The Science of snowflakes with Professor Brian Cox | the Royal Society
Transcript
- Snowflakes are intricate, beautiful, mysterious,
- and totally captivating.
- But for all their complexity - and endless variety -
- the structure of a snowflake can be explained
- by a few universal laws of nature.
- Laws that explain everything from snowflakes to galaxies.
- Let's start at the beginning.
- What is a snowflake?
- Or, to use its more technical name, a snow crystal?
- A snow crystal forms up in the clouds
- when water vapour meets little specks of dust or pollen.
- This forms its tiny hexagonal heart.
- The tips stick out and are rough.
- This attracts water molecules.
- And then more water molecules.
- And then more.
- These form the branches of our snowflake.
- The size and shape of these branches
- depends on the exact temperature and humidity
- that the snowflake meets on its journey through the clouds,
- pulled down by the force of gravity.
- Each one takes a very slightly different route -
- meaning no two snowflakes are quite the same.
- When a snowflake lands on your sleeve,
- it has been on its own, totally unique, journey to reach you.
- Before melting away in a moment.
- Way back in 1611, on a bitterly cold January morning in Prague,
- a snowflake landed on the sleeve of mathematician Johannes Kepler.
- And it got him thinking
- "Why do snowflakes have six sides?"
- Kepler's breakthrough was his theory that this hexagonal pattern
- is the most efficient use of space.
- Whether it's a honeycomb within a beehive.
- Or piles of stacked cannonballs.
- Or a delicate, transient snowflake.
- It took 400 years
- - 400 years! - for his theory to be proven.
- What Kepler didn't know at the time is that each molecule of water,
- or H2O, is made up of two hydrogen atoms and one oxygen atom.
- As the water molecules cluster together when they freeze,
- the angle between the hydrogen atoms is always,
- approximately, 105 degrees.
- And that gives us the six sides.
- At its heart, 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 like a needle.
- Cylindrical like a bullet.
- Or, just occasionally, triangular.
- The truth is though, most snowflakes are kind of...well, blob-like.
- If you speak to a snowflake photographer -
- there are just a handful in the world -
- they'll tell you it takes days and days out in the cold
- to get that "money shot".
- And the conditions have to be just right -
- between minus 15 and minus 13 degrees.
- But ever since Wilson Bentley,
- a farmer from the US state of Vermont,
- painstakingly took the first photos of stunning snowflakes in 1885,
- we've been hooked.
- Scientists have shown that symmetry
- is incredibly pleasing to the human brain.
- Snowflakes are all radially symmetrical,
- which means you can cut them into identical slices, like a cake.
- Shells, flowers, starfish,
- even spiral galaxies,
- like the Milky Way, share this type of symmetry.
- And nature has one last trick up its sleeve.
- Snowflakes aren't actually white.
- They're clear, but they have lots of edges,
- and this scatters the light, making them appear white.
- Each snowflake is a microcosm of the laws of physics.
- Gravity makes it fall.
- Electromagnetism dictates its shape.
- And you've got symmetry.
- It's the same with the stars, and solar systems, and planets.
- And with us.
- When you look at a snowflake, you can read its history.
- Its own unique story.
- The experiences it encounters shape it into what it is.
- Just like us, really.
Join us for a wintery deep dive into the wonderful world of snowflakes, voiced by Professor Brian Cox. Made in partnership with BBC Ideas.
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