How do we know?
↻ One of the pages with a moving picture
People photographed snow crystals, and even grew one in a lab.
- High in a cold cloud, water vapor freezes onto a speck of dust. A tiny six-sided ice prism is born.
- Ice crystals are built in a six-sided pattern, so the crystal grows six flat sides.
- Little bumps catch extra vapor and grow faster. They stretch out into branches.
- As the flake falls, the air around it keeps changing. Each change shapes it, so every flake takes its own trip.
On 15 January 1885, Wilson Bentley took the first photo of a single snow crystal, in Jericho, Vermont. In March 1936, Ukichiro Nakaya grew the first snow crystal in a lab, on a rabbit hair, in Sapporo, Japan.
A snow crystal holds so many molecules that it can grow in countless ways. Nobody can check every flake. Scientists think two big, branchy flakes being exactly alike is extremely unlikely.
Snow and sleet are different. Snowflakes grow from vapor.
Wow number
1 billion billion water molecules can be in one small snow crystal. That’s a 1 with 18 zeros!
Myth or fact?
Snowflakes are frozen raindrops. Myth. Frozen raindrops are sleet. Snowflakes grow from vapor.
Two tiny, simple snow crystals can look alike. Fact. Plain six-sided prisms often match.
Think about it
The six arms of one snowflake usually look alike. Why? (Hint: they all grew at the same time, in the same air.)
Where in the world?
Jericho, Vermont, USA where Wilson Bentley took the first photo of a single snow crystal on 15 January 1885. In Sapporo, Japan, Ukichiro Nakaya grew the first snow crystal in a lab in March 1936 — 44.5039° N, 72.9873° W.
Where these facts come from
Every number on page 35, and who measured it
This page explains how a snowflake grows from a speck into six branches.
How Do Snowflakes Form? — NOAA's weather-satellite service
nesdis.noaa.gov/about/k-12-education/ice-snow/how-do-snowflakes-form
We checked it on 31 October 2026
This page tells us how many molecules are in a snow crystal and whether two flakes can be alike.
Snowflakes - No Two Alike? — A snow-crystal physicist at Caltech, a science university in California
its.caltech.edu/~atomic/snowcrystals/alike/alike.htm
We checked it on 31 October 2026
This page tells us about Wilson Bentley's first snow-crystal photo in 1885.
First photograph of a snowflake — Guinness World Records, which keeps lists of world records
guinnessworldrecords.com/world-records/606626-first-photograph-of-a-snowflake
We checked it on 31 October 2026
This page shows Wilson Bentley's snow-crystal photos and the date of his first one.
About the Bentley Collection · Bentley Photomicrographs · AOSS Library Digital Collections — The University of Michigan's climate and space science library
aosslibrary.omeka.net/exhibits/show/bentley_photomicrographs/about
We checked it on 31 October 2026
This page tells us how Ukichiro Nakaya grew a snow crystal on a rabbit hair.
Low temperature science: the past, present, and future — Hokkaido University in Japan, where Ukichiro Nakaya worked
global.hokudai.ac.jp/blog/low-temperature-science-the-past-present-and-future
We checked it on 31 October 2026
This page tells us that frozen raindrops are called sleet.
What is the Difference between Sleet, Freezing Rain, and Snow? — The U.S. National Weather Service
weather.gov/iwx/sleetvsfreezingrain
We checked it on 31 October 2026
Has this changed?
How snowflakes grow is not going to change.
The answer to whether two flakes can match is a matter of chances: scientists say exactly alike is extremely unlikely, but nobody can check every flake.
Words from this page
- water vapor
- Water as an invisible gas in the air.
- molecule
- A tiny bit of something. A snow crystal is made of a huge number of water molecules.
- sleet
- Frozen raindrops.
Try it!
Catch a snowflake and count its arms.
1. Put a piece of dark paper in the freezer for 15 minutes. 2. When it snows, bundle up and catch a few flakes on the paper. 3. Look with a magnifying glass. Count the arms!
What happens: on cold paper the flakes don’t melt right away, so you can see their six-sided shapes.
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