What’s the opposite of a bubble?

The last time I tried telling someone about antibubbles, they asked me if I was making stuff up. I honestly wasn’t. Weird as it might sound, there is such a thing as an antibubble, and it is exactly what it sounds like. Something like a bubble, but the opposite. You’ve probably seen them dozens of times in the past, and not recognised what they are…

…that probably wasn’t a very good explanation. Let me elaborate. A regular soap bubble is basically a little sphere of air, enclosed by a thin film of water. Bubbles can form using any two substances with suitable properties. A film of liquid, enclosing a pocket of gas. An antibubble, on the other hand, is a pocket of liquid trapped by a film of gas.

Seriously. You’ve almost definitely seen antibubbles before. Though you very likely won’t have realised it. Have a look, the next time you fill the kitchen sink or run a bath. In fact, the easiest way to see a few for yourself is to get a large glass bowl of soapy water (soap lowers the surface tension of water and allows the bubbles to persist for a little longer) and drip more water slowly into it. Antibubbles look a little bit like regular soap bubbles, but glassier because they’re filled with water. Instead of acting like regular bubbles and sticking together as foam, antibubbles are repelled by each other. They skitter along the surface of liquids (known as “boules” or “globules”). Unlike air bubbles, a floating antibubble will bounce off the side of its container, or off any other objects it encounters, including air bubbles. If pushed below the liquid surface, they’re buoyant and rise to the top, but they take a lot longer to do so.

If you didn’t know about antibubbles before, you do now. And you’ll probably start noticing them all the time!

There’s a lot more information at antibubble.org!

About Invader Xan

Molecular astrophysicist, usually found writing frenziedly, staring at the sky, or drinking mojitos.
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