From: veritasium
Dr. Ken Libbrecht is known as “the snowflake guy” [00:00:15]. He served as the snowflake consultant for the movie “Frozen” [00:00:19] and his pictures have been used by the US Post Office for snowflake stamps [00:00:30]. Ken has also authored books on snowflakes [00:00:41].
The Lab Snowflake Creation Process
Creating snowflakes in the lab begins by turning on 2000 volts [00:00:00]. This process involves using needles with tips around a hundred nanometers in diameter [00:00:09]. Ken Libbrecht refers to the snowflakes he creates as “designer snowflakes” [00:00:59] because he designs them on the fly, by hand, making each one unique [00:01:06].
To grow a snowflake, it starts at a certain temperature, for example, -13 Celsius [00:01:37]. To encourage the growth of branches, the temperature can be lowered to -15 Celsius [00:01:41], and the humidity, or super saturation, can be increased [00:01:43]. Changing these conditions can cause a plate to stop growing and then start forming branches [00:01:50].
A key aspect of the process is that only a small nub of the snowflake touches the sapphire substrate [00:02:00]; the rest grows above it [00:02:05]. Airflow is increased, and droplets form, which kicks the growth “into gear” [00:02:08]. The humidity can then be turned down to zero, causing droplets to recede and the snowflake to stop growing and start to facet [00:02:17]. If branches are desired again, a lot of moisture can be added [00:02:27].
Ken Libbrecht states that he can predict the future with his snowflakes [00:02:46], as he understands the conditions well enough to make specific growth happen [00:02:39].
Comparison to Natural Snowflakes
Ken Libbrecht believes his lab-grown snowflakes are “better than nature” [00:02:49] because their facets are sharp and crisp [00:02:53]. Natural snowflakes, by the time they are collected and examined, often show signs of evaporation, dulling their edges [00:02:59].
The first close-up photograph of a snowflake in the wild was taken in 1885 by American meteorologist Wilson A. Bentley [00:03:12]. Bentley originated the idea that no two snowflakes are alike [00:03:21] and took over 5,000 photos of snowflakes during his lifetime, published in his book “Snow Crystals” [00:03:28]. However, Bentley only selected snowflakes in pristine condition with uncommon beauty and symmetry [00:03:41]. In reality, finding such perfect natural snowflakes is difficult, described as “one in a million” [00:04:03].
Creating Identical Twin Snowflakes
While natural snowflakes are unique, in the lab, it is theoretically possible to create almost identical snowflakes due to controlled conditions [00:11:19]. Ken Libbrecht has achieved this by growing two snowflakes next to one another, calling them “identical twin snowflakes” [00:11:55]. While not exactly the same, they are clearly more alike than expected [00:12:04].
The process involves placing seed crystals, referred to as “sparkly snow crystals,” onto a sapphire disc within a cold chamber [00:11:32]. The crystals waft onto the disc and ideally stay there [00:11:47]. If growing too close together, twin snowflakes will compete for moisture, stunting their growth [00:12:41].
Ken Libbrecht views the question “Is it really true that no two snowflakes are alike?” as silly [00:12:17], stating that anything with complexity will be different from everything else because there are an uncountable number of ways to create it [00:12:29].
Scientific Understanding and Motivation
The types and structures of snowflakes formed depend on temperature and super saturation, summarized in the Nakaya Diagram [00:09:25]. This diagram shows patterns like plates forming around -2 Celsius, columns and needles at -5 Celsius, plates again at -15 Celsius, and columns and plates below -20 Celsius [00:09:40]. Ken Libbrecht has built his own version of this chart from his experiments [00:12:55].
The diagram helps understand a snowflake’s history; for instance, capped columns are often produced when a cloud moves up and gets colder, making columns first, then branches and plates [00:10:10]. The intricate symmetry of a snowflake is due to all sides growing under the exact same conditions [00:10:45]. Different snowflakes, however, experience unique conditions, leading to their unique forms [00:11:10].
A long-standing mystery, essentially since Nakaya’s diagram in the 1930s, has been why ice crystals form this way—why the alternating patterns of plates and columns [00:13:00]. Ken Libbrecht’s hypothesis is that the nucleation barriers, which dictate how easily new layers can form on crystal facets, vary with facet size [00:14:42]. He proposes that narrow basal facets have a dip in their nucleation barrier around -4 Celsius, and narrow prism facets have a dip at -15 Celsius [00:14:53]. This hypothesis aligns with the observed different forms of snowflakes at various temperatures [00:15:06]. Experiments conducted by Ken show results that agree with this hypothesis [00:16:10]. This research may finally explain the molecular physics behind the diverse shapes of snowflakes [00:16:37].
Ken Libbrecht’s motivation for studying snowflakes stems from a desire to understand something fundamental that is not yet known [00:17:15]. He wants to be the scientist who figures out how snowflakes work [00:17:29].