How do snowflakes form?

Scientist and author Ainissa Ramirez joins Hari Sreenivasan to discuss one of her latest podcast episodes, “Why Snowflakes Have 6 Sides.”


Ainissa Ramirez is a scientist, author, and a self-proclaimed science evangelist.

She's calling for big changes in science education and just launched a new podcast series, called 'Science Underground.'

Here to discuss one of her podcast episodes, called 'Why Snowflakes Have Six Sides,' is Ainissa Ramirez.

Basic question.

[ Chuckles ]

But I never really thought about it until now.

What are the props here?

And how does this help explain this answer?

Well, when we are in school, we usually have props that look like this.

We draw snowflakes that look like that, and that's actually scientifically correct.

It has six sides.

And if you want to know the answer, you have to go to the grocery store, over to the produce section.

Look at the oranges.


You look at how oranges are arranged, you'll see that each orange is touching six other oranges.

If I were to draw a line around this, it would be a hexagon.

And this is what water molecules do -- they arrange themselves the same way as these oranges, and they grow from each one of these sides and create branches.

And so that's how we get a snowflake.

What's the advantage?

Why do they want to touch six other molecules?

Well, this is how you can have the most number of neighbors, so you can have the most number of bonds.

So this is sort of like the atomic level of what's going on.

In order for atoms to have the most number of nearest neighbors, this hexagonal arrangement is one of the ways to do it.

So, but if the oranges were smaller -- let's say they were golf balls -- couldn't you have 18 neighbors or 27 neighbors?

No, it ends up that it scales.

So if I went down to, you know, BBs or if I went up to bowling balls, it would still be six.

That's called the closest way that you can compact something.

And how exactly -- You know, when we think about snowflakes' being created, explain that for me.

When those water molecules are touching these neighbors, what's happening?

Well, it all starts with a piece of dust or a piece of ice.

And water molecules in their vapor form collect on this piece of dust, and they start to arrange themselves, and they want to make sure that they're the closest packed, so they create this hexagonal array.

So at the center of every snowflake is dust?

Is a piece of dust.

Every time you put your tongue out, you're actually -- that piece of dust -- it's like, 'Mmm. Yummy.'

How many water droplets?

You said a hundred --

100,000 water droplets makes one snowflake.

And how do we know that?

It's been proven.

[ Laughs ]

There's a gentleman in Caltech, Ken Libbrecht, and he helped me out and he told me about the math of how -- It takes a lot of water molecules to make a snowflake, and so it takes about 100,000 water droplets to do that.

Okay. When I think of a droplet, I'm thinking of what comes out of an eye dropper.

That's right. That's right.

100,000 of those?

100,000, 'cause you have to remember, a liquid has water molecules moving around, and they're not densely packed.

But in a solid, like in a snowflake, everything's as packed as it could be.

It's sort of like being in the subway in New York rush hour.

There's no other space.

However, a liquid is sort of like being on the subway, 2:00 on a Saturday.

Not too much -- Not too many atoms around there.

So that's the difference between a liquid and a solid.

It's much more closely packed, so you have many more water molecules hanging out.

So 100,000 water droplets per snowflake, and --

It's mind-blowing.

The blizzard -- That's -- I don't know what even, jillions of water droplets?


So it ends up that it's about an inch of rain equals about a foot of snow.


So, you know, next time you see rain, just be grateful it's not snow, 'cause that could be a foot of snow.

So that can just give you a sense of how many water droplets are in liquid and how many water droplets are in a solid.

So, is there a greater implication, I guess, to scientific research when they went after this quest to figure out how a snowflake forms?


Why would they do this?

Why would they do this?

What were they hoping to learn?

Well, snowflakes are crystals, and that's interesting to everyone because crystals are inside your cellphone.

The semiconductors are crystals, so if we know about crystals in a snowflake, the lessons kind of parallel to a snowflake in a cellphone.

So a snowflake is a crystal just like a ruby or a diamond.

And so the calculations wasn't -- It wasn't like someone was crazy and they said, 'I'm just gonna figure out a snowflake.'

[ Laughs ]

It is that that information translates to so many other technologies as well.

Okay. So it might be from the diamond department that someone...

That's right.

It's probably a crystal grower.

There's people who grow different types of crystals on a very pure scale, and you can learn a lot about properties 'cause a crystal is sort of like the purest material, and so you can learn a lot of physics and a lot of material science that's going on.

And then it wasn't too hard to make a calculation for what a snowflake -- what it takes to make a snowflake.

All right. Ainissa Ramirez, science evangelist, thanks so much for joining us.

Thank you.