNOWFALL in Pasadena, California, is so uncommon, it’s nearly remarkable. Besides, that’s, on the California Institute of Know-how, 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 interior workings of the solar. However he additionally has a pleasant sideline within the science of snowflakes, that are way more advanced and mysterious than you would possibly assume. One of many largest unanswered questions on them is why they seem to come back in two distinct sorts.

Libbrecht went on a 20-year odyssey to unravel this thriller. Not too long ago, he printed the fruits of that journey within the type of a monograph that runs to greater than 500 pages. It incorporates a form 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 every of my college students and we obtained speaking about how crystals develop and tackle shapes. We began occupied with what we might examine on this space and I believed: nicely, water could be low-cost and simple. Then I believed: truly, that will 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.

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

What was the large query about snowflakes?

The usual snowflakes you see in vacation decorations – six-pointed, skinny and flat – nicely, that’s not the best way they at all times type. 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 type at completely different temperatures. Plates will type 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 wished to know why it occurs, but it surely turned on the market was no reply – it was an entire thriller.

How did you examine this conundrum?

I made a decision the best way to reply this query was to systematically develop loads of snowflakes in several circumstances and measure their development. This was 20 years in the past, and for a number of years I saved hitting issues and made no progress. I ultimately discovered the entire experiment must 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 take advantage of to push issues round and switch issues on and off. Then I might develop crystals – principally I grew ones which can be smaller than the width of a human hair after which studied them underneath a microscope. In the event that they get too giant, they’re too difficult in form to review simply.

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

Folks had at all times thought that in case you have a flat floor in a crystal, it at all times grows in the identical manner underneath given circumstances. What I discovered is that in snowflakes, the scale of the floor issues rather a lot. In case you think about a hexagonal, plate-like snowflake, it has two huge 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 development reverses – at sure temperatures, it’s the broader surfaces that develop quicker, and so that you get column-like crystals.

To know this absolutely, 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. Thus far, my mannequin appears to suit all the info, 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 by way of the air impacts snowflakes’ development 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 will 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 can be laborious to foretell.

You may have additionally grown two an identical snowflakes. I believed that was alleged to be unimaginable.

This began when, early on in my snowflake work, I realised there have been no good movies of snowflakes rising. I wished to make one exhibiting a perfect-looking crystal. Finally, I labored out the right way to develop crystals on a set help and movie them. They regarded so a lot better than crystals that fall from the sky. They have been crisper, sharper. Actual snowflakes have had form 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 rounded.

Within the lab, although, I can flip knobs to regulate 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 if you happen to develop two snowflakes subsequent to one another within the field and develop them on the similar time, underneath the identical circumstances, they arrive out very comparable. Everyone appears to have heard this previous adage that no two snowflakes are alike, however then this loopy individual is making snowflakes which can be alike.

What sorts of questions are nonetheless unanswered in terms of snowflakes?

My mannequin may be very difficult. Nevertheless it makes loads of 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 would possibly occur to snowflakes near their melting level. You would possibly see what’s referred to 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 prefer to make the world’s largest snowflake. For no explicit cause… there’s simply at all times one thing new to attempt.

If you exit within the snow nowadays, do you see it in a brand new mild?

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