A few months ago, at her office in Houston, Kate Rubins was feeling weird.
She was dizzy, she says — "staggering around like a 2-year-old who had just learned to walk." She was constantly looking at her desk to make sure the objects on top weren't floating away.
Rubins wasn't going nuts. She was just readjusting to Earth after living without gravity for four months, hundreds of miles above the planet's surface.