Nature's Archive Podcast

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[00:00:00] Michael Hawk: All right, Dr. Libre, thank you so much for joining me today. This is gonna be a really fun discussion, I think.

[00:00:04] Dr. Kenneth Libbrecht: I hope so.

[00:00:05] Michael Hawk: Yeah, and I’m super honored to have you here on Nature’s Archive because you know, most of my guests in the past as we were talking about it, kind of ecology centric, but there’s really nothing more fundamental to nature than physics.

[00:00:18] And you know, snow and snowflakes are nature too. So I think we’re gonna be able to go down maybe a slightly different path today than typical, and it’s gonna be a lot of fun. I reached out to you because I’ve heard you on npr. I’ve seen you in lots of different places. Veritasium had a great segment, and I came to realize, as I was researching this, I remember these wonderful US Postal Service stamps from, I don’t know, 10 or 15 years ago that had snowflakes on them.

[00:00:46] And I came to realize here that those were actually your photos.

[00:00:51] Dr. Kenneth Libbrecht: Yeah, that was a long time ago. 2006 I believe. I was sitting in my office minding my own business, as I like to say, and the post office called and said, Hey, we saw your pictures. And we were thinking about putting ’em on stamps and it was just like, awesome.

[00:01:06] My guy at the post office said they, they printed up like 2 billion of those.

[00:01:10] Michael Hawk: They were popular. I bought plenty of them. I remember I had them on hand for a while. I just thought they were so cool and so different. And you know, at the time I remember learning that they were actual real snowflakes. They weren’t like an artist rendition of a snowflake. And that just blew my mind. So this is the core of the topic today is snowflakes.

[00:01:28] And why do they look the way they do? How do they form what can we learn from them? So many different side threads that we can go into, maybe to kick things off. You know, I normally ask my guess, you know, how did you get in interested in nature in the first place? And in your case, Nature has a deeper meaning.

[00:01:45] You know, it’s this physics base. So how or when did you recognize that you had this interest?

[00:01:51] Dr. Kenneth Libbrecht: Well, I’m a professor in physics and I do research on a variety of topics and this kind of just popped into my head 25 years ago, that crystal growth and just the molecular dynamics of how crystal growth was kind of an intriguing subject. And I was talking to somebody, one of my students about it and just kind of realized quickly that ice was the ideal material to look at cuz it was just there and cheap and.

[00:02:17] And that was like well, that’s the physics of snowflakes. I said to myself. And so, so I started reading about it cuz you know, it’s how you start doing research is you start reading. And of course people have been looking at snowflakes and pondering how, where they come from and how they grow for centuries.

[00:02:35] And the first real scientific inquiry into snowflakes was by Johannes Kepler, who did work on planetary science and Kepler’s third laws and orbit of Mars and all these very famous scientists. And he saw snowflakes and just, they’re all six sided. And he wondered why they were six sided. And he wrote this little treatise on that question

[00:02:55] and he didn’t know it was 400 years ago. There was no Atomic theory of matter back then. Not much anyway. But he decided that, you know, when you stack things like you stack cannonballs, you get a hexagonal pattern. you stack uh, anything round, you get a hexagonal pattern. And so he just decided that maybe stacking had something to do with it, and he left it at that saying he didn’t really understand it, but maybe stacking was related

[00:03:21] and sure enough, about 300 years later, people figured out that crystals were made of molecules stacked together and they stacked together in different ways. And one way they stack is in a hexagonal arrangement, which is how water molecules stack up. And that’s, you know, the underlying physics of why they have the sixfold symmetry.

[00:03:39] But then you can keep the science going and ask us why they have these different shapes. anyway, it just got to be a very interesting subject for me. The more I read about it, the deeper I got into it, the kind of more interesting it was. And it’s still something I’m working on even after 25 years.

[00:03:55] There’s a lot of good physics left to appreciate.

[00:03:59] Michael Hawk: how would you characterize Would you call it snowflake, genesis, or ice crystal genesis, or you know, what’s the proper term there?

[00:04:05] Dr. Kenneth Libbrecht: I call it, you know, physics of snowflakes, but you could call it crystal morphogenesis , but really it’s just the physics of how molecules combine and connect together. From, in this case, a gaseous state water vapor to a solid state. And if they just formed a block of ice, that would be somewhat uninteresting.

[00:04:24] But they don’t do that. They tend to form in these very elaborate patterns. And the ones that we know about most, the canonical holiday snowflakes are these sixfold stars thin plates. That’s what we call ’em flakes, because they’re thin plate like crystals. But when I started reading about this, first thing I learned which people had known for about the last hundred years is that this is not the only type of snowflake.

[00:04:50] You also can see a column or snowflakes. So imagine a hexagonal wooden pencil that’s a columnar snowflake, and they fall out of the sky very readily. . And there are a whole just menagerie of exotic forms capped columns. You start with a column or snowflake, and then you put two plates, one on either side.

[00:05:09] Like two wheels on an axle, and that’s called a cap column. And those are, they’re out there. They’re somewhat rare but easy to find. Nevertheless, if you go looking for them hexagonal plates and columns, and there’s even triangular crystals, sometimes all kinds of wacky stuff if you just go looking for it.

[00:05:28] And the funny part was that people just didn’t understand this at all. That intrigued me as a scientist that, you know, here’s this stuff. It falls out of the. It seems simple. It’s just water vapor, turning to ice, and yet when you get down into the details you find that there’s a lot of really enigmatic things going on, and I’ve made some progress in explaining some of these things, but there’s still a lot to understand.

[00:05:55] Michael Hawk: I had a guest, it was about a year ago. Tell me about this concept. The illusion of explanatory depth. And it’s basically when you see something, when you work with something day in and day out, you start to believe that you understand it, even if you have no basis for that belief. and I think that snowflakes are a really great example of that.

[00:06:14] It’s something you just, you’re aware of them, you see them most people anyway in the Northern Hemisphere from a very young age. And maybe that’s why so few people had really dug into it. The way you have is because it was just taken for granted and you started looking at this and seeing this. I wanted to point out before I forget your website, snow crystals.com.

[00:06:34] Dr. Kenneth Libbrecht: That’s right.

[00:06:35] Michael Hawk: You have photos showing all of the different forms that snowflakes can take, including the capped column that you mentioned, which is super cool. So are all of these, even though if they don’t look like it, they’re six-sided.

