I have a problem, there is a specific water phenomenon

that I see happening all around me

but I have no idea how it works

I've been trying to figure it out for

years, in fact i put a video on this

channel in 2011, asking people to help me

figure it out!

there's something interesting happening

here I don't understand it it looks like

water droplets are standing on water

droplets. It looks like water is

hydrophobic it looks like when a bead of

water skates across the hot griddle it

creates a layer of water vapor underneath it

only that's not what it is

If you have any information please let me know

I'd appreciate it

you've seen this right? If you watch the

world with a critical eye like I do

you'll see this everywhere for example

if you've ever allowed yourself to watch

a drip coffeemaker when the conditions

are just right you'll notice that coffee

beads up on top of coffee

what does it do that sometimes when you

turn the shower head on the water will

blast to the other side of the tub

instead of making the bottom of the tub

wet these pearls of water will dance on

top of the water that's already in the

bottom of the tub. Don't let this weird you

out it's just water and food coloring

but the interesting thing is if you get

the stream in just the right location

and interacts with a porcelain and the

water that's in the toilet and just the

right fashion you'll get these little drops

that bead up. I don't understand what the

conditions required to make it happen

are, but I get really excited about it and I

want to understand.

Seriously one time we landed an Apache helicopter on the pad

at work, and the environmental control system

was leaking condensate down onto the

asphalt, and the beads were happening there

that was the moment I realized i have to

know why this is happening. In order to

figure it out we're going to Science Garage

to see my friend Don Pettit who

has out-of-this-world experience in the

area of surface chemistry

let's go get Smarter Every Day.

its water dancing on water, but we're gonna do it

here on earth, and then in space, that OK?

Yeah, and we're going to water down this one!

Yeah, and we're going to water down this one! [laughs] that's bad.

if you know who Don Pettit is you understand why I came to him

it's rare to find a person that not only

understands how to capture beautiful photos

but also understands the

fundamental science behind each image

seriously who else do you know that

collects books on surface chemistry and

wedding phenomena you own these

references?

Yeah. Really?

Well I mean when you're into this kind of

stuff you need it, right?

Anyways scientists all over the world

have created elaborate setups in their

labs to try to observe these dancing

drops and they've got some really great

data but I knew if I got the right type

of camera in Don's hands

and just turned him loose

we would not only get the data but

we would do it beautifully

it's a Phantom v2511 which is a very very

fast camera and its really loud but

we're gonna turn on the science here

and give it a go

after only about an hour of

working through the lenses and lighting

with Don, he quickly came up with a setup

to observe a beautiful single drop of

water landing on, bouncing, and then

coalescing into a larger pool of water

alright so we have a drop balancing on a

still surface of water and you'll notice

that it isn't coalescing.

Coalescence is when you have two pieces of water that

touch and then merge to become one piece.

Now you notice there's this delay time

where the drop is sitting there before

coalescence that's called the 'Residence Time'

tand scientists have a pretty good

understanding of what's going on here.

As a drop touches the surface scientists

believe there's air trapped in-between

as the drop rests that air starts to

seep out of that gap and then

coalescence occurs.

The National Institute of Health did this really cool

study where they verified the air gap theory

by reducing the air pressure

around coalescing water drops and as

you'd expect the lower the air pressure

to lower the residence time which is

really cool

anyway you can plainly see on the video

that Don captured that as the drop comes

to a rest it starts to slowly bob up and

down and then it's like a little water bridge

is built in that air gap and then

coalescence occurs so this is my

question in the phenomenon I'm seeing

I'm seeing a steady state bouncing of a

drop which means there's impacts

happening over and over

why is that not punching through that

air gap and causing coalescence to

happen easier? In order to understand this

we actually have to look at that impact

which means this is about to get awesome

this is a device that's been shipped to me

from another youtube channel

Ben at NightHawkInLight and he has

drops of water that he puts on water

which is sitting in a speaker so we're

about to basically recreate the setup

that Ben did. So full disclosure you've

done this in space right? I have!

