Since the early 1990s, we humans have been doing something both odd and eminently sensible: We've been launching jellyfish into space. And we have been doing so for science. During NASA's first Spacelab Life Sciences (SLS-1) mission in 1991, NASA began conducting an experiment: "The Effects of Microgravity-Induced Weightlessness on Aurelia Ephyra Differentiation and Statolith Synthesis." To carry it out, the space shuttle Columbia launched into space a payload of 2,478 jellyfish polyps—creatures contained within flasks and bags that were filled with artificial seawater. Astronauts injected chemicals into those bags that would induce the polyps to swim freely (and, ultimately, reproduce). Over the course of the mission, the creatures proliferated: By mission's close, there were some 60,000 jellies orbiting Earth.

The point of all this, as the experiment's title (sort of) suggests, was to test microgravity's effects on jellyfish as they develop from polyp to medusa. And the point of that, in turn, was to test how the jellyfish would respond when they were back on Earth. Jellyfish, foreign to us in so many ways, are like humans in one very particular manner: They orient themselves according to gravity.