What snowflakes tell us about our universe
Professor Brian Cox: Snowflakes are complex, beautiful, mysterious and absolutely fascinating. However, despite the complexity and infinite variety of snowflakes, their structure can be explained by some universal laws of nature. Laws that explain everything from snowflakes to galaxies. Let’s get started. What is a snowflake? Or, to use a more technical name, snowflakes? Snowflakes form in clouds when water vapor meets tiny dust particles and pollen. This forms a small hexagonal heart. The tip is protruding and is rough. This attracts water molecules. And the number of water molecules increases. more. These form the branches of the snowflake. The size and shape of these branches is determined by the exact temperature and humidity that the snowflake encounters on its way through the cloud due to gravity. Each snowflake follows a slightly different route. This means that no two snowflakes are exactly alike. When a snowflake falls on your sleeve, it’s on its own, totally unique journey until it reaches you. Before it melts in an instant. Back in 1611, on a bitterly cold January morning in Prague, a speck of snow fell on the sleeve of mathematician Johannes Kepler. So he thought, “Why does a snowflake have six sides?” Kepler’s breakthrough was his theory that this hexagonal pattern was the most efficient use of space. Even if it’s a beehive within a beehive. Or a pile of shells. Or a delicate and ephemeral snowflake. It took him 400 years to prove his theory. What Kepler didn’t know at the time was that each molecule of water, his H2O, was made up of two hydrogen atoms and one oxygen atom. When water molecules freeze, they form clusters, so the angle between the hydrogen atoms is always about 105 degrees. This gives him six sides. The center of a snowflake is always a hexagon. But it can grow into all sorts of weird and wonderful shapes. Long and thin like a pencil. Sharp as a needle. Cylindrical shape like a bullet. Or, occasionally, a triangle. But the truth is, most snowflakes are some kind of thing, a lump. Talk to any snowflake photographer (of which there are only a few in the world) and they’ll tell you that it takes days in the cold to get a “money shot.” And we need exactly the right conditions: between -15 degrees Celsius and -13 degrees Celsius. But ever since Vermont farmer Wilson Bentley painstakingly captured the first stunning photo of a snowflake in 1885, we’ve been hooked. Scientists have proven that symmetry is incredibly soothing to the human brain. All snowflakes are radially symmetrical, so you can cut them into equal slices like a cake. Seashells, flowers, starfish, and even spiral galaxies like the Milky Way share this type of symmetry. And nature has one final trick up its sleeve. Snowflakes are not actually white. Although it is transparent, it has many edges and scatters light, making it appear white. Each snowflake is a microcosm of the laws of physics. It falls due to gravity. Electromagnetism determines its shape. And you have symmetry. The same goes for stars, solar systems, and planets. And with us. When you look at a snowflake, you can understand its history. A unique story of your own. The experiences you encounter shape it. It’s really just like us.