There’s a long, long list of fun things to do in zero gravity, but when you spend an entire year in space, you probably get quite bored. That’s where space ping-pong with water droplets and hydrophobic paddles comes in.

Commander Scott Kelly has spent nearly an entire year in space as part of an experiment on the long-term effects of zero gravity on the body. In has latest video, he shows how a pair of hydrophobic paddles can be used to guide a droplet of water around inside the International Space Station. Surface tension keeps the droplet of water together, while the hydrophobic paddles repel the water when it comes into contact.