Take a look at the International Space Station, where Don Pettit constructs what can only be called Russian Nesting Bubbles - a series of thick-rimmed bubbles inside other bubbles, all of which center themselves.

I'm beginning to think that gravity is the force most responsible for not letting us have any fun. Take a look at the latest demonstration conducted by Don Pettit, an astronaut on the International Space Station. Because there is not gravity pulling down on the water bubble he constructs, it can have very thick rims and it lasts for a long time. While it's bubbling around (I don't know the verb for what bubbles do with themselves.), it is injected with more bubbles, many of which have bubbles inside them.

Later, when there's just a water droplet, the water is set to spin, and the air bubbles are injected inside it. (Then there are lasers just for fun.) What's strange is, why do the bubbles inside the water droplet seem to clump around the center of the spinning drop? They bumble (that's what bubbles do!) around a bit, but eventually they all head towards the center. To understand the answer, we have to understand that we're not just seeing a droplet, we're seeing a centrifuge. The surface tension of the droplet, not having to contend with gravitational force, does a pretty good job keeping the droplet together, and it spins just like a centrifuge would spin. The reason why we have centrifuges in labs is to separate out materials. Dense materials will shoulder their way to the outer edge of the spinning centrifuge, while lighter material will get pushed to the center. Since water is denser than air, the same thing happens here, and the bubbles get pushed to the center of the spinning drop.

And, this doesn't have anything to do with anything, but we'd like to thank Don Pettit for not just doing these experiments, but for uttering the phrase, "That's where I'd go if I were a bubble."

Via Physics Central