[00:06:48] Dr. Kenneth Libbrecht: Mostly like I said, sometimes they’re a little bit more triangular in shape. But the underlying symmetry is always from the molecular stacking of the crystal. And so that’s always sixfold.

[00:07:00] Michael Hawk: So maybe you can walk us through in a little more detail how snowflake forms in nature. We can start there. Cause I know you also create them in the lab and that’s pretty fascinating too.

[00:07:10] Dr. Kenneth Libbrecht: , you’re right. And that when you see something a lot, you start to think that maybe it’s understood and and you just sort of grow accustomed to it. People think of, what are the great mysteries of science, you know, out in the outer reaches of the universe.

[00:07:23] And it’s oh, just look down at your hand. That’s a big mystery. . What does any of that work? How did it grow in the first place? It came from, you know, some molecular blueprint, which we don’t understand anyway. So it’s the same is true of lots of things.

[00:07:37] When you look at them more carefully, you find that you don’t understand nearly as much as you thought. so as I started reading about snowflakes, there were these various questions about why the morphology, the shape of the crystal changes so much with temperature into these columnar and platelet shapes.

[00:07:56] And people have been puzzling over that for many years. So I started studying it in some detail. So let’s get back to how uh, a snowflake forms in the atmosphere, cuz that part is fairly well understood. You start with a cloud, okay? And a cloud forms from water vapor in the air. So the water evaporates, you get water vapor in the air, and then as the air cools, that water vapor will start to condense.

[00:08:21] And and there’s a rule in physics that you don’t condense from the vapor to the solid state immediately. You tend to go through the liquid state unless there’s some solid already available. And so when the water vapor starts to condense in the atmosphere, it condenses into liquid droplets.

[00:08:37] Even when it’s below freezing. And so you get a cloud that is made of liquid droplets and each droplet condenses on a little piece of dust. And so these droplets are a few microns in size, tens of microns in size, they all contain some dust and they’re all floating around in a big cloud. But there’s still liquid water.

[00:08:58] As the cloud starts to get cool so maybe it rises cuz the cold front goes in the cloud rises in the atmosphere and it starts to cool. And it, when it gets to about minus five Celsius or mi colder so that’s 20 degrees Fahrenheit. That’s when the ice starts to freeze.

[00:09:16] It doesn’t freeze at the normal freezing point. It has to get colder than that. And so the water initially is super cooled and each of the droplets are super cooled. But then some of them will start to freeze just one by one. They will get cold enough and it depends on what dust they contain. Some of the dust particles will nucleate freezing process at higher temperatures, and so some of the droplets will freeze.

[00:09:40] And so those then are a little drops of ice small round particles of ice, and they’ll start to grow by absorbing water vapor from the. And that water vapor is supplied by the liquid droplets, which start to evaporate. And so the solid ice droplet will grow and grow into a snowflake while the surrounding liquid droplets will evaporate.

[00:10:03] And it takes about a hundred thousand liquid droplets all evaporating to make one good size snowflake. , once this crystal gets big enough, then it will start to fall and eventually falls to the ground and land on your sleeve and you can have a look at it. And the whole growth process maybe takes half an hour, 45 minutes, depending on various conditions

[00:10:25] Michael Hawk: So any flake that we see landing on the ground was a good 30 to 45 minutes in the making.

[00:10:29] Dr. Kenneth Libbrecht: usually.

[00:10:30] Michael Hawk: Wow. So in, in a typical scenario that you described, then there’s a mix of of ice crystals and water droplets. Together. That’s interesting to think about. So even if it was much colder, you know, you mentioned around negative five Celsius is where some of these droplets start to freeze.

[00:10:46] If it was colder still, do you still get the super cooled water droplets occurring or is there a point where it just, everything is frozen?

[00:10:53] Dr. Kenneth Libbrecht: If you get cold enough, then the time it takes to freeze is very short. And that happens around minus 35, Celsius minus 40 and minus 40 Celsius and minus 40 Fahrenheit are the same. So that gives you a reference. But yeah, if it gets cold enough then everything’s frozen. But normally snowfall start at higher temperatures and and the cloud starts as a, with liquid water droplets.

[00:11:18] And as it gets colder, it’ll start to snow, the droplets will freeze, and by the time it gets to minus 20 Celsius, say most of the droplets have frozen or evaporated. And what’s left over is just little ice particle. And and so people talk about that it can be too cold to snow. That’s true.

[00:11:38] The snowfalls typically form around minus five, minus 10, 15, 20. But if it, as it gets colder and colder, it’s already snowed basically. And what’s left in the air is very dry. So yeah, once it gets down to 2030 below Fahrenheit, then it’s just too cold to snow anymore.

[00:11:57] Michael Hawk: Yeah, it, I think a general principle is the colder the air, the less moisture content, the less carrying capacity that it has.

[00:12:04] Dr. Kenneth Libbrecht: Yeah. That and the fact that once the water, liquid water droplets freeze to snow, then freeze to ice, then it doesn’t make snowflakes anymore. There’s no nothing to drive. You’ve gotta have the, that water evaporating to grow snowflakes from.

[00:12:20] Michael Hawk: Interesting. I never realized that you need this nearby evaporation happening concurrently for this to occur.

[00:12:26] Dr. Kenneth Libbrecht: And weather’s kind of a complicated thing when you get into the details.

[00:12:31] Michael Hawk: , you made an excellent point by your hand is a complicated thing, , so Yeah. Yeah. The deeper you look, one of the things that really caught my eye is this idea that you need some sort of condensation nuclei, the dust or pollen or whatever it is that begins to allow this water droplet to form what would happen just as a thought experiment.

[00:12:51] If the air was pure and we didn’t have any of these condensation nuclei, what would occur then?

[00:12:56] Dr. Kenneth Libbrecht: It, you would just have to get colder and colder. Eventually water vapor will condense on its own even if there’s no dust. But it happens much more readily in the presence of dust and there’s almost always dust in the air. It’s hard to make pure. That doesn’t condense, but in the lab we can do that.

[00:13:14] We kind of, some of the experiments we do are kind of self-cleaning. We make the super saturation so high that the droplets will form on dust particles and then pull them out of the air. And so the super saturation, which is the humidity, can be much higher. And so we can obtain conditions in the lab that are much higher humidity than we can do in the see in the clouds.

[00:13:36] So we can actually make different kinds of snowflakes that don’t appear in the clouds as well.

