Identical Snowflakes? Possible but not Probable!

Posted by Ellen on 11/19/2014
We've all heard (and probably repeated) the old adage that no two snowflakes are ever the same. I used to use the analogy all the time with my students when describing how each of us is also different and has our own special gifts and talents. Well, I may have to amend my whole diatribe! There was an article in the Washington Post by Brian Palmer ( about the uniqueness of snowflakes. It gets pretty technical at certain points, but according to his snowflake expert source, it is mathematically and statistically possible for two snowflakes to be identical; it is just highly, highly unlikely given the number of combinations of molecular arrangements. Palmer quotes Kenneth Libbrecht of the California Institute of Technology, "Now, it’s not a law of nature that no two snowflakes could be truly identical. So, on a very technical level, it’s possible for two snowflakes to be identical...[t]here are a limited number of ways to arrange a handful of bricks...but if you have a lot of bricks, the number of combinations grows very quickly. With enough of them, you can make a driveway, a sidewalk or a house. Water molecules in a snowflake are like those bricks. As the number of building blocks increases, the number of possible combinations increases at an incredible rate." Palmer continues by explaining, "[c]onsider the math, which Libbrecht helps explain using a bookshelf analogy. He points out that, if you have only three books on your bookshelf, there are only six orders in which you can arrange them. (That’s 3 times 2 times 1.) If you have 15 books, there are 1.3 trillion possible arrangements. (Fifteen times 14 times 13, etc.) With 100 books, the number of combinations increases to a number that is far, far greater than the estimated number of atoms in the universe." Like I said, it gets a little technical, but if you have 6th grader (or older) child, it's very likely that she's worked with combinations in math class. While she's not going to be able to figure out the total number of snowflake combinations in the world on her own (Palmer shares that "Libbrecht estimates that around a septillion — that’s a 1 with 24 zeros — snowflakes fall every year."), this is a nice connection to make.
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