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Snowflake

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A snowflake is a single ice crystal large enough to fall through the Earth's atmosphere as snow. While individual ice is clear, snow appears white to the human eye. This happens because the many small crystal facets scatter sunlight between them. Each snowflake begins its life by forming around a tiny particle known as a nucleus. This nucleus can be a speck of mineral dust, clay, or even a biological particle. As the flake falls, it moves through changing zones of temperature and humidity. These shifting microenvironments cause each flake to grow in a unique way.

ComputerHotline - Snow crystals (by)
ComputerHotline - Snow crystals (by)

The growth of a snowflake follows a specific mechanism called the Wegener–Bergeron–Findeisen process. It begins when a water droplet freezes around an ice nucleus in a supersaturated environment. In these conditions, liquid moisture and ice coexist beyond their equilibrium point. The crystal then grows through deposition, where water vapor from the air turns directly into ice on the crystal surface. Because water droplets are much more abundant than ice crystals, the crystals grow at the expense of the droplets. This causes the droplets to evaporate while the crystals reach sizes of hundreds of micrometers or even millimeters.

Snowflake 300um LTSEM, 13368
Snowflake 300um LTSEM, 13368

As these crystals grow, they can collide and stick together to form clusters called aggregates. Most snow that falls to the ground consists of these aggregates rather than single crystals. While single crystals the size of a dime have been observed, most aggregated flakes are only three or four inches wide. However, history records a massive exception in January 1887 at Fort Keogh, Montana. During that time, aggregated snowflakes were claimed to be 15 inches wide. Some crystals also become encapsulated in rime frost, forming ice balls known as graupel.

Bentley snowflake micrograph no. 777
Bentley snowflake micrograph no. 777

The specific shape of a snowflake is determined by the temperature and humidity of the atmosphere. Most snowflakes exhibit a six-fold radial symmetry due to the hexagonal crystalline structure of ice. This structure starts as a minute hexagon, from which six arms called dendrites grow outward. While many flakes look symmetrical, empirical studies suggest that less than 0.1% of snowflakes show an ideal six-fold symmetric shape. Rarely, at temperatures around -2°C, snowflakes can even form with threefold symmetry, appearing as triangles.

Snowflake 300um LTSEM, 13368
Snowflake 300um LTSEM, 13368

Scientists have developed complex ways to classify these various forms. Ukichiro Nakaya created a morphology diagram relating crystal shape to temperature and moisture. He discovered that crystals in supersaturated air tend to be lacy and ornate. In contrast, crystals in air below saturation are more solid and compact. For example, freezing air down to -5°C promotes thin, flat plates. In much colder air, such as -15°C, crystals may form as hollow columns, prisms, or needles.

Snowflakeschapte00warriala-p11-p21-p29-p39
Snowflakeschapte00warriala-p11-p21-p29-p39

Beyond Nakaya's work, researchers Magono and Lee devised a classification including 80 distinct shapes. They grouped these into categories such as needle crystals, columnar crystals, and plate crystals. They also identified rimed crystals, such as graupel, and irregular snow crystals. This detailed study helps scientists understand the different types of precipitation. The variety is so vast that it is unlikely any two snowflakes are exactly alike. This is because a typical snowflake contains approximately 10^19, or 10 quintillion, water molecules.

Bentley snowflake micrograph no. 777
Bentley snowflake micrograph no. 777

Humans have studied these patterns for over a century. Starting in 1885, Wilson Alwyn Bentley used a microscope to photograph thousands of snowflakes. His work revealed the incredible diversity of shapes that exist in nature. Today, the snowflake remains a powerful symbol in many cultures. It is used in the emblems of several Winter Olympics and as a symbol of purity in some traditions. In Canada, a six-pointed stylized snowflake is used for the Order of Canada to represent northern heritage.

3 Order of Canada grades
3 Order of Canada grades

Snowflakes also appear in specialized technical and historical contexts. A snowflake symbol is used on snow tires to indicate they provide traction in winter conditions. In the Tang Dynasty, snowflake poetry served as a symbol for the Milky Way galaxy and cosmic energy. Even in modern technology, different snowflake symbols are encoded in Unicode. Whether viewed through a microscope or as a cultural icon, the snowflake connects the physics of the atmosphere to human creativity.

Lumijoki.vaakuna
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🖼️ Images & Media (8)
File:Snowflake (lumehelves).jpg
Snowflake (lumehelves).jpg
File:ComputerHotline - Snow crystals (by).jpg
ComputerHotline - Snow crystals (by).jpg
File:Snowflake 300um LTSEM, 13368.jpg
Snowflake 300um LTSEM, 13368.jpg
File:Snow crystals glittering in strong direct sunlight 45 - tight crop - high contrast.jpg
Snow crystals glittering in strong direct...
File:Snowflakeschapte00warriala-p11-p21-p29-p39.jpg
Snowflakeschapte00warriala-p11-p21-p29-p39.jpg
File:Bentley snowflake micrograph no. 777.jpg
Bentley snowflake micrograph no. 777.jpg
File:Lumijoki.vaakuna.svg
Lumijoki.vaakuna.svg
File:3 Order of Canada grades.JPG
3 Order of Canada grades.JPG
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