Devices for simulating changes in gravity range from centrifuges to “vomit comets,” but simple magnetism may offer the most versatile method. Living tissues are diamagnetic, meaning that they become magnetic in response to an external magnetic field. Researchers have used a powerful magnet to levitate frogs, effectively putting them in zero gravity; now the same Brown University group has varied and reversed the gravity felt by the singlecelled paramecium, which senses gravity and swims against it. The scientists found that the cells keep swimming in magnetic fields that simulate up to 10 g's, at which point they tread water or poop out. The technique might serve to grow hard-to-produce tissues for medical research, says Brown physics Ph.D. candidate Karine Guevorkian, who presented the results at the March meeting of the American Physical Society.