OK. Can you just turn it on?

Should we wear like goggles in case, sand-- oh yeah, you got the button behind you.

I don't think it's going to go anywhere.

You don't think so?

No.

Can I go for it?

Yeah.

[YELL] You said it wasn't going to go anywhere.

[LAUGHS] You lied.

I trusted you.

You were leaning over it.

It couldn't have been any better.

I'm pretty sure they put sand in toothpaste, so how bad could it be?

Hey, I'm Diana.

You're watching "Physics Girl," and I am here with William Osman.

I drove up to Ventura to meet with William and his cameraman, John, who you may know from such works of art as-- Sandwich Vin Diesel.

DIANNA COWERN: Yeah, sandwich Vin Diesel on YouTube.

WILLIAM OSMAN: I think that's it.

No one else knows anything else.

Well you've got this-- what is it called?

Retina Smelter.

Retina Smelter 9000.

Yeah.

And what I wanted to do, I saw this GIF on the front page of Reddit.

And it was turning sand into liquid by bubbling air through it.

Had you seen it?

WILLIAM OSMAN: I did, yeah.

I actually had.

DIANNA COWERN: Yeah.

I thought it was going to be a lot easier than it has been, to be honest.

Yep.

I ate sand.

Oh, my god.

Oh.

OK. That, it didn't, like, work at all.

What do we do?

[MUSIC PLAYING] WILLIAM OSMAN: Oh, wow.

DIANNA COWERN: Oh, yeah.

WILLIAM OSMAN: Minus the fact that it's going literally everywhere.

DIANNA COWERN: OK, first problem, too much air.

It took us much longer than we should admit to eventually figure this out, and switch from using a shop vac to using an air compressor.

But in the meantime, the sand quality problem.

[VACUUM] 65 00:01:46,600 --> 00:01:51,039 Who knew all sand from hardware stores is wet in Ventura?

67 00:01:56,992 --> 00:01:59,714 Now this is so much better.

There's not much on the internet for how to do something like this, besides especially academic papers.

So we looked really closely at Google Images.

And noticed that the sand grains are particularly fine.

Get it?

Particularly, like particle, get it?

No?

OK.

So I order some sandblasting glass beads like these really, really, really tiny spherical glass beads from McMaster, which had the added bonus of acting like water droplets when light shines on them.

Because they're pretty uniform in shape and size.

And so they reflect and disperse light to make a rainbow.

I love rainbows.

Our first setup was a Tupperware container with a wooden box we had made with a laser cutter, with a bunch of holes cut in the top by the Retina Smelter 9000.

And the holes were an attempt to get the air from the input into the wooden box to go uniformly up through the sand.

It didn't work.

[VACUUM] 93 00:02:58,490 --> 00:03:01,540 The problem was once the air finds a path through the sand, it makes that the preferred path.

It's like a river cutting a valley through a mountain.

Eventually all the water will follow that path.

So we had to make it so that the air would want to follow all paths equally, like a mountain that you can't cut a valley into.

So over the weekend, William made a new setup.

Thanks, William.

With a bigger wooden box as the lower chamber that gets pressurized by the air input, and then we used a cloth instead of all those little holes to equally distribute the air pressure.

And then our main sand chamber was a white plastic bucket.

Here's how that went.

WILLIAM OSMAN: Ready?

DIANNA COWERN: Mm-hmm.

Ah-ha!

That's awesome.

WILLIAM OSMAN: That's really cool.

DIANNA COWERN: So that's cool.

So I've really got some-- I mean it's like buoyant.

The problem I think here is that the t-shirt material we used was too stretchy.

So it bulged up in one place.

And that became the preferred path of the air like, the river valley.

So we tried a thicker material from a tablecloth and stretched it really taut over the ring and glued it.

And-- Yes!

It worked.

This is so exciting.

Oh, we blew through that part.

For a little bit.

[MUSIC PLAYING] 130 00:04:34,140 --> 00:04:36,960 The reason that this strange phenomenon occurs that sand can act like a liquid and you can stir it and float things, is that we're causing fluidization.

Fluidization happens when you bubble fluids like air through solid particles, like sand.

I know you may be thinking, but air is not a fluid.

Well, in the world of fluid dynamics, gases are fluids.

They flow like fluids.

So the fluid, the air, acts to decrease friction between the sand grains because it keeps them more separated, which is important.

And of course, there's not much friction between the fluid and the particles.

So with this decreased friction, the sand can act like a liquid.

And as you increase the amount of gas you're bubbling up through, the particles eventually come to an equilibrium between a force upward by the gas and a force downward by gravity.

And the particles become sustained in the flow.

It's like they're floating.

And then they form a nice soft bed, which is why engineers call this a fluidized bed.

Now if you increase the gas velocity, the particles will no longer form this nice bed and they'll be carried upward by the gas flow.

[VACUUM] [YELL] Fluidization is incredibly common in industry.

For example, it's used to control the temperature of combustion.

So if you want things to burn at a lower temperature, because when they burn at a higher temperature you can produce more harmful pollutants.

NOx and SOx.

So bubbling up a cooler gas between your solid fuel particles will cause them to burn at a lower temperature.

Fluidization is also used in the food industry, like if you want to cool down something particulate really fast, like peas or corn, you bubble cool air up through them.

And an everyday example of fluidization is those hot air popcorn cookers where you bubble up hot air, and the popcorn kernels look like they're boiling.

Anyways, this was a super fun project to fail at.

Somehow when I do these experiments, I always end up unscathed.

You shouldn't work with me.

It's not good for your health.

But thanks anyways to William and John for making this happen.

Check out their channel.

It's called William Osman.

It's hilarious and informative.

Thanks for watching.

And happy physics-ing.