hey it's me Destin welcome back to
smarter every day I have a problem there
is a specific water phenomenon that I've
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 a hot griddle it creates a layer
of water vapor underneath it only that's
not what it is do you have any
information please let me know it
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 coffee maker when the
conditions are just right you'll notice
that coffee beads up on top of coffee
why does it do that sometimes when you
turn the showerhead on the water will
blast to the other side of the tub and
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 in just the right
fashion you'll get these little drops
that beat 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
then 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
it's water dancing on water but we're
going to do it here on earth and then in
space okay yeah and we're gonna water
down this one 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 be with
your ended
kind of stuff you need it right anyway
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've 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 v25 11 which is a very very fast
camera and it's really loud but we're
going to turn on the science here and
give it a go after only about an hour of
working through 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 all right so
we have a drop bouncing 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 it
coalesces that's called the residence
time and 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 verify 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 bin at night
Hawking light 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 a baños
destin are you and this is dawn
we're in science garage here having fun
awesome
nan : cold air from what frequency and
amplitude worked out best for you 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 it anything will change one
variable okay that's me turning on the
vibration of the speaker so so 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 draw
it helps maintain that you can say here
and postulate they'd stir you're blue in
the face and tell you make an
observation to see what that fundamental
physics is then you can back out what's
going on in high-speed of what's going
on with that draw 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 you agree yeah this is just
totally awesome but you've been to space
it's alright 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 hand
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 zero 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 draw the greater the gravitational
force pushing down on it but what if you
did this somewhere where there was no
weight on the draw 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 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
okay trying a wave so dumb 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
this video sets my brain on fire we
learned two main mechanisms for
coalescence we have the weight of the
drop that squishes that air boundary and
makes it go well we have no weight so
we're left with collisional kinetic
energy every collision that results in
the coalescence everything is right
there and you can just directly see
what's happening the side wall that's
vibrating it makes the small drops go
faster than the big drops because
there's lower mass but it's the same
amount of excitation energy I really
like this video it's beautiful on
multiple levels and I want you to think
it's beautiful too
you
this has been a huge science goal for me
for a really long time so I want to say
thank you to the Google making and
science team for making this video
possible thank you so much if you wanna
see really cool videos check out the
hashtag science goals there's all kinds
of videos being uploaded all the time
for example check out being at Nighthawk
and light obviously he helped me make
this video it was his speaker setup
they helped us do the stable bouncing
droplets in this video or check out
diana AKA physics girl who teaches you
how to make anti bubbles in your own
home using household items or you can go
check out this cool video by derek at
veritasium who explains that the
bouncing drop mechanism can be used to
model quantum theory he uses bouncing
drops of silicone oil to reproduce the
double slit experiment check out any of
these other videos under the hashtag
science goals to go see really awesome
science content a huge thank you to don
pettit for sharing his knowledge of
surface chemistry and his orbital
footage in a really humble way that was
awesome thank you Don last thing the V
2511 the phantom that we used in this
video that's now a thing on smarter
every day which has also been a science
goal for a really long time so if you're
interested in subscribing you've ever
thought about it now's a really good
time to do that because the slo-mo is
about to get slower and it's about to
get higher resolution and it's about to
get more fun feel free to click my face
if you like to subscribe if not that's
it I'm Destin you're getting smarter
every day have a good one