NASA astronaut Don Pettit has helped YouTuber Steve Mould with the final step in his "weird chain theory": testing the idea in space.

In 2013, YouTuber and science communicator Steve Mould brought the "chain fountain", an unsolved problem in physics, to the attention of the wider public. The effect, sometimes referred to as the "Mould effect" for his work on it, is strange to see. Simply put, place a long chain in a container, pull one end out, and let it fall to the floor. Now watch as the whole chain seems to jump up out of the glass, before falling towards the floor: Watch video

The effect, though independently found by Mould, was known about before, even if it was unexplained. Since the effect was popularized by Mould, he, Mehdi Sadaghdar of YouTube channel ElectroBOOM, and several academic studies have attempted to explain it. Mould has also set the record for the biggest chain fountain.