[00:13:42] Michael Hawk: and are those some of the ones that you refer to as designer snowflakes?

[00:13:46] Dr. Kenneth Libbrecht: The designer snowflakes. We, I, we like to make snowflakes, right? I like to make snowflakes that in the lab they look a lot like these canonical holiday snowflakes. Those are the most , beautifully formed things. And so those are a lot like what fall out of the sky. It’s just that we can make them a little cleaner.

[00:14:02] We can make them very symmetrical and we can make them just two nearly identical ones, which is kind of fun. Some of the other kinds we form are these highly dendritic structures, very high humidity. They don’t fall out of the sky and they’re a little weird looking, but they have a place, it’s just they don’t fall out of the sky normally. That kind of stuff is helpful when we’re trying to really explore the physics, cuz we like to be able to create unusual conditions. And then it all tries to, you know, you’d like to form a theory that sort of everything holds together. And so it’s nice to have a lot of different conditions to grow crystals in.

[00:14:40] Michael Hawk: That makes sense. You can control the variables and really test the boundaries then in, in that environment. But I kind of got a little ahead of myself. I wanted maybe to talk a little bit more about some of the natural ice crystal. That form and how this relates to different precipitation types people might be familiar with.

[00:14:58] So I I grew up in Nebraska and in Nebraska we had all types of ice formation from freezing rain to sleet, to grapple, to snow. And within that, like maybe you can help us understand a little bit what is, what would be a scenario where these water droplets would fall as freezing rain, for example, as opposed to actually turning into an ice crystal.

[00:15:22] Dr. Kenneth Libbrecht: Well, Freezing rain is usually when you first make rain and then the droplets freeze on the way down. Grapple is when you have a lot of droplets and some ice, and then the droplets will hit the ice and stick. And so sometimes you get these funny things where you’ll make a fully formed snowflake with a stellar structure, and then it runs into a dense part of the cloud with a lot of droplets.

[00:15:50] And the droplets will hit and stick and freeze. And so you end up with a hexagonal, blobby thing with a lot of little ice particles stuck to it. But usually grapple is also called soft hail. And that’s when you take a bunch of little frozen droplets and stick them together. And that’s, that, just those are just kind of dense particles.

[00:16:13] You also get these puff balls, which are individual, a bunch of individual snowflakes, which are light and airy, and they stick together, but not very densely. So imagine these very thin plate that’s got branches and side branches on it. And uh, these act like barbs. And so when they stick together, they tend to stick together at the tips.

[00:16:33] And so they form a very lightweight structure. And these are little puff balls that fall out of the sky. And and those are the kinds that are fun to catch on your tongue because they’re big and they’re not falling very fast. And if you just look straight up, you see them falling toward you and you just, your mouth naturally opens and your tongue comes out and you you have to try to catch them.

[00:16:54] So that’s just great fun.

[00:16:56] Michael Hawk: And you said those are essentially multiple flakes, then that just kind of stuck together.

[00:17:00] Dr. Kenneth Libbrecht: Yeah, usually hundreds of thousands of flakes stuck together. But as opposed to grapple, which is much more dense and that’s just a little ball of ice falling out the sky. So it falls very fast.

[00:17:11] , if you look at your sleeve when you’re outside, you can see all of this stuff all the time. And it depends a lot on the conditions that you’re looking at. Of course, cuz different types of crystals fall into different conditions and most people, they really wanna see some beautiful holiday style stellar crystals when it’s warm outside so they don’t have to get too cold and that doesn’t work that way.

[00:17:37] if you wanna see some really nice snowflakes they only form these stellar crystals only form in a fairly narrow temperature range, around minus 15 Celsius, five degrees Fahrenheit, which in most people’s book is pretty cold. And I’ve taken a lot of photographs of snowflakes over the years.

[00:17:56] And I live in Los Angeles, so no snow here. And I travel around to cold places. And minus 15 Celsius is pretty much the edge of civilization. That’s the average temperature in January. That’s when people start not wanting to live there. And so I usually go to these places that are kind of on the edge.

[00:18:16] You can still get a flight there but it’s pretty cold. The exception was Fairbank’s, Alaska, where it’s often 40 below and people like to live there. That’s an adventure all its own. But so the key to finding nice snowflakes is cold.

[00:18:31] If you want nice, stellar crystals and when it’s warm, you tend to get all this sort of glossy stuff. and then of course you get different snow when it’s snowing hard or if it’s windy. And so you have to be kind of patient. If you want to see, you know, really beautiful stellar crystals and it helps deva magnifying glass of some kind, a little $5 magnifier is great.

[00:18:54] You go outside and you can just sort of see what’s falling. Of course I grew up in North Dakota and it never really occurred to me to look carefully at these things. There’s only, when I moved to California, Southern California, no less that I started looking at snowflakes very seriously. And I like to say it’s, you know, it’s partly because when you live in the snow you don’t really like it so much.

[00:19:17] Oras, I also like to say it’s easier to appreciate a snowflake when you don’t have a shovel in your hand. But if you do live in a cold climate, it is great fun to go outside and look at the snowflakes and it’s a little treasure hunt. Sometimes you see some great stuff and sometimes you don’t like beach combing.

[00:19:32] So I, I think it’s great fun.

[00:19:34] Michael Hawk: So I know a lot of my listeners being naturalists, they have different kinds of macro photography gear either for their phones or dedicated cameras, and it seems like a natural question. Then since we’re talking about going out and looking at snowflakes up close with magnifying glass, how might somebody go about photographing a snowflake even if it’s not one of these ideal wines?

[00:19:56] I think they’re probably still pretty fascinating to look at.

[00:19:58] Dr. Kenneth Libbrecht: Certainly the photographing snowflakes is a, is another great hobby. And I would say that looking at the crystals with a magnifier is the first step because a lot of people tend to assume that every snowfall has these beautiful snowflakes, and that’s not true. And so if you go out and look with a cheap magnifier, you can soon kind of size.

[00:20:19] What kind of crystals you’re going to see. And it’s a little like if you look at mineral crystals, if you get by a book of mineral crystals, you see these gorgeous, faceted, almost gem like minerals. But if you go out walking around in the mountains, all you see is a bunch of rocks. It’s a little like that when you’re snowflake watching.

[00:20:39] So the first step if you wanna photograph snowflakes is just go outside and see what you got in your backyard, see if it’s worth photographing. But then there’s lots of online discussion of how you photograph snowflake.

