0G

0g, or zero gravity, denotes an environment in which the effective gravitational force acting on a body is essentially zero. In practice, this occurs in orbital spacecraft and during specialized flight regimes where objects are in continuous free fall, producing weightlessness despite the presence of Earth’s gravity. The term microgravity is often used to describe these conditions, though gravity is never truly zero.

Common methods to achieve microgravity include orbital flight where the spacecraft is in free fall around Earth; parabolic flight regimes that generate short periods of weightlessness; and drop towers that expose experiments to brief free fall. In each case residual accelerations are small but detectable, and experiments must account for vibrations, residual drag, and tidal forces.

In science and engineering, microgravity enables unique observations: fluids form nearly perfect spheres, diffusion-dominated processes prevail, and combustion occurs with altered flame dynamics. Biological experiments study cell growth and tissue development without sedimentation. Human spaceflight research notes physiological changes such as bone and muscle loss, fluid redistribution, and vestibular adaptation, requiring exercise regimens and other countermeasures.

Other uses of the term 0g include pre-cellular or pre-1G telecommunications, sometimes called zero-generation networks, used to describe technologies preceding first-generation cellular networks. In popular culture, 0g is a shorthand for weightlessness and appears in branding and media related to spaceflight.