Gosh, I’d like to believe this one, it’s just such a “cool” idea. One argument against this idea is that if you take thousands of pictures of snowflakes, it’s still not a very good statistical sample. Kenneth Fuller writes about this, and other modern myths taught as science. He hypothesized that this myth arose from the publication of a wide sample of snow crystals by Wilson Bently in 1931. Bently only published his very best pictures, which were taking from a specific type of storm. While the final result was astounding (6000 photographs), this is not a very good sample when you consider all the snowflakes that have ever existed in the world.
A counter-argument (which Fuller rejects) is that on the molecular level, no two snowflakes will ever be quite the same, because some of the water molecules will be slightly different from the others (e.g., they’ll contain an isotope of hydrogen or oxygen). Fuller poo-poos this idea, since it also says that no two drops of water are exactly alike, which begs the question of whether or not the beautiful symmetrical crystal, above, might be replicated from one snowflake to the next.
However, the math of combinatorics comes into play when you consider all the different ways that a snow crystal might form. By that, I mean that as each snow crystal forms, it has several different “choices” about how to continue its growth. There are many crystal structures available, and different paths that each crystal may take as it continues its growth. So, there is a huge number of different crystal structures that could arise. Snow researcher Kenneth Librecht from Caltech claims at Snowcrystals.com that it’s statistically unlikely that two snowflakes might be exactly the same (even though we could never actually check them all to make sure).
See some beautiful (public domain) pictures of snowflakes at Wikimedia Commons.
Find out how to preserve a snowflake for 30 years with superglue on a later post.