When astronauts come back down to Earth, it can take a moment to adjust to the return of gravity. A viral video of NASA astronaut Tom Marshburn cursing gravity as he tries to place a pen mid-air was actually a parody. But it's not too far off what really happens to astronauts after prolonged time in space, as a new study almost 20 years in the making explains. Researchers from the Catholic University of Louvain in Belgium and the Basque Foundation for Science in Spain compared the way