Myth 4: No two snowflakes are the same shape

by Stephanie Chasteen on April 12, 2008

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 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.


Shane November 19, 2008 at 11:45 pm

I think you mean Fuller “pooh-poohs” the idea, not “poo-poos.” Poo-poo means to defecate.

Laurel January 12, 2009 at 7:05 pm

May I have permission to use your photograph of this snowflake for a power point presentation. It would be used on a welcome slide for a church group gathering this week in Duluth Minnesota.

sciencegeekgirl January 12, 2009 at 9:08 pm

Hi Laurel,

All my images are taken from Wikimedia Commons, which is licensed under the Creative Commons. Usually I link back to the original image there but I neglected to do so for that post. But take a look here for a bunch of open license images on snowflakes, including the one on my post.

Doc November 10, 2009 at 4:19 am

Although it sounds overly simplistic: No two objects can be completely identical, no matter how much they are alike.

Stan June 2, 2011 at 2:17 pm

I agree with the concept that you are presenting that there may be, or have been, identical snowflakes. Statistically the number of snowflakes being generated at one time must be enormous, somewhere in the trillions I am sure. Given this large number and the length of time that snowflakes have been falling on Earth (billions of years), it appears logical to assume that water molecules would have arranged themselves in an identical fashion, at least twice, for the production of a snowflake. And if you consider snowflake development, the very earliest stages of ice crystal formation must have produced many, many duplicate crystals. It is only when they become twinned and more complicated that they begin to diverge in shapes.

jony trump June 13, 2012 at 8:04 pm


Erica W January 19, 2013 at 2:38 pm

The snowflake doesn’t have much choice in the shape it takes – different types of crystals form under different conditions of moisture and temperature. Plates are the broad flat shapes, dendrites the feathery branching ones, needles are pointy, columns are thicker prisms. Each snowflake’s shape reflects the conditions it went through as it swirled around in and fell out of the cloud. The new type of shape are added onto the old, usually faster at the tips because they stick out more. I thought that was pretty cool.
There are simpler types of snow crystals that you get below saturation – mostly simple columns or discs, again determined by temperature. These can look very close to identical, where the more complex composite flake-crystals are much more unique.
Caltech has a pretty good morphology diagram showing what shapes form under conditions:
We had a very exciting moment this winter when we found columns falling outside, checked the diagram and the temperature, and they matched! I suppose the fact that that was exciting tells you something either about me, or about the kind of winters we get up here.

Martin January 28, 2014 at 12:06 pm

It kind of depends on the definition of a snow flake doesn’t it? At a molecular level, if a flake only consists of a few molecules as it gets started its not hard to envisage some that `are the same` , certainly a higher probability 🙂 I also wonder on the definition of `the same` – there’s the same scientifically and there’s the same `visually` which has allowance for some variance.

Pam Ulla April 23, 2015 at 5:23 am

Just asking, folks, so please don’t dis me for wanting to learn. So does this mean that snowflakes can repeat its shape because of the lower combination of molecules than those of a human whose fingerprints, looks & ‘cornea identification thing’ are never repeated? Remember people, I am just a curious person wanting to learn the facts. I can’t help it if my past education does not cover my understanding of the facts printed here. My thanks to Stephanie for being brave enough to present even one of the topics on your website, much less all the controversial ones. Because we all know that somebody is always going to ‘be smarter than anybody else, at least in their own mind,’ than the obvious facts. Again, thank you!

Simoncaneplz June 13, 2015 at 7:25 am

Agree with this more, though, I dunno if this is true or not.

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