The Science of Snowflakes, and Why No Two Are Alike



The snowflakes that settle upon our sleeves and scarves during a snowstorm have more variations in shape than you might think. There’s the classic snowflake: a flat plate with branchlike, dendritic arms. Some look like hexagonal prisms; others like hollow pencil-shaped columns or tiny needles.

We tracked down two ice experts to help answer the question: Kenneth Libbrecht, a physics professor at the California Institute of Technology and avid snowflake photographer, and John Hallett, director of the Ice Physics Laboratory at the Desert Research Institute in Reno, Nev.

Scientists use the term “snow crystal” more than snowflake. According to Libbrecht’s website, “A snow crystal, as the name implies, is a single crystal of ice. A snowflake is a more general term; it can mean an individual snow crystal, or a few snow crystals stuck together, or large agglomerations of snow crystals that form ‘puff-balls’ that float down from the clouds.”

ig35_snowflakes_08_02A few facts about snow crystals: They are formed from water vapor that condenses directly into ice inside of clouds. They take shape as water vapor molecules from cloud droplets condense and freeze on the surface of a seed crystal, and patterns emerge as these crystals grow. The seed crystal itself forms on a tiny particle, like a speck of dust in the air, which serves as a base for ice growth.

And though it may appear otherwise, the arms of a snowflake are not perfectly symmetrical.

“If you look at the dendritic arms of a snowflake carefully, they usually are a bit different,” Hallett said. “The atmosphere is a turbulent place, and crystals tend to oscillate as they are blown around, so even different corners see slightly different environments.”

So is it really true that no two snowflakes are alike?ig35_snowflakes_09_02

“It’s like shuffling a deck and getting the exact same shuffle for 52 cards,” Libbrecht said. “You could shuffle every second for the entire life of the universe, and you wouldn’t come close to getting two of the same.”


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