Aren’t we all unique little snowflakes with our unique temperaments, setting us apart from each other? What about real snowflakes? Are they truly unique? What are the odds of finding two identical snowflakes?
How snowflakes form?
It all begins within the water vapour in the air. When the surrounding air is below the freezing point of water, the vapour freezes by nucleation to form an ice crystal around a dust particle. This forms the nucleus of the snowflake. When this tiny little nucleus bumps into other supercooled water molecules that are floating around the clouds as vapour, it freezes them on contact, forming a bigger ice crystal.
When this ice crystal travels around through the unpredictable atmosphere, it gets to meet more supercooled water molecules, which now sticks to the hexagonal corners and starts forming those beautiful arms of the snowflake.
Why are snowflakes hexagonal?
The reason for the hexagonal crystalline shape is due to the bond angle (104.5°) between the two hydrogen atoms in the water molecule. In case if you have forgotten, a water molecule looks like this.
So when the ice forms, the molecules in it would arrange themselves (crystallizes) in a hexagonal pattern, with six oxygen atoms at the hexagon’s vertices, thanks to the hydrogen bond between the hydrogen and oxygen atoms of the water molecules.
Beautiful little unique snowflakes
When the microscopic tiny hexagonal crystals grow in size by bumping into adjacent water molecules, they begin to form the six arms from the vertices. Depending on the atmospheric conditions at the time of the crystal growth, each snowflake will develop in a unique pathway, resulting in different variations, all governed by the simple hexagonal structure of the ice crystal.
I’m sure you all know the dendrite snowflake, the one with the six arms, which is more of a pop figure in the world of snowflakes. Dendrites usually form when the temperature is around 0 °C to -3.5 °C and -10 °C to -22 °C and sometimes when it’s colder and the air is supersaturated. For the arms to form, the vapour around the nucleus had to undergo deposition to ice. In a supersaturated condition, the favourable vapour pressure difference would be more likely in the vertices of the nucleus. Therefore, the arms start out from there and begin to grow against all the conditions to form a symmetrical pattern.
And depending on the temperature, the snowflakes could take other forms as well. Some common types of snowflakes would have the shape of a column like needles, or simple hexagonal plates, and sometimes a thick hexagonal column of prisms. It all depends on the atmospheric conditions it originates and how it ends up on the surface.
Could any two snowflakes be identical?
No. It’s really hard even for the nature to come up with two identical snowflakes. Though the starting point may be a simple hexagonal framework of molecules, throughout the crystal growth, there are so many variables that can affect the crystal in unique ways. The whole process is so dynamic that the chances are way too small, and absolutely close to impossible.
One compelling reason for this to be hard is due to the presence of a few naturally occurring deuterium atoms on Earth. So even if you miraculously find two identical snowflakes, the molecular concentration of deuterium will still be unique for both the snowflakes. Yeah! Water is an interesting molecule!
Go get a snowflake, if you are lucky enough to be in cold areas! Put it under a microscope, take a photograph, and then preserve and gift that unique little thing to someone you love.