Uniqueness

December 29, 2006 3:16 PM

No two snowflakes are alike. True or false?
posted by richg to science & nature (12 comments total)

Well, true on an atomic level at least -- I'd highly doubt that any two snowflakes in the history of time have actually contained the same grouping of atoms in the same arrangement...

... whether you accept this answer of course depends on how you want to measure uniqueness; at a small enough level everything's unique.
posted by jacobian at 3:30 PM on December 29, 2006

No two snowflakes can exist together and be made out of the same atoms, so true. The chance of two snowflakes that share an identical shape and size at the same time is really really small, even having two crystals with identical structure at any point in time is improbable. Take into account all water ice crystals formed anywhere at any time point in the 15 billion odd year history of the universe and the probability goes up, but not much.

There is a chance that two crystals of the same size and shape formed during the entirety of existence, a smaller one that they formed at the same time, and I would say even a smaller chance that the same set of atoms froze and re-thawed into the same structure. Sure, why not? All it takes is time and we've got plenty of it out there ahead of us.
posted by Science! at 3:31 PM on December 29, 2006

Well, a snowflake is a physical structure with zillions of atoms (including impurities, imperfections, varying isotopes, etc.), so, in an absolute sense, it is extremely extremely unlikely that any two have ever been exactly, atom-for-atom the same. If you lower your standards of "alike," the odds improve. With a low enough standard, the odds converge to one, as I'm sure you, or someone else has already found two snowflakes that match under that standard.

If you type "two snowflake alike" into google, you'll get useful links like this.
posted by blenderfish at 3:31 PM on December 29, 2006

err, "two snowflakes alike"
posted by blenderfish at 3:33 PM on December 29, 2006

I suspect that the question is impossible to answer; nobody has found two snowflakes that are exactly alike, but there's no way to prove that two identical ones don't exist.

Wikipedia seems to agree with me here, from the article on Snow:

There is a widely-held belief that no two snowflakes are alike, but that claim has not been proven, and, due to the astronomical number of snowflakes that fall, is impossible to prove by exhaustive methods. Strictly speaking, it is extremely unlikely for any two objects in the universe to contain an identical molecular structure; but, there are, nonetheless, no known scientific laws which prevent it.

posted by Kadin2048 at 3:35 PM on December 29, 2006

Depends on what you mean by 'identical.' Google gives me this reference. Or, as the Straight Dope puts it, "The crystals in question admittedly aren't flakes in the usual sense but rather hollow hexagonal prisms. They are also not absolutely identical, but come on, if you insist on getting down to the molecular level, nothing's identical. They're close enough for me. "
posted by Andrhia at 3:40 PM on December 29, 2006

Everything everyone's said is true, but we have this saying about snowflakes in my language too, and I think that there was always an implication within it that there was some "magical" quality about snowflakes that made them less likely to be the "same" than other natural things like leaves or raindrops or flowers or something. Of course, on an atomic level, nothing's the same, but even relative to magical snowdrops, I always thought it was sort of a dumb thing to go around saying. But I am a cynical girl!
posted by Dee Xtrovert at 3:55 PM on December 29, 2006

"No two snowflakes are alike" is really an aphorism that illustrates the principle: if you look close enough, no two things are ever truly the same. Which is, of course true.

Snowflakes are a convenient example to use to illustrate this principle because we can all wrap our minds around snow (which all looks the same to the naked eye) and a magnifying glass(which demonstrates that they all look different).

I think it is possible that two snowflakes have existed that look identical under the magnifying glass, but the basic law of nature that the aphorism illustrates holds if you use more sophisticated means of measurement, like mass spectography (or whatever smart physicists use to look at crystals).

So, in summary, "No two snowflakes are alike," true.
posted by Slarty Bartfast at 5:02 PM on December 29, 2006

False. Of course they are alike, or the word "snowflake" wouldn't mean anything.
posted by owhydididoit at 5:25 PM on December 29, 2006

Platonic issues aside, snowflakes are merely finite-sized (small, even!) crystals, and there are only so many ways that water atoms can fit together.

There are a lot of snowflakes created every day. Some small fraction falls to earth.

You're not asking if there are any snowflakes like a snowflake you have in mind; you're asking if there are two snowflakes that are like each other, so the birthday paradox applies.

In short, for any given snowstorm, I bet there are a few thousand identical snowflakes, plus or minus a few orders of magnitude.
posted by cmiller at 7:42 PM on December 29, 2006

I think that there was always an implication within it that there was some "magical" quality about snowflakes that made them less likely to be the "same" than other natural things

I think what you have in the case of snowflakes is a combination of properties-- plentiful (or seemingly infinite in number,) sharing almost all properties, structurally complex, yet very different from each other.

This particular combination of properties makes it a particularly apt metaphor for humanity, which is what I've always heard it used to describe. But, it also tends to get across the general, albeit less poetic sentiment, that "homogeneity is often superficial."

Some snowflakes.
posted by blenderfish at 12:48 AM on December 30, 2006

"You are not a beautiful and unique snowflake." — Tyler Durden
posted by WCityMike at 10:38 AM on December 30, 2006