[00:20:51] It’s become pretty popular Javi for a lot of people. It’s become kind of a thing now to see how good a snowflake picture you can get just with a smartphone. Because a lot of smartphones have pretty respectable macro capabilities now, there’s a lot you can do in photographing snowflakes, and I find that just looking at them with a magnifier already gives you a wonderful view. But a cheap microscope, not super cheap, but it doesn’t have to be very expensive, gives you an even better view.

[00:21:20] And then you can see smaller crystals and some of the smaller ones up close are quite fascinating and they have beautiful facets.

[00:21:29] Michael Hawk: what would you want to capture one of these snowflakes on to look at up close? Like you mentioned your sleeve. You could, you know, of course you could look at your sleeve when they land there, but I’m guessing there’s a better surface that you could collect them on.

[00:21:39] Dr. Kenneth Libbrecht: When I’m photographing I usually use a piece of black or blue foamcore. It’s cuz it’s smooth and dark. And when you’re photographing snowflakes you are often out at night cuz that’s when it’s cold. And also if you’re up far enough north to find good snowflakes, it’s usually dark cause it’s the middle of winter.

[00:21:59] And so a light is good and street lights are fine, or porch lights and and they’re even better because with a porch light or some point like source of light you can really see the sparkle very nicely. And so that’s how you can tell you really got some good snow is when you can, when if the snow is sparkly, when it comes down.

[00:22:19] Those are really nice crystals.

[00:22:21] Michael Hawk: I remember one time trying to photograph snowflakes and I didn’t plan ahead very much, and I had a, it’s like a piece of black plastic, and the major mistake I made is I didn’t let it get cold. So , so I brought it outside and the flake, of course just melts right away. So, after, five or 10 minutes, it was fine.

[00:22:39] I was able to do it and and as you said, it wasn’t the right conditions. They weren’t these beautiful, , movie style snowflakes, but they were still a lot of fun to look at and photograph and work on technique and so forth. So there’s always an opportunity.

[00:22:53] And I won’t try to explain my train of thought here because it would be very convoluted, but you were talking about how the flakes can look different too, depending on not just the moisture and temperature, but also wind conditions. So tell me a little bit more about that with wind.

[00:23:06] Can flakes actually get torn apart from wind or is it that they’re accumulating together from the wind?

[00:23:11] Dr. Kenneth Libbrecht: I grew up in North Dakota. It’s always windy in North Dakota. And yeah, everything just gets kind of beaten up. So the crystals break and they just slime into one another. So it’s much better if you’ve got a very calm, quiet almost eerie conditions make the best crystals. And I, I always like this little town up in northern Ontario by the name of Cochrane. It snows a lot and it’s very calm and just the right temperature. And I’ve seen some of these crystals falling, big stellar crystals.

[00:23:41] They’re about the size of a dime a centimeter from tip to tip, and I photographed some of those. They’re very, And I think they’re still the largest snowflake, snow crystals ever photographed. And it was just like these ice flowers falling out of the sky and they just drifted down very slowly. And so you could easily see with a little bit of wind, they would just be torn to shreds cuz they’re just little ice doilies.

[00:24:06] And it wouldn’t take much to break ’em up. And those, I only saw those twice, for 10 minutes at a time. these things are quite rare and you gotta stand out and watch a lot of snow before you see these.

[00:24:19] Michael Hawk: How do you catch something like that without a breaking upon.

[00:24:22] Dr. Kenneth Libbrecht: Oh, I just had my foam core. And they would fall on there and some of them break, but some of them don’t. They are the smaller ones, say four or three millimeters in size, they are remarkably durable in that they will fall on a piece of cardboard and rarely. They’re stronger than they look.

[00:24:39] And in fact, once they would fall on a, my phone cord, I would pick them up using a little paintbrush and then drop them under a microscope slide and put them under my microscope to photograph. And all of that was pretty easy and they didn’t much break. The worst part was I would pick one up and I’d be about to put it on my microscope slide and then a little gust away and a poof, and it was gone.

[00:25:00] I’m like, no, I wanted that one. And that was a really good one. Now when I say I’m looking for a good ones, my phone, my foam core would just get covered with snow every few minutes. And and by covered, very loosely covered for the, with crystals. So there may be a couple of thousand crystals on the board and there might not be any that really look very nice.

[00:25:22] Because most of them are a little lopsided and broken or this or that. There’s just all kinds of things that they’re perfectly fine to photograph, but they’re not the beautiful stellar crystals very symmetrical.

[00:25:34] , so I would just brush the snow away every couple of minutes and wait for some more to fall. And your eye is really good at picking out these large symmetrical crystals. You know, your eye just recognizes patterns instinctively. And so you just glance and after a while you can really just see the good ones.

[00:25:51] And so a lot of the photographs I show people on my website, they’re like literally one in a million crystals, cuz I’m brushing off a thousand crystals every few minutes. And you do that for hours on end. And then you take the very best pictures from all of that. And you say, look, a characteristic snowflake,

[00:26:11] That’s what falls out of the sky. And people have, you know, questioned me once I got an email once somebody said, you know, it’s I read your theory of how snowflakes form and that can’t be right cuz they’re all perfect and that wouldn’t happen. And it’s yeah, you gotta go outside and look at the snow a little more if you think they’re all perfect, cuz they’re certainly not

[00:26:31] Michael Hawk: I really like this discussion because there’s so many parallels I’m thinking of when it comes to some of the naturalist endeavors that I do and that my listeners. Do you develop this search image if you’re out looking for something. To your point your brain kind of knows what to look for and you can find this tiny little three millimeter fly that nobody else would see.

[00:26:53] But because you know what to look for and your brain is accustomed to looking for that, you can find it. And it sounds like that’s exactly what’s happening for you when it comes to snowflakes.

[00:27:01] Dr. Kenneth Libbrecht: Oh yeah you can sort of train yourself a little bit. But it’s frustrating for the beginner. It’s like when you go bird watching and if you go bird watching with some seasoned bird watchers, they will just see so much more than you can see , , they just see a glance of something and yep, I know what that is.

[00:27:19] Michael Hawk: So these, you were talking about these really large flakes that were falling the size of a dime. Now they’re very thin, right? Like they’re the growth pattern is almost two dimensional.

[00:27:30] Dr. Kenneth Libbrecht: Very much so.

[00:27:31] Michael Hawk: About how thick would that snowflake be on its like on the thin dimension?

