Did You Know? The Science of Unique Snow Crystals

Is it true that no two snow crystals are alike? If so, how do we know?

The Librarian in the Science Reference section of the Library of Congress has the answer!

The scientific consensus states that the likelihood of two large snow crystals being identical is zero.

The probability that two snow crystals (a single ice crystal) or flakes (a snow crystal or multiple snow crystals stuck together) will be exactly alike in molecular structure and in appearance, is very minute. And to prove otherwise would not be easy. Each winter there are about 1 septillion (1, 000, 000, 000, 000, 000, 000, 000, 000 or a trillion trillion) snow crystals that drop from the sky!

To go through all of the snow crystals produced every winter would be a daunting task. So, we rely on cloud physicists, crystallographers, and meteorologists to study snow crystals and explain to us why there are no two snow crystals alike.

First, we need to understand that not all water molecules are exactly alike. Generally speaking, water molecules have two hydrogen molecules with one 16O atom. However, not all water molecules will have this arrangement. Some water molecules will have an atom of deuterium in place of one of the hydrogen atoms and some water molecules will have an atom of 18O. Since the molecular makeup of snow crystals varies greatly from one to another, it follows that each snow crystal will be slightly different.

Furthermore, the unique and complex features of snow crystals are very much affected by unstable atmospheric conditions. Snow crystals are sensitive to temperature and will change in shape and design as they fall from the cloud and are exposed to fluctuating temperatures. To have two snow crystals or flakes with the same history of development is virtually impossible.

So the next time you look closely at snowflakes on your gloved hands, you can marvel at their complete uniqueness!