National Geographic : 1989 May
someone to Mars who won't be able to stand up when he gets there?" Some specialists think artificial gravity will be required. It could be attained in a slowly rotating space vehicle, creating a centrifugal effect as in the film 2001: A Space Odyssey. A revolving spacecraft could also alleviate problems the Soviets have found in trying to grow plants in space greenhouses. In zero gravity, plants can grow with roots up and stems down, while weightless water cannot percolate through soil, which itself is floating away from roots. These are serious problems: Plants will be essential for providing food and oxygen during interplanetary flights. Science has gleaned a lot about the most mysterious force in the universe since Newton gave us an inkling of how it works. But does the knowledge do us any good? Right now orbiting satellites like LAGEOS and GEOSAT are taking readings of variations in the earth's gravitational field. To do this, researchers determine whether a satellite has bobbed up or down with a change in earth's gravity below. For instance, satellites drop noticeably over the "Indian Ocean anomaly" off Africa, where the earth's surface bulges and gravity's pull is particularly strong. CONFUSEDIN SPACE, plants in zero g often send their roots up, a problem on long flights requiringcrops. CosmonautV. Kubasov checks an experiment on a 1980 Salyut mission (below). Within two hours of being turned, a corn seedling bends its root, compared with onejust rotated by Ohio State University's MichaelEvans.