Welcome to the science.

Have you seen this experiment before, with the milk and the food coloring?

And then you put some dish soap on the end of a Q-tip, and you dip it in the middle of the liquid to get this awesome experiment.

This is the kind of experiment that never gets old.

But if you're like me, and you fidget a lot and you keep playing with it, you'll notice that if you flick the Q-tip across the surface of the water, you get these little beads that roll across.

They're like little bowling balls that roll across-- oh, my god.

That's so pretty.

I have to take a picture.

Thanks to some phantom high speed footage from "BeyondSlowMotion"-- awesome channel, definitely check it out, link is in the description-- you can see that these beads form as strings of milk break up into individual droplets and then bounce on the surface.

It's so mesmerizing.

But what are they?

I drove myself crazy, googling every different combination of soap and milk and food coloring and liquid.

And I could not figure out what they are.

So I did what I always do when I need to know something.

And I asked my physics friend, Dan Walsh, who immediately said-- Antibubbles.

I thought he was joking.

You think I'm joking.

Turns out he was close.

Anitbubbles are even cooler than this.

DIANNA COWERN: Dan, are you ready for this?

I was born ready.

Oh!

DIANNA COWERN: Ah, yeah!

That's amazing!

I am here with Ashley who's my intern, and Dan who is my friend.

And he's just really enthusiastic about physics.

Also s PhD student in physics.

That's another reason why I'm so interested.

Yeah.

Also a student of physics.

So much physics here!

So antibubble is the exotic sounding name given to these little spheres that we've made underwater.

Because they're kind of like the opposite of a regular bubble.

A regular bubble is a thin film of a liquid, enclosing a gas and then typically floating in a gas, like air.

Whereas an antibubble is a thin film of gas, enclosing a sphere of liquid and then typically fully submerged in a liquid.

ASHLEY: Do you want to try this one?

Oh, yeah.

Just try and bunch of different parameters.

DIANNA COWERN: So you've got to put water in both of these containers, then add soap, mix it all in.

And then you squeeze water from this container onto the surface of this one.

Oh, that was a good one.

ASHLEY: You got some good ones.

DIANNA COWERN: Those are awesome.

The water drags some air along with it, which closes off into a shell.

DAN: It takes some time to get used to it.

DIANNA COWERN: It is like a sweet spot angle.

You have to find a sweet spot.

But it's easy to see the structure of the antibubbles when we added food coloring into the squeeze bottle.

Because then when they pop, you can see that colored liquid come out, typically making the shape of a vortex ring.

ASHLEY: Oh!

DAN: Did you see how there was a little regular bubble that came up?

DIANNA COWERN: By using high speed cameras, physicists have observed that the air at the bottom of the antibubble floats to the top, popping the air film.

You've now got a little air droplet that floats to the surface, which is just the opposite of a popped bubble, where the liquid film falls because of gravity.

Thank you guys!

Sure, thank you.

High fives.

[laughter] So despite sounding like some exotic form of matter, antibubbles are actually just as common as regular bubbles.

You make them when you wash your hands with soapy water.

But they pop much more easily than regular bubbles.

Why?

Wait, so why do regular bubbles pop?

So you form a regular bubble by decreasing the surface tension of water.

And when you decrease the surface tension, bubbles can live a lot longer.

There's actually a really interesting molecular reason why bubbles keep their nice spherical shape.

It works like this.

Each soap molecule has a hydrophilic, that is a water-attracting head, and a hydrophobic-- or a water repelling-- tail.

When you make a soap bubble, the soap molecules line up so that hydrophobic heads are in contact with the water.

They have a slight electric charge, which means that the soap molecules on one surface of the film repel the soap molecules on the other surfaces, which helps keep the film from collapsing in on itself.

That is, until the film evaporates.

Now an antibubble, on the other hand, is also made of soapy water.

But there are a few key differences.

Everything's all flipped around.

So in the antibubble air film, the hydrophobic tails are now facing each other in the film.

And the hydrophilic heads are facing away in the liquid.

Soapy water is actually a good electrical conductor, which means that electric charges can flow easily through it.

So those slightly charged hydrophilic heads attract oppositely charged molecules in the water, basically neutralizing the charge of the surface of the antibubble air film.

Those electric repulsive forces that basically help the bubble keep its shape don't exist in antibubbles.

And so they pop much more easily than their regular bubble cousins.

No!

So as you can see, they're kind of hard to make.

Like, we struggled with a lot of the steps.

Don't put too much food coloring.

Yeah.

DAN: I would suggest practicing without food coloring first.

Because otherwise you're going to make all the fluid read.

DIANNA COWERN: Yeah.

The other trick is that if you add some corn syrup into this bottle, you'll increase the density of this liquid-- because corn syrup is more dense than water-- so that you can get your antibubbles to sink.

Or even get a little bit of the corn syrup in here, mixed in the bottom, so that you've got a gradient of density from more dense to less dense.

Then when you squeeze this liquid into the cup, you could get them to float right in the middle, kind of like a neutral buoyancy in that level of the liquid density.

It takes a lot of patience.

They're so cool!

I love science.

So if you were to make an antibubble in space, where there is no buoyant forces caused by gravity, you could make the antibubble last a lot longer.

Even after all this explanation, there's still a lot we don't really understand about antibubbles.

So stay tuned for the research on this and potential applications.

But in the meantime, I did find out you can make antibubbles in beer.

So cheers to anti-suds.

Happy physics sudsing.