an extraordinary journey from their formation to snowfall. Were two bows ever the same?


Spectacular macro photography of some snowflakes that have just landed on the ground.
Luca Lombroso Luca Lombroso 7 minutes

Snow is dalso known as the White Lady for her honesty and beauty. Snowflakes falling from the clouds they move as if in a magical dance, and it is no accident that they have inspired many songs and many films and unleashed passions and manias like street lamps.

For the shape of the flakes is extraordinary microphysics. Clouds, cold and ice are not enough to create flakes, but the exact ingredients in the right amount are needed. Boom fall is a really long way, and its shape can take on several very complex geometric shapes.

Basic ingredients of “Snowflake Ice Cream”

We could compare snowmaking to a dessert recipe. Of course, this is a simplification, but it helps to understand a complex phenomenon in a simple way.

The ingredients they are basic Earth’s atmosphere, water present in three phases: solid (ice), liquid (water droplets) and gas (water vapor). However, other substances are also needed which function technically as a condensation nucleus: dust (especially clay) e sea ​​salt.

You need freezer to freeze everything (basically cold air) but also a slight but correct amount of warmer air. Alas, if there was too much, it would turn from snow to frost or rain in a flash.

In practice, back to reality, the vapor freezes on the condensation nuclei and an extraordinary process begins that will lead to the birth of a snowflake.

Once the condensation nucleus has attracted enough water molecules, it will begin the decisive phase of crystallization through the process of sublimation that is, the steam directly becomes the “embryo” of ice needles.

Water molecules cluster around the snowflake embryo into a six-armed crystalline structure that forms the basis of the future snowflake. The secret, which we will not explain further here, lies in the shape of the water molecule.

This step is crucial because it determines the symmetry and unique shape of each crystal.

Shape of snowflakes

PUSH Snowflake growth and shape are strictly dependent on temperature and humidity conditions and altitude, and thus the pressure at which the process takes place. It all depends on the temperature, humidity and speed of the process.

Between -6°C and -10°C, crystal grows on surfaces; between -10°C and -12°C, on the sides; is between -12°C and -18°C, at the corners, giving life to typical star-shaped flakes called dendrites. The secret to growth lies in the attraction of ice to water droplets, a complex phenomenon that causes the crystals to grow at the expense of the droplets.

Once created, the flake remains in suspension in the air inside the cloud e when it becomes heavy enough, it begins to slowly fall.

The journey until it hits the ground is slow due to the lightness of the bow it often swings in the air like a dance. Flakes fall at a speed of about 1 m/s, less than 4 km/h, and then ithey take 3-4 hours to reach the groundconstantly changing.

Were two bows ever the same?

There are real”snowflake hunter“, snowflake hunters. She was one of the first Japanese scientist Ukichiro Nakaya, who photographed them in 1933 and collected over 3000 images and classified the form according to the standard it is still used today. Currently an American scientistKenneth Libbrecht, going bow hunting with a 4×4 vehicle equipped with a cooled optical bench, macro photography is collected on the extraordinary website

youtube video id=fKubU0L6PGk

Based on mathematical-statistical calculations, the possible combinations are huge, 1035, The 10 is followed by 35 zeros of various shapes. An estimated 10 have fallen since Earth’s formation24 snowflakes, 10 followed by 24 zeros. Consequently the probability that two identical flakes have ever fallen is infinitesimally small. In short, two flakes of the same shape in every detail hardly ever fell.

Snowflake movement model

Snowflakes, although unique in size, density and ice crystal shape depending on atmospheric conditions, they show a strikingly similar pattern of falling in motion single flakes. This conclusion resulted from a University of Utah study that analyzed half a million fallen flakes near Salt Lake City.

Despite the complexity of their accelerated motion, affected by gravity, air friction and turbulence, researchers have identified a universal behavior in falling ice crystals. Using devices with lasers and cameras, they detected a Laplace distribution in velocity and acceleration from each flake, although the reason for this regularity still remains unclear.

The scientists intend to study further with more precise instruments to obtain detailed data. It seems incredible, but these details can be useful both in weather forecasting models and in models for studying climate change.


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