zerogravity

ZeroGravity is the term commonly used to describe the condition of apparent weightlessness experienced by objects that are in free fall relative to their surroundings. In physics, gravity itself is not zero; weightlessness occurs when the only forces acting on an object are gravity and the object is falling alongside its surroundings. In orbital flight, spacecraft and their occupants experience microgravity, characterized by very small residual accelerations caused by vibrations, tidal forces, and maneuvers. The phrases zero gravity and weightlessness are widely used, but zero gravity is not a literal state achievable on Earth.

Achieving zero gravity on Earth is possible only for limited periods or in specific setups. Parabolic flights, often marketed as zero-G flights, produce brief intervals of weightlessness during each ballistic arc, typically lasting about 20 to 30 seconds. Drop towers provide a momentary free-fall environment during a controlled fall. Neutral buoyancy facilities, such as large water tanks, simulate some aspects of microgravity for training by balancing buoyant and gravitational forces, giving participants a sense of working in a weightless environment.

In practice, long-duration microgravity is studied in space, aboard orbiting spacecraft and laboratories such as the International Space Station. These environments support experiments across biology, materials science, fluid physics, combustion, and fundamental physics. Parabolic flights and other Earth-based demonstrations continue to be used for education and research, while commercial and academic programs explore microgravity in training, research, and outreach initiatives.

See also microgravity, weightlessness, orbital mechanics.