The next time you're catching one with your tongue, you might stop to consider the long and arduous plight of the snowflake. Those delicate and intricate crystals have traveled many miles before they plummet to the ground alongside their trillions of cousins. And although they fly in multitudes, the word on the snow-slicked street is that no two of those little flakes are alike. Can every snowflake really be different?
The short answer is yes, snowflakes really are different from one another. You might find some that are exceedingly similar (particularly at the beginning of a flake's development) but fully formed snowflakes are indeed structurally different, if only by tiniest of degrees.
Understanding why snowflakes take unique forms means understanding how they're formed in the first place. It all starts at the Earth's surface, as water evaporates from oceans, rivers and lakes and rises into the atmosphere in the form of gaseous water vapor, which we sometimes see as clouds.
In summertime, those clouds drift around the skies, providing shade and breaking up the blue horizon. But in winter, things change. Cold air forces molecules of water vapor into little liquid droplets which tend to condense onto any nearby particulate matter, such as pollen or dust. These tiny ice crystals are the baby versions of what soon become full-grown snowflakes.
The crystals float through the sky and collide with molecules of water vapor. As vapor contacts the crystals, the water vapor skips straight from its state as a gas straight to a solid crystal, adding to the original nucleus of the snowflake. This process happens over and over again, building the snowflake from a nearly imperceptible crystal into a larger flake that, given the right conditions, falls to the ground and may cause you to utter a lot of swear words when you realize your gas-powered snowblower is broken.
Knowing all of this, it may still be difficult to believe that in a sky full of snowflakes no two are alike. On the next page you'll see how the flake-making process practically ensures that these little crystals are all unique, even when they fall by the billions.
What makes a snowflake?
As the very first ice crystals come together in a group of fledgling snowflakes, the new flakes often look strikingly similar. That's in large part due to the fact that ice crystals typically take a hexagonal (six-sided) lattice shape because of the way hydrogen atoms bond with oxygen to make water.
Certain edges of the ice crystals are jagged. These ragged, uneven areas attract more water molecules than the smoother and more uniform parts of the hexagon. Each little arm sprouts more of the same, growing into an intricate and uniform snowflake.
If snowflake development stopped within the first few moments of birth, we'd wind up with a lot more flakes that look suspiciously alike. But snowflakes keep gathering more and more crystals, clustering together on top of one another in distinct patterns.
As those clusters of crystals continue their snowflake fiesta, other guests visit the flake-making party. They come in the form of environmental factors, notably humidity and temperature. Both play major roles in whether the snowflake gets bigger and bigger or fizzles out.
You can imagine how critical temperature is to ice crystal formation and structure. Between temperatures of 27 and 32 degrees Fahrenheit (-2.8 and 0 degrees Celsius), crystals take on a plate-like or prism appearance. These are prototypical six-armed snowflakes that lack much visual interest.
Drop the temperature a few degrees and you'll see needle-like structures. Hollow columns develop at even lower temperatures. And when it's crazy cold you'll see stars sprouting fern-like arms.
Lower humidity tends to result in flatter flakes. Higher humidity means more crystal development in edges and on corners.
Add some extra moisture at those really frigid temperatures and suddenly snowflakes may become mesmerizingly beautiful. They contain a multitude of intersecting plates and needles and spaces, minute masterpieces falling from the heavens.
They may result in tiny, granule-like flakes. Or they may add layer upon layer until they are monstrous snowflakes like the record-breaking 15-inch (38-centimeter) wide flakes that fell in Montana in 1887.
The Snowflake Lottery
Physics and weather conditions determine snowflake shape and size. Math determines that those flakes are unique.
Consider that each snowflake is made up of a huge number of water molecules. By one estimate, a flake may have as many as a quintillion molecules [source: Washington Post]. Because each little branch of a snowflake can spawn many others, there are dozens and dozens of ways for various crystalline features to join. There are so many possible arrangements that some scientists say there are two times as many possible crystal combinations as there are atoms in the whole universe [source: The Naked Scientists].
Those kinds of numbers are so large that we can't really even comprehend them. But if the math holds, those numbers mean it's awfully unlikely that any two snowflakes have ever been or will ever be exactly alike.
Furthermore, there are all kinds of other factors at play in snowflake formation at any given instance. Even the tiniest fluctuation in temperature and humidity alters crystal construction. Minute impurities like flecks of dust change the crystals, too. The angles at which water molecules collide with existing crystals matter as well.
In the swirling atmosphere miles above the Earth's surface, all of these variables ceaselessly change. Conditions that hold in one small space are just a tiny bit different than those inches in any direction, and all of it transforms crystals and their subsequent snowflakes in infinite ways.
Snowflakes smash into each other as they zoom and swoop through the air. Where their branches shatter, new ones form, adding to the uniqueness of every translucent little flake.
So snowflakes really are nearly infinite in their specialness. They're tiny and ephemeral testaments of the strange and constant change in the world and universe all around us.
Author's Note: Is every snowflake actually unique?
As I researched this article, I was amazed to read that the largest snowflakes in history were roughly 15 inches wide. Of course, there's no concrete evidence that those enormous flakes existed. But scientists say that huge snowflakes of around 6 inches do routinely fall all over our planet, so it seems reasonable that with the right conditions they could get even bigger. If I'm ever lucky enough to see snowflakes that are almost as big as basketballs, I don't know if I'd be excited or terrified... but it would definitely be an unforgettable experience.
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- Zentile, Catherine. "The Science of Snowflakes." The Naked Scientists. Dec. 22, 2007. (Dec. 18, 2014) http://www.thenakedscientists.com/HTML/articles/article/science-of-snowflakes/