But we're going to use this high-speed

camera to understand the phenomenon here

on earth and then you're going to teach

me about what you discovered in space

right? Yeah we're gonna, we're gonna start

on earth and end up in space

[phone ringing]

Hello? Hey Ben it's Destin, how are you Yeah and this is Don

we're in science garage here having fun

Awesome, Don it's cool to hear from you

what frequency and amplitude

worked out best for you?

worked out best for you. [Beep]

if we were to turn that speaker off right now they

would go away right? Well let's see. Okay

See? They're there but they coalesce very quickly

So, okay keep doing that don't

change anything we'll change one variable

OK. That's me turning on the vibration of

the speaker. So what I think is

happening is; the water is trying to

settle and go down and press against the surface

Uh-huh that's right. But because it's

being pushed back up due to that

vibration it, it adds energy back into

the system and then pushes it away

And I'm saying that that process keeps the

small air gap between the drop, it helps maintain that

You can sit here and postulate things till you're blue in the face,

until you make an observation to see

what that fundamental physics is, then

you can back out what's going on and

high-speed of what's going on with that

drop it would do a lot to help answer these questions

this is quickly becoming

one of the most awesome setups I've ever

been a part of, would y'agree?

Yeah this is just totally awesome.

But you've been to space!

Allright, here we are

the moment of truth after years of waiting

we finally have everything we

need in order to make

an actual observation. Here we go.

and there it is

did you see it? When i first saw this

footage it stood out to me like a sore

thumb instead of crashing into the drop

like I anticipated it's almost like

those peaks and valleys make some type

of moving catcher's mitt that gently

catches the drop and lets it down gently

without breaking that air layer

now i want to zoom in and see if we can

see that wave catch the drop

there it is it's pretty clear what's

going on here think about it this way if

somebody threw you a water balloon would

you rush your hand up and try to meet it

really quickly and risk bursting that

surface tension? No, you would try to

match the velocity of the balloon with

your hands so you could decrease the

collisional kinetic energy in fact

there's an equation for how to calculate

collisional kinetic energy and that's

what factors into whether or not the

drop survives if the velocity of the

liquid and the small drop are about the

same then that factor goes to 0 and the

collisional kinetic energy quickly

decreases to zero now that we understand

this we can infer that timing is a huge

factor here and there's probably a bunch

of drops that just don't survive because

they hit the wave wrong

in fact that's exactly what we see in

the high-speed. One more thing to think

about is the fact that gravity is

constantly pulling the drops back down

to that vibrating surface which means it

always has to find the soft spot to land

the larger the drop, the greater the

gravitational force pushing down on it.

But what if you did this somewhere where

there was no weight on the drop?

Oh, then it bounces off

I've got the video. Can we see it?

Yeah!

I discovered this phenomenon for myself

occurring naturally in the woods of

alabama in 2011, the same year that

Don Pettit launched to the international

space station where he accidentally

recreated the phenomenon in a really

remarkable way. He performed a very

similar water speaker experiment, except

in weightlessness the water forms a

sphere. Just to make it interesting Don

put an air bubble on the inside of that

water sphere and then he played tones

through the speaker just to see what

would happen

[Don]... and the air bubble is attached to the speaker cone, and so is

the water and i'm at 60 Hertz i'm going

to start increasing the amplitude, here we go

Wow. So we're getting a series of

standing nodes on the interface of the

air bubble with the water. I'm going to

put a square wave in

OK... triangle wave

So Don played with different frequencies, amplitudes,

he played different types of music like rock

and roll, and then he played the cello

Don said whenever he played cello music specifically,

little drops would break off

on the inside of the sphere

and start bouncing around on the inside.

A Cello!?

There's something about the Cello!

[Music: Bach's Cello Suite No. 1 - Prelude]

This video sets my brain. on. fire.

We've learned two main mechanisms for

coalescence we have the weight of the

drop that squishes that air boundary and

makes it go