Student Features

High Tea on the International Space Station
06.14.03

Tea droplets

Explanation: It's a competition: surface tension vs. gravity. Surface tension holds droplets of water together. Gravity pulls them apart. On Earth, gravity usually wins. Only small droplets have enough surface tension per unit mass to remain intact. Onboard the International Space Station (ISS), however, surface tension rules. Weightless water can form big floating drops, large enough to quench your thirst and tough enough to handle using chopsticks.

Eating droplets of tea

ISS science officer Don Pettit paused for afternoon tea -- above -- and showed us how it's done: "It's easy," says Pettit. "You just take your chopsticks, pick up a blob of tea, and pop it in your mouth. This is a practical demonstration of all the surface chemistry we learned about in college."

Because fluid droplets onboard the space station are undisturbed by their own weight, they make marvelous research tools for investigations in basic fluid physics. The applications are many: Firefighters are interested because water mists can be used to extinguish flames. Weather forecasters are interested because rain clouds are made of water droplets. Automakers are interested because internal combustion engines burn tiny drops of fuel. And so on....

Plus, they're fun -- and the entertainment value shouldn't be underestimated. One day, perhaps, luxury space hotels will offer their guests afternoon tea 300 miles above Earth . No cups or plates. Just chopsticks and droplets. Now that's high tea!

Editor's note: Don Pettit has filmed a series of afternoon tea demonstrations. The movies show how honey, peanut butter and tea behave in low gravity, and how astronauts clean up after snack time.