[00:27:36] Dr. Kenneth Libbrecht: So maybe , 10 millimeters in diameter, but maybe a 10th of a millimeter or so in width. They’re not quite flat, they’re a little wavy, so, so it’s not perfect, but but yeah, we call ’em flakes because they’re thin and flat.

[00:27:48] Michael Hawk: So why don’t we do this? Why don’t we talk a little bit about your lab, and I’m gonna recommend that everybody checks out that Veritasium video that I mentioned at the beginning, because you can actually see some of the lab work that you do in that video.

[00:28:01] But tell me a little bit about your lab and what it is you’re doing, how you’re growing snowflakes and what you’re looking to achieve.

[00:28:07] Dr. Kenneth Libbrecht: goes back a long time too, in that the first person to really grow snowflakes in the lab was a Japanese physicist here in Naka in the thirties, 1930s. And and that’s when you really start to see what’s going on because you can grow crystals under well controlled conditions and then see what happens.

[00:28:27] And whereas , in nature, crystals fall and you know the temperature on the ground, but you don’t know if the temperature and the humidity up in the clouds, and it’s quite variable. . You can learn a lot by growing crystals under well controlled conditions. And when I first started reading about this 25 years ago, that was my first impression.

[00:28:46] I’m a experimental physicist. I like to measure things and build experiments to measure and things quite precisely. The existing measurements at that time just weren’t really good. They were just few crystals grown and conditions that weren’t quite as well controlled as one would like. And so that was my first inclination was to start making really precise measurements of growth rates, because that seemed to me the way to make progress in understanding the theory and the physical processes that are involved in making these crystals.

[00:29:22] And so that’s what I do. I started just slowly learning how to make crystals in the lab. And in the beginning, I didn’t know what I was doing at all. I’d make these styrofoam boxes and put some dry ice in there to get cold and, you know, you could make crystals, but didn’t know what I was doing very well, and you couldn’t measure much.

[00:29:42] And then I slowly graduated to getting a refrigerator of recirculating chiller and lots of temperature control, and then some good optics. And over quite a few years, just really kind of developed these techniques for growing crystals in different environments. Not only changed in the temperature and the humidity, but also the air pressure.

[00:30:03] We’ve grown crystals using different chemical additives in the air to see what that does. And always the goal is just to measure as many things as we can and try to understand just the growth and make these theories of what’s going on. And the biggest puzzle at the time when I started was just this business that when you grow crystals at different temperature, you get different morphologies and just below freezing say minus two Celsius, you get plate like crystals and then a little colder minus five you get columns.

[00:30:37] And then at minus 15 you get really thin plates. And then if you go to like minus 30, you get columns again. This has been a puzzle’s why you have these transitions from plates to columns, to plates to columns . Used to change the temperature. And it really is hard to understand because it’s just water vapor freezing and ice.

[00:30:55] Your natural income inclination is to think, that’s not a hard problem. It’s just a phase transition. And, you know, we freeze things all the time and we’re supposed to know how that works. . As I like to say, it was a bit of an embarrassment to the scientific community that this stuff was falling out of the sky.

[00:31:14] And we didn’t know , we didn’t know what to make of it. So I made a bunch of measurements and it’s complicated. You know, I can’t really explain it to you in a short amount of time. It’s, cuz it’s, there’s a lot going on at once. There’s sort of the molecular, what’s called the attachment kinetics, which is just how the molecules stick.

[00:31:32] And then there’s diffusion through the air, which changes the shape as well. And then there’s these weird things like pre melting where the top layers of ice will start to melt a little bit. Just below freezing, the whole block of ice doesn’t melt, but the surface does. That’s called pre melting.

[00:31:49] And that’s a well-known phenomenon. And that changes with temperature on the different facets of ice. And so there’s different prem melting on different surfaces, and this is all happening at once as you change the conditions and. And slowly, I slowly kind of put together a theory where I can kind of explain it all.

[00:32:08] It’s quite a beast of a theory, so . It’s not like, Eureka. This is this one thing that now explains everything. And if it were that simple, people would’ve thought about it 50 years ago. It’s just a whole lot of little eurekas when then you have to carefully stack them all together and then it all fits together. So I started making measurements, doing targeted experiments based on the predictions. And I found that it really seemed to hold up pretty well. And one of the things, for example I did recently, which I’m very proud of , although it’s a weird thing to be proud of, but the theory predicted in a fairly clean way exactly when you could grow triangular snowflakes, , believe it or not, and instead of hexagons, almost ecological triangles with the corners dinged off a little bit.

[00:32:58] So, but very triangular in shape and it’s only at temperatures around minus 14. And the humidity has to be just at this, very specific value when there’s this transition happening. People had seen triangular crystals falling from the sky for about 150 years. But of course that was another weird mystery. So I tuned up on my, my equipment and went to that temperature and lo and behold I got triangular crystals.

[00:33:27] And you know, it’s one of those things that it’s kind of simple, but the theory, it made sense and the theory explained. It, It was a kind of thing where you see it and you go this is really working. I, whenever you make a theory, you’re never sure if it’s right or not. You’re making the stuff up as you go along and you, it’s a lot of guesswork involved.

[00:33:47] That’s how science works. And you just make educated guesses. And then when you you put the guesses together into this lumpy theory. The theory makes predictions. And then you go into the lab and you see the predictions come true and you go, God, that’s really, this might actually be right.

[00:34:05] And , that’s very satisfying. So, so I think I’m on the right track, at least, you know, for what it’s worth.

[00:34:12] Michael Hawk: I can only imagine how satisfying that would be to be able to go and actually test it and see it, and you know, right before your eyes materialize in the way that you were hoping it would

[00:34:22] Dr. Kenneth Libbrecht: Yeah. It’s not like this is good for anything. It’s it’s just . It’s like I can grow triangular crystals in just a certain way. It’s not gonna cure into diseases or anything. But I to say too there’s 8 billion people on the planet. Maybe one or two of us can be spared, ponder how snowflakes work.

[00:34:40] not everybody, just a few.

[00:34:42] Michael Hawk: Yeah, we just hit 8 billion. So I think that one or two of those people can do this. And, you know, actually one application I was wondering about when you were talking about this is some of the weather forecasting models, as you know, they get more and more complicated every year as computing power gets stronger and as knowledge of the atmosphere gets better.

[00:35:01] Do you know if the type of crystal formation actually contributes to say snowfall predictions, for example?

[00:35:09] Dr. Kenneth Libbrecht: Well, Some of the physics, you know, the underlying physics matters, and in those predictions, what I’m looking at is very esoteric. As I mentioned, some of these beautiful crystals are one in a million, so if you’re looking at weather, You don’t wanna look at one in a million crystals, you wanna look at all the rest , because the rest of the glop stuff is what makes up the weather.

[00:35:31] And so, so it doesn’t quite apply to that. But but it is, you know, making progress in kinda material science and how ICE works. But I’ll give you one, you know, potential application, which to me makes sense. So, so I’ve been growing ice crystals and trying to make a model of how ice growth works and how you can make snowflakes.

[00:35:53] And a lot of it comes down to the molecular dynamics of what’s going on at the surface. And I have things to say about that based on how the crystals grow, but I cannot see the molecules. I’m just basing my assertions on. One’s understanding of the molecular theory of how crystals grow, which is incomplete and not perfect.

[00:36:14] But nevertheless, you can learn some things. And on the other hand, people are make in biology especially, and chemistry, are making molecular dynamics simulations on the computer for things like water and ice and how they. And so one can bring these together. And so I’m making predictions and you could try to confirm that using these molecular dynamics simulations and people are doing that now.

[00:36:38] And from that you can refine your models of how water works, you know, at the molecular level and how the molecules interact with one another. And by itself that is of limited use. But until you remember that everything in biology takes place in water. And so the biologists are really keen on having a very accurate model of the water molecules.

[00:37:03] So, so you know, it all lumps together, right? Biology is really hard to understand cuz it’s so complicated. But water’s in there and you can take out the water and just look at how water works and how water forms ice. And then test your models over there on a simpler system. And then hopefully you learn a little more and you can do your biological simulations better.

[00:37:28] Stuff like that. It’s not useless, but but it’s weird.

[00:37:32] Michael Hawk: And I suppose you never know what discovery is going to unlock some other previously unthought of aspect of nature as well.

[00:37:40] Dr. Kenneth Libbrecht: Well, I’d always like to say too, you know, when you’re, when I study ice, I’m trying to figure out how this particular material works. and it’s good to know how materials work because that’s what we make our stuff out of. So . So yeah, there’s it all hangs together at some level. And you know, you study things in science partly because it’s easy enough, you’re at the frontiers.

[00:38:02] And the frontiers are where it’s easy enough, you can make some progress. And then the frontiers push back a little bit and now other things become easier and it goes on for centuries. And you know, every little bit contributes.

[00:38:16] Michael Hawk: absolutely. This fascination that you’ve had with the science of snowflakes and also the appreciation you’ve had from their artistic beauty has led you to creating a number of different books, different snowflake books. So tell me about these books. How did these come to be?

[00:38:33] How did you determine there was even a market for people that wanted this level of depth in the world of snowflakes?

[00:38:39] Dr. Kenneth Libbrecht: I grew up in North Dakota where it snows a lot, and when I was a kid it just never occurred to me much to look at snowflakes. I had seen what everybody sees about snowflakes in school, but it snowed a lot and I never really paid much attention to it. And it was only when I started reading about the physics of this, I learned that there are all these different types of crystals.

[00:39:03] And then it just happened to be visiting North Dakota in the winter when I was reading one of these books early on and they had just talked about cap columns and I thought I’ll go outside and see if I can see a cap column. And sure enough, they were right there. And so just like, this is awesome.

[00:39:19] I mean, There’s all this cool stuff happening, Falling out of the sky. And I never knew it existed and. that sort of clicked in my brain cuz it, I’d always kind of wanted to write a book on something that’s kind of been my bucket list to find a topic I could write a book about. And I thought this is would be a great idea.

[00:39:36] Snowflakes are cool and there’s a lot more there than I never knew was there and just seemed like a book. Talking about the different types of crystals and just what falls out of the sky and sort of the basic physics with lots of pictures of snowflakes would be a lot of fun. So I got into snowflake photography.

[00:39:55] There weren’t many good pictures and the old pictures were in black and white and, you know, you obviously wanted color pictures and I used colored lights to make colorful looking snowflakes. And I found a publisher . And the first book was great. It sold a lot of copies. People were really of interested in snowflakes and that led to another one and another one. You got a field guy, just snowflakes and sort of an artistic tabletop book and a big chunky book and just one after another and they sold.

[00:40:23] Okay. And yeah, this one, the latest one at from Princeton University Press is a different beast. It’s a thick monologue of the physics of snowflakes and not for everybody by any means, but a labor of love for me. And I’ve been out at this for 25 years, and after a while you get to be a certain age in the science biz, and you feel you better write down what you know while you still can for the next generation.

[00:40:48] But no, it’s been a lot of fun to try to convey this stuff to everybody. Other scientists, but also just the general public, and especially my target audiences. You know, anybody who lives in a cold climate, because if it snows outside and you’re not looking at the snowflakes you’re missing something and you ought to go and take a look.

[00:41:07] , when I was in college, I roomed with a ornithologist uh, and he showed me about bird watching. I’d never bird watched before, and he showed me his book. You know, I’m Field Guide to Birds and I’ve been a bird watcher ever since. It’s great fun. You don’t really know to do it unless somebody shows you to do it.

[00:41:24] And so I learned about bird watching from another bird watcher . And so I tried to write a book about Snowflake watching for anybody who might find that appealing.

[00:41:34] Michael Hawk: I have visions of the American Snowflake Association or something like that. Like they know all these birding associa.

[00:41:41] Dr. Kenneth Libbrecht: you have to be a hearty soul to get into Snowflake. Watching it’s cold out there. Bird watching is more fun in a way, but that’s okay.

[00:41:50] Michael Hawk: All right. So, I do have a few questions from some listeners. So I sent out a notice on my Patreon that I was gonna have a Snowflake expert on, and, you know, what do you have? So some of these questions I’ll run through. So one of ’em was an anonymous, they wanted to remain anonymous, but they wanted to know more about wet snow.

[00:42:07] Like, why is it when you shovel snow? Sometimes it’s a lot heavier than other times. And how does that relate to the crystal form?

[00:42:15] Dr. Kenneth Libbrecht: There’s a lot there going on there in that sometimes the snow pack, as it’s called, is dense and sometimes it’s light. And that depends on a number of things. One is the snowflakes themselves. For example if you get a lot of these thin plate like crystals, stellar dendrites and if they fall in abundance you’ll they stack together, they pack together very lightly and you can get just a wonderful, fluffy bank of snow.

[00:42:42] For a while. And the skiers love this, that, that’s called powder snow. And that’s the stuff you put your skis on and you sink in up to your waist with skis on cuz it’s very light and airy. And I’ve talked to people who do this and they know that this is the kind of snow that makes that that kind of powder.

[00:43:01] And so it, but it only lasts for a while. So they’re always watching the weather and if they see good powder snow falling, they know to run out there as soon as they can and go skiing. Because after some days it starts to, to pack down and get more dense. And it’s not potter skiing anymore.

[00:43:19] It’s more like regular downhill skiing. And so that’ll happen all by itself. Sometimes you get denser snow just if you have different kinds of crystals. Like a lot of grale, especially if it’s warm, the snow pack is usually very dense when it’s warm. And so shoveling snow when it’s warm is always really hard.

[00:43:37] cuz it’s packed very tight. And so a shovel full of snow weighs an off a lot. So that’s kind of, there’s a lot of stuff going on and it depends on the crystals that fell and the whole history of, what happened after the snow pack has been sitting on the ground. That kind of makes the density of the snowpack.

[00:43:54] Michael Hawk: Yeah, I see some kind of self-reinforcing processes at work there. So the warmer it is, the more moisture perhaps in the air so that more snow could fall. And if it’s already denser, it’s gonna compact more. So you, you get all these forces working together, it sounds like, to create this really heavy snow in those conditions.

[00:44:13] Dr. Kenneth Libbrecht: Yeah, generally warmer conditions have heavier packed snow and colder climates you’ll get the lighter snow. I bet. That’s just a general rule.

[00:44:23] Michael Hawk: And another skiing question from Richard. He was interested in snowmaking at ski resorts and the big machines that they have. Is there any special physics behind that? How does it work?

[00:44:34] Dr. Kenneth Libbrecht: Snowmaking is a fascinating business in that it’s just engineering and you’re trying to make as much snow as you can for as little money as possible. It does not form snowflakes via a water vapor, which is, you know, what snowfall from the, in the atmosphere is. It’s basically just spraying out little water droplets and freezing them very quickly.

[00:44:56] The way you do this usually is you just have a nozzle that sprays liquid water droplets out, but then you mix in the nozzle compressed air, and that when the compressed air expands, it cools in, it gets cold enough that it’ll freeze the droplets in just very short period of time. And so you just spray that stuff out into the.

[00:45:18] And you get little frozen droplets of water, little tiny ice cubes. So it’s, it packs fairly densely. But that’s okay cuz for downhill skiing you don’t want super light snow all the time. And it gets really fascinating as a business when you try to make that so you can do it as cheaply as possible.

[00:45:36] And so people have all kinds of tricks for getting those droplets to freeze at higher temperatures. Sometimes they, you’ll only freeze the outer shell of the droplet cuz that’s cheaper. And then it just has to sit for a few hours so the rest of it’ll freeze. and they’re very sophisticated now.

[00:45:53] They, these machines have computers that measure the temperature and humidity and they will just tune up the system cuz those compressors cost a lot of money to run air compressors. So they’re trying to do it as cheaply as possible. Anyway, when you really get into the details it’s quite fascinating to see, but mostly you’re just trying to spray water out, getting cold as quickly as you can and just cover the slopes with it.

[00:46:17] Michael Hawk: Are they using customized nuclei to form the water droplet around, or is that not even part of the process? It’s just freezing the water droplets directly.

[00:46:24] Dr. Kenneth Libbrecht: This is a little piece of the puzzle. Yeah. That there’s a bacterium of all things that has been sort of trains itself A protein makes a protein that causes ice to freeze at quite high temperatures. So , I kid you not, so it normally ice will not start to freeze till it’s minus five Celsius and just barely then.

[00:46:45] And if you look at your freezer in your kitchen, the temperature’s usually around minus 15. And the reason it’s that temperature is that’s how cold it has to be to get your water to freeze into ice in a reasonable amount of time. At minus five, it might take weeks sitting in there for freeze, but at minus 15 it’ll freeze in a few hours and you’re good.

[00:47:05] But this bacterium will allow ice to freeze at minus two. So that’s good. And there’s lots of talk about. You know why it does that and what biologically why this thing exists. And probably to cause frost damage to plants so it can infect the plants. And then there are antifreeze proteins that can be as, there’s all kinds of crazy stuff going on in sort of the technology of freezing people use antifreeze proteins and ice cream, so when it melts and refreezes, it doesn’t get so crystalling and it maintains more of a creamy texture.

[00:47:40] And so a lot of interesting chemistry going on and of all this stuff. So, yeah, I, water is everywhere and ice is a very common thing. So people have developed a lot of tricks of the trade for sort of making ice better, even making clear ice cubes. There’s a technology for making clear ice cubes as well.

[00:47:59] And so, you know, you can buy machines that do that.

[00:48:02] Michael Hawk: And, and the last questions actually is from me but I remember one I was gonna say one time, but I’m sure it was more than one time where I was outside on an extremely cold day. It was clear, but there were little dust particle snowflakes falling, and I didn’t see a cloud in the sky, but these little glimmering, you know, pieces of dust were falling.

[00:48:20] And I saw some reference on your website called Diamond Dust. Is that what I was seeing? And if so, how does that form.

[00:48:27] Dr. Kenneth Libbrecht: that sounds exactly like what’s called diamond dust. So there are different ways of forming ice crystals you don’t really need. I told you you need these liquid water droplets and there are no absolutes in meteorology . So whenever you say, you know, it has to be done this way, that’s like most of the time.

[00:48:44] There are times when you can get just the right conditions has to be pretty cold. So, so you start with water vapor in the air and you cool the air down enough or get the humidity a little bit higher. And it will start to form droplets that freeze rather quickly right away into little particles of ice.

[00:49:02] And they will often facet as well. So you’ll get little faceted prisms floating around in the sky even though there’s no clouds. It’s just that the humidity is high enough that the water will condense and quickly freeze. It has to be cold. It’s al always cold when this happens. And you see those little crystals.

[00:49:22] And because if there’s no clouds, then the sun is out and then you can really notice them because they’re floating around like dust. They’re very light and they sparkle. and this is how you see halos and things of that nature as well. Atmospheric kilos, they’re also little ice particles. So the big flakes, to make those big flakes, you need liquid water droplets.

[00:49:44] But these little flakes can form under different conditions when it’s very cold and yep, they’re very pretty. That’s why we call ’em diamond dust.

[00:49:51] Michael Hawk: I too am in California. I don’t have opportunities to see things like this very often, but if I ever find myself back in a cold climate, I will definitely have a greater appreciation for these different atmospheric phenomena that you’ve described

[00:50:05] Dr. Kenneth Libbrecht: Well, If you ever go to Fairbanks in the middle of winter, which I highly recommend, it’s a, it’s quite an adventure. You’ll see a lot of diamond dust if you don’t mind. 40 below.

[00:50:14] Michael Hawk: It’s going on my list. That’s on my bucket list.

[00:50:17] Dr. Kenneth Libbrecht: I like to say going to Fairbanks in winter is is like visiting another planet, one that’s far from the sun, except you can fly there and they have hotels

[00:50:27] Michael Hawk: Well, I

[00:50:27] I suppose the challenge with Fairbanks in the winter is, as you said before, there’s very little sunlight time, so , so you’re gonna have to be a little bit lucky to catch that two hours of sun.

[00:50:37] Dr. Kenneth Libbrecht: Oh, you stayed at night in the streetlights too.

[00:50:39] Michael Hawk: All right. Well, This has really been an enjoyable conversation. To wrap things up, I’m curious, through your study of snowflakes, do you have any transferable concepts or frameworks or lessons that you think would benefit the general public

[00:50:53] Dr. Kenneth Libbrecht: Oh gosh. Stay curious my friend. It’s not . No, it’s just, there’s a lot of interesting stuff. It, if you sort of pick any topic and sort of look into it deeply enough it really can be quite interesting. And it’s good to keep an open mind about things you never quite know where you know, things lead you.

[00:51:11] And I did not intend to be a Snowflake physicist. It just popped into my head one day that something to read about. And as I started reading about it, it just got more and more interesting. And then I started really studying it for real. And And growing crystals in the lab. And it got even more interesting.

[00:51:29] And so that’s kind of kept me captivated by the subject for 25 years. And it wasn’t something I really signed up for. It just just kind of happened.

[00:51:38] Michael Hawk: It would be really interesting to see what would happen if you could go back in time and talk to yourself and say, Hey, this one little question I had is going to turn into, I don’t know how many books, five books, 25 years a whole lab, , you know, all these different things.

[00:51:52] Dr. Kenneth Libbrecht: Like I say, it kind of, it kind of snowballed.

[00:51:56] Michael Hawk: I think there’s a lot of puns in here. You talked about snowflakes being cool at one point. I don’t know if that was intentional.

[00:52:02] Dr. Kenneth Libbrecht: You know, one of the fun things about studying snowflakes as opposed to other things I’ve done in physics is that everybody knows what you’re talking about. You know, you’re talking about Bose-Enstein Condensates and that just like, well, what is that? But snowflakes, we all know something about it and it’s kind of fascinating stuff.

[00:52:21] Michael Hawk: So do you have any upcoming projects or other books or papers or whatever the case might be that you would like to point people towards?

[00:52:28] Dr. Kenneth Libbrecht: Oh, I don’t know. . Never know what’s gonna happen. I keep publishing papers on the subject. There was a big breakthrough when I kind of figured out I think I figured out how to understand these morphologies changing with temperature. And that’s a hard act to follow cuz that’s been a puzzle for 75 years and I’m kind of claiming that I mostly understand it now.

[00:52:49] Come back in 50 years and see if anybody agrees with me, . But no I’m still growing crystals, still trying to do more with what I call my designer snowflakes, which is just growing crystals in the lab for fun for the artistic aspects of it. I describe what I do in that realm is being miniature ice sculpture where instead of getting a block of ice and carving it into something, I start with rules that nature provides.

[00:53:15] And I use them to grow little crystal sculptures and just following the rules how snowflakes grow and seeing if I can find some uber snowflake that has never been done before and you’ll never see in the, natural world. And nothing too extraordinary yet, but still working on that.

[00:53:36] So, so we’ll see.

[00:53:37] Michael Hawk: So if people want to follow your work, we mentioned your website earlier and maybe you can give another plug for that, but where else can they go? Are you on social media? Any other outlets?

[00:53:47] Dr. Kenneth Libbrecht: I’m not so big on social media. I mostly try to keep my website up. I find social media’s a little too ephemeral for my tastes. I post things and five people see them and that’s the last it’s ever seen before. But I like my website cuz it just sits there and anybody can see it any time and little more of an encyclopedia model than a talking about it model.

[00:54:08] So I try to put things on there and I publish a lot of things in on, in the archive, which is this physics archive. So it’s very, it’s all open source. But yeah, the website’s a good place to start.

[00:54:21] Michael Hawk: And that website, you could spend days or weeks, I think, with all the different resources that you’ve put into there. So, definitely highly recommended, especially I’m not exactly sure when this is going to air, but if if anyone has kids that are making those paper snowflakes, I think you even have instructions as to how to make true to life.

[00:54:38] Paper snowflakes, on the website.

[00:54:40] Dr. Kenneth Libbrecht: Well, My, my website in snow crystals.com, it started out as a pretty small affair. I’m old enough that I, I was around when the web was kind of invented and content was pretty scarce back then. And so I decided I would make a Snowflake website and so it, you immediately caught some attention. And so I’ve just kept it going for 20 years.

[00:55:03] so now I’ve got quite a bit of stuff on it. So, lots of pictures, little bit of explanation of what’s going on. Talking about, you know, how to go out and find snowflakes and what kinds of snowflakes you can see. All that stuff. It’s it’s a fun subject.

[00:55:18] Michael Hawk: of course the show notes will link to that and to some of the other topics and resources that we talked about. So, Ken, is there anything else that you would like to say today that maybe we’ve neglected to cover? I’m sure there’s a lot,

[00:55:30] Dr. Kenneth Libbrecht: Yeah, it really, the subject goes off in lots of different directions, but I can ramble on about it for quite a while I’m afraid. So maybe it’s good time to stop.

[00:55:39] Michael Hawk: All right. I appreciate you taking the time today to talk about this. It’s been as I said, a lot of fun . So thank you very much.

[00:55:46] Dr. Kenneth Libbrecht: Thanks